AP bio review : cellular energetics

endergonic reaction

not spontaneous, absorbs energy, ADP+Pi →ATP

exergonic reaction

energy released, spontaneous, ATP →ADP + pi

What is Gibbs Free Energy?

Energy available to do work

Enzyme functions

biological catalysts, speed up chem reactions, reduces activation energy

• Enzymes are __________

• Enzymes ____ consumed in the reaction

• Enzymes (do/don’t) have an effect on the change in Gibbs Free Energy

proteins, not, don’t

They don’t effect change in Gibbs energy because it takes energy to do the reaction, but this energy is separate from Gibbs energy. Gibbs energy is the energy change between the reactants and products.

What is activation energy?

The energy needed to make a reaction happen

Activation energy needed for an uncatalyzed reaction is (more / less) than activation energy needed for a catalyzed reaction?

More because enzymes lower the activation energy

Enzymes catalyzing a reaction

1) Substance enters _______ site of __________

2) Enzyme-substrate _________ forms

3) Induced fit : enzyme bends / squeezes substrate, WEAKENS BONDS, so less energy is needed to break the substrate bond

3) Substrate is converted to _______________

4) Products leave the _____________ site

1) active enzyme

2) complex

3) products

4) active

competitive inhibitor

binds to active site

noncompetitive inhibitor

binds to allosteric site

denaturation

environmental temp / pH / salinity (salt) is outside of optimal range

catabolic pathway

breaks down large molecules, bonds break and energy released, energy captured in ATP

ATP stores energy released from _____________ reactions. This energy is available for _____________ reactions.

anabolic pathway

small molecules assembled into larger molecules, energy from ATP consumed

metabolic pathway

begins with specific molecule and ends with product. there are many steps catalyzed by specific enzymes

Energy coupling

use of exergonic process to drive endergonic process, usually mediated by ATP

ATP is re_____________. It is regenerated by adding a __________ group to ADP.

renewable. phosphate

How do enzymes change activation energy?

• Reactions need activation energy to start

• This is hard to reach, high energy, unstable

• Enzymes bind to substrate in ways that strain bonds, stabilize charges, closer together

cofactors

nonprotein molecules that help enzymes work, can be inorganic or organic

Inorganic Cofactor

A metal ion that assists enzyme activity (e.g., Mg²⁺, Zn²⁺, Fe²⁺).

by stabilizing charges, binding substrates, or participating in reactions

Coenzyme

An organic cofactor, usually derived from vitamins, that helps carry chemical groups or electrons during reactions (e.g., NAD⁺, FAD).

ENZYME PRODUCTION REGULATION: To regulate enzyme activity, genes are turned on and off. Genes have instructions to make _________. When genes are on, enzyme is produced. When off, it isn’t made. This controls what reactions occur In a cell. Ex) Cells turn on lactase enzyme only when lactose is present

enzyme

ENZYME ACTIVITY REGULATION: To regulate enzyme activity, cells control how _________ an enzyme is.

• __________ can bind to the enzyme

• Changes in pH, temp, substrate concentration

• Activators

• Feedback inhibition

active

Feedback Inhibition

End product of a pathway inhibits an earlier enzyme to stop overproduction.

Allosteric Regulation

A molecule binds to a site other than the active site, changing enzyme activity by inhibiting or activating

Cooperativity

Binding of one substrate affects to the enzyme changes the binding of additional substrates (often increases affinity).

• First substrate makes all subsequent binding easier or faster

Negative feedback

Output of a process reduces or shuts down that process to maintain balance.

• Change occurs, change detected by sensor, processed and effectors activated, effectors counteract change to make condition back to normal

pH vs Enzyme Activity graph

Activity peaks at an optimal pH; too acidic or basic conditions reduce activity.

Substrate Concentration vs Enzyme Activity graph behavior

Activity increases with substrate concentration, then levels off when enzymes become saturated (Vmax).

Enzyme Concentration vs Activity graph behavior

Activity increases linearly as enzyme concentration increases (if substrate is abundant).

Competitive Inhibition graph behavior

More substrate is needed to reach the same activity, but the maximum activity stays the same.

Noncompetitive Inhibition Graph

The maximum activity is lower, even if more substrate is added.

how to find average rate of change

(y2-y1) / (x2-x1)

What happens if enzyme amalyse doubled in a reaction?

The reaction rate increases (it goes faster) because there are more active sites available to break down starch. However, the final amount of product stays the same if substrate is limited.