BIO1005 CH 6

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Why is glycolysis considered to be the oldest metabolic reaction?

Because it occurs in all cells

How many ATP are made as a result of glycolysis?

Four ATP are made, but the net gain is two

Where does the food come from in the first place?

In most ecosystems, plants and other autotrophs use photosynthesis to make organic molecules such as glucose (C6H12O6) out of carbon dioxide (CO2) and water (H2O). Light supplies the energy. The glucose produced in photosynthesis feeds not only autotrophs but also all of the animals, fungi, and microbes that share the ecosystem

What is the role of ATP synthase?

It uses a hydrogen ion gradient to make ATP

Unlike chemiosmotic phosphorylation,substrate-level phosphorylation does not require

a proton gradient or the ATP synthase enzyme to produce ATP

Which of the following molecules can be used to generate ATP energy?

all- carbs, amino acids and fats

Proteins are digested into monomers called

amino acids

Most cells use carbohydrates as a primary source of energy, but cells can also use

amino acids and lipids to generate ATP.

The Krebs cycle and electron transport chain

are the key ATP-generating processes

The circulatory system

carries the inhaled O2 to cells, where gas exchange occurs.

Krebs cycle is also known as

citric acid cycle

Which of the following best describes anaerobic respiration?

The production of ATP energy from glucose in the absence of oxygen

Glycolysis always occurs in the

cytoplasm

Other yields in respiration cycle

each glucose yields two NADH molecules from glycolysis, two NADHs from acetyl CoA production, and six NADHs and two FADH2s from two turns of the Krebs cycle.

anaerobic respiration

generate ATP from glucose without using O2 -most common in microorganisms.

fermentation

generate ATP from glucose without using O2 -most common in microorganisms.

The pathways of aerobic respiration oxidize

glucose

equation for aerobic respiration

glucose + oxygen → carbon dioxide + water + ATP C6H12O6 + 6O2 → 6CO2 + 6H2O + 36ATP

What are the starting materials of glycolysis?

glucose and 2 molecules of ATP

Glycolysis

glucose splits into two molecules of pyruvate, producing a net yield of two ATPs and two NADHs -

the 2nd five steps of glycolysis

the pathway then stores some energy in two molecules of the electron carrier, NADH. Other steps extract more of the energy, regaining the two ATP molecules invested earlier plus producing two more. The net gain is therefore two NADHs and two ATPs per molecule of glucose.

glycolysis

(literally, "breaking sugar"), a six-carbon glucose molecule splits into two three-carbon pyruvate molecules. This process harvests energy in two forms. First, some of the electrons from glucose are transferred to an electron carrier molecule called NADH (nicotine adenine dinucleotide). Second, glycolysis generates two molecules of ATP.

Electron transport occurs in

-inner mitochondrial membrane in eukaryotic cells - in the thylakoid membranes of chloroplasts

How can plants release more O2 in photosynthesis than they consume in respiration?

...

How is substrate-level phosphorylation different from chemiosmotic phosphorylation?

...

What is endosymbiosis?

A possible explanation for the origin of mitochondria

How does the Krebs cycle generate CO2, ATP, NADH, and FADH2?

by rearranging and oxidizing citrate though several intermediate molecules. the energy and electrons derived from these chemical reactins are stored in ATP, NADH, and FADH2. A molecule of CO2 is released in two of these chemical reactions.

