Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

381 - Biochemistry (COMPLETED) > Tutorial - Week 10 - Carbohydrate Metabolism > Flashcards

Tutorial - Week 10 - Carbohydrate Metabolism Flashcards

1
Q

Define Pathways:

A

consecutive reactions catalysed by enzymes
The products of one reaction become the reactants of
the next one

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Define Catabolic pathways:

A

pathways that degrade nutrients/biomolecules into simpler end products
to extract chemical energy and convert it into a form useful to the cell (e.g. ATP, NADH, NADPH, FADH2)

  • These processes are often oxidative (i.e. substrates are oxidised, lose electrons),
    electrons are transferred to electron carriers (e.g. NADH is obtained)
  • These processes are energy releasing and drive synthesis of ATP (i.e. energy
    stored in chemical bonds of nutrients is transferred/captured as ATP
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Define Anabolic pathways:

A

pathways that start with small precursor molecules and convert them
into more complex molecules (e.g. glycogen, proteins, lipids) and store energy in the chemical
bonds of these molecules. These require the use of energy.

  • these processes are often reductive (i.e. substrates are reduced), they use electrons from
    electron carriers, which become oxidised (e.g. NAD(P)H is converted to NAD(P) + )
  • These processes are energy requiring, they use ATP (i.e. ATP is converted to ADP or AMP
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Define Metabolism:

A

the overall network of enzyme catalysed pathways
(anabolic & catabolic)

It is convenient to divide metabolic processes into “pathways”, but such
separation does not exist in the living cell. Pathways occur simultaneously
in living organisms

  • Catabolic pathways: degradation of complex macromolecules into
    smaller molecules, releasing energy
  • Anabolic pathways: synthesis of complex macromolecules, using
    energy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

ATP is…?

NADH/NADPH/FADH are…?

A

the universal currency of energy in biological systems

electron carriers, they provide reducing power

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How does ATP store energy?

What can ADP be hydrolysed into?

A

ATP, adenosine triphosphate: chemical energy stored in bonds
* breakage of a phopshoanhydre bond generates ADP + Phosphate ion (Pi), very exergonic reaction that is normally coupled to endergonic reactions in cells

  • ADP can also be hydrolysed to AMP + Pi to obtain energy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is NADH

A

nicotinamide adenine dinucleotide: reducing power, electron carrier

  • Donate electrons in processes that generate ATP (e.g. in respiratory chain)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is NADPH

A

nicotinamide adenine dinucleotide phosphate: reducing power, electron carrier

  • Drive reductive steps in biosynthetic (anabolic) pathways
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Metabolic pathways maintain the levels of…?

A

key metabolites, such as ATP and NADH in cells and glucose in the blood.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

The rate of metabolic pathways is regulated by ____________, which can be regulated in different ways:

A

enzyme activity

See image for different ways

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Regulation of the amount or the activity of an enzyme:

Define course control - describe both answers

A
  • long term control of enzymes, it can take hours, or days
  • it normally relates to changing the amount of enzyme
    available

See image for explanations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Regulation of the amount or the activity of an enzyme:

Define fine control - describe all answers

A
  • short term control, it can take milliseconds up to min
  • it normally relates to a direct effect on the catalytic
    activity of existing enzyme

See image for explanations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Define Control of the amount of certain enzymes

A
  • Extracellular signals (e.g. hormones such as insulin) (1)
  • Transcription of genes (2)
  • mRNA processing or degradation (3)
  • mRNA translation & posttranslational modification (4)
  • Enzyme stability (turnover: synthesis vs. degradation) (5)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Define control by spacial segregation

A
  • Multienzyme complexes that require assembly of subunits
  • Compartmentation: enzymes and substrates locate in
    different compartments/organelles (6)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Define Control of catalytic activity of existing enzyme molecules

A
  • Changes in substrate concentration (7)
  • Allosteric regulations (e.g. non-competitive uncompetitive inhibition (8)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Define Control by the energy status and availability of reducing power

A
  • NAD(P)+/NAD(P)H ratios (8)
  • ATP/ADP ratios (energy change) (8)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Define Control via allosteric regulation

A
  • feedback inhibition
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Define Control via covalent modification

A
  • phosphorylation/dephosphorylation (reversible) (9)
  • proteolytic activation: zymogens (irreversible)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

This catabolic process is often subdivided into three pathways:

What are they?

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Anaerobic processes:

When do they occur? In the presence or absence of?

Where do they occur in the cell?

Inefficient…?

Where in the body does this occur?

A

Anaerobic processes (AKA as fermentation or anaerobic respiration):

  • occur in the absence of oxygen: glycolysis
  • occur in the cytoplasm
  • Inefficient energy yield: 2ATP/glucose molecule

Occurs in red blood cells (no mitochondria)
and anaerobic microorganisms (e.g. yeast)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Aerobic processes:

When does it occur (in the presence of what)/what is this process called?

Where do they occur in the cell?

Energy yield efficiency?

Where in the body do they occur?

A

Aerobic processes (AKA as aerobic respiration, cellular respiration) :

  • occur in the presence of oxygen: oxidative phosphorylation
  • occur in the mitochondria
  • efficient energy yield: 32ATP/glucose molecule

Occurs in cells/tissues with mitochondria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What does glycolysis mean?

A

Lysis of glucose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Glycolysis:

Does it occur in most cells?

1 molecule of glucose is degraded in…?

Some of the energy released from glucose is conserved in the form of…?

A

Yes

a series of enzyme-
catalysed reactions to obtain 2 molecules of pyruvate (2 x C3

ATP and NADH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What are the three stages glycolysis is subdivided into?

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Glycolysis uses ________ and generates ________; the balance is 2 ATP molecules

A

2 ATP

4 ATP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

_________ of _________ is degraded in a series of _______________
reactions to yield ___ molecules of _________

A

1 molecule

glucose

10 enzyme-catalysed

2

pyruvate

27
Q

In the sequential reactions of glycolysis, three types of chemical transformations are particularly relevant:

What are they?

A

(1) degradation of the carbon skeleton of glucose to yield pyruvate;
(2) phosphorylation of ADP to ATP;
(3) transfer of electrons to NAD+, forming NADH.

28
Q

There are three regulatory enzymes, which catalyse irreversible reactions:

What are they?

A
  1. Hexokinase (reaction 1): inhibited by the products
  2. Phosphofructokinase-1 (PFK-1; reaction 3)
  3. Pyruvate kinase (reaction 10, last step): inhibited by ATP & acetyl-CoA
29
Q

is the key enzyme in the control of glycolysis
(it catalyses the phosphorylation of fructose-6-phosphate to fructose-1,6-biphosphate)

A

Phosphofructokinase-1

30
Q

__________ allosterically inhibits PFK-1 (it reduces its affinity for the substrate)

__________ allosterically activates PFK-1 (it increases its affinity for the substrate)

A

High [ATP]

High [AMP]

31
Q

High [ATP]/[AMP] ___________, decreases glycolysis

________________ PFK-1 activity, and increases glycolysis

A

decreases PFK-1 activity

Low [ATP]/[AMP] increases

32
Q

T/F: Pyruvate can be an intermediary in anabolic pathways

How?

A
33
Q

Pyruvate can be an intermediary in…?

How?

A

other catabolic pathways, to obtain more energy:

34
Q

___________ is the metabolite that links two central catabolic pathways: ____________ and the ____________

A

Pyruvate

glycolysis and the TCA cycle

35
Q

________________ (“new formation of sugar”), converts pyruvate and related three-
and four-carbon compounds to glucose.

A

Glucogenesis

36
Q

Why is glucogenesis important?

A

Important when glucose levels are low:

  • The brain alone requires about 120 g of glucose each day — more than
    half of all the glucose stored as glycogen in muscle and liver.
  • Between meals and during longer fasts, or after vigorous exercise,
    glycogen is depleted.
  • When the glycogen is depleted, organisms need a method for
    synthesizing glucose from noncarbohydrate
37
Q

n gluconeogenesis: the three ____________ steps are bypassed by a separate
set of enzymes, they catalyze reactions that are sufficiently exergonic to be
effectively irreversible in the direction of glucose synthesis

A

irreversible

38
Q

What is the result of the glucogenesis reaction?

A

1 Glucose is formed
2 pyruvate, 4ATP, 2GTP and 2NADH are consumed

39
Q

What is meant by the Reciprocal regulation of glycolysis and glucogenesis?

A

One pathway is relatively inactive, while the other is highly active

40
Q

Molecules that induce reciprocal regulation by allosteric control on the enzymes that differ in
the two pathways:

What are they?

A
41
Q

What is the most tightly regulated enzyme in glycolysis?

A

Phosphofructokinase-1:

42
Q

What is the most tightly regulated enzyme in gluconeogenesis

A

Fructose 1,6 biphosphatase-1

43
Q

What is the major allosteric regulator factor of the
two pathways (it activates glycolysis, and inhibits gluconeogenesis)

A

Fructose 2,6-biphosphate (F26BP)

44
Q

What is this reaction catalysed by?

What is the reaction responsible for?

A

Reaction catalysed by Pyruvate dehydrogenase complex (PDH)
(it occurs in the mitochondrial matrix)

Pyruvate + CoA + NAD + —> Acetyl-CoA + CO2 + NADH + H

Responsible for catalysing the synthesis of acetyl-CoA
(i.e. activated acetate)

45
Q

Activity of pyruvate dehydrogenase is tightly regulated:

What is it activated and inhibited by?

A
46
Q

What do all these molecules get turned into?

A
47
Q

What are the 8 steps, roughly, of the TCA cycle?

A
48
Q

What is the TCA cycle also known as?

It is a ________ pathway

Where does it occur?

Central pathway in…?

1 ________ enters the cycle, 2 _______ leave the cycle

It includes 8 _____________

It is a source of…?

It converts chemical energy from…?

A
49
Q

Describe TCA cycle regulation

A
50
Q

What is Isocitrate dehydrogenase?

A

is the key regulatory enzyme in the TCA cycle and
responds to levels of ATP, ADP and NADH in the cell:

  • if ATP and NADH are high, TCA cycle is inhibited
  • If ADP levels are high, TCA cycle is activated
51
Q

There are two ways to obtain ATP in cells: What are they? Describe them

A

See image

52
Q
  • Oxidative phosphorylation is the culmination of…?
  • All the oxidative steps in the degradation of _________________ converge to
    this pathway to synthesise ATP
  • It occurs in…?
A

catabolism in aerobic organisms

sugars, fats and proteins

the inner mitochondrial membrane

53
Q

Oxidative phosphorilation:

  • electron flow?
  • The free energy, G, from _____________ is…?
  • The flow of protons back down provides…?
A
  1. Electrons flow from electron carriers (NADH and FADH2 generated in TCA cycle) through a chain of membrane-bound carriers to a final electron acceptor (O2 )
  2. The free energy, G, from exergonic electron flow is coupled with
    transport of protons (H + ) across a proton-pump in the membrane
    (electron transport chain)
  3. The flow of protons back down provides free energy for synthesis
    of ATP, catalysed by a membrane protein complex: ATP synthase
54
Q

Cellular respiration occurs in the mitochondria and refers to?

A
55
Q

(LEARN) What are the four parts to carbohydrate catabolism? Explain each step

A
56
Q

Complete oxidation of _____ molecule of glucose to CO2 using ________________
yields ____________ molecules

A

1

oxidative phosphorylation

30 or 32 ATP

57
Q

The catabolic pathways that allow for carbohydrate catabolism to occur are regulated by cellular energy status (2 points)

A
  • High [ADP] increases the pathways
  • High [ATP] decreases them
58
Q

Key concept:

Catabolism vs anabolism & basic strategies of metabolism (3 points)

A
  1. Catabolic pathways degrade nutrients/biomolecules into simpler end products to extract chemical energy
    and convert it into a form useful to the cell (e.g. ATP, NADH)
  2. Anabolic pathways start with small precursor molecules and convert them into more complex molecules (e.g. glycogen, proteins, lipids) and store energy in the chemical bonds of these molecules.
  3. Nucleotides are used to store energy, enzymes control the rate of the reactions,
59
Q

Key concept:

Regulation of metabolic regulation: coarse control and fine control strategies: (2 points)

A
  • Coarse control: long term control of enzymes, it can take hours, or days; it normally relates to
    changing the amount of enzyme available
  • Fine control: short term it can take milliseconds up to min; it normally relates to a direct effect on
    the catalytic activity of existing enzyme
60
Q

Key concept:

Overview of glycolysis pathway (1 point)

A

1 molecule of glucose is degraded in a series of 10 enzyme-catalysed reactions to yield 2 molecules of pyruvate, 2
molecules of ATP, 2 molecules of NADH. It occurs in the cytoplasm

61
Q

Key concept:

Overview of gluconeogenesis pathway (2 points)

A
  1. Synthesis of glucose molecules; it converts pyruvate and related three- and four-carbon compounds
    into glucose: 1 Glucose is formed; 2 pyruvate, 4 ATP, 2 GTP and 2 NADH are consumed.
  2. Reciprocal regulation of glycolysis and glucogenesis
62
Q

Key concept:

Overview of TCA cycle (3 points)

A
  1. It is a central pathway in the catabolism of sugars, fats and proteins; it uses compounds derived from
    the breakdown of carbohydrates, lipids and proteins), which are converted to CO2
  2. 1 Acetyl-CoA enters the cycle, 2 CO2 leave the cycle
  3. 3 NADH, 1 FADH 2 , 1 ATP (or 1GTP)
63
Q

Key concept:

Overview of oxidative phosphorylation (4 points)

A
  1. All the oxidative steps in the degradation of sugars, fats and proteins converge to this
    pathway to synthesise ATP
  2. ATP is generated using electron flow from electron carriers (NADH and FADH2
    generated in TCA cycle) to O2
  3. The protons gradient provides free energy for synthesis of ATP
  4. Complete oxidation of 1 molecule of glucose to CO2 yields 30 or 32 ATP molecules

381 - Biochemistry (COMPLETED) (47 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions