AP Biology — Unit 3

What is an enzyme?

a macromolecule that acts as a catalyst

What is the main property of an enzyme, and how does it do it?

Speeding up a reaction by lowering the activation energy needed to begin the reaction.

What is the active site?

the region of an enzyme that binds the substrate.

What must happen for an enzyme-mediated chemical reaction to occur?

The shape, charge, and chemical properties of the substrate must be compatible with the active site of the enzyme.

What does the compatibility (between the substrate and enzyme) depend on?

The tertiary structure of the enzyme

What is the previous model of enzymes and substrates?

lock-and-key model

What is the current model of enzymes and substrates?

induced-fit model

What does the induced-fit model of enzymes and substrates explain?

how enzymes may exhibit broad specificity and how catalysis might occur

What is activation energy?

the initial energy input required to begin a reaction

Describe an endergonic reaction

low to high energy; absorbs energy

Describe an exergonic reaction

high to low energy; releases energy

What is the correlation between energy and stability (negative/positive/none)

negative

What might the change to the molecular structure of a component in an enzymatic system result in?

change of the function or efficiency of the system

What is denaturation?

loss of functional or 3D shape

What might cause an enzyme to denature?

temperature or pH levels above the optimal range

What are the 3 factors that can affect the speed of a reaction?

temperature, pH, and substrate concentration

what happens to the speed of a reaction when temperature is low?

low temperature is insufficient thermal energy for the activation of enzyme-catalyzed reactions to proceed

What happens to the speed of reaction when temperature is high (but within optimal range)? Why?

increase, because higher temperature, increase speed of movement, increase frequency of collisions, increase rate of reactions

How will higher pH levels affect the enzyme?

change pH, change charge and disrupt hydrogen bonds of enzyme, denature protein

What is increasing the substrate concentration basically doing?

increasing probability of substrate binding to enzyme

What is an enzyme inhibitor?

a molecule that disrupts the normal reaction pathway between an enzyme and a substrate

Where do competitive inhibitors bind?

active site of enzyme

Where do noncompetitive inhibitors bind?

allosteric site of enzyme

What happens to the active site when noncompetitors bind to the enzyme?

active site denatures

Is competitive and noncompetitive inhibition reversible or irreversible?

depends

What does energy have the capacity to do

cause change

What is bioenergetics?

study of how organisms manage their energy resources

What are some forms of energy?

kinetic, thermal, potential, chemical

Can energy be converted from one form to another? yes or no

yes

What is the role of energy in living organisms?

to conduct life processes, such as growth, reproduction, and movement

What is thermodynamics?

study of how energy transforms through a pathway

What is a system and what are the surroundings?

System is whatever we’re interested in, and the surroundings are everything else.

What is the universe?

system + surroundings

What is an isolated system?

no matter or energy exchange

What is a closed system?

only energy exchange

What is an open system?

energy and matter exchange

What is the first law of thermodynamics?

Conservation of energy — energy cannot be created or destroyed

What is the second law of thermodynamics?

Energy transfer increases the entropy of the universe.

What is the third law of thermodynamics?

Entropy of a system at absolute zero Kelvin is zero

What is entropy?

measure of disorder of a system

What do all living organisms require?

a constant input of energy

What is energy coupling?

cellular processes that release energy may be coupled with cellular processes that require energy

What happens in every energy transformation process?

some energy is unusable, often lost as heat

What do catabolic pathways do?

release energy by breaking down complex molecules into simpler compounds

What do anabolic pathways do?

consume energy to build complex molecules from simpler ones

What does free-energy change of a reaction tell us?

it tells us whether or not the reaction occurs spontaneously

What is free energy?

energy that can do work when temperature and pressure are uniform, as in a living cell

Glycolysis transforms ________ to _________.

1 glucose, 2 pyruvate

Glycolysis occurs in the ________.

cytoplasm

What are the three steps of cellular respiration?

Glycolysis, Link Reaction and Krebs Cycle, Oxidative Phosphorylation

What is the net gain of molecules in glycolysis per 1 glucose?

2 ATP, 2 NADH

Is glycolysis an aerobic or anaerobic process?

anaerobic process

To where are the electrons in NADH produced in glycolysis transported to? for what?

to the mitochondria for ETC

What is the equation of cellular respiration?

glucose + 6 oxygen —> 6 carbon dioxide + 6 water + 32 ATP

What is the equation of photosynthesis?

Light + 6 carbon dioxide + 6 water —> glucose + 6 oxygen

What does CoA do in the link reaction?

helps acetate enter the mitochondria

What are the inputs in the Krebs Cycle?

Acetyl CoA, NAD+, FAD, ADP +P(i)

What are the outputs of the Krebs Cycle?

4 NADH, 1 ATP, 1 FADH2, 3CO2

Is the Krebs Cycle an aerobic or anaerobic process?

aerobic process

Where does the Krebs Cycle occur?

mitochondrial matrix

Where does the NADH used in Oxidative Phosphorylation come from?

glycolysis and the Krebs Cycle

Where does the FADH2 used in Oxidative Phosphorylation come from?

Krebs Cycle

Where does the P(i) that attaches to ADP to create ATP at ATP synthase come from?

various molecules that have been broken down

What powers the proton pumps that transports H+ to the intermembrane space?

energy released throughout the ETC

What takes the electrons that travel through the protein pumps in cellular respiration?

oxygen

Is oxidative phosphorylation an aerobic or anaerobic process?

aerobic process

What are the 2 steps in photosynthesis?

light-dependent reaction, calvin cycle

What do the electrons released through photolysis do?

replenish electrons in photosystem II

what replenishes the electrons in photosystem I?

the electrons from photosystem II

Where is the photosystem complex located?

in the thylakoid membrane

is the lumen (inside of the thylakoid) low or high pH compared to the stroma? why?

low pH because higher concetration of H+

What are the 3 steps of the calvin cycle?

carbon fixation, reduction, RUBP regeneration

What is RuBisCo?

most abundant enzyme int he biosphere, and it helps carbon dioxide and RUBP combine.

How many cycles of the Calvin Cycle is required to produce one glucose molecule?

6

How many ATP and NADPH is produced in one cycle of the Calvin Cycle?

3 ATP and 2 NADPH

Where does the ADP and NADP+ from the Calvin Cycle go? for what?

thylakoid for light-dependent reaction

Where does the Calvin Cycle occur?

stroma

What is oxidation?

loss of electrons and hydrogen atoms

What is reduction?

gain of electrons and hydrogen atoms

Does oxidation or reduction happen when NAD+ becomes NADH?

reduction

Does oxidation or reduction happen when FADH2 becomes FAD?

oxidation

What does individual fitness refer to?

an organism’s ability to survive AND reproduce

Does variation increase fitness? yes or no

yes

the more variation in a species, the more likely ________

the species will demonstrate fitness under changing environmental conditions

Does every individual in a species need to show fitness for continuity of that species? yes or no

no