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PJ1311 YEAR 1 (THE HUMAN BODY) > Metabolism > Flashcards

Metabolism Flashcards

1
Q

Name the metabolic pathways

A

Catabolic
Anabolic
Amphibolic

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2
Q

anabolic pathway

A

are a series of biochemical reactions in living organisms that involve the synthesis of complex molecules from simpler ones

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3
Q

catabolic pathway

A

is a series of biochemical reactions in living organisms that involve the breakdown of complex molecules into simpler ones

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4
Q

amphibolic pathway

A

metabolic pathways that have characteristics of both catabolic and anabolic pathways

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5
Q

which of the metabolic pathways requires energy?
which one produces energy?

A

anabolic

catabolic

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6
Q

metabolism

A

set of chemical reactions that occur within living organisms to maintain life

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7
Q

glycolysis
forms of glycolysis?

A

It is defined as a sequence of reactions transforming glucose to lactate & pyruvate with the production of ATP.

aerobic and anaerobic glycolysis

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8
Q

aerobic glycolysis

what does it form

A

the breakdown of glucose in the presence of oxygen

Acetyl Co-A

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9
Q

anaerobic glycolysis

what does it form

A

the breakdown of glucose in the absence of oxygen

lactic acid, which is the final product(in mammals)

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10
Q

how many pyruvates will be formed per glucose molecule?

A

2 per glucose

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11
Q

purpose of glycolysis

A

to produce intermediates for other biosynthetic pathways

to produce energy

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12
Q

site of glycolysis

A

the cytoplasm

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13
Q

outline the steps of glycolysis

A

Hexokinase catalyzes the phosphorylation of glucose (from ATP) to form glucose 6-phosphate

Glucose 6-phosphate is converted to fructose 6-phosphate by phosphoglucose isomerase
This reaction involves the conversion of an aldose to a ketose

Fructose 6-phosphate is phosphorylated by phosphofructokinase(PFK) to form fructose 1,6-bisphosphate and ADP

Fructose 1,6-bisphosphate (a six-carbon molecule) is split by aldolase into two three-carbon molecules: glyceraldehyde 3-phosphate and dihydroxyacetone phosphate

Only glyceraldehyde 3-phosphate(G3P) is used for the remainder of glycolysis
But dihydroxyacetone can be converted back to G3P

G3P is converted to 1,3 biphosphoglycerate.
The enzyme involved is glyceraldehyde 3-phosphate dehydrogenase and uses Pi and NAD+

The high-energy phosphate bond in 1,3-bisphosphoglycerate is then used to generate ATP
1,3-bisphosphoglycerate is converted by phosphoglycerate kinase to3-phosphoglycerate

3-phosphoglycerate is converted by phosphoglycerate mutase to 2-phosphoglycerate* This step moves the phosphate group to a different carbon on the same molecule

2-phosphoglycerate is converted to phosphoenolpyruvate (PEP) by enolase
This dehydration reaction changes the low-energy phosphate ester bond of the former to the high-energy phosphate bond of PE

The final reaction involves the conversion of phosphoenolpyruvate to pyruvate via pyruvate kinase

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14
Q

what is the TCA cycle also known as

A

the Krebs cycle

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15
Q

via which cycle can lactate be turned back into glucose

A

the Cori cycle

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16
Q

what are the primary control steps in glycolysis catalyzed by

A

PFK(phosphofructokinase)
hexokinase
pyruvate kinase

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17
Q

how is PFK inhibited and by what?

A

allosterically by ATP

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18
Q

what inhibits hexokinase

A

glucose-6-phosphate

note that hexokinase levels increase after PFK inhibition

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19
Q

TCA cycle unabbreviated

A

tricarboxylic acid cycle

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20
Q

is the TCA cycle an aerobic or anaerobic pathway

A

aerobic pathway

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21
Q

purpose of TCA cycle

A

it contributes to glucose formation from the carbon skeleton of some amino acids

Oxidative Decarboxylation

Generates high-energy molecules in the form of NADH and FADH2, which participate in oxidative phosphorylation to produce ATP.

it provides building blocks for the synthesis of some amino acids

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22
Q

outline the steps in generating acetyl COA

A

pyruvate moves into the mitochondria

Pyruvate dehydrogenase(PDH) catalyzes the reaction between pyruvate and CoA to form acetyl CoA and CO2. NADH is formed during this step

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22
Q

is the TCA cycle a closed cycle?

A

no, it is a traffic cycle, because as compounds can enter and leave as required

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23
Q

what reaction does PDH catalyze?

