Module 2

Question 1

Define metabolism

Answer 1

The term used to describe all of the chemical reactions inside a cell

Question 2

Compare the terms catabolic and anabolic in the context of metabolism

Answer 2

The term anabolism refers to those endergonic (require energy) metabolic pathways involved in biosynthesis, converting simple molecular building blocks into more complex molecules, and fueled by the use of cellular energy.
The terms catabolism refers to exergonic (release energy) pathways that break down complex molecules into simpler ones.
Catabolism - Large molecules broken down to smaller ones, releasing energy
Anabolism: small molecules are assembled into larger ones, using energy

Question 3

Compare and contrast autotrophs and heterotrophs in terms of their sources of carbon source and energy source

Answer 3

-Autotrophs - Organisms that convert inorganic carbon dioxide into organic compounds
- Heterotrophs - Rely on more complex organic nutrients, these are provided to them initially by autotrophs.

Question 4

What is an oxidation-reduction (redox) reaction?

Answer 4

Because electrons can move from one molecule to another, oxidation and reduction occur in tandem. These pairs of reactions are called redox reaction.

Question 5

Describe why ATP, FAD, NAD+, and NADP+ are important in a cell

Answer 5

The energy released from the breakdown of the chemical bonds within nutrients can be stored either through the reduction of electron carries or in the bonds of ATP.

Question 6

What is an electron carrier in cell metabolism

Answer 6

In living systems, a small class of compounds functions as mobile electron carriers, molecules that bind to and shuttle high-energy electrons between compounds in pathways.

Question 7

How can electron carriers play a role in catabolism (e.g extracting energy from molecules?)

Answer 7

NAD+/NADH and FAD/FADH2 are extensively used in energy from sugars during catabolism in chemoheterotrophs. Whereas NADP+/NADPH plays an important role in anabolic reactions and photosynthesis.

A living cell must be able to handle the energy released during catabolism in a way that enables the cell to store energy safely and release it for use only as needed, cells accomplish this by using ATP

Question 8

Briefly describe how enzymes speed up chemical reactions

Answer 8

Enzymes lower the activation energy by binding to the reactant molecules and holding them in such a way as to speed up the reaction

Question 9

What effect do enzymes have on the activation energy of a reaction?

Answer 9

Enzymes lower the activation energy

Question 10

Define enzyme

Answer 10

Proteins that serve as catalysts for biochemical reactions inside cells.

Question 11

Define substrate

Answer 11

The chemical reactants to which an enzyme binds are called substrates

Question 12

Define active site

Answer 12

The location within the enzyme where the substrate binds

Question 13

Define enzyme-substrate complex

Answer 13

When an enzyme binds to its substrate it forms an enzyme-substrate complex

Question 14

Define products

Answer 14

.

Question 15

Phototrophs?

Answer 15

Those that get their energy for electron transfer from light

Question 16

Chemotrophs?

Answer 16

Obtain energy for electron transfer by breaking chemical bonds.

Question 17

Oxidation reactions

Answer 17

Reactions that remove electrons from donor molecules, leaving them oxidized

Question 18

Reduction reactions

Answer 18

Reactions that add electrons to acceptor molecules leaving them reduced.

Question 19

What are the inputs of glycolysis

Answer 19

The input of glycolysis is glucose.

Question 20

How many carbons does glucose have?

Answer 20

6

Question 21

How many carbons does pyruvate have?

Answer 21

3

Question 22

What are the outputs of glycolysis?

Answer 22

Two molecules of 3-carbon sugar pyruvate

Question 23

Does glycolysis require oxygen?

Answer 23

No

Question 24

Describe how the process of glycolysis produces: three-carbon molecules, ATP, and NADH

Answer 24

EMP (found in animals and most common microbes:
Energy investment phase:
- Uses energy from 2 ATP molecules to modify a glucose molecule, so it can be split evenly into 2 phosphorylated 3-carbon molecules (G3P)
Energy Payoff phase:
- Extracts energy by oxidizing G3P to pyruvate, producing 4 ATP molecules and reducing 2 molecules of NAD+ to two molecules of NADH, using electrons that originated from glucose.

• ATP molecules produced during energy payoff phase of glycolysis are formed by substrate-level phosphorylation. High energy phosphate groups from the intermediate molecules are added to ADP to make ATP.

Overall, in this process of glycolysis, the net gain from the breakdown of a single glucose molecule is:

two ATP molecules
two NADH molecule, and
two pyruvate molecules.

Question 25

How does 3-carbon pyruvate (from glycolysis) get converted to a 2-carbon acetyl group that enters the Krebs cycle?

Answer 25

For pyruvate to enter the next oxidative pathway, it must first be decarboxylated by the enzyme complex pyruvate dehydrogenase to a two-carbon acetyl group in the transition reaction. In the transition reaction, electrons are also transferred to NAD+ to form NADH.

Question 26

What is the job of Coenzyme-A (CoA)?

Answer 26

The two carbon acetyl must be attached to a very large carrier compound called CoA. The CoA carrier does not enter the Krebs cycle from the transition reaction.

Question 27

What happens to the 3rd carbon atom in the Krebs cycle?

Answer 27

Maybe leaves as CO2 not too sure

Question 28

What is the ultimate fate of the carbons that complete the Krebs cycle?

Answer 28

All six of of the carbons combine with oxygen to produce CO2

Question 29

Describe the intermediate products of the Krebs cycle and how they can be useful to a cell?

Question 30

What is glycolysis?

Answer 30

The most common pathway for the catabolism of glucose

Question 31

Where does glycolysis occur in prokaryotes vs. eukaryotes

Answer 31

In a eukaryotic cell, glycolysis takes place within the mitochondria, whereas in a prokaryotic cell, it occurs in the cytoplasm.

Question 32

Explain the difference between substrate-level phosphorylation and oxidative phosphorylation

Answer 32

Oxidative phosphorylation occurs during cellular respiration. Cellular respiration begins when electrons are transferred from NADH and FADH2 through a series of chemical reactions to a final inorganic electron acceptor. The energy of the electrons is harvested to generate an electrochemical gradient across the membrane, which is used to make ATP by oxidative phosphorylation.

In substrate-level phosphorylation, a phosphate group is removed from an organic molecule and is directly transferred to an available ADP molecule, producing ATP.

Question 33

Explain the relationship between chemiosmosis and proton motive force

Answer 33

The exergonic movement of protons (called a proton-motive force) across the membrane during chemiosmosis provides the direct energy needed for the endergonic process of ATP synthesis.

Question 34

Why is vital that ETS are located in membranes?

Answer 34

It helps in releasing and utilizing the energy stored in NADH2 and FADH2.

Question 35

How do PMF and ATP synthase work to link electrons moving through the ETS to the formation of ATP

Question 36

Why is chemiosmosis and PMF called oxidative phosphorylation?

Question 37

Describe the difference between aerobic respiration and anaerobic respiration

Question 38

What is the fate of electrons at the end of the ETS in both cases

Question 39

Can a cell carry out both aerobic and anaerobic respiration?

Question 40

What is the proton motive force?

Answer 40

The electrochemical gradient formed by the accumulation of H+ on one side of the membrane compared with the other.

Question 41

What is chemiosmosis

Answer 41

The flow of hydrogen ions across the membrane that must occur through a channel in the membrane via a membrane-bound enzyme complex called ATP synthase.