Ch 13/14 Molec Cell Smartwork Questions (Exam 2)

Most of the energy released by oxidizing glucose is saved in the high-energy bonds of what molecules?

ATP and other activated carriers

Useful energy is obtained by cells when sugars derived from food are broken down by which processes?

glycolysis, the citric acid cycle, and oxidative phosphorylation

Together, glycolysis, the citric acid cycle, and oxidative phosphorylation

capture the energy released from the oxidative breakdown of sugars

Catabolic reactions include

glycolysis and the citric acid cycle

Glycolysis is the breakdown of

glucose into pyruvate

The citric acid cycle completes the

oxidation of the carbons in pyruvate

What process describes a breakdown process in which enzymes degrade complex molecules into simpler ones?

catabolism

Where does the oxidative (oxygen-dependent) stage of the breakdown of food molecules occur in a eukaryotic cell?

mitochondrian

Oxidative phosphorylation takes place on the

inner mitochondrial membrane

The citric acid cycle occurs in the

mitochondrial matrix

The electron transport chain in the inner mitochondrial membrane generates

large amounts of ATP from electrons donated by the active carriers produced during glycolysis and the citric acid cycle

Glycolysis produces

a small amount of ATP (net of 2 ATP) for each molecule of glucose that enters the pathway

The citric acid cycle generate a

small amount of GTP, a molecule that is related to ATP

• also produces NADH and FADH2

What are the end products of glycolysis?

2 pyruvate, 2 ATP, and 2 NADH

What is required for glycolysis to take place?

Pi, NAD+, ATP, and ADP

During glycolysis,

one molecule of ATP is consumed during step 1 and a second molecule of ATP during step 3

How many ATP molecules must be invested during the first part of glycolysis for each molecule of glucose broken down?

2

The synthesis of ATP in glycolysis occurs by which process?

substrate-level phosphorylation

Substrate-level phosphorylation is a process in which

a phosphate group is transferred directly from a substrate molecule, such as one of the intermediates in glycolysis, to ADP

For many anaerobic microorganisms, which metabolic pathway is a principal source of ATP?

glycolysis

Glycolysis can occur in the

absence of oxygen

Fermentation reactions convert the pyruvate produced during glycolysis into

lactate or ethanol

• NADH gives up its electrons producing NAD+

Under anaerobic conditions, which metabolic pathway regenerates the supply of NAD+ needed for glycolysis?

fermentation

What type of enzyme catalyzes the rearrangement of chemical bonds within a single molecule?

isomerase

In steps 2 and 5 of glycolysis,

a rearrangement of chemical bonds by an isomerase prepares the substrates for the chemistry

Although the citric acid cycle itself doesnt use O2, it requires a functioning ETC (which uses O2) in order to regenerate which molecule for further use in the citric acid cycle?

NAD+

Like glycolysis, the citric acid cycle uses

NAD+ as an electron acceptor

The citric acid cycle converts the carbon atoms in acetyl CoA to what?

CO2

The NADH generated during glycolysis and the citric acid cycle feeds its high-energy electrons to what?

the ETC

In eukaryotic cells, what is the final electron acceptor in the ETC?

O2

In plant cells, where does the citric acid cycle take place?

mitochondria

During the citric acid cycle, what happens to the acetyl group in acetyl CoA?

it is oxidized to produce CO2

Which two-carbon molecule enters the citric acid cycle?

acetyl CoA

In the first step of the citric acid cycle, acetyl CoA

donates a 2-carbon acetyl group to oxaloacetate to form citrate

What occurs in the first step of the citric acid cycle?

a 2-carbon molecule is combined with a 4-carbon molecule to form citrate

• forms 6-carbon citrate

CO2 is released in which steps of the citric acid cycle?

steps 3 and 4

How do fermentation reactions in oxygen-starved muscle cells and anaerobically grown yeast cells differ?

fermentation in muscle cells produce lactate and in yeast produces ethanol + CO2

What happens to the energy captured during glycolysis and the citric acid cycle by the activated carriers NADH and FADH2?

it’s passed to an ETC that uses it to generate a proton gradient across the inner mitochondrial membrane

In the absence of oxygen, yeast cannot

perform aerobic respiration and instead switch to fermentation

• fermentation products in yeast include CO2 and ethanol

Glycolysis and the citric acid cycle provide precursors to

synthesize many organic molecules, including lipids

Step 3 of glycolysis:

• enzyme uses an ATP

• enzyme that catalyzes step 3 is phosphofructokinase

• the reaction generates the product fructose 1,6-biphosphate

• reaction is irreversible

The first step of glycolysis is the

phosphorylation of glucose to glucose-6-phosphate

• uses a phosphate from ATP hydrolysis

What processes require a membrane?

• generation of ATP by photosynthesis in plants

• generation of ATP by photosynthesis in bacteria

• generation of ATP by oxidative phosphorylation

• generation of energy by mitochondria

What drives the production of ATP from ADP and Pi by ATP synthase?

a proton (H+) gradient

In the ETC, as electrons move along a series of carriers, they release energy that is used to do what?

pump protons across a membrane

What is true of the organelles that produce ATP in eukaryotic animal cells?

they evolved from bacteria engulfed by ancestral cells billions of years ago

What organisms have mitochondria in their cells?

• animals

• plants

• protozoa

• yeasts

In what ways can mitochondria adapt to the changing needs of a cell?

• changing their location

• changing their number

• changing their shape

The inner mitochondrial membrane, which is folded into cristae, contains the proteins that carry out

oxidative phosphorylation, including the ETC and the ATP synthase that makes ATP

What are consumed as fuel within the mitochondria?

• amino acids

• acetyl CoA

• pyruvate

• fatty acids

The ETC in mitochondria accepts high-energy electrons directly from which molecule?

NADH

As electrons move through the ETC,

electrons start out at very high energy and lose energy at each transfer step along the ETC

In mitochondria, what is the final electron acceptor in the ETC?

oxygen

Mobile electron carriers are

small proteins or hydrophobic molecules that are components of the respiratory chain

What is true of mobile electron carriers?

they ferry electrons between one respiratory complex to the next

The ETC pumps protons in which direction?

from the matrix to the intermembrane space

ATP synthase can use the energy provided by the movement of

protons to produce ATP

• can also operate in reverse; using the energy of ATP hydrolysis to pump protons across the membrane

During oxidative phosphorylation, why does a single molecule of NADH result in the production of more ATP molecules than a single molecule of FADH2?

FADH2 and NADH feed their electrons to different carriers in the ETC

Which metal is fcound in all three respiratory enzyme complexes?

iron

During electron transport, which serves as a ready source for protons that can be pumped across the membrane?

H2O

Why can electron carriers move a proton from one side of a membrane to the other?

they can accept an electron (along with an H+ from water) on one side of the membrane and then release the H+ on the other side of the membrane as they pass the electron to the next carrier