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BIO-330: Cell Biology > Exam 3 > Flashcards

Exam 3 Flashcards

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1
Q

What is glucose being split into in Glycolysis?

A

2 Pyruvate molecules (3C)

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2
Q

How many ATP molecules are consumed during the “energy investment” phase of Glycolysis? Which steps are these?

A

1 ATP used in Steps 1 and 3 (TOTAL = 2 ATP used)

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3
Q

How many ATP molecules are produced during the “energy payoff” phase of Glycolysis? Which steps are these?

A

2 ATP generated in Steps 7 and 10 (TOTAL = 4 ATP produced)

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4
Q

What are the starting and ending molecules for Glycolysis and the transition step?

A

STARTS: one glucose molecule
ENDS: net 2 ATP, 2 NADH, 2 Pyruvate molecules

TRANSITION: 0 ATP (1 required for each molecule of pyruvate to actively transport into mitochondria), 2 acetyl CoA (2C), 2 NADH

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5
Q

What is substrate-level phosphorylation?

A

the transfer of a phosphate group directly from a substrate molecule

formation of ATP from ADP and a phosphorylated intermediate, rather than from ADP and inorganic phosphate

depends on differences in bond energies

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6
Q

Is molecular oxygen required for glycolysis?

A

No

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7
Q

If oxygen is present in the cell, what is the fate of the NADH produced by glycolysis?

A

This will be oxidized to reform NAD+ to be used in glycolysis again

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8
Q

Define Glycolysis

A

breakdown of glucose (into two pyruvate molecules)

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9
Q

Define Gluconeogenesis

A

synthesis of glucose (essentially a reversal of glycolysis) from noncarbohydrate precursors when glucose dietary intake is insufficient or absent

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10
Q

Define Glycogenesis

A

synthesis of glycogen from glucose

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11
Q

Define Glycogenolysis

A

breakdown of glycogen into glucose in the liver when blood glucose levels drop

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12
Q

What does Insulin do to blood glucose levels?

A

Lowers blood glucose (stimulates glucose uptake by cells via facilitated glucose diffusion)

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13
Q

What does Glucagon do to blood glucose levels?

A

Raises blood glucose (stimulates glycogenolysis)

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14
Q

What does Epinephrine do to blood glucose levels?

A

Raises blood glucose (stimulates glycogenolysis)

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15
Q

Why must fermentation occur?

A

When there is no oxygen, glycolysis occurs, converting NAD+ to NADH. However, NADH can’t deposit its electrons (into ETC) because there is no oxygen present. Fermentation is needed to convert NADH back to NAD+, so glycolysis can continue steadily

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16
Q

Broadly, what are the three stages in obtaining energy from food?

A
  1. Breakdown of macromolecules to simple subunits (polysaccharides to simple sugars, fats to fatty acids, proteins to amino acids)
  2. Glycolysis where a glucose molecule is broken into two pyruvates, which are used to build the activated carrier Acetyl CoA). Occurs in the cytosol.
  3. Acetyl CoA undergoes complete oxidation into H2O and CO2, which is accompanied by the production of large amounts of ATP in the mitochondria (as well as NADH)
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17
Q

In eukaryotes, most of the energy generation occurs where?

A

mitochondria

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18
Q

What allows for pyruvate to be actively pumped into the mitochondria, and does it use energy to do so?

A

Pyruvate Translocase (active transport: symport with proton)

1 ATP is required per pyruvate molecule…so 2 ATP

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19
Q

In Tremetol, there is an inhibition of citric synthase. What will happen?

A

Can’t make ATP from Krebs, so body will use other energy sources - fat breakdown leads to buildup of ketose sugars which are unstable and convert to acetone compounds

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20
Q

What types of tissues is the level of blood glucose especially important?

A

Brain, muscle

metabolically active tissues rely primarily on glucose metabolism

21
Q

Where do you get molecules like glycogen when blood glucose is low?

A

Mostly liver

can also come from tissues such as brain, skeletal muscle, cardiac muscle

22
Q

Why does a cell store glucose as glycogen rather than as many individual molecules of free glucose?

A

Glucose is soluble in water and may cause the cell to become hypertonic in nature, leading to water rushing in the cell and causing it to lyse

Glycogen is insoluble in water, not causing an imbalance in osmotic pressure

23
Q

Is the pH lower in the mitochondrial matrix or in the intermembrane space?

A

intermembrane space = 7.4

mitochondiral matrix pH = 7.8

24
Q

What is the final electron acceptor in the Electron Transport Chain?

A

Oxygen

25
Q

Would you expect the last carrier in the Electron Transport Chain the be the most or least electronegative, and why?

A

MOST electronegative

electrons move energetically “downhill” such as energy is released in each step, meaning that at each point the carrier becomes more and more electronegative which allows movement

26
Q

Does the ETC directly produce ATP, why or why not?

A

No - energy from NADH and FADH2 is used to create a proton gradient by donating electrons to a transport chain that pumps hydrogen. ATP is produced through these proton-powered ATPases

27
Q

How many molecules of ATP are produced from each:

FADH2

NADH

A

FADH2 = 1.5 molecules of ATP

NADH = 2.5 molecules of ATP

28
Q

What is the function of the ATP synthase in the mitochondrion?