Besides continuing the breakdown of glucose, the Krebs cycle also has another function not directly related to respiration, what is it

cell uses intermediate compounds formed in the Krebs cycle to manufacture other organic molecules, such as amino acids or fats. the reverse process also occurs; amino acids and fats can enter the Krebs cycle to generate energy from food sources other than carbohydrates

How many ATP, NADH, CO2, FADH2, and H2O molecules are produced at each stage of respiration?

converting glucose to 2 pyruvates 2 ATP and 2 H2O -shuttling 2 pyruvates into the mitochondrian produces 2 NADH -The 2 acetyl CoA enter the Krebs cycle and produce 2 APT, 6 NADH, and 2 FADH2 -From all these products, the electron transport chain can produce up to 36 ATP

ATP synthase

enzyme tacks a phosphate group onto ADP, yielding ATP

None of the steps in glycolysis require

O2, so cells can use glycolysis in both oxygen-rich and anaerobic environments

ATP yields in respiration cycle

Substrate-level phosphorylation yields two ATPs from glycolysis and two ATPs from the Krebs cycle (one ATP each from two turns of the cycle). These are the only steps that produce ATP directly. -the ATP yield from electron transport is three ATPs per NADH and two ATPs per FADH2. Electrons from the 10 NADHs from glycolysis and the Krebs cycle therefore yield up to 30 ATPs; electrons from the two FADH2 molecules yield four more. Add the four ATPs from substrate-level phosphorylation, and the total is 38 ATPs per glucose. However, NADH from glycolysis must be shuttled into the mitochondrion, usually at a cost of one ATP for each NADH. This reduces the net theoretical production of ATPs to 36.

Which respiratory reactions occur in each part of the mitochondrion?

The electron transport chain is located on the inner michondrial membrane. The Krebs cycle occurs in the mitochondrial matrix. (In prokaryotes the electron transport chain is embedded in the cells outer membrane and the Krebs cycle occurs in the cytoplasm.

Mitochondria and chloroplasts share what similarities

Both types of organelles contain DNA and ribosomes. Mitochondrial DNA encodes ATP synthase and most of the proteins of the electron transport chain.

The Krebs cycle completes the oxidation of each acetyl group, releasing

CO2

products generated in glycolysis, acetyl CoA formation, and the Krebs cycle

CO2, ATP, NADH, and FADH2 The cell ejects the CO2 as waste

anaerobic respiration

essentially the same as aerobic respiration, except that an inorganic molecule other than O2 is the electron acceptor at the end of the electron transport chain. Alternative electron acceptors include NO3- (nitrate), SO42- (sulfate), and CO2. The number of ATPs generated per molecule of glucose depends on the electron acceptor, but it is always lower than the ATP yield for aerobic respiration. bacteria and archaea generate ATP by anaerobic respiration

Explain how to arrive at the estimate that each glucose molecule theoretically yields 36 ATPs

glycolysis yields 2 NADH and 2 ATP; the formation of acetyl CoA yields 2 NADH; the Krebs Cycle yields 6NADH, 2 ATP, 2 FADH2. When the NADH and FADH2 from flycolysis and the Krebs cycle contribute their electrons to the ecectron transport chain, they yield a total of 34 ATP that were derived from NADH and FADH2. Once 2 ATP are subtracted (the cost of moving NADH from glycolysis to the intermembrane space), the net yield is 36 ATP per molecule of glucose

Cellular Respiration Includes Three Main Processes

glycolysis, the Krebs cycle, and electron transport

plants absorb much more CO2 in photosynthesis than they release in respiration, and

hey release more O2 than they consume.

glycolysis requires 10 steps, all of which occur in

the cell's cytoplasm

summary of respiration through the Krebs cycle

the combined net output to this point (glycolysis, acetyl CoA formation, and the Krebs cycle) is four ATP molecules, 10 NADH molecules, two FADH2 molecules, and six molecules of CO2. Of course, this process does not capture all of the potential energy in glucose. According to the second law of thermodynamics, some is always lost as heat.

The difference between anaerobic and aerobic respiration is

the electron acceptors.

cell's mitochondria

the sites of respiration

How do NADH and FADH2 power ATP formation?

they deliver energy rich electrons to the electron transport chain to power the concentration of hydrogen ions. those concentrated hydrogen ions are used to power the addition of a phosphate group to ADP

The Krebs cycle turns

twice per glucose molecule

first five steps of glycolysis

use ATP to "activate" glucose, redistributing energy in the molecule and splitting it in half.

what happen in electron transport

uses energy stored in the electron carriers NADH and FADH2 to create a gradient of hydrogen ions across the inner membrane of the mitochondrion. ATP synthase uses this gradient to phosphorylate ADP to form ATP

What do cells do with the ATP they generate in respiration?

