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Metabolism II > Session 2 > Flashcards

Session 2 Flashcards

1
Q

Define Cell metabolism

A

Highly integrated network of chemical reactions that occur within cells

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2
Q

What do cells metabolise nutrients for?

A

Energy for cell function
Building block molecules
Organic precursor molecules
Biosynthetic reducing power

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3
Q

Define Catabolism

A

Breakdown of larger molecules into smaller ones

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4
Q

Define Anabolism

A

Smaller molecules are built up into larger ones

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5
Q

What are the properties of Catabolism?

A

Oxidative

Release large amount of energy

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6
Q

What are the properties of Anabolism?

A

Reductive

Uses ATP

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7
Q

Define Exergonic

A

Energy releasing

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8
Q

What is Creatinine Phosphatase

A

A reserve of high energy that can be used immediately. Catalysed by creatine kinase

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9
Q

What are the high energy signals?

A

ATP
NADH
NADPH
FAD2H

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10
Q

What are high energy signals?

A

Signals the cell has adequate energy levels for its immediate needs or reducing power is available for anabolism.

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11
Q

What are 2 important physico-chemical properties of carbohydrates?

A

Hydrophillic

Partially oxidised

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12
Q

What are the properties of Glycogen?

A

Polymer of glucose found in animals. The units join together in alpha-1,4 and alpha-1,6 glycosidic linkages.
Glycogen is highly branched

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13
Q

What are the properties of Cellulose?

A

Found in plants - structural role. Glucose monomers are joined by Beta-1,4 linkages to form long linear polymers.
Humans do not posses the required enzymes to digest Beta-1,4 linkages.

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14
Q

How are dietary Polysaccharides digested?

A

Hydrolysed by glycosidase enzymes. Releases glucose, maltose and leaves dextrins.
Begins in the mouth with salivary amylase and continues in the duodenum with pancreatic amylase.

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15
Q

How are dietary Disaccharides digested?

A

Occurