TERM 3 BIOLOGY- Sem 2 24'

C1.1.2, C1.1.3, C1.1.4, C1.1.10, C1.1.1, C1.1.5, C1.1.6,C1.1.7, C1.1.8, C1.1.9, C1.2.1, C1.2.2, C1.2.3, C1.2.4, C1.2.5, C1.2.6

metabolism describes the totality of

all enzyme catalysed reactions that occur within a living cell or organism

control over metabolism can be exerted through

enzyme specificity

two key metabolic reaction functions

provide source of energy for cellular processes and enable the synthesis and assimilation of new materials

anabolic reaction

metabolic reaction that builds up complex molecules from simpler ones

production of glucose by photosynthesis is

an anabolic reaction

catabolic reaction

metabolic reaction that breaks down complex molecules into simpler ones

oxidation of substrates in cell respiration is

a catabolic reaction

an enzyme is a globular protein which

acts as a biological catalyst by speeding up the rate of a chemical reaction

enzymes are not changed or consumed by

the reactions they catalyse and can be reused

enzymes are named after the substrate they react with meaning

they end with the suffix ase

lipids are broken down by the enzyme

lipase

proteins are digested by

proteases

the active site

region on the surface of the enzyme where the substrate binds to

interactions between active sites and animo acids

ensures that the overall shape and chemical properties complement the substrate

activation energy

every chemical reaction requires a certain amount of energy

enzymes speed up the rate of a biochemical reaction by

lowering the activation energy

less energy is required to convert

substrate into product with enzymes speeding up the reaction

exergonic

if reactants contain more energy than products, free energy is released into the system

exergonic reactions are usually

catabolic as energy is released from broken bonds

endergonic

reactants contain less energy than the products, free energy is lost to the system

endergonic reactions are usually

anabolic as energy is required to synthesise bonds

factors that affect enzymatic reactions

temperature, ph and substrate concentration

catalyst

a substance that allows a reaction to proceed at a faster rate or under different conditions

enzymes

biological catalysts that are not consumed by the specific reaction

enzymes allow chemical reactions to proceed within

a biologically relevant passage of time and biologically appropriate temperatures

without enzymes food would be unable to be chemically digested

within the period of transit through the digestive tract

without enzymes chemical reactions would

require higher temperatures which could denature components

enzyme catalysis requires that the substrate be brought into

close physical proximity with the active site

when a substrate binds to the enzymes active site

an enzyme-substrate complex is formed

enzymes catalyse the conversion of substrate into product

creating an enzyme-product complex

enzyme and product dissociate as

the enzyme was no consumed

induced fit model

enzyme’s active site is not a complete fit for the substrate

the active site will undergo a

conformational change when exposed to a substrate to improve binding

enzyme reactions occur in

aqueous solutions

brownian motion

substrate and enzyme moving randomly

sometimes, enzymes maybe be fixed in position

serving to localise reactions to particular sites

for enzymatic reaction to occur

substrate and enzyme must physically collide in correct orientation

rate of enzyme catalysis can be increased by improving

the frequency of collisions

two ways to increase frequency of collisions in enzyme catalysis

increasing molecular motion of particles, increasing concentration of particles

all enzymes have an indentation or cavity to

which the substrate can bind with high specificity

shape and chemical properties of the active site are highly

dependent on the three dimensional shape of the enzyme

enzyme structure can be modified by

high temperatures and extreme ph

high temperatures and extreme ph in enzyme structure can

disrupt chemical bonds, necessary to maintain shape and chemical properties

denaturation

change to the structure of the active site

denaturation will negatively affect

the enzyme’s capacity to bind to the substrate

inhibitors may also reduce

enzyme-substrate interactions by altering the shape of an active site

low temperatures reduce thermal energy

slowing enzyme-catalysed reactions

more kinetic energy means

more frequent enzyme-substrate collisions

excessive heat

destabilises enzymes, breaking hydrogen bonds

ph alters enzyme

charge, solubility and shape

enzymes work best at an optimal ph

outside of this activity decreases

more substrate

increases enzyme activity

high substrate concentration leads to

more collisions and reactions

beyond a certain point activity

plateaus as all enzymes are occupied

three key decisions to be made when designing an experiment to test the effect of factors affecting enzyme activity

specific enzyme/substrate reactions, experimental factor to manipulate, how to measure enzyme

rate of an enzyme-catalysed reaction can be calculates and plotted through

measure time take of consumed substrate, reaction rate is inverse of time take

reaction rate calculation

1/ time taken (s)

ATP is a molecule that

functions to distribute energy within cells

ATP is a ribonucleotide consisting of

an adenine base and three phosphate groups attached to the central ribose sugar

one molecule of ATP contains three covalently linked

phosphate groups which store potential energy in their bonds

when ATP is hydrolysed to release the outermost phosphate

energy store in the phosphate is released to be used by the cell

presence of adenine and ribose provides

additional sites for attachment to enzymes allowing ATP to fuel enzymatic activities

structure of ATP

there are a wide range of biochemical processes

that require use of ATP as an energy source

biosynthesis

assembly of organic polymers that requires ATP hydrolysis

anabolic reactions use ATP to construct

complex molecules from simpler subunits

with active transport ATP is required

to move material against a concentration gradient

nerves utilise ATP

to establish a resting potential prior to generating a nervous impulse

vesicular transport requires ATP

to break and reform membranes

movement of cell components or the whole cell is

dependent on ATP

chromosomes are segregated during mitosis and meiosis in an

energy-dependent process

contraction of muscle cells involves

the use of energy

coenzymes

non-protein organic compounds that facilitate enzyme reactions by cycling between a loaded and unloaded form

ATP is a loaded coenzyme that

transfers chemical energy to enzymes and enables the activation energy threshold to be reaches

ATP stores chemical energy

in the covalent bonds between phosphate groups

phosphates are negatively charged and hence

require high amounts of energy to keep in place

when ATP is hydrolysed

the terminal phosphate is released an coenzyme is converted to its unloaded form

chemical energy released by ATP hydrolysis is used by

an enzyme to catalyse a metabolic reaction within the cell

energy transfer

cell respiration is the controlled

release of energy from the breakdown of organic compounds to produce ATP

the main organic compound used for cell respiration is

carbohydrates

lipids and proteins can also be digested

in the process of cell respiraiton

lipids produce more energy per gram however

they are harder to digest and transport

proteins can produce the same amount of energy as carbs but

also produce toxic nitrogenous waste

energy sources

cell respiration can either be

anaerobic or aerobic

the two forms of cell respiration anaerobic and aerobic

differ in the products that are formed, where the reaction occur ad the overall ATP yield

not all respiratory substrates can undertake

both form of respirations

fatty acids can only be digested

aerobically

anaerobic respiration begins with

the process of glycolysis

glycolysis

glucose is partially broken down into two pyruvate molecules with a small yield of ATP

certain amino acids and glycerol may feed into

the glycolytic pathway and produce pyruvate anaerobically

the absence of oxygen the pyruvate molecules are

fermented to form lactic acid in animals or ethanol and carbon dioxide in plants

the anaerobic processes of glycolysis and fermentation both occur within

the cytosol of the cell

aerobic respiration also begins with the process of glycolysis but

oxygen is then used to completly break down the pyruvate for a much larger ATP yield

in aerobic respiration the pyruvate is transported to the mitochondria and

is broken down into carbon dioxide and water

the complete breakdown of pyruvate involves

the link reaction, the Krebs cycle and the electron transport chain

both anaerobic and aerobic respiration use

digestion and oxidation of organic molecules to synthesise ATP

glycolysis is common to both

anaerobic and aerobic respiration

while sugars are the main respiratory substrate

lipids and proteins can both be converted into usable intermediates