Bio- Proteins and Enzymes (B1.1 and C1.1)

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1

what is the structure of an amino acid?

amine group (NH2) and carboxyl (COOH) on the sides and hydrogen or R group on top/bottom. All attached to a central alpha carbon

<p>amine group (NH2) and carboxyl (COOH) on the sides and hydrogen or R group on top/bottom. All attached to a central alpha carbon</p>
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2

what are proteins made up of?

all organisms are made up of the same twenty amino acids (all will have amine group, carboxyl group, and hydrogen attached) (will have diff R groups that will determine the diff chemical properties and behavior)

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3

how are dipeptides formed?

amino acid + amino acid → dipeptides + water (condensation reactions)

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4

what is the formation of a dipeptide?

OH and H bond together to form water and the C connects to the N

<p>OH and H bond together to form water and the C connects to the N</p>
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5

what is the difference between a protein and a polypeptide?

  • polypeptide- string of amino acids but is NOT yet functional

  • protein- string of amino acids but is in functional form

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6

where is the peptide bond always?

between the C and N of neighboring amino acids

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7

where are polypeptides formed?

ribosomes during the process of translation

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8

what are essential amino acids?

amino acids that must be consumed through the diet of a person (9 of the amino acids)

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what are non-essential amino acids?

amino acids the body naturally produces (11 of the amino acids can be synthesized)

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10

where are amino acids coded?

in the DNA (genetic code)

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11

how many amino acids can peptide chains have?

any number

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true or false: amino acids can be in any order

true

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the variety od possible polypeptides is ____

infinite

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14

what is denaturation?

conformational change in the shape of a molecule (like a protein) resulting in the loss of function

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15

when proteins are broken up, what structure is very unlikely to break?

primary structure

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16

what do R groups determine?

chemical properties

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17

what are the two kinds of R groups?

hydrophobic and hydrophilic

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18

R groups can be _____, _____, _____, and/or _____

hydrophobic, hydrophilic, acidic, and/or basic

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19

what determines the functions of proteins?

the shape of the protein

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20

what are gene products?

EVERYTHING

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21

what is the primary structure?

the number and sequence of amino acids in a polypeptide

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22

what determines the three-dimensional shape of proteins?

the sequence of amino acids and the precise position of structure

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23

the precise sequence of amino acids in a polypeptide determines the ____ of the poly peptide due to the reactions between the _____

shape, R groups

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24

what kind of bonds are in the primary structure?

ONLY peptide bonds

<p>ONLY peptide bonds</p>
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25

what is the protein folding problem?

  • the challenge of predicting the three-dimensional structure of a protein based solely on its amino acid sequence

  • the folding process is caused by diff factors and can result in multiple possible structures

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what kind of bonds are in the secondary structure?

ONLY hydrogen bonds

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27

what structures can be formed because of the hydrogen bonds between the C=O of one amino acid and the N-H of a second amino acid

  • alpha helices

  • beta-pleated sheets

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where are hydrogen bonds formed?

regular intervals

<p>regular intervals</p>
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what is the tertiary structure?

  • further folding of the polypeptide into 3-D structure

  • because of interactions between the R groups

<ul><li><p>further folding of the polypeptide into 3-D structure</p></li><li><p>because of interactions between the R groups</p></li></ul>
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what interactions occur in the tertiary structure?

  • ionic bonds between charged R groups (amine group becomes positive and carboxyl becomes negative forming ionic bonds)

  • covalent bonds between R groups (disulfide bonds between 2 cysteines)

  • hydrogen bonds between polar R groups

  • hydrophobic and hydrophilic interactions of R groups (proteins in organisms are surrounded by water)

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31

what are disulfide bridges?

form between R groups of two cysteine amino acids in close proximity in a polypeptide

<p>form between R groups of two cysteine amino acids in close proximity in a polypeptide</p>
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what can happen to carboxyls and amine groups in R groups?

can become positively charged or negatively charged because of binding or dissociation of hydrogen ions causing them to be able to participate in ionic bonding

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33

where are the hydrophobic and hydrophilic amino acids in a protein?

  • hydrophobic

    • non-polar R groups

    • in the core/inside of the globular protein

  • hydrophilic

    • polar/ionic R groups

    • outside the protein

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what are integral proteins?

  • embedded within the phospholipid bilayer

  • the part of the integral protein that is in the middle of the bilayer is surrounded by hydrophobic fatty acid tails and is hydrophobic because of the non-polar R groups

  • the part of the integral protein that is exposed to water is hydrophilic because of the polar and charged R groups

<ul><li><p>embedded within the phospholipid bilayer</p></li><li><p>the part of the integral protein that is in the middle of the bilayer is surrounded by hydrophobic fatty acid tails and is hydrophobic because of the non-polar R groups</p></li><li><p>the part of the integral protein that is exposed to water is hydrophilic because of the polar and charged R groups</p></li></ul>
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35

what are channel proteins?

have a tunnel lined with hydrophilic amino acids to allow hydrophilic molecules through the bilayer

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what is the quaternary structure of a protein?

  • not all proteins have them

  • proteins composed of more than one polypeptide chain

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what is involved with the quaternary structure?

  • held together due to the R groups on each polypeptide like:

    • hydrogen bonds

    • covalent bonds (disulfide bridges)

    • ionic bonds

    • hydrophobic/hydrophilic interactions

<ul><li><p>held together due to the R groups on each polypeptide like:</p><ul><li><p>hydrogen bonds</p></li><li><p>covalent bonds (disulfide bridges)</p></li><li><p>ionic bonds </p></li><li><p>hydrophobic/hydrophilic interactions</p></li></ul></li></ul>
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38

NOS: what does technology allow?

imaging of structures that would be impossible to observe with the unaided senses

For example, cryogenic electron microscopy has allowed imaging of single-protein molecules and their interactions with other molecules

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39

what is a conjugated protein?

protein attached to a non-polypeptide group known as a prosthetic group (helper molecule)

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40

what is an example of an conjugated protein?

  • hemoglobin (globular conjugated protein)

    • two alpha polypeptide chains

    • two beta polypeptide chains

    • four heme groups (not polypeptides) (heme= iron groups / make the hemoglobin attract oxygen)

    • heme group is the helping molecule

    • function: carries oxygen within red blood cells

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what is a non-conjugated protein?

composed of only polypeptides

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what are examples of a non-conjugated protein?

  • insulin (globular non-conjugated protein)

    • two polypeptide chains linked by two disulfide bridges

    • function: regulates the blood glucose levels by causing the liver to release glucose from the blood

  • collagen (fibrous non-conjugated protein) (shown in the pic)

    • three polypeptide chains that are tightly coiled together into a triple-helix structure

    • has beta-pleated sheets that form the helical structure

    • function: main structural protein found in connective tissue like skin, cartilage, and bones

    • the fibrous nature provides strength and elasticity to tissues

<ul><li><p>insulin (globular non-conjugated protein)</p><ul><li><p>two polypeptide chains linked by two disulfide bridges</p></li><li><p>function: regulates the blood glucose levels by causing the liver to release glucose from the blood</p></li></ul></li><li><p>collagen (fibrous non-conjugated protein) (shown in the pic)</p><ul><li><p>three polypeptide chains that are tightly coiled together into a triple-helix structure</p></li><li><p>has beta-pleated sheets that form the helical structure</p></li><li><p>function: main structural protein found in connective tissue like skin, cartilage, and bones</p></li><li><p>the fibrous nature provides strength and elasticity to tissues</p></li></ul></li></ul>
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what are the similarities between insulin and collagen?

  • composed of amino acids joined by peptide bonds during the process of translation on ribosomes

  • they have a quaternary structure with more than one polypeptide

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what are the differences between insulin and collagen?

  • insulin

    • globular

    • spherical

    • irregular amino acid sequence with hydrophobic amino acids in the core

    • soluble in water (polar)

    • 2 polypeptides held together by disulfide bridges

    • functional

      • hormone with a specific globular shape with a binding site for receptors on target cells

  • collagen

    • fibrous

    • long and narrow

    • repetitive amino acid sequence

    • insoluble in water (non-polar)

    • 3 polypeptides held together by hydrogen bonds

    • structural

      • 3 polypeptides in collagen form flexible fibers with high tensile strength and elasticity which provide structural support to body tissues

    • (the function is to provide support)

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45

what are the differences between globular and fibrous protein shapes?

Differences

  1. Shape: Globular proteins have a compact, spherical shape, while fibrous proteins have an elongated, thread-like shape.

  2. Solubility: Globular proteins are generally soluble in water, while fibrous proteins are often insoluble.

  3. Function: Globular proteins are involved in enzymatic reactions, transport, and regulation, while fibrous proteins provide structural support and stability.

  4. Structure: Globular proteins have a complex and irregular three-dimensional structure, while fibrous proteins have a repetitive and extended structure.

<p><strong>Differences</strong></p><ol><li><p>Shape: Globular proteins have a compact, spherical shape, while fibrous proteins have an elongated, thread-like shape.</p></li><li><p>Solubility: Globular proteins are generally soluble in water, while fibrous proteins are often insoluble.</p></li><li><p>Function: Globular proteins are involved in enzymatic reactions, transport, and regulation, while fibrous proteins provide structural support and stability.</p></li><li><p>Structure: Globular proteins have a complex and irregular three-dimensional structure, while fibrous proteins have a repetitive and extended structure.</p></li></ol>
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primary = 1

secondary = 2

tertiary = 3

quaternary = 4

  1. peptide bonds

  2. hydrogen bonds

  3. ionic / disulfide bridges / hydrophobic + hydrophilic reactions

  4. more than one strand

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47

DNA codes proteins so….

enzymes are also from DNA because they are proteins

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48

what are enzymes?

  • globular proteins

  • catalysts in metabolic reactions

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49

what are catalysts?

speed up rate of reaction without changing the structure

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50

what is metabolism?

all the chemical reactions that occur in living organisms

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51

what happens without enzymes in metabolism?

metabolic reactions occur slowly, if at all, at body temperature

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52

true or false: each enzyme is specific and catalyzes ONE specific chemical reaction

true

ex. catalase (one enzyme) → hydrogen peroxide (one chemical reaction)

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53

the cell can do what to metabolism through the use of enzymes?

control

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true or false: because of enzyme specificity only one enzyme is required by living organisms

false; many diff enzymes are required by living organisms to control all the different kinds of chemical reactions

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55

what is anabolism?

  • storing energy

  • synthesis of complex molecules from simpler molecules

  • formation of macromolecules from monomers by condensation reactions

  • includes:

    • protein synthesis

    • glycogen formation

    • photosynthesis

<ul><li><p>storing energy</p></li><li><p>synthesis of complex molecules from simpler molecules</p></li><li><p>formation of macromolecules from monomers by condensation reactions</p></li><li><p>includes:</p><ul><li><p>protein synthesis</p></li><li><p>glycogen formation</p></li><li><p>photosynthesis</p></li></ul></li></ul>
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what is catabolism?

  • releasing energy

  • breakdown of complex molecules into simper molecules

  • hydrolysis of macromolecules into monomers

  • includes:

    • digestion

    • oxidation of substrates in respiration

<ul><li><p>releasing energy</p></li><li><p>breakdown of complex molecules into simper molecules</p></li><li><p>hydrolysis of macromolecules into monomers</p></li><li><p>includes:</p><ul><li><p>digestion</p></li><li><p>oxidation of substrates in respiration</p></li></ul></li></ul>
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57

what is the active site?

  • region where substrates bind and are catalyzed to products

  • has to have a complementary shape that allows the substrate to bind (like puzzle pieces)

  • composed of a few amino acids but the overall 3-D shape ensures that the active site can catalyze the reaction of the substrate

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what do enzymes act on in a reaction?

substrates

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59

what are substrates?

reactants in enzyme-catalyzed reactions

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60

what do most enzymes end in?

-ase

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61

what are the components of the E-S Complex?

(Enzyme-Substrate Complex)

<p>(Enzyme-Substrate Complex)</p>
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what is the induced fit model?

explains how most substrates are converted to products by enzymes

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what happens in the induced fit model?

  • substrate approaches and enters the active site of the enzyme

  • the substrate induces the active site of the enzyme to change shape so there is an optimal fit between the substrate and the active site

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64

the product has ___ chemical properties to the substrate and is released from the active site

different

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true or false: both enzyme and substrate change shape when binding occurs

true

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what is the collision theory?

chemical reactions happen when particles collide

(random movement of particles)

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what must particles have in order for reactions to occur?

  • sufficient energy

  • correct orientation

<ul><li><p>sufficient energy</p></li><li><p>correct orientation</p></li></ul>
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particles, including enzymes and substrates, are in what?

constant motion

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69

an enzyme can only catalyze a reaction when the ___ collides with the ___ of the enzyme

substrate, active site

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70

the more frequently substrates collide with active sites of enzymes → the ____ the rate of reaction

faster

<p>faster</p>
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71

what is immobilization of substrates?

substrates are so large they don’t move much and therefore the enzyme must do the moving

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what is immobilization of enzymes in membranes?

keeps it in close proximity to the substrate that it catalyzes (the substrate does the moving)

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73

what is enzyme-substrate specificity?

the shape and chemistry of an enzyme’s active site allows one specific type of substrate to be catalyzed

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74

how is an enzyme denatured?

  • permanent change in the shape of the proteins

  • results in the loss of the proteins’ biological function

  • substrates can no longer bind to the active site or catalyze reactions

  • the active site is the part that gets denatured

<ul><li><p>permanent change in the shape of the proteins</p></li><li><p>results in the loss of the proteins’ biological function</p></li><li><p>substrates can no longer bind to the active site or catalyze reactions</p></li><li><p>the active site is the part that gets denatured</p></li></ul>
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75

true or false: enzymes are denatured by low temperature

false; they are not denatured by low temperature

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76

how does temperature affect enzyme activity?

  • low temperature

    • kinetic energy of particles is low

    • number of collisions between substrates and active sites is low

    • low rate of reaction

    • (when graph is at 0 → frozen and not denatured)

  • as temperature increases

    • particles gain energy and move faster

    • number of collisions increases

    • rate of reaction increases until the enzymes’ reach optimum temperature (each enzyme has an optimal temperature)

    • increase in correct orientations as well

  • above optimum temperature

    • bonds in enzyme start breaking

    • enzyme becomes denatured

    • substrate is no longer able to bind with active site

    • rate of reaction drops quickly

  • each enzyme has a specific optimum temperature

  • always loss of function because of loss of shape/structure

<ul><li><p>low temperature</p><ul><li><p>kinetic energy of particles is low</p></li><li><p>number of collisions between substrates and active sites is low</p></li><li><p>low rate of reaction</p></li><li><p>(when graph is at 0 → frozen and not denatured)</p></li></ul></li><li><p>as temperature increases</p><ul><li><p>particles gain energy and move faster</p></li><li><p>number of collisions increases</p></li><li><p>rate of reaction increases until the enzymes’ reach optimum temperature (each enzyme has an optimal temperature)</p></li><li><p>increase in correct orientations as well</p></li></ul></li><li><p>above optimum temperature</p><ul><li><p>bonds in enzyme start breaking</p></li><li><p>enzyme becomes denatured</p></li><li><p>substrate is no longer able to bind with active site</p></li><li><p>rate of reaction drops quickly</p></li></ul></li><li><p>each enzyme has a specific optimum temperature</p></li><li><p>always loss of function because of loss of shape/structure</p></li></ul>
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how does pH affect enzyme activity?