A

in the oxidative decarboxylation of pyruvate (pyruvate decarboxylation)

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24
Q

how many enzymes is PDH comprised of

name some of the co-enzymes required by PDH

A

3

Thiamine
FAD
NAD
Co-A
lipoic acid

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25
Q

briefly outline the steps involved in the TCA cycle

A

the formation of citric acid
formation of isocitrate
isocitrate oxidative decarboxylation
α-ketoglutarate oxidative decarboxylation
succinate formation
oxidation of succinate
hydration of fumurate
oxidation of malate

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26
Q

two carbon atoms enter the TCA cycle and leave as?

A

2 CO2 molecules

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27
Q

how many of the following molecules does the TCA cycle form?
NADH
FADH
ATP

A

3
1
1

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28
Q

when oxidized, how many ATP molecules would the following form?
NADH
FADH

A

3
2

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29
Q

in total, how many ATP molecules are formed per acetyl-CoA molecule during the TCA cycle

A

12

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30
Q

the first five steps in glycolysis can be termed as

A

the preparatory phase

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31
Q

the last five steps of glycolysis can be termed as

A

the payoff phase

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32
Q

how many irreversible steps are involved in glycolysis, and which steps are these

A

3

step 1
step 3
step 10

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33
Q

what inhibits pyruvate kinase

A

allosterically inhibited by ATP

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34
Q

the function of the PPP

A

generates NADPH
provides the body with pentoses required for the biosynthesis of nucleotides

35
Q

PPP unabbreviated

A

Pentose phosphate pathway

36
Q

where does the PPP take place in the cell

A

the cytoplasm

37
Q

what are the speed and direction of the two irreversible reactions of the PPP determined by

A

the availability of intermediates and how much they are needed

38
Q

how many irreversible reactions is the PPP made of

A

2

39
Q

difference in function between NADH and NADPH

A

NADH used in oxidative phosphorylation while NADPH is used for powering biosynthesis

40
Q

in which cells is the PPP particularly important in

A

cells that synthesise lipids and steroids

41
Q

the products of the two irreversible oxidative reactions of the PPP

A

ribulose-5-phosphate, CO2,2NADPH (for each oxidized glucose)

42
Q

the irreversible oxidative reactions of the PPP are important in the?

A

cells that synthesise fatty acids(like mammary and liver cell)

Adrenal cortex, where
steroid synthesis is dependant on NADPH

Red blood cells, which needs NADPH to keep glutathione in a reduced state

43
Q

briefly describe the irreversible oxidative reactions in the PPP

A

Glucose-6-phosphate is oxidized by NADP to form 6-phosphogluconolactone, under the action of Glucose-6-phosphate dehydrogenase

NADPH is formed

6-phosphogluconolactone is oxidized to form Ribulose-5-phosphate, under the action of 6-phosphogluconate dehydrogenase.

CO2 is formed, and NADP is reduced to form NADPH

44
Q

where do the reversible non-oxidative reactions of the PPP happen

A

all cells that synthesise nucleotides and nucleic acids

45
Q

briefly describe what happens during the reversible non-oxidative reactions of the PPP

A

Ribulose 5-phosphate undergoes isomerisation to ribose 5-phosphate

46
Q

uses for ribulose 5-phosphate

A

for nucleotide biosynthesis
intermediate for glycolysis

47
Q

what is G6PD deficiency

A

lack of the enzyme glucose-6-phosphate dehydrogenase

48
Q

function of G6PD

A

helps red blood cells to produce NADPH

49
Q

effects of G6PD deficiency

A

lack of NADPH, red blood cells will be susceptible to reactive oxygen species and oxidative stress. Therefore, proteins in membranes get oxidized
RBC will be lysed

50
Q

gluconeogenesis

A

The metabolic process by which organisms produce glucose from non-carbohydrate precursors

51
Q

name three sources of glucose

A

diet
glycogenolysis
gluconeogenesis

52
Q

substrates used in gluconeogenesis

A

lactate
amino acids
glycerol

53
Q

name the two enzymes involved in the conversion of pyruvate phosphoenolpyruvate

A

pyruvate carboxylase
PEP Carboxykinase

54
Q

how is pyruvate converted to phosphoenolpyruvate in gluconeogenesis

A

First pyruvate is converted to oxaloacetate via pyruvate carboxylase.- Then, oxaloacetate is converted to PEP via PEP carboxykinase

55
Q

process by which fructose-1,6-bisphosphate is converted to fructose-6-phosphate in gluconeogenesis

A

remove phosphate from fructose 1,6-biphosphate.- This is mediated by: fructose 1,6-biphosphatase

