Question 1

What is chemiosmosis?

Accepted Answer

The process in which there is a production of adenosine triphosphate (ATP) in cellular metabolism by the involvement of a proton gradient across a membrane.

Question 2

What is dephosphorylation?

Accepted Answer

Removal of a phosphate group from a molecule.

Question 3

What is oxidative phosphorylation?

Accepted Answer

Production of ATP using the process of chemiosmosis and oxygen.

Question 4

What is phosphorylation?

Accepted Answer

Addition of a high-energy phosphate to a compound, usually a metabolic intermediate, a protein, or ADP.

Question 5

What is a redox reaction?

Accepted Answer

Chemical reaction that consists of the coupling of an oxidation reaction and a reduction reaction.

Question 6

What is substrate-level phosphorylation?

Accepted Answer

Production of ATP from ADP using the excess energy from a chemical reaction and a phosphate group from a reactant.

Question 7

How do redox reactions affect energy?

Accepted Answer

An oxidation reaction removes an electron from an atom in a compound, and a reduction reaction adds the electron to another compound. Oxidation results in a decrease in potential energy in the oxidized compound, and reduction results in an increase in the potential energy of the reduced compound. Most of the energy stored in atoms and used to fuel cell functions is in the form of high-energy electrons.

Question 8

What is an electron carrier?

Accepted Answer

Compounds which bind and carry high-energy electrons between compounds in pathways. These compounds can be easily reduced or oxidized.

Question 9

Where is NAD derived from?

Accepted Answer

Nicotinamide adenine dinucleotide (NAD) is derived from vitamin B3 (niacin).

Question 10

What is the difference between NAD+ and NADH?

Accepted Answer

NAD+ is the oxidized form and NADH is the reduced form. NADH has accepted two electrons and a proton.

Question 11

What is the general equation for converting NAD+ to NADH?

Accepted Answer

NAD+ can accept electrons from an organic molecule according to the general equation: RH (reducing agent) + NAD+ (oxidizing agent) -\> NADH (reduced) + R+ (oxidized)

Question 12

Where is FAD derived from?

Accepted Answer

Flavin adenine dinucleotide (FAD+) is derived from B2 (riboflavin). Its reduced form is FADH2.

Question 13

What is NADP?

Accepted Answer

NADP contains an extra phosphate group.

Question 14

Where are NAD and FAD used?

Accepted Answer

NAD+ and FAD+ are extensively used in energy extraction from sugars, and NADP plays an important role in anabolic reactions and photosynthesis.

Question 15

How do phosphate groups store energy?

Accepted Answer

The addition of a phosphate group to a molecule requires energy. Phosphate groups are negatively charged and repel one another when arranged in series, such as in ADP and ATP. This makes them inherently unstable.

Question 16

Where does the energy to produce ATP come from?

Accepted Answer

The energy to produce ATP comes from the metabolism of glucose. ATP is a direct link between the limited set of exergonic pathways of glucose catabolism and the multitude of endergonic pathways that power living cells.

Question 17

Where does chemiosmosis take place?

Accepted Answer

Chemiosmosis occurs in mitochondria of eukaryotic cells, and in the plasma membrane of prokaryotic cells.

Question 18

What is the purpose of chemiosmosis?

Accepted Answer

Chemiosmosis is used to generate 90% of the ATP made during glucose catabolism, and is the method used in the light reactions of photosynthesis to harness the energy of sunlight.

Question 19

In what ways can oxidative phosphorylation be impacted?

Accepted Answer

In type 2 diabetes, the oxidation efficiency of NADH is reduced, impacting oxidative phosphorylation.

Question 20

What is aerobic respiration?

Accepted Answer

The process by which organisms convert energy in the presence of oxygen.

Question 21

What is an anaerobic process?

Accepted Answer

A process that does not use oxygen.

Question 22

What is glycolysis?

Accepted Answer

The process of breaking glucose into two three-carbon molecules with the production of ATP and NADH.

Question 23

What is an isomerase?

Accepted Answer

An enzyme that converts a molecule into its isomer.

Question 24

What is pyruvate?

Accepted Answer

A three-carbon sugar that can be decarboxylated and oxidized to make acetyl CoA, which enters the citric acid cycle under aerobic conditions; it is the end product of glycolysis.

Question 25

What is the purpose of glycolysis?

Accepted Answer

Glycolysis is the first step in the breakdown of glucose to extract energy for cellular metabolism. Nearly all living organisms carry out glycolysis as part of their metabolism.

Question 26

Is glycolysis aerobic or anaerobic?

Accepted Answer

This process is anaerobic.

Question 27

Where does glycolysis take place?

