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Medicine 1 COPY > Introduction to Metabolism > Flashcards

Introduction to Metabolism Flashcards

1
Q

Metabolic Pathways

A

Enzymatic reactions producing specific products; branched and interconnected

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2
Q

Metabolites

A

Reactants, intermediates & products that vary by cell type, nutritional status and developmental stage

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3
Q

Catabolism

A

Degradative metabolism

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4
Q

Anabolism

A

Biosynthetic metabolism

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5
Q

Which is the rate determining step of metabolic flux

A

The slowest step of a metabolic pathway with the largest -ve gibbs free energy value

They act as dams as they are the most one way reactions

REVISE THIS

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6
Q

Why do many reactions have two different enzymes for the forward and reverse reaction

A

To allow more effective metabolic control and regulation

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7
Q

Energy sources in humans and recommended percentage intake of calories

A

Carbohydrates 55%, fats/lipids 30% and protein 15%

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8
Q

Energy yielded by carbohydrates, proteins and lipids per gram

A

Carbs and proteins (4kcal - 17kJ)

Lipids
9kcal - 37kJ

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9
Q

How does body digest carbohydrates

A

Salivary amylase digests carbohydrates in mouth to oligosaccharides

Further digestion in small intestine by pancreatic enzymes until they become disaccharides (e.g. pancreatic amylase)

Final digestion into monosaccharides by mucosal cells

Glucose taken into cells along with Na+ by active transport

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10
Q

Oligosaccharides

A

Simpler carbohydrates that have three to six units of sugars

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11
Q

Glucose

A

C6H12O6

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12
Q

Which enantiomer of glucose is used in metabolism

A

D Glucose

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13
Q

How can glucose exist

A

Either linearly or as a hexagonal ring (In solution)

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14
Q

Pyranose and Furanose

A

Pyranose - 6 Membered ring structure (e.g. glucose)

Furanose - 5 Membered ring structure (e.g. ribose)

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15
Q

What concentration is glucose generally kept at in the blood

A

5mM

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16
Q

How badly does the brain need/like glucose

A

Badly

17
Q

Why does anaerobic glycolysis lead to the formation of lactate

A

The reduction of pyruvate to lactate is needed to reoxidise NADH that is made in the conversion of glyceraldehyde 3-P into 1,3-Bisphosphoglycerate

18
Q

Na+ independent facilitated diffusion transport

A

One of two main methods for glucose to enter cells

Glucose moves via concentration gradient; binds to glucose transporter protein that allows it into the cell when bound

Various GLUT forms (GLUT 1-14) for the various tissue types
Respond to insulin

19
Q

ATP-Dependent Na+-monosaccharide transport system

A

One of two main methods for glucose to enter cells
Against concentration gradient

Co-transport system

Na+ pumped out of cell against gradient
When Na+ moves along gradient towards transporter; ion causes conformational change that allows it to bind to glucose and brings the sugar and Na+ into the cell

Found in Intestinal epithelial cell

20
Q

Two main stages in glycolysis

A

Energy investment reaction (First 5 reactions)
- Phosphorelates molecules using ATP

Energy Generation Phase

21
Q

How is glucose committed to glycolysis

A

It is phosphorylated to keep it in the cell ready for the reaction to occur

22
Q

Hexokinases

A 
Regulatory enzymes of glycolysis
Different forms (I-III) found in different tissues

Inhibited allosterically by G6P

Low Km to permit efficient phosphorelation of low glucose levels

Low Vmax so no overabundance of G6P

23
Q

Glucokinase

A

Hexokinase IV
In liver parenchymal/β cells

Higher Km so only active after carb rich meal
High Vmax allowing glucose in liver to be maximally absorbed

24
Q

Phosphoglucose Isomerase

A

Reversible enzyme that catalyses the isomerisation of G6P to/from F6P

25
Q

Phosphofructokinase

A

PFK

Irreversible Rate limiting reaction that phosphorylates:
F6P –> F-1,6-BP

High ATP causes inhibition, AMP activates it; Reaction Uses ATP

Allosterically Inhbited by Citrate (TCA intermediate)

26
Q

Aldolase

A

Reversible enzyme catalysing the cleavage reaction of FBP into DiHydroxyAcetone Phosphate (DHAP) and GlycerAldehyde-3-Phosphate (GAP)

27
Q

Triose Phosphate Isomerase

A

Enzyme that reversibly converts DHAP (Dihydroxyacetone Phosphate) into GAP (Glyceraldehyde-3-Phosphate) since only GAP is used in glycolysis

28
Q

Glyceraldehyde-3-Phosphate Dehydrogenase

A

GAPDH

Enzyme that oxidates GAP using NAD+ and Phosphate into 1,3-Bisphosphoglycerate (1,3-BPG) and NADH

29
Q

Phosphoglycerate Kinase

A

Reversible enzyme that synthesises 3-Phosphoglycerate from 1,3-BisphosPhoglycerate and produces ATP via substrate level phosphorelation

2 ATP (from lysis) to ‘repay’ previously used up ATP

30
Q

Phosphoglycerate Mutase

A

Enzyme that reversibly converts 3-phosphoglycerate to 2-phosphoglycerate (figure out what the reaction dumbass)

31
Q

Enolase

A

Reversible enzyme that Redistributes the energy within the molecule by Dehydration

2-Phosphoglycerate to PhosphoEnolPyruvate (high energy intermediate)

32
Q

Pyruvate Kinase

A

3rd Irreversible Enzyme of glycolysis

Forms Pyruvate from Phosphoenolpyruvate through substrate level Phosphorelation (2 more ATP)

33
Q

Lactate Dehydrogenase

A

Reversible enzyme that converts Pyruvate into Lactate and uses up NADH (or NAD in reverse)

Has different Isozymes

34
Q

Energy balance in glycolysis

A

Glucose - G6P (-ATP)
F6P - F1,6bP (-ATP)

2 GAP - 2 1,3bPG (+2NADH)
2 1,3bPG - 3PG (+2ATP)

2 PEP - Pyruvate (+2ATP)

Yields 2 ATP and 2 NADH (which means extra 6 ATP in mitochondria)

35
Q

Haemolytic Anaemia

A

Usually issue with pyruvate kinase

Not generating full amount of ATP needed for blood cells to fuel ion pumps in their membrane that leads to incorrect osmotic flow; strains membrane and forms odd shapes
Spleen sends phagocytes to attack them and thus haemolytic anaemia

Often spleen is removed as treatment
Regular transfusions needed

Medicine 1 COPY (88 decks)

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