56
Q

process by which glucose-6-phosphate is converted to glucose in gluconeogenesis

A

remove phosphate from
glucose-6-phosphate under the action of glucose-6- phosphatase

57
Q

is the osmotic balance affected by glycogen

A

no

58
Q

glycogenesis

A

a biological process that involves the formation and storage of glycogen

59
Q

where does glycogenesis occur in the cell

A

the cytosol

60
Q

is the cytosol the same as the cytoplasm

A

no
it is the liquid portion of the cytoplasm

61
Q

what is required for glycogenesis to occur

A

D-glucose and energy provided by ATP

62
Q

describe the process of glycogenesis

A

Glucose is phosphorylated to form glucose-6-phosphate. ATP is used, and ADP is formed in this step. This step is catalysed by hexokinase

Glucose-6-phosphate is converted to glucose-1-phosphate, under the action of phosphoglucomutase

G-1-P interacts with UTP to form UDP-glucose, under the action of glucose-1-phosphate uridylyl transferase. PPi is formed in this step

UDP-glucose delivers glucose to growing glycogen. this is catalysed by glycogen synthase. UDP is formed in this step

63
Q

is glycogenolysis a hydrolysis reaction? what enzyme is it catalysed by

A

no, it is a phosphorolysis reaction.
it is catalysed by phosphorylase

64
Q

what does phosphorylase do

A

breaks down alpha 1-4 glycosidic bonds

65
Q

which hormones activate phosphorylase

A

epinephrine
glucagon

66
Q

the preliminary effect of the hormones that activate phosphorylase

A

to enhance the formation of cAMP

67
Q

function of cAMP

A

it initiates a series of reactions that lead to the activation of phosphorylase

68
Q

is the TCA cycle viewed as a closed cycle?

A

no

69
Q

all the intermediates in the TCA cycle are glucogenic. why is this?

A

because the TCA cycle leads to the formation of oxaloacetate which is transformed to PEP, under the action of PEP carboxykinase

70
Q

functions of cholesterol

A

important constituent of cell membranes

serves a precursor to the synthesis of steroid hormones and bile salts

71
Q

beta oxidation

A

Beta-oxidation is a metabolic pathway that occurs in the mitochondria of cells and is responsible for breaking down fatty acids to produce energy in the form of adenosine triphosphate (ATP)

72
Q

requirements for beta oxidation to occur

A

activated acyl-CoA molecules, NAD+, FAD

73
Q

is beta oxidation aerobic or anaerobic

A

it is aerobic

74
Q

in beta oxidation, fatty acids are converted to an active intermediate known as

A

Fatty Acyl-coA

75
Q

where does the activation of fatty acids occur
where does the oxidation of fatty acids occur

A

in the cytosol
in the mitochondria

76
Q

can the Fatty Acyl-CoA pass the mitochondrial membrane
how are they transported into the mitochondria then?

A

no

via translocation by carnitine

77
Q

the process of acyl group translocation

these steps/processes are required for beta oxidation to occur, as fatty acids cannot pass the mitchondrial membrane without it

A

Activation with CoA
Formation of Acylcarnitine
Transport into Mitochondria
Formation of Acyl-CoA in Mitochondria

78
Q

the formation of acyl-CoA is catalysed by?

A

acyl-CoA synthethase

79
Q

function of carnitine palmitoyltransferase I (CPT-I)

this is an enzyme of the outer mitochondrial membrane

A

The enzyme carnitine palmitoyltransferase I (CPT-I) catalyzes the transfer of the acyl group from acyl-CoA to carnitine, forming acylcarnitine.

80
Q

free carnitine is acquired due to it

function of carnitine-acylcarnitine translocase

A

catalyses the transfer of Acylcarnitine into the mitochondrial matrix in exchange for free carnitine

81
Q

function of Carnitine palmitoyltransferase II

this is an enzyme of the inner mitochondria membrane

A

catalyses the transfer of the acyl group from carnitine to CoA

82
Q

in beta oxidation, the fatty acid is cleaved between the …………….. and …………… carbon

A

alpha and beta

83
Q

describe the process of beta oxidation

A

Oxidation that produces FADH2 (acyl-CoA dehydrogenase)

Hydration step (enoyl-CoA hydrolase)

Second oxidation that produces NADH (dehydrogenase)

A thiolytic cleavage that releases a molecule of acetyl-CoA (β-ketothiolase)

84
Q

at which end does the cleavage of the fatty acid in beta oxidation start

A

the carboxylic end

85
Q

the products of each cycle of beta oxidation

A

1 NADH, 1 FADH2 and a molecule of acetyl CoA

PJ1311 YEAR 1 (THE HUMAN BODY) (34 decks)

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