AP Bio Insta-Review - Unit 3

Which macromolecules are enzymes?

Protein

Why can morphine provide the same response as endorphins?

Morphine and endorphins have a similar molecular shape. Due to this, it binds to the same active site to result in the same response.

Why does the substrate binding activate the enzyme?

Changes shape

What does osmotic pressure mean?

Pressure from the solute. The more solute, the higher the osmotic pressure. The less solute, the lower the osmotic pressure.

What is Gibbs free energy and do enzymes affect the Gibbs free energy of a reaction?

Gibbs free energy is the energy available to do work. If a reaction releases stored energy, it is available for work. (Water falls from a waterfall releases potential energy as it falls and the water turns a turbine). Enzymes DO NOT AFFECT the Gibbs free energy of a reaction. The reaction must be able to take place with or without the enzyme. The enzyme only makes it faster because the enzyme decreases the activation energy.

What are plastids?

Family of organelles... for example: ChloroPLAST

What is the function of enzymes?

Enzymes act as a biological catalyst, which speeds up chemical reactions

How does an enzyme speed up the chemical reaction?

Decrease the activate energy required

Where does the substrate bind on an enzyme?

Active site

How does an enzyme affect ΔG (change in Gibbs free energy)?

No effect

Describe what happens when the substrate binds to the active site.

The enzyme undergoes a conformational shape change. Recall, enzymes are proteins. Whenever something binds to a protein, the protein changes shape. When the enzyme changes shape, the bonds are strained (to break bonds) or reactants are closer together (to form a bond).

What is activation energy?

The energy required to start the reaction. It is the energy that must be added to get the reactants into their transition state.

How does an enzyme affect activation energy?

Decrease

Due to lower activation energy, how is the reaction rate affected?

Increase

What does an enzyme do to reaction rate?

Increase

How is the activation energy different with an enzyme?

Decrease

How does the enzyme affect the change in Gibbs?

Stays the Same

What happens to an enzyme if the temperature increases too high?

Enzyme denatures

What happens to an enzyme if the temperature decreases too low?

Enzyme decreases rate

If the enzyme is denatured...

Reaction rate decreases

Enzymes get consumed by reaction and must be re-added

False

Describe what happens when the enzyme is denatured

The secondary structure and up are disrupted. The bonds between the R groups (tertiary / quaternary) and hydrogen bond between the backbone (secondary) will break, but the peptide bonds (primary) will stay intact.

If the pH increases, why does the enzyme denature?

pH affects the charged R groups

What is reaction rate?

rate = change in x over time. Reaction rate is the amount of product formed over time. If there is an increase in reaction rate, then there is an increase in product formed over time.

Inhibitor that binds to the active site

Competitive inhibitor

How does a noncompetitive inhibitor block binding of substrate?

As you can see, the competitive inhibitor binds to the same site as the substrate/ligand to block it from binding. As you can see, the noncompetitive inhibitor causes a conformational change which blocks the substrate/ligand from binding.

Any increase in heat will denature enzyme

False

What happens with a small increase in temperature?

As the temperature increases, the particles will move faster. This increases the kinetic energy of substrate which increases the interactions with the enzyme. As the enzyme has more interactions, it will cause an increase in reaction rate. Also, the increased temperature can provide energy for activation of the reaction.

As pH increases, what happens to the hydrogen ion concentration?

Decreases

During cellular respiration, protons are pumped from the matrix to the intermembrane space. What happens to the pH of the matrix?

Increases

How do you overcome a competitive inhibitor?

Add more reactants

What happens to the reaction rate as the reaction proceeds? Why?

Reaction rate will decrease. As the reaction proceeds, there is less reactants to bind to the enzyme for the reaction and more products that act as a competitive inhibitor.

What conditions will affect the structure of an enzyme?

Environmental condition changes of pH and temperature outside of optional range (directly from CED). But also, salinity and chemical binding

When an enzyme denatures, which structure is not affected?

Primary

When the structure changes, how is the function affected?

All of the above (Does not affect function, Gains new function, Nonfunctional)

A decrease in temperature will denature an enzyme.

False

What happens to reaction rate if temperatures decrease?

Decrease

If the concentration of hydrogen ions increases?

pH decreases

If the pH increases, what happened to the hydrogen ion concentration?

Decrease

How does an increase in substrate affect reaction rate?

Increase until enzyme saturated

As the product concentration increases, reaction rate ____?

Decrease

What is a competitive inhibitor?

Binds to the same site as the substrate

Which describes an endergonic reaction?

Positive ΔG, nonspontaneous

Which describes an exergonic reaction?

Negative ΔG, spontaneous

What is energy coupling?

Energy coupling is pairing an exergonic reaction with an endergonic reaction. The exergonic reaction releases the energy that is used to fuel the endergonic reaction. Example: Hydrolysis of ATP (exergonic) & move Na against concentration gradient (endergonic)

What is the first law of thermodynamics?

Energy cannot be created or destroyed but can be transformed or transferred. All of the energy on Earth comes from the solar radiation that was released that was released by reactions on sun from its creation. That energy was transformed from stored potential chemical energy to solar energy to heat energy, chemical energy, etc. Then all of the energy leaves Earth in the form of heat.

What does the second law of thermodynamics state about disorder?

Every reaction increases the entropy

Loss of energy results in...

Death

What is the function of B in the metabolic pathway? A ->B -> C

B is an intermediate. It is the product of the A -> reaction AND the reactant for the B -> C reaction

A -> B -> C -> D Enzyme B is inhibited. What happens to the concentration of C?

C decreases

Every reaction increases the entropy of the universe...

