Unit 4 Test C1

What is a catalyst?

A catalyst is a substance that speeds up a chemical reaction without being used up or apart of the chemical reaction

• Help the molecules of the reaction interact with each other

How do living things depend on enzymes?

• Enzymes are biological catalysts that control almost all reactions in the body

• The reactions that keep thehuman body alove would not happen fast enough without enzymes

  • Happens 10^7x faster with enzymes

  • Digestion

  • Cell respiration

  • Growth

Metabolism

All of the chemical reactions that keep the organism alive

• Building molecules (anabolism)

• Breaking down molecules (catabolism)

How do enzymes control metabolic pathways/cascades?

• Major chemical conversions happen through a series of reactions, catalyzed by different enzymes

• The product of one enzymes reaction is the substrate for the next enzyme

• Interdependence: series of reactions that depend on each other

How does Enzyme A impact Enzyme B in a pathway?

• Enzyme A produces a product that becomes the substrate for Enzyme B

• So if Enzyme A slows/stops → Enzyme B has no substrate → pathway stops

Anabolic reactions

• Add molecules: build larger molecules from smaller ones

• Require energy (ATP)—> energy is absorbed to make bonds

• Example:

  • Protein synthesis in muscle growth

  • Glucose—> glycogen

  • DNA replication

• Caused by enzymes

Catabolic reaction

• Cut molecules apart: break down large molecules into smaller ones

• Release energy—> break bonds

• Example:

  • Digestion

  • Breakdown of glucose in cellular respiration

• Caused by enzymes

Sketch induced fit model

.

What type of macromolecule are enzymes?

• Globular proteins- multiple polypeptides

  • 4º structure

• Folded tertiary or quaternary shape allows them to to form specific active sites where substrates can bind

Induced-fit binding

The active site changes shape slightly to better fit the substrate when it binds

• Improves binding strength and reaction efficiency

Why is movement needed for enzyme–substrate interactions?

• Enzyme reactions occur in fluids so that the enzymes and substrates can move around

• Successful reactions are random and happen when they collide

• More movement = higher chance of successful collisions

What benefits does immobilization provide?

• Immobilized enzymes are fixed in place (not free-moving

• Enzymes can be reused multiple times

  • Cost effective

• Special cases:

  • Substrate is really large compared to enzymes

  • Enzyme is immoblized for industrial purposes

How can immobilization occur?

Natural:

• Enzymes attached to cell membranes

• Enzymes inside organelles

Artificial:

• Attached to surfaces

• Encapsulated in gels

Denaturing

When an enzyme loses its 3D shape due to extreme conditions

• High temperature

• Extreme pH

What happens to the structure when an enzyme is denatured?

• Bonds between amino acids break

• The tertiary structure changes

• The active site changes shape—> substrates not able to bind permanently

Collision theory

Particles collide with sufficient energy in the correct orientation

How do we measure rates?

Rate of enzyme activity = change per unit time

• Measure product formed over time

• Measure substrate used up over time

Techniques to measure enzyme activity

• Colorimetry

  • Measures color change as product forms

• Gas collection

  • Measures volume of gas produced (e.g., oxygen)

• pH change

  • Tracks change if reaction produces/uses acids

• Mass change

  • Loss of mass if gas is released

• Titration

  • Measures concentration of reactants/products at intervals

Graph activation energy for catabolic and anabolic reaction

Activation energy is the amount of energy that has to go into a reaction to cause it to happen.

Exothermic

• Releases energy to surroundings

• Energy is released when bonds are formed

• Products have lower energy than reactants

Endothermic

• Absorbs energy from surroundings

• Energy is required to break bonds

• Products have higher energy than reactants

Cell respiration

Converts glucose into ATP

• Photosynthesis makes glucose—> cell resp uses glucose to make ATP—> ATP used as energy currency in living things

Define ATP

Energy currency in living things

Sketch an ATP molecule

3 phosphates, ribose sugar, and adenine

List the processes that need energy (ATP) in cells

• Active transport (across membranes)

• Protein synthesis

• DNA replication

• Muscle contraction

• Vesicle transport (endocytosis/exocytosis)

• Cell division

What happens to phosphate when energy is stored?

• A phosphate group is added to ADP

• Forms ATP

• Energy is stored in the new bond

What happens when energy is released?

• A phosphate group is removed from ATP

• ATP → ADP + Pi

• Energy is released from free phosphate

ATP → ADP is what type of reaction?

Hydrolysis reaction

ADP → ATP is what type of reaction?