  • all enzymes have an optimal pH

  • changes in pH affect the shape of enzymes

  • an increase or decrease in pH away from the optimum results in a decrease in enzyme activity as the active site is no longer as efficient at binding to the substrate

  • a large change of pH will disrupt ionic bonds and denature the enzyme

  • the enzyme will stop working as the substrate is no longer able to bind to the active site

  • diff enzymes have diff optimum pHs

<ul><li><p>all enzymes have an optimal pH</p></li><li><p>changes in pH affect the shape of enzymes</p></li><li><p>an increase or decrease in pH away from the optimum results in a decrease in enzyme activity as the active site is no longer as efficient at binding to the substrate</p></li><li><p>a large change of pH will disrupt ionic bonds and denature the enzyme</p></li><li><p>the enzyme will stop working as the substrate is no longer able to bind to the active site</p></li><li><p>diff enzymes have diff optimum pHs</p></li></ul>
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how does substrate concentration affect enzyme activity?

  • as the substrate concentration increases

    • increased collisions between substrate and the enzymes’ active sites

    • rate of reaction increases

    • reaction rate continues to increase as substrate concentration increases until all of the enzymes’ active sites are saturated (catalyzing as fast as they can because they are surrounded by substrate)

    • rate plateaus as all enzymes are working at their optimum rate (reaches V-max)

<ul><li><p>as the substrate concentration increases</p><ul><li><p>increased collisions between substrate and the enzymes’ active sites</p></li><li><p>rate of reaction increases</p></li><li><p>reaction rate continues to increase as substrate concentration increases until all of the enzymes’ active sites are saturated (catalyzing as fast as they can because they are surrounded by substrate)</p></li><li><p>rate plateaus as all enzymes are working at their optimum rate (reaches V-max)</p></li></ul></li></ul>
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when looking at graphs what do you always assume?

that all other factors and conditions are the same

ex. measuring substrate concentration = same temperature and same pH (and vice versa)

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NOS: the generalized sketches of enzyme activity represent scientific models which can be used to develop hypotheses when investigating enzyme activity

(the three graphs of temperature, pH, and substrate concentration)

both temperature and substrate concentration have no denaturation while pH is denatured on both ends of the graph

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how do you calculate the rate of reaction in enzyme-catalyzed reactions?

rate of reaction = change in reactant or product / time

  • changes that can be measured include:

    • mass or volume of the reactants or products

    • pH (if the reaction causes a change in the pH)

    • temperature change (as reactions involve a gain or loss of heat)

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82

what is activation energy?

the minimum amount of energy required for a chemical reaction to occur

enzymes lower the activation energy for chemical reactions allowing metabolism to occur at body temperature

all chemical reactions require a certain amount of activation energy

more energy is needed without enzymes

less energy is needed for enzyme / catalase reactions

reactants = substrates

<p>the minimum amount of energy required for a chemical reaction to occur</p><p>enzymes lower the activation energy for chemical reactions allowing metabolism to occur at body temperature</p><p>all chemical reactions require a certain amount of activation energy </p><p>more energy is needed without enzymes</p><p>less energy is needed for enzyme / catalase reactions</p><p>reactants = substrates</p>
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83

what is the transition state of enzymes?

enzymes must reach the transition state before an enzyme reaction goes forward

bonds in substrate are weakened as it binds to active site

highly unstable state between substrate and product

<p>enzymes must reach the transition state before an enzyme reaction goes forward </p><p>bonds in substrate are weakened as it binds to active site</p><p>highly unstable state between substrate and product</p>
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84

how do enzymes lower activation energy?