A

catalyzes the synthesis of ATP from ADP and inorganic phosphate through oxidative phosphorylation, driven by a flux of hydrogen protons generated by the electron transfer from the ETC

29
Q

What is chemiosmosis?

A

When electrons are passed from one member of the transport chain to another in a series of redox reactions, with the energy released in these reactions being captured as a proton gradient, which is then used to make ATP

30
Q

What is the role of uncoupling proteins in cellular respiration?

How may this be used in weight loss management?

A

channels that allow protons to pass from the intermembrane space to the matrix without traveling through ATP synthase. By providing an alternate route for protons to flow back into the matrix, the uncoupling proteins allow the energy of the gradient to be dissipated as heat, reducing the amount of ATP generated

31
Q

What powers the transport of ADP or ATP across the mitochondrial membranes?

A

ADP/ATP mitochondrial carrier protein allows for the transport of one ADP into the mitochondria for one ATP molecule to be moved out

32
Q

Cyanide block cytochrome a3. How might this alter ATP production by the mitochondrion?

A

The ETC would stop and the proton gradient across the inner mitochondrial membrane would decrease, leading to a disruption in the area where the greatest amount of ATP is produced

Blood acidosis, normal body temperature, normal lipids, high cellular NADH (indicator of this toxin)

33
Q

DNP (dinitrophenol) was used as a weight loss product in the 1930s, but unfortunately, it turned out to be very toxic.

Describe its mechanism of action that could lead to weight loss.

A

DNP is an “uncoupler,” or an uncoupling agent, making the inner mitochondrial membrane leaky to protons (i.e. carries protons across mitochondrial membranes)

causes potential energy to dissipate as heat, which decreases ATP production to increase metabolism

normal blood pH, increased temperature, hyperlipidemia, normal cellular NADH

34
Q

What are two other roles that mitochondria play in a cell besides energy production?

A

control intrinsic pathway for cellular death (apoptosis) through cytochrome c

storing of calcium ions

35
Q

Describe ways by which the cell monitors ATP production

A

Hexokinase (STEP 1 of Glycolysis) - conversion of glucose to glucose 6-phosphate traps it in the cell because the phosphate group confers a negative charge, meaning that it does not cross through the usual routes and has limited diffusion

Phosphofructokinase (STEP 3 of Glycolysis) - commits cells to use glucose for energy rather than storing it as glycogen

Pyruvate dehydrogenase - acetyl CoA is made only when it’s needed (and when there’s plenty of pyruvates available)

36
Q

How does a cell use energy stored in fat?

A

Fatty acids are turned into acetyl-CoA and then oxidized in the citric acid cycle. No glycolysis is involved.

37
Q

Where does Glycolysis occur?

A

In the cytosol for both prokaryotes and eukaryotes

38
Q

In which steps of Glycolysis does each happen twice for each glucose molecule that enters glycolysis?

A

Steps 6-10 each happen twice for every molecule of glucose that enters glycolysis.

39
Q

Which step of glycolysis does fermentation allow to occur in the absence of oxygen?

A

Fermentation is necessary for Step 6 to occur.

40
Q

How many mitochondria are in most cells?

A

MANY, usually more than 1000

41
Q

TRUE OR FALSE: Pyruvate diffuses freely through porins in the outer membrane of the mitochondria

A

TRUE

42
Q

Where is Pyruvate broken down?

A

In the mitochondrial matrix

43
Q

What type(s) of phosphorylation occurs in the mitochondria?

A

Both substrate-level phosphorylation and oxidative phosphorylation

44
Q

Describe the regulatory step that is regulated by Hexokinase?

A

Hexokinase (STEP 1 of Glycolysis) - conversion of glucose to glucose 6-phosphate traps it in the cell because the phosphate group confers a negative charge, meaning that it does not cross through the usual routes and has limited diffusion

45
Q

Describe the regulatory step that is regulated by PFK

A

Phosphofructokinase (STEP 3 of Glycolysis) - commits cells to use glucose for energy rather than storing it as glycogen

46
Q

Describe the regulatory step that is regulated by fructose 1,6 biphosphate.

A

fructose 1,6 biphosphate (6C) is cleaved into two 3C sugar intermediates so that the number of molecules at every stage afterward doubles

47
Q

What is the final yield of ATP from 1 molecule of glucose?

A

30 ATP

48
Q

What are examples of how metabolism can be altered by diseases, toxins, or drugs

A

Tarui Disease (deficiency of phosphofructokinase)

Tremetol (inhibits citric synthase) - stops glycolysis, leading body to use other energy sources that may lead to the buildup of ketones

Malonate (inhibits succinate dehydrogenase)

Arsenic (alloseteric inhibition of pyruvate dehydorgenase) - pyruvate cannot ve converted into acetyl CoA, meaning that the citric acid cycle cannot occur

Cyanide (inhibits cytochrome c oxidase) - stops ETC from continuing

DNP (“uncoupler,” or an uncoupling agent) - making the inner mitochondrial membrane leaky to protons (i.e. carries protons across mitochondrial membranes), causes potential energy to dissipate as heat, which decreases ATP production to increase metabolism

BIO-330: Cell Biology (6 decks)

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