Chapter 6 Mastering Biology

In cellular respiration, glucose becomes _____ to carbon dioxide (CO2) as it loses electrons (in hydrogen atoms).

oxidized

During fermentation, __________ that was produced during glycolysis is converted back to __________.

NADH; NAD+ This NAD+ is used again in a new round of glycolysis, where it will be reduced to NADH.

During cellular respiration, NADH

delivers its electron load to the first electron carrier molecule.

Fat is the most efficient fuel molecule because __________.

with their numerous hydrogen atoms, fats provide an abundant source of high-energy electrons

In glycolysis, ATP molecules are produced by _____.

substrate-level phosphorylation A phosphate group is transferred from glyceraldehyde phosphate to ADP.

Why are wine barrels and beer fermentation vats designed to keep air out?

Facultative anaerobes prefer aerobic pathways. Exposing facultative anaerobes to anaerobic pathways only ensures that they will use these pathways, which yield alcohol. Because they are facultative rather than obligate anaerobes, they can use the more productive aerobic pathways, which, however, do not yield ethanol.

Select the correct sequence of steps as energy is extracted from glucose during cellular respiration.

glycolysis → acetyl CoA → citric acid cycle → electron transport chain Glycolysis produces pyruvic acid, which enters the mitochondrion. There, it is converted to acetyl CoA, which enters the citric acid cycle. Electron carriers bring electrons from the first three steps to the electron transport chain, and ATP is made.

A molecule that functions as the electron donor in a redox reaction __________.

loses electrons and becomes oxidized

Given the relatively modest number of calories burned by any but the most vigorous activities, why can most people consume more than 2,000 kilocalories per day yet maintain a healthy body weight?

A large proportion of the energy consumed in food is needed to maintain the body's functions, so only a fraction of food energy needs to be burned in exercise.

How many NADH are produced by glycolysis?

2

Which of these is NOT a product of glycolysis?

FADH2 FADH2 is a product of the citric acid cycle. True: ATP pyruvate NADH + H+ water

A person's basal metabolic rate (BMR) is equal to about __________.

1,300-1,500 Calories/day (Capitalize Calories)

For each glucose that enters glycolysis, _____ NADH enter the electron transport chain.

10 For each glucose molecule that enters glycolosis, a total of 10 NADH are produced -- 2 are produced in glycolysis, 2 are produced in acetyl CoA production, and 6 are produced in the citric acid cycle.

In glycolysis there is a net gain of _____ ATP.

2 It takes 2 ATP to produce 4 ATP.

In glycolysis, how many ATP are invested? How many ATP are produced?

2 invested 4 produced net of 2

Each turn of the citric acid cycle generates one ATP molecule as well as which energy-rich molecules?

3 NADH and 1 FADH2 These reduced molecules carry high-energy electrons that will be delivered to the electron transport chain.

How many carbon atoms are in glucose?

6

In cellular respiration, which of the following outcomes is the result of electrons moving through the electron transport chain (or its components)?

A proton gradient is formed. The energy released by the electron transport chain is used to create a proton gradient across the inner mitochondrial membrane. This allows the production of ATP by chemiosmosis.

The energy released from the redox reactions in the electron transport chain is used by the cell to make _____.

ATP

Which energy-rich molecule produced by cellular respiration directly powers cell work?

ATP

Which of the following statements about glycolysis is INCORRECT?

Glycolysis became a universal cellular process about the time that significant levels of O2 appeared in the atmosphere. True: Glycolysis is the first stage of cellular respiration. Early prokaryotes probably generated ATP exclusively via glycolysis. Glycolytic pathways do not require membrane-bound organelles.

Which of the following statements about glycolysis is correct?

Glycolysis requires ATP to make ATP.

What is the role of the dehydrogenase enzyme at the beginning of the electron transport chain in cellular respiration?

It transfers two electrons from the glucose molecule to NAD+, reducing it to NADH.

In cellular respiration, organic molecules become oxidized as _____ picks up electrons and H+ and becomes reduced to NADH.

NAD+

During electron transport, energy from _____ is used to pump hydrogen ions into the _____.

NADH and FADH2 ... intermembrane space The energy released as electrons, which have been donated by NADH and FADH2, is passed along the electron transport chain and used to pump hydrogen ions into the intermembrane space.

Evidence suggests that heat-generating brown fat is most active in __________.

babies and lean people exposed to cold temperatures

Which statement describes the citric acid cycle?

This process produces some ATP and carbon dioxide in the mitochondrion. The citric acid cycle breaks down carbon molecules, releasing carbon dioxide and forming some ATP.

Outputs of cellular respiration a. gas we exhale: b. water: c. Energy pats that cells use to do the work:

a. CO2 b. H2O c. ATP

Inputs of cellular respiration a. fuel: b. gas we inhale:

a. glucose b. O2

When proteins are used as a source of energy for the body, the proteins

are converted mainly into intermediates of glycolysis or the citric acid cycle.

At what point in cellular respiration is the first molecule of CO2 produced?

in the reaction that creates acetyl CoA (coenzyme A) from pyruvate Carbon dioxide is produced in the transition between glycolysis and the citric acid cycle when each 3-carbon pyruvate is cleaved to a 2-carbon acetyl molecule with the remaining carbon of pyruvate released as carbon dioxide. This is the first step in cellular respiration where carbon dioxide is released.

In what organelle would you find acetyl CoA formation, the citric acid cycle, and the electron transport chain?

mitochondrion All of the steps of cellular respiration except glycolysis take place in the mitochondrion.

What does the proton pump do?

moves H+ across the inner mitochondrial membrane to the intermembrane space.

In cellular respiration, most ATP molecules are produced by _____.

oxidative phosphorylation This process utilizes energy released by electron transport.

NADH delivers electrons to an electron transport chain, which passes the electrons through carrier molecules in a series of redox reactions to the final electron acceptor, _____.

oxygen

The final electron acceptor of cellular respiration is _____.

oxygen Oxygen is combined with electrons and hydrogen to form water.

In cellular respiration, oxygen becomes _____ to water (H2O) as it gains electrons (in hydrogen atoms) that came from glucose.

reduced

NADH is also used by cells when making certain molecules. Based on your knowledge of the role of NADH in cellular respiration, what do you think NADH's role is in biosynthesis of molecules?

reducing molecules

What "powers" ATP synthase, allowing it to catalyze the conversion of ADP to ATP in the presence of phosphate?

the flow of H+ ions down their concentration gradient. H+ is pumped across the inner mitochondrial membrane by electron transport chains, resulting in a higher concentration of H+ in the intermembrane space than in the mitochondrial matrix. As H+ diffuses down its concentration gradient back into the mitochondrial matrix, the flow of ions "turns the rotor" of ATP synthase, activating sites within the enzyme that result in the phosphorylation of ADP to ATP.

As electrons move through the mitochondrial space

the pH of the intermembrane space changes.

The main function of glycolysis and the citric acid cycle is...

to supply oxidative phosphorylation, the last stage of cellular respiration, with electrons carried by NADH and FADH2.

Describe how food molecules reach the body's cells and fuel cellular respiration. Start with the ingestion of food on the left.

1. Eating food provides fuel and building blocks for your body. 2. After food is broken down in the digestive system, it is transported to cells via the circulatory system. 3. Fuel molecules are broken down further in glycolysis and the citric acid cycle (also called the Krebs cycle). 4. ATP is produced with the help of the electron transport chain.

Each glucose molecule yields __________ molecule(s) of ATP during the citric acid cycle.

2 Each molecule of glucose yields two molecules of pyruvate, and each of these yields one molecule of acetyl CoA that enters the citric acid cycle. Each acetyl CoA molecule, in turn, yields 1 molecule of ATP as it moves through the cycle. Thus, a total of two ATP molecules are generated from 1 glucose molecule.

How many carbon atoms are in pyruvate?

3

About how much ATP is produced by the metabolism of one molecule of glucose in cellular respiration?

32 molecules This is the number of molecules of ATP that are produced by glycolysis, the citric acid cycle, and oxidative phosphorylation.

In glycolysis, what starts the process of glucose breakdown?

ATP

Cellular respiration is a series of chemical reactions that harvest energy in the form of ______ from ______ and other organic molecules. ______ and ______ are also released.

ATP from glucose CO2 and water

What is the correct general equation for cellular respiration?

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + ATP energy Cellular respiration extracts energy from glucose (C6H12O6) to produce smaller energy packets (ATP).

Which of the following statements about the energy yields from cellular respiration is true?

Cellular respiration is more efficient at harnessing energy from glucose than car engines are at harnessing energy from gasoline.

Which of the following statements about the energy yield of aerobic respiration is false?

Oxidative phosphorylation resulting from 1 glucose molecule yields about 12 ATP molecules.

Which statement describes glycolysis?

This process splits glucose in half and produces 2 ATPs for each glucose. In glycolysis, glucose is split into two molecules of pyruvic acid. The released energy is stored in ATP and the electron carrier NADH.

Which statement describes the electron transport chain?

This process uses energy captured from electrons flowing to oxygen to produce most of the ATPs in cellular respiration. In the electron transport chain, electrons move from one electron carrier to another, eventually reaching oxygen. The released energy is used to make ATPs.

Let's look at the big picture here: Fueled by the ATP generated during cellular respiration, the intermediates of glycolysis and the citric acid cycle, such as pyruvate and acetyl CoA, are siphoned off and used to __________.

build proteins, fats, and carbohydrates

In an experiment, mice were fed glucose (C6H12O6) containing a small amount of radioactive carbon. The mice were closely monitored, and in a few minutes, radioactive carbon atoms showed up in __________.

carbon dioxide Cellular respiration, or the oxidization of glucose, involves the release of CO2.

How does the electron transport chain run?

electron transfers by higher-energy molecules to lower-energy molecules, which releases energy used to synthesize ATP.

The transfer of _____ from one molecule to another is an oxidation-reduction reaction, or redox reaction.

electrons

The electron transport chain is, in essence, a series of redox reactions that conclude cellular respiration. During these redox reactions, __________.

electrons are transferred through a series of electron acceptors embedded within the inner mitochondrial membrane NADH provides these electrons to the membrane-embedded electron acceptors.

What process regulates the rate of cellular respiration?

feedback inhibition

Which of the following molecules is broken down in cellular respiration, providing fuel for the cell?

glucose

In cellular respiration, ______ is oxidized when it loses electrons in hydrogen atoms, and ______ is reduced as it gains electrons in hydrogen atoms.

glucose, oxygen

Which of the following processes takes place in the cytosol of a eukaryotic cell?

glycolysis Glycolysis, the breakdown of glucose into two molecules of pyruvic acid, takes place in the cytosol, outside the mitochondria.

The proximate (immediate) source of energy for oxidative phosphorylation is _____.

kinetic energy that is released as hydrogen ions diffuse down their concentration gradient Concentration gradients are a form of potential energy.

In muscle cells, fermentation produces _____.

lactate and NAD+ These are the products of fermentation as it occurs in muscle cells.

In cellular respiration, glucose __________ electrons and oxygen __________ electrons.

loses, gains

Glycolysis begins with __________ and ends with __________.

one molecule of glucose, two molecules of pyruvate

In oxidative phosphorylation, electrons are passed from one electron carrier to another. The energy released is used to __________.

pump protons (H+) across the mitochondrial membrane

Most NADH molecules generated during cellular respiration are produced during __________.

the citric acid cycle There are 6 NADH molecules produced by the citric acid cycle per molecule of glucose. Two molecules of FADH2 are also produced by this cycle, which makes it a big source of high energy electron carriers.

Sunlight is essential for the varied life on Earth because it provides __________.

the energy necessary to power the rearrangement of chemical bonds in H2O and CO2 This is what photosynthesis accomplishes in the conversion of water and carbon dioxide to sugars.

Oxidative phosphorylation could not occur without glycolysis and the citric acid cycle because __________.

these two stages supply the electrons needed for the electron transport chain.

Which of the following is the role of cellular respiration?

to harvest energy from organic molecules