Accepted Answer

It takes place in the cytoplasm of both prokaryotic and eukaryotic cells.

Question 28

How does glucose enter heterotrophic cells?

Accepted Answer

Glucose enters heterotrophic cells in two ways. One is through secondary active transport which takes place against the glucose concentration gradient. The other uses a group of integral proteins called GLUT proteins, or glucose transporter proteins, which assist in the facilitated diffusion of glucose.

Question 29

What are the inputs and outputs of glycolysis?

Accepted Answer

Glycolysis begins with the six carbon ring-shaped structure of a single glucose molecule, and ends with two molecules of a three-carbon sugar called pyruvate.

Question 30

What are the phases of glycolysis?

Accepted Answer

Glycolysis consists of two distinct phases. The first part of the pathway traps the glucose molecule in the cell and uses energy to modify it so that it can be split evenly into the two pyruvate molecules. The second part extracts energy from the molecules and stores it as ATP and NADH.

Question 31

What are the (energy-requiring) steps of the first half of glycolysis?

Accepted Answer

The first step of glycolysis is catalyzed by hexokinase, an enzyme with broad specificity that catalyzes the phosphorylation of six-carbon sugars. Hexokinase phosphorylates using ATP, producing glucose-6-phosphate, which is more reactive than glucose. This molecule will no longer interact with GLUT proteins, and cannot cross the membrane to leave the cell (because of the negative charge of the phosphate). In step 2, an isomerase converts glucose-6-phosphate into fructose-6-phosphate. In step 3, fructose-1,6-biphosphate is produced, catalyzed by phosphofructokinase using ATP. This enzyme is rate-limiting, more active when the concentration of ADP is high. In step 4, aldolase catabolizes this intermediate into two three-carbon isomers: dihydroxyacetone-phosphate and glyceraldehyde-3-phosphate. In step 5, an isomerase transforms the dihydroxyacetone-phosphate into glyceraldehyde-3-phosphate.

Question 32

What are the (energy-releasing) steps of the second half of glycolysis?

Accepted Answer

In step 6, the sugars are oxidized by NAD+ (producing NADH), and phosphorylated to produce 1,3-bisphosphoglycerate (which does not occur by ATP, rather an independent phosphate molecule). This is a limiting factor for this pathway, which depends on the availability of NAD+ (and hence NADH and an oxidizing agent such as oxygen). In step 7, phosphoglycerate kinase catalyzes 1,3-bisphosphoglycerate to donate a phosphate to ADP, forming ATP (substrate-level phosphorylation). A carbonyl group on the molecule is oxidized to a carboxyl group, forming 3-phosphoglycerate. In step 8, a mutase (which is a kind of isomerase) moves the phosphate from the third carbon to the second carbon, producing 2-phosphoglycerate. In step 9, enolase catalyzes a dehydration reaction, resulting in the formation of a double bond that increases the potential energy in the remaining phosphate bond and produces phosphoenolpyruvate (PEP). The 10th and final step is catalyzed by pyruvate kinase, which results in the creation of an additional ATP molecule by substrate-level phosphorylation and the compound pyruvic acid (or its salt form, pyruvate).

Question 33

How many ATP and NADH molecules are produced during glycolysis?

Accepted Answer

A net gain of two ATP molecules and two NADH molecules are produced, with an investment of two ATP molecules.

Question 34

What is acetyl CoA?

Accepted Answer

Combination of an acetyl group derived from pyruvic acid and coenzyme A, which is made from pantothenic acid (a B -group vitamin).

Question 35

What is the citric acid cycle?

Accepted Answer

A series of enzyme-catalyzed chemical reactions of central importance in all living cells.

Question 36

What are some other names of the citric acid cycle?

Accepted Answer

The Krebs cycle and the TCA cycle.

Question 37

Why is the Krebs cycle so named?

Accepted Answer

The Krebs cycle is named after Hans Krebs who first identified the steps in the pathway in the 1930s in pigeon flight muscles.

7: Cellular Respiration Flashcards

Energy in Living Systems, Glycolysis, Oxidation of Pyruvate and the Citric Acid Cycle, Oxidative Phosphorylation, Metabolism without Oxygen, Connections of Carbohydrate, Protein, and Lipid Metabolism, Regulation of Cellular Respiration

Brainscape's Knowledge GenomeTM

7: Cellular Respiration Flashcards

Energy in Living Systems, Glycolysis, Oxidation of Pyruvate and the Citric Acid Cycle, Oxidative Phosphorylation, Metabolism without Oxygen, Connections of Carbohydrate, Protein, and Lipid Metabolism, Regulation of Cellular Respiration

Brainscape's Knowledge Genome^TM