Biology SAC 2

Enzyme

A protein that acts as a biological catalyst speeding up reactions without being consumed

Why are enzymes important?

They lower activation energy so biochemical reactions occur fast enough for life

Why are enzymes specific?

Their 3D active site shape matches only specific substrates

Enzyme-substrate complex

A temporary complex formed when a substrate binds to an enzyme’s active site

Components of enzyme reaction

Enzyme, substrate, active site, products

Competitive inhibition

Inhibitor binds to active site and competes with substrate

Non-competitive inhibition

Inhibitor binds to allosteric site and changes enzyme shape

Temperature effect on enzymes

Increases rate to an optimum, then denatures enzyme at high temperatures

pH effect on enzymes

Extreme pH alters shape and can denature enzyme

Substrate concentration effect

Rate increases until enzymes are saturated

Enzyme concentration effect

More enzymes increase reaction rate if substrate is available

Denatured enzyme

Permanent loss of shape and function

Interrupted enzyme action

Temporary slowing or stopping of enzyme activity

Reversible inhibition

Inhibitor can detach from enzyme

Irreversible inhibition

Inhibitor permanently disables enzyme

Where competitive inhibitors bind

Active site

Where non-competitive inhibitors bind

Allosteric site

Photosynthesis reaction type

Endergonic reaction requiring light energy

Photosynthesis word equation

Carbon dioxide + water → glucose + oxygen

Photosynthesis chemical equation

6CO2 + 6H2O → C6H12O6 + 6O2

Chlorophyll location

Thylakoid membranes in chloroplast

Chlorophyll function

Absorbs light energy

Light-dependent reactions location

Thylakoid membranes

Light-dependent inputs

Light, water, ADP, NADP+

Light-dependent outputs

Oxygen, ATP, NADPH

Light-independent reactions location

Stroma

Calvin cycle inputs

CO2, ATP, NADPH

Calvin cycle outputs

Glucose (G3P)

RuBisCo function

Enzyme that fixes CO2 in the Calvin cycle

Carbon fixation

Conversion of CO2 into organic molecules

NADPH role

Electron carrier used in Calvin cycle

C3 plants

Use standard photosynthesis and are prone to photorespiration

C4 plants

Store CO2 in bundle sheath cells to reduce photorespiration

CAM plants

Take in CO2 at night and use it during the day

Photorespiration

RuBisCo binds O2 instead of CO2, wasting energy

Limiting factors of photosynthesis

Light, CO2, temperature, water

Light intensity effect

Increases rate until plateau

Temperature effect (photosynthesis)

Increases enzyme activity to optimum

CO2 concentration effect

Increases rate until limiting

Water availability effect

Lack of water closes stomata and reduces CO2 intake

Cellular respiration reaction type

Exergonic reaction producing ATP

Respiration word equation

Glucose + oxygen → carbon dioxide + water + ATP

Respiration chemical equation

C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP

Glycolysis location

Cytoplasm

Glycolysis inputs

Glucose, ATP, NAD+

Glycolysis outputs

2 pyruvate, 2 ATP (net), 2 NADH

Krebs cycle location

Mitochondrial matrix

Krebs cycle purpose

Produces NADH and FADH2 electron carriers

Electron transport chain location

Inner mitochondrial membrane

ETC requirement

Oxygen

ETC output

Large amount of ATP

Total ATP yield respiration

Approximately 36–38 ATP per glucose

Role of NADH and FADH2

Carry electrons to the electron transport chain

Anaerobic respiration in animals

Pyruvate converted to lactic acid

Anaerobic respiration in yeast

Pyruvate converted to ethanol and CO2

ATP yield anaerobic respiration

2 ATP

Aerobic vs anaerobic respiration

Aerobic produces more ATP and requires oxygen; anaerobic produces less ATP without oxygen

Factors affecting respiration

Glucose, oxygen, temperature

Temperature effect on respiration

Affects enzyme activity and rate

Oxygen effect on respiration

Limits ATP production in ETC

CRISPR-Cas9

A gene-editing tool that cuts and modifies DNA

CRISPR application in plants

Improves photosynthesis efficiency and crop yield

Biomass

Organic material used as fuel

Bioethanol production

Produced by anaerobic fermentation of sugars by yeast

Purpose of biofuels

Renewable energy and reduced fossil fuel use

Issues with biofuels

Land use, food competition, environmental impact