ATP is the source of energy to power most of the chemical reactions that take place in the cell

what enzyme facilitates the final stage of ATP synthesis

ATP synthase

No cell can survive without

ATP —adenosine triphosphate

What compound enters the Krebs cycle

Acetyl CoA

plants use O2 to respire

half of the glucose they produce.

a gradient represents a form of

potential energy

Why is it important to regenerate NAD+ during fermentation?

t helps maintain the reactions of glycolysis.

Overview of Aerobic Cellular Respiration

Glucose is broken down to carbon dioxide in three main stages: glycolysis, the Krebs cycle, and the electron transport chain. Along the way, energy is harvested as ATP. Except for glycolysis, these reactions occur inside the mitochondria of eukaryotic cells.

For every glucose molecule that entered glycolysis, how many acetyl CoA molecules are ready to enter the Krebs cycle

2

How many ATP molecules per glucose does fermentation produce?

2

What is the net gain of ATP and NADH for each glucose molecule undergoing glycolysis?

2 ATP and 2 NADH for each molecule of glucose

Electron Transport Chain

3rd step in respiration Energy-rich electrons removed from NADH and FADH2 slowly release their energy as they are transferred along the proteins of the electron transport chain. Membrane-bound enzymes use this energy to pump protons (H+) from the matrix to the intermembrane compartment, establishing a gradient across the inner mitochondrial membrane. As the protons pass through a channel in ATP synthase, the gradient dissipates, and ADP is phosphorylated to form ATP.

Which stage in cellular respiration directly requires the presence of O2?

Electron transport

What happens to the CO2 and H2O waste products of respiration?

Excess CO2 and H2O lave the cell through the plasma membrane; water is used throughout the organism and CO2 is retuned to the external environment

Which of the following molecules has the greatest amount of potential energy?

Glucose

lactic acid fermentation

a cell uses NADH to reduce pyruvate, but in this case, the products are NAD+ and the three-carbon compound lactic acid reduces pyruvate to lactic acid.

aerobic cellular respiration

a cell uses oxygen gas (O2) and glucose to generate ATP. -Plants, animals, and many microbes, especially those in O2-rich environments, use aerobic respiration.

he resulting six-carbon molecule of Krebs cycle is called

a citrate

CO2

a metabolic waste, is exhaled

reduce

add electrons to

How Many ATPs Can One Glucose Molecule Yield?

add the maximum number of ATPs generated in glycolysis, the Krebs cycle, and the electron transport chain -Breaking down glucose to carbon dioxide can yield as many as 36 ATPs, mostly from chemiosmotic phosphorylation at the electron transport chain

three categories of generating ATP

aerobic cellular respiration anaerobic respiration fermentation

What are the three general ways to generate ATP from food, and which organisms use each pathway?

aerobic cellular respiration- plants, animals, bacteria in oxygen rich environments anaerobic respiration- microorganisms fermentation- microorganisms

What are two examples of fermentation pathways?

alcoholic fermentation and lactic acid fermentation

Where in the cell does each of stage of respiration occur?

in a eukaryotic cell, respiration takes place in many different places. glycolysis takes place in the cytoplasm where glucose is converted into pyruvate. Also in the cytoplasm, pyruvate is converted to acetyl CoA which enter the matrix of the mitochondria. within the mitochondrial matrix, the Krebs cycle reactions take place; the results of the Krebs cycle are CO2, NADH and FADH2 molecules. The electron transport chain uses electrons from NADH and FADH2 to pump hydrogen ions across the inner membrane of the mitochondria to the intermembrane compartment. From that compartment hydrogen returns to the mitochondrial matrix through the ATP pump producing ATP from ADP. ATP is then shuttled throughout the cell.

What is the role of O2 in the electron transport chain?

it functions as the final electron acceptor. o2 binds to electrons that have traveled to the end of the transport chain which allows subsequent electrons to move along the pathway.

fermentation is not respiration because

it generates ATP from glycolysis only.

Pyruvate contains three carbon atoms; an acetyl group has only two. What happens to the other carbon atom?

it is released as CO2

ATP is essential because

it powers nearly every activity that requires energy input in the cell: synthesis of DNA, RNA, proteins, carbohydrates, and lipids; active transport across the membranes surrounding cells and organelles; separation of duplicated chromosomes during cell division; movement of cilia and flagella; muscle contraction; and many others

substrate-level phosphorylation

means that a high-energy "donor" molecule physically transfers a phosphate group to ADP, forming ATP.

Krebs cycle occurs in

mitochondrial matrix in eukaryotic cells

What are some examples of alternative electron acceptors used in anaerobic respiration?

nitrate, sulfate and CO2

Where do the O2 and glucose used in respiration come from?

o2 from the environment enters the cell through the plasma membrane, Glucose is provided from digesting other organisms or from photosynthesis

respiration is a--------reaction

oxidation—reduction

fermentation

pathways oxidize NADH to NAD+, which is recycled to glycolysis, but these pathways do not produce additional ATP. Some microorganisms, including many inhabitants of your digestive tract, use fermentation. In these organisms, glycolysis still yields two ATPs, two NADHs, and two molecules of pyruvate per molecule of glucose. But the NADH does not donate its electrons to an electron transport chain, nor is the pyruvate further oxidized. Instead, in fermentation, electrons from NADH reduce pyruvate. This process regenerates NAD+ so that glycolysis can continue, but it generates no additional ATP. Fermentation is therefore far less efficient than respiration. Not surprisingly, fermentation is common among microorganisms that live in sugar-rich environments where food is essentially unlimited In fermentation, ATP comes only from glycolysis. (a) Yeasts produce ethanol and carbon dioxide by alcoholic fermentation.

equation for aerobic respiration is essentially the reverse of

photosynthesis

Why do plants have a reputation for producing O2, if they also consume it?

plants incorporate much of the remaining glucose into cellulose, starch, and other stored organic molecules. Therefore, they absorb much more CO2 in photosynthesis than they release in respiration, and they release more O2 than they consume.

all organisms use the ------stored in food to make ATP

potential energy

Energy-rich ATP is generated from

potential energy in food

electron transport chain therefore uses the energy in NADH and FADH2 to establish a

proton gradient across the inner mitochondrial membrane

chemiosmotic phosphorylation

protons move down their gradient through ATP synthase channels back into the matrix, and ADP is phosphorylated to ATP.

Is pyrucate used directly in the Krebs Cycle

pyruvate moves into the mitochondrial matrix, but it is not directly used in the Krebs cycle because it is ozidized removing CO2 and NAD+ is reduced to NADH. The remaining two-carbon molecule, called an acetyl group, is transferred to a coenzyme to form acetyl coenzyme A (abbreviated acetyl CoA). Acetyl CoA is the compound that enters the Krebs cycle

The pathways of aerobic respiration

reduce (add electrons to) O2

alcoholic fermentation

reduces acetaldehyde to ethanol and loses carbon dioxide

what happens in Krebs cycle

releases CO2 and produces additional ATP and NADH as well as FADH2

is respiration an exothermic or endothermic reaction

releases energy which make it

oxidize

remove electrons from

C6H12O6 + 6O2 → 6CO2 + 6H2O + 36ATP

reveals that aerobic cellular respiration requires organisms to acquire O2 and get rid of CO2

what happens in glycolysis

splits glucose into two pyruvate molecules and produces ATP and some NADH for later use

Glycolysis produces ATP by

substrate-level phosphorylation


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