energy is required to break bonds in the substrate molecules and the formation of bonds in the product releases energy

enzymes catalyzing a reaction does not affect the change in energy between the substrates and reactants

on graph:

triangleG does not change (free energy)

Ea goes from A + BC to the transition state height wise and is the activation energy

<p>energy is required to break bonds in the substrate molecules and the formation of bonds in the product releases energy</p><p>enzymes catalyzing a reaction does not affect the change in energy between the substrates and reactants</p><p>on graph:</p><p>triangleG does not change (free energy)</p><p>Ea goes from A + BC to the transition state height wise and is the activation energy</p>
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what is exergonic vs endergonic reactions?

  • exergonic

    • less energy in products than reactants; ie condensation reactions

    • exothermic (warmer)

  • endergonic

    • more energy in products than reactants; ie hydrolysis

    • endothermic (colder)

<ul><li><p>exergonic</p><ul><li><p>less energy in products than reactants; ie condensation reactions</p></li><li><p>exothermic (warmer)</p></li></ul></li><li><p>endergonic</p><ul><li><p>more energy in products than reactants; ie hydrolysis</p></li><li><p>endothermic (colder)</p></li></ul></li></ul>
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what are intracellular enzymes?

  • produces on free floating ribosomes (they make proteins) in the cytoplasm

  • active within the cell

  • required for most stages of aerobic (cell) respiration

    • produced by mitochondrial enzymes

  • required for photosynthesis

    • produced by chloroplast enzymes

  • examples of metabolism include:

    • glycolysis

    • Krebs cycle of respiration

<ul><li><p>produces on free floating ribosomes (they make proteins) in the cytoplasm</p></li><li><p>active within the cell</p></li><li><p>required for most stages of aerobic (cell) respiration</p><ul><li><p>produced by mitochondrial enzymes</p></li></ul></li><li><p>required for photosynthesis</p><ul><li><p>produced by chloroplast enzymes </p></li></ul></li><li><p>examples of metabolism include:</p><ul><li><p>glycolysis</p></li><li><p>Krebs cycle of respiration</p></li></ul></li></ul>
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what are extracellular enzymes?

  • active outside the cell

  • synthesized by ribosomes attached to the rough ER - proteins sent to Golgi apparatus for processing - packaging in secretory vesicles and released outside of cell in exocytosis

  • example:

    • digestion

      • enzymes secreted from specialized cells into the lumen of the digestive system from the human gut

  • in photo:

    • blue near the top = secretory vesicles

    • green bean shapes = golgi apparatus

    • spikey caterpillar shapes = rough ER

<ul><li><p>active outside the cell</p></li><li><p>synthesized by ribosomes attached to the rough ER - proteins sent to Golgi apparatus for processing - packaging in secretory vesicles and released outside of cell in exocytosis</p></li><li><p>example:</p><ul><li><p>digestion</p><ul><li><p>enzymes secreted from specialized cells into the lumen of the digestive system from the human gut</p></li></ul></li></ul></li><li><p>in photo:</p><ul><li><p>blue near the top = secretory vesicles</p></li><li><p>green bean shapes = golgi apparatus</p></li><li><p>spikey caterpillar shapes = rough ER</p></li></ul></li></ul>
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what is heat generation?

  • inevitable consequence of metabolism

  • metabolic reactions are NOT 100% efficient in energy transfer

  • endotherms depend on the release of heat from metabolism to maintain a constant body temperature

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what are the metabolic pathways?

  • most metabolic reactions happen in a sequence of small steps

  • two main types of pathways:

    • linear / chains

    • cyclical

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what is a linear pathway?

  • glycolysis (breaking up glucose into 2 pyruvate) in respiration is an example of a linear metabolic pathway

  • all chemical reactions in the pathway require specific enzymes

<ul><li><p>glycolysis (breaking up glucose into 2 pyruvate) in respiration is an example of a linear metabolic pathway</p></li><li><p>all chemical reactions in the pathway require specific enzymes</p></li></ul>
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what is a cyclical pathway?

  • the krebs cycle in respiration is an example of a cyclical metabolic pathway

  • the calvin cycle in photosynthesis is an example of a cyclical metabolic pathway

  • all chemical reactions in the pathway require specific enzymes

  • (citric acid cycle = krebs cycle)

<ul><li><p>the krebs cycle in respiration is an example of a cyclical metabolic pathway</p></li><li><p>the calvin cycle in photosynthesis is an example of a cyclical metabolic pathway</p></li><li><p>all chemical reactions in the pathway require specific enzymes</p></li><li><p>(citric acid cycle = krebs cycle)</p></li></ul>
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what is enzyme inhibition?

  • molecules that stop or slow down an enzyme’s ability to catalyze a reaction

  • messes with the active site and interferes with the substrates access to the active site

  • can be:

    • competitive inhibitors (bind to the active site) (directly)

    • non-competitive inhibitors (bind to allosteric / alternate site on the enzyme) (indirectly)

<ul><li><p>molecules that stop or slow down an enzyme’s ability to catalyze a reaction</p></li><li><p>messes with the active site and interferes with the substrates access to the active site</p></li><li><p>can be:</p><ul><li><p>competitive inhibitors (bind to the active site) (directly)</p></li><li><p>non-competitive inhibitors (bind to allosteric / alternate site on the enzyme) (indirectly)</p></li></ul></li></ul>
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what is competitive inhibition?

  • have a similar shape and chemistry that mimics the substrate

  • competes with the substrate and prevents it from binding to the active site

  • reversible

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how do competitive inhibitors affect reaction rate?

  • reduce the reaction rate of the enzyme activity as many of the enzymes have an inhibitor in the active site instead of the substrate

  • reaction rate increases but at a slower rate

  • only the substrate concentration changes

  • it is possible to reach the same rate as with no inhibitor

  • increasing substrate concentration increases the rate of enzyme activity

  • enzymes have a higher chance of colliding with the substrate than the inhibitor

  • the graph eventually plateaus

<ul><li><p>reduce the reaction rate of the enzyme activity as many of the enzymes have an inhibitor in the active site instead of the substrate</p></li><li><p>reaction rate increases but at a slower rate</p></li><li><p>only the substrate concentration changes</p></li><li><p>it is possible to reach the same rate as with no inhibitor</p></li><li><p>increasing substrate concentration increases the rate of enzyme activity</p></li><li><p>enzymes have a higher chance of colliding with the substrate than the inhibitor</p></li><li><p>the graph eventually plateaus</p></li></ul>
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95

what are examples of competitive inhibitors?

  • statins

    • used to treat high cholesterol levels

  • if no statins are present:

    • enzyme HMG-CoA reductase converts HMG-CoA into mevalonic acid

    • mevalonic acid is then converted into cholesterol through a series of enzyme-catalyzed reactions

    • statins are the competitive inhibitors of the enzyme HMG-CoA reductase

<ul><li><p>statins</p><ul><li><p>used to treat high cholesterol levels</p></li></ul></li><li><p>if no statins are present:</p><ul><li><p>enzyme HMG-CoA reductase converts HMG-CoA into mevalonic acid</p></li><li><p>mevalonic acid is then converted into cholesterol through a series of enzyme-catalyzed reactions</p></li><li><p>statins are the competitive inhibitors of the enzyme HMG-CoA reductase</p></li></ul></li></ul>
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how do statins affect cholesterol?

  • have a similar chemistry and shape to HMG CoA

  • binds to the active site of the HMG CoA reductase enzyme

  • competitively inhibits the production of mevalonic acid

  • if there is less mevalonic acid produced - there will also be less cholesterol produced

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what are non-competitive inhibitors?

  • different in structure to the substrate (doesn’t mimic)

  • binds to allosteric site on the enzyme

  • changes the shape of the active site and prevents the substrate from binding

  • reversible

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98

how does non-competitive inhibition affect reaction rate?

  • reduces the number of functioning enzymes

  • reduces the reaction rate

  • increasing substrate concentration only increases reaction rate to a point because of the inhibitors

  • can never reach V max like competitive inhibition

<ul><li><p>reduces the number of functioning enzymes</p></li><li><p>reduces the reaction rate </p></li><li><p>increasing substrate concentration only increases reaction rate to a point because of the inhibitors</p></li><li><p>can never reach V max like competitive inhibition</p></li></ul>
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99

what is feedback/end product inhibition?

  • final product binds to allosteric site of first enzyme in reaction

  • active site changes shape, 1st intermediate substrate can’t bind

  • prevents the rest of reactions in pathway from occurring

  • pathway starts again when concentration of final product is low and no longer inhibits the first reaction in the pathway

  • on photo:

    • green triangle = substrate 1

    • sub. 1 connects to enzyme 1

    • purple rectangle = product from ES1

    • purple rectangle = becomes sub 2 for enzyme 2

    • and continues until

    • the yellow square = end product

    • yellow square = becomes the inhibitor

<ul><li><p>final product binds to allosteric site of first enzyme in reaction</p></li><li><p>active site changes shape, 1st intermediate substrate can’t bind </p></li><li><p>prevents the rest of reactions in pathway from occurring </p></li><li><p>pathway starts again when concentration of final product is low and no longer inhibits the first reaction in the pathway</p></li><li><p>on photo:</p><ul><li><p>green triangle = substrate 1</p></li><li><p>sub. 1 connects to enzyme 1</p></li><li><p>purple rectangle = product from ES1</p></li><li><p>purple rectangle = becomes sub 2 for enzyme 2</p></li><li><p>and continues until </p></li><li><p>the yellow square = end product</p></li><li><p>yellow square = becomes the inhibitor</p></li></ul></li></ul>
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100

what is an example of end product inhibition?

  • isoleucine inhibits threonine deaminase

    • amino acid threonine is converted to the amino acid isoleucine through a series of enzyme-catalyzed reactions

    • isoleucine is a non-competitive inhibitor of the enzyme threonine deaminase that catalyzes threonine

    • if there is an excess of isoleucine it binds to the allosteric site of threonine deaminase causing the active site to change shape and the enzyme is no longer able to catalyze the first reaction in the pathway

    • if the first reaction in the pathway is not working all reactions in the pathway stop working

    • when there is not an excess of isoleucine then it is released from the enzyme threonine deaminase and the isoleucine production restarts

  • threonine is the substrate and isoleucine is the product that becomes the inhibitor

  • in the photo:

    • enzyme 1 = threonine deaminase

    • A = product from ES1 and new substrate for enzyme 2

    • and so on

<ul><li><p>isoleucine inhibits threonine deaminase</p><ul><li><p>amino acid threonine is converted to the amino acid isoleucine through a series of enzyme-catalyzed reactions</p></li><li><p>isoleucine is a non-competitive inhibitor of the enzyme threonine deaminase that catalyzes threonine</p></li><li><p>if there is an excess of isoleucine it binds to the allosteric site of threonine deaminase causing the active site to change shape and the enzyme is no longer able to catalyze the first reaction in the pathway</p></li><li><p>if the first reaction in the pathway is not working all reactions in the pathway stop working</p></li><li><p>when there is not an excess of isoleucine then it is released from the enzyme threonine deaminase and the isoleucine production restarts</p></li></ul></li><li><p>threonine is the substrate and isoleucine is the product that becomes the inhibitor</p></li><li><p>in the photo:</p><ul><li><p>enzyme 1 = threonine deaminase</p></li><li><p>A = product from ES1 and new substrate for enzyme 2 </p></li><li><p>and so on</p></li></ul></li></ul>
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