Second law of thermodynamics

What is entropy?

Entropy is the disorder or chaos. For example, 1 glucose is broken down to 6 carbon dioxide and 6 water molecules. Think about how organized glucose is, but how much disorder is in those gas molecules.

Energy cannot be created or destroyed, but transferred or transformed...

First law of thermodynamics

What molecule is responsible for powering cellular processes?

ATP

Where did photosynthesis originate?

Cyanobacteria

Earth included oxygen when it was first formed

False

What evidence do scientists have to determine when O2 came?

Iron oxide (rust) layers in the rock layers of fossils

Where was oxygen initially formed?

Ocean

Based on endosymbiotic theory, where did chloroplasts come from?

Engulfed photosynthetic prokaryotes

Which step of photosynthesis stores solar energy as ATP?

Light Reactions

Which step of photosynthesis stores high energy electrons as NADPH?

Light Reactions

Which step of photosynthesis synthesizes G3P?

Calvin Cycle

Which step of photosynthesis takes place in stroma?

Calvin Cycle

Which step of photosynthesis takes place in the thylakoid?

Light Reactions

In a plant cell, where is ATP synthesized?

In the electron transport chain... Chloroplast has an ETC in the light reactions of the thylakoid. Mitochondria has an ETC in oxidative phosphorylation on the cristae. Don't get tripped up on this type of question. ATP synthesized by mitochondria is for cellular energy vs. ATP synthesized by chloroplast is for synthesis of G3P.

Where does photolysis take place?

Photosystem II

What is photolysis?

The process of using light energy to split a water molecule. The water molecule is split into oxygen and hydrogen and electrons. These electrons replace the ones that were taken from the reaction center complex.

Describe the flow of electrons through the light reactions.

Electrons are taken from the reaction center complex in Photosystem II, travel down an electron transport chain to Photosystem I, then down another electron transport chain to be stored in NADPH.

Which direction are hydrogen ions pumped for the electron transport chain in photosynthesis?

Into the thylakoid space

What is synthesized in the light reactions for use in the Calvin Cycle?

ATP & NADPH

Where does Calvin Cycle take place?

Stroma

What are the three steps of the Calvin Cycle?

Carbon fixation, Reduction, Rearrangement

What enzyme used is for carbon fixation?

Rubisco

How many carbon dioxides are used in the Calvin Cycle?

3

What is the product of the Calvin Cycle?

G3P

How many ATPs and NADPHs are needed for the Calvin Cycle? Where do the extra come from?

9 ATP and 6 NADPH (6 ATP and 6 NADPH in reduction & 3 ATP in rearrangement) The extra ATP comes from cyclic electron flow.

What is cyclic electron flow?

Electrons flow from the Photosystem II to Photosystem I through the ETC to facilitate ATP synthesis, then when the electron gains energy in Photosystem I it goes down the ETC between Photosystem II and Photosystem I. It cycles using only the ETC and Photosystem I only.

How are the light reactions and the Calvin cycle related?

The light reactions synthesizes the 9 ATP and 6 NADPH to use in the Calvin cycle

What is the function of photosynthesis?

Capture sunlight and produce sugars

Which provided evidence of oxygen generation in the atmosphere?

Production of iron oxide bands in rock layers

Which describes light independent reactions?

Calvin cycle to synthesize organic compounds

Where do the light independent reactions take place?

Stroma

Which describes light dependent reactions?

Light is absorbed to synthesize ATP & NADPH

Describe how ATP is synthesized in the light dependent reactions.

The light energy is absorbed by pigments in the reaction center complex causing the electrons to move to a higher energy level. As these electrons pump protons across the membrane, the electron falls in energy level. The proton gradient will flow through ATP synthase which phosphorylates ADP to synthesize ATP.

Where would you find chlorophyll?

Thylakoid

Which step is anaerobic?

Glycolysis

Where does glycolysis take place? Cytosol

How does glycolysis taking place in the cytosol prove that glycolysis was the first evolved metabolic step?

All organisms undergo glycolysis. Glycolysis takes place in the cytosol and does not require membrane bound organelles. Evolved before the membrane bound organisms since the process does not need it. Glycolysis does not require oxygen. Pre-historic earth did not have oxygen and so it evolved before oxygen was found in the atmosphere.

Fermentation synthesizes ATP...

False

What is the function of fermentation?

To regenerate the NAD+ that is needed for cellular respiration steps. NAD+ takes an electron (and a hydrogen) to become reduced. This NADH is the electron shuttle around the steps of Cellular Respiration. If all the NADH is reduced there is no available NAD+ and the processes will halt. Fermentation allows the NADH to offload the electrons (and become oxidized)

Where does Krebs Cycle take place?

Matrix

Where does the electron transport chain of cellular respiration occur?

Cristae

ATP is synthesized in the electron transport chain...

False

If the ETC doesn't make ATP, what is the function of the electron transport chain?

ETC generates the proton gradient that is used in chemiosmosis to synthesize ATP from ADP. Proton gradient is the concentration gradient of the protons on one side of the membrane resulting in a potential energy that is used to add the terminal phosphate to the ADP molecule.

Which side has the high proton concentration?

Intermembrane space

What is the first step of cellular respiration?

Glycolysis

What is the starting material for glycolysis?

Glucose (NAD+ & ADP)

What are the products of glycolysis?

2 pyruvate, 2 ATP, 2 NADH

Why is the step of glycolysis important?

Provide NADH with high energy electrons to shuttle to the ETC in the mitochondria. Break down glucose into pyruvate for the next step. Substrate level phosphorylation of ATP

What is the second step of cellular respiration?

Krebs Cycle