Metabolism Flashcards by Kelvin Gyan

Name the metabolic pathways

Catabolic
Anabolic
Amphibolic

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anabolic pathway

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

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catabolic pathway

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

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amphibolic pathway

metabolic pathways that have characteristics of both catabolic and anabolic pathways

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

anabolic

catabolic

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metabolism

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

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glycolysis
forms of glycolysis?

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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aerobic glycolysis

what does it form

the breakdown of glucose in the presence of oxygen

Acetyl Co-A

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anaerobic glycolysis

what does it form

the breakdown of glucose in the absence of oxygen

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

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how many pyruvates will be formed per glucose molecule?

2 per glucose

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purpose of glycolysis

to produce intermediates for other biosynthetic pathways

to produce energy

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site of glycolysis

the cytoplasm

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outline the steps of glycolysis

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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what is the TCA cycle also known as

the Krebs cycle

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via which cycle can lactate be turned back into glucose

the Cori cycle

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what are the primary control steps in glycolysis catalyzed by

PFK(phosphofructokinase)
hexokinase
pyruvate kinase

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how is PFK inhibited and by what?

allosterically by ATP

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what inhibits hexokinase

glucose-6-phosphate

note that hexokinase levels increase after PFK inhibition

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TCA cycle unabbreviated

tricarboxylic acid cycle

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is the TCA cycle an aerobic or anaerobic pathway

aerobic pathway

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purpose of TCA cycle

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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outline the steps in generating acetyl COA

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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is the TCA cycle a closed cycle?

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

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what reaction does PDH catalyze?

in the oxidative decarboxylation of pyruvate (pyruvate decarboxylation)

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how many enzymes is PDH comprised of name some of the co-enzymes required by PDH

3 Thiamine FAD NAD Co-A lipoic acid

briefly outline the steps involved in the TCA cycle

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

two carbon atoms enter the TCA cycle and leave as?

2 CO2 molecules

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

3 1 1

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

3 2

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

the first five steps in glycolysis can be termed as

the preparatory phase

the last five steps of glycolysis can be termed as

the payoff phase

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

3 step 1 step 3 step 10

what inhibits pyruvate kinase

allosterically inhibited by ATP

the function of the PPP

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

PPP unabbreviated

Pentose phosphate pathway

where does the PPP take place in the cell

the cytoplasm

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

the availability of intermediates and how much they are needed

how many irreversible reactions is the PPP made of

difference in function between NADH and NADPH

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

in which cells is the PPP particularly important in

cells that synthesise lipids and steroids

the products of the two irreversible oxidative reactions of the PPP

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

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

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

briefly describe the irreversible oxidative reactions in the PPP

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

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

all cells that synthesise nucleotides and nucleic acids

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

Ribulose 5-phosphate undergoes isomerisation to ribose 5-phosphate

uses for ribulose 5-phosphate

for nucleotide biosynthesis intermediate for glycolysis

what is G6PD deficiency

lack of the enzyme glucose-6-phosphate dehydrogenase

function of G6PD

helps red blood cells to produce NADPH

effects of G6PD deficiency

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

gluconeogenesis

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

name three sources of glucose

diet glycogenolysis gluconeogenesis

substrates used in gluconeogenesis

lactate amino acids glycerol

name the two enzymes involved in the conversion of pyruvate phosphoenolpyruvate

pyruvate carboxylase PEP Carboxykinase

how is pyruvate converted to phosphoenolpyruvate in gluconeogenesis

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

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

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

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

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

is the osmotic balance affected by glycogen

glycogenesis

a biological process that involves the formation and storage of glycogen

where does glycogenesis occur in the cell

the cytosol

is the cytosol the same as the cytoplasm

no it is the liquid portion of the cytoplasm

what is required for glycogenesis to occur

D-glucose and energy provided by ATP

describe the process of glycogenesis

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

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

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

what does phosphorylase do

breaks down alpha 1-4 glycosidic bonds

which hormones activate phosphorylase

epinephrine glucagon

the preliminary effect of the hormones that activate phosphorylase

to enhance the formation of cAMP

function of cAMP

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

is the TCA cycle viewed as a closed cycle?

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

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

functions of cholesterol

important constituent of cell membranes serves a precursor to the synthesis of steroid hormones and bile salts

beta oxidation

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)

requirements for beta oxidation to occur

activated acyl-CoA molecules, NAD+, FAD

is beta oxidation aerobic or anaerobic

it is aerobic

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

Fatty Acyl-coA

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

in the cytosol in the mitochondria

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

no via translocation by carnitine

the process of acyl group translocation ## Footnote these steps/processes are required for beta oxidation to occur, as fatty acids cannot pass the mitchondrial membrane without it

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

the formation of acyl-CoA is catalysed by?

acyl-CoA synthethase

function of carnitine palmitoyltransferase I (CPT-I) ## Footnote this is an enzyme of the outer mitochondrial membrane

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

# free carnitine is acquired due to it function of carnitine-acylcarnitine translocase

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

function of Carnitine palmitoyltransferase II ## Footnote this is an enzyme of the inner mitochondria membrane

catalyses the transfer of the acyl group from carnitine to CoA

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

alpha and beta

describe the process of beta oxidation

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)

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

the carboxylic end

the products of each cycle of beta oxidation

1 NADH, 1 FADH2 and a molecule of acetyl CoA

Metabolism Flashcards

(86 cards)