Condensation reaction

How is water involved in the interconversion?

• ATP → ADP (hydrolysis):

  • Water is used

  • Breaks the bond between phosphate groups

• ADP → ATP (condensation):

  • Water is produced

Forms bond between ADP and phosphate

Write the word equation for cell respiration

Glucose+oxygen—> carbon dioxide+ water+ATP

Inputs to cellular respiration?

• Glucose

• Oxygen

Outputs of cell respiration?

• Carbon dioxide

• Water

• ATP

Differences between anaerobic and aerobic respiration

• Aerobic

  • Uses oxgyen

  • Uses glucose

  • High ATP produced: (30-32 ATP)

  • Location: Mitochondria (after glycosis)

  • Slower process

  • Output of CO2 and H2O

  • Process: glycolysis—> Krebs cycle —> Electron transport chain

• Anaerobic

  • Happens when oxygen is not present

  • Only uses glucose

  • Location: Cytoplasm

  • Low ATP produced: (2 ATP)

  • Faster process

  • Output of lactic acid in animals

  • Process: Glycosis+fermentation

How do we measure cell respiration experimentally?

A respirometer measures the rate of cell respiration by tracking oxygen consumption

Does a respirometer directly or indirectly measure?

• It does not measure ATP directly

• It infers respiration rate from oxygen consumption

What are the parts of a respirometer and their purposes?

Organism (e.g., seeds, insects):

• Carries out respiration

Chamber/container:

• Encloses the organism in a controlled space

Capillary tube with fluid (manometer):

• Measures movement of liquid as gas volume changes

CO₂ absorber (e.g., soda lime or KOH):

• Absorbs carbon dioxide produced

• Ensures volume change is only due to oxygen uptake

Marker fluid (colored liquid):

• Makes movement visible and measurable

Sealed system (airtight):

• Prevents gas exchange with surroundings

How does temperature impact cell respiration?

• Increases → enzymes work faster → higher respiration rate

• Too high → enzymes denature → rate decreases

How does oxygen availability impact cell respiration?

• More oxygen—>allows aerobic respiration—> more ATP!

• Low oxygen—> anaerobic respiration—> less efficient

Glucose availability impact on cell respiration?

• More glucose—> more substrate—> higher respiration rate

• Low glucose—> limits respiration

Enzyme activity impact on cell respiration?

• Enzymes control each step of respiration

• More active enzymes → faster reactions

Photosynthesis

Process where organisms use light energy to convert carbon dioxide and water into glucose, releasing oxygen

Where does photosynthesis take place? What organelle is involved?

Chloroplast cell is he pallisade mesophyll layer

Word equation for photosynthesis

Carbon dioxide + Water → Glucose + Oxygen

How is water split during photosynthesis and what does it result in?

• Water is split during photosynthesis through photolysis: a light-dependent process occurring in the chloroplast's thylakoid membrane

• Produces:

  • Oxygen

  • Hydrogen

  • Electrons

What are the three groups of organisms that do photosynthesis?

• Plants

• Algae

• Cyanobacteria

Where does the oxygen come from in photosynthesis?

From the H2O that was broken down during photolysis

How does the colour of the pigment relate to the absorbance of light?

• The color we see is the light that is reflected, not absorbed

• Pigments absorb all other wavelengths

• Example

  • Chlorophyll appears green—> reflects green light and absorbs red and blue

What happens in the pigment when it absorbs a photon?

• A photon excites an electron

• Electron moves to a higher energy level

• This energy is then used in the light-dependent reactions

Sketch a graph of absorption and action spectra

What to draw:

• X-axis: Wavelength of light (nm)

• Y-axis:

  • Absorption spectrum: % light absorbed

  • Action spectrum: rate of photosynthesis

Draw two curves:

• Both with peaks in:

  • Blue region (~450 nm)

  • Red region (~680 nm)

How are the spectras similar?

• Both show peaks in blue and red wavelengths

• This shows absorbed light is used for photosynthesis

How are the spectras different?

• Absorption spectrum:

  • Shows how much light pigments absorb

• Action spectrum:

  • Shows how effective light is at driving photosynthesis

What methods are possible to measure photosynthesis?

• Measure oxygen production (gas volume or bubbles)

• Measure carbon dioxide uptake

• Measure starch production (iodine test)

• no simple direct measurement of photosynthesis as a whole process

What factors impact photosynthesis?

• Light intensity

• Carbon dioxide concentration

• Temperature