chapter 9

When compounds lose electrons, they gain energy; when compounds ____ electrons, they ____ energy.

gain, lose

The starting product of glycolysis is the six-carbon sugar ____ and the ending products are two ___ carbon molecules of ____.

glucose, 3, pyruvate

As the citric acid cycle is completed what compound is regenerated?

oxaloacetate

NAD+

oxidized lower energy

Which strongly electronegative atom, pulling electrons down the electron transport chain, is the final electron acceptor?

oxygen

Fermentation allows the production of ATP without using either ____ or any _____

oxygen, electron transport chain

What three organic macromolecules are often utilized to make ATP by cellular respiration?

proteins, carbs, and fats

Use Figure 9.10 from your text to help you answer the following summary questions about the citric acid cycle: a. How many NADHs are formed? b. How many total carbons are lost as pyruvate is oxidized? c. The carbons are lost in which molecule? d. How many FADH2 are formed? e. How many ATPs are formed? f. How many times does the citric acid cycle occur for each molecule of glucose?

3 2 carbon dioxide 1 1 2

The breakdown of glucose is linked to cellular work by a chemical driveshaft known a

ATP

NAD+ is a coenzyme. What are coenzymes?

Coenzymes act as cofactors and they are organic molecules, such as many vitamins.

Explain the difference between fermentation and aerobic respiration.

Fermentation is able to occur without the use of oxygen but anaerobic respiration must use oxygen in order to occur.

Glycolysis is thought to have evolved very early in the evolution of life on Earth. Provide three pieces of evidence that justify this hypothesis.

Glycolysis evolved very early and evidence of this is that it is the most widespread metabolic pathway in organisms on Earth. Glycolysis occurs in the cytoplasm of the cell, which suggests that it is of great age. In the eukaryotic cell, there are organelles that have membranes and these came into evaluation about 1 billion years after the prokaryotic cell, glycolysis does not require these, which suggests that it evolved very early in the evolution of life on Earth.

What is the meaning of glycolysis? What occurs in this step of cellular respiration?

Glycolysis means "sugar splitting" and in this step of cellular respiration, glucose is split into two three carbon sugars.

Where does glycolysis occur in the cell? Is oxygen required?

Glycolysis occurs in the cytoplasm of the cell and does not require oxygen.

Oxygen stabilizes the electrons by combining with two hydrogen ions to form what compound?

H2O

Explain the difference in energy usage between the catabolic reactions of cellular respiration and the anabolic pathways of biosynthesis.

In cellular respiration, ATP is synthesized via energy but in biosynthesis, other molecules are synthesized via the energy present in ATP.

What is the function of the electron transport chain in cellular respiration?

In cellular respiration, the electron transport chain is responsible for the moving of electrons down redox reactions which release that acts in the production of ATP.

Three types of phosphorylation (adding a phosphate) are covered in the text, and two of these occur in cellular respiration. Explain how the electron transport chain is utilized in oxidative phosphorylation.

In oxidative phosphorylation energy is released via redox reactions and the energy brings about a concentration gradient across the membrane on the inside of the mitochondria and ATP synthesis is caused by chemiosmosis.

Electron transport involves a series of electron carriers, mostly proteins. Where are these carrier molecules found in eukaryotic cells? Where are the carrier molecules found in prokaryotic cells?

In the mitochondrial membrane. In the plasma membrane.

Phosphofructokinase is an allosteric enzyme that catalyzes an important step in glycolysis. Explain how this step is a control point in cellular respiration

It is a control point in cellular respiration because is aids in the synching of glycolysis and the citric acid cycle

Explain what has happened to the six carbons found in the original glucose molecule.

It is oxidized and two pyruvate molecules are the result here and they form NADH, FADH2, and ATP.

. For aerobic respiration to continue, the cell must be supplied with oxygen—the ultimate electron acceptor. What is the electron acceptor in fermentation?

NAD+

In cellular respiration, electrons are not transferred directly from glucose to oxygen. Following the movement of hydrogens allows you to follow the flow of electrons. What electron carrier is hydrogen transferred to first?

NAD+

Lactic acid fermentation starts with glucose and yields lactate. Explain this process and be sure to describe how NAD+ is recycled.

NAD+ and lactate are formed in this process when pyruvate is reduced by NADH.

The step that converts pyruvate to acetyl CoA at the top of the diagram occurs twice per glucose. This oxidation of pyruvate accounts for two additional reduced ____ molecules and two molecules of CO2.

NADH

What are the two electron carrier molecules that feed electrons into the electron transport system?

NADH and FADH2

Summarize the catabolic degradation of food by aerobic respiration in words (rather than using chemical symbols).

Organic compounds, combined with oxygen, yields carbon dioxide, water, and energy.

Both cellular respiration and photosynthesis are redox reactions. In redox reactions, pay attention to the flow of electrons. What is the difference between oxidation and reduction?

Oxidation is when something loses electrons and reduction is when something gains electrons.

Explain why oxygen is considered the ultimate electron acceptor.

Oxygen itself is very electronegative in nature.

What molecule is the "pacemaker" of cellular respiration?

Phosphofructokinase

Alcohol fermentation starts with glucose and yields ethanol. Explain this process, and be sure to describe how NAD+ is recycled.

Pyruvate becomes ethanol in this process because CO2 is released from pyruvate and then NAD+ and ethanol are present. After this, NAD+ is recycled because it has the ability to be used in glycolysis after this.

Completely label the following figure and then explain why pyruvate is a key juncture in metabolism.

Pyruvate is a key juncture in metabolism because in regards to fermentation and aerobic cellular respiration, it is what decides what will occur based upon the presence or lack of oxygen in this process.

NADH

Reduced higher energy

Use Figure 9.13 in your text of ATP synthase to explain and label the five steps to the production of ATP.

The H+ ions that are going down their gradient go in a channel in a stator in the membrane. The H+ ions go into binding sites in a rotor and the subunit shapes are altered and allow the rotor to rotate along with the membrane. The H+ ions go around once and then leave the rotor and go through another channel to the matrix of the mitochondria. A rod spins due to the rotor spinning and the rotor extends in a knob underneath of it, which does not move because of the stator. Catalytic sites become active due to the rod rotating and this is in the knob and causes the production of ATP which comes from ADP and also Pi.

Study Figure 9.19 in your text. Explain how AMP stimulates cellular respiration, whereas citrate and ATP inhibit it.

The accumulation of AMP denotes that more ATP is needed which stimulates cellular respiration but the buildup of ATP impedes the enzyme and glycolysis so therefore cellular respiration is inhibited due to this.

Why is the total count about 30 or 32 ATP molecules rather than a specific number?

The ratio of NAD+ to ATP isn't a whole number therefore the yield is not a specific number. The result also can be different based on the shuttle used.

The breakdown of glucose in cellular respiration yields of energy, meaning this reaction has a positive/negative ΔG and is exergonic/endergonic.

This reaction has a negative delta G and is exergonic.

Describe what happens when NAD+ is reduced. What enzyme type is involved?

When NAD+ is reduced, it becomes NADH and the enzyme involved is dehydrogenase.

Track coaches used to think that lactic acid accumulated in the muscles as a result of intense exertion, and would have athletes slowly jog to move more oxygen into the muscles so lactic acid would be oxidized and there would be less soreness the next day. What is currently known about lactate production and muscle soreness?

When carbohydrate catabolism is faster than the supply of O2 that goes to the muscles, the lactate is not oxidized to pyruvate. According to research, lactate production can be good for the performance of a person when they work out

What is the role of the electron transport chain in forming the H+ gradient across the inner mitochondrial membrane?

When energy is released, the electrons here go down the electron transport chain and then a gradient is present when the H+ can move from the matrix of the mitochondria to the intermembrane space.

Two key terms are chemiosmosis and proton-motive force. Relate both terms to the process of oxidative phosphorylation.

With the electron transport chain also comes the presence of a H+ concentration gradient and the potential energy here is proton-motive force, while chemiosmosis utilizes this factor in order to power the synthesis of ATP.

The following is a generalized formula for a redox reaction: Xe- + Y → X + Ye- Draw an arrow showing which component (X or Y) is oxidized and which is reduced. Is the reducing agent in this reaction, and is the oxidizing agent.

Xe- is oxidized and Y is reduced. Y is the reducing agent and Xe- is the oxidizing agent.

explain the three steps in the conversion process.

a. -COO- becomes fully oxidized and is released as CO2 b. The two-carbon fragment that is left over becomes oxidized and the electrons from this move to NAD+ and energy is stored as NADH. C. CoA forms acetyl CoA and high a larger amount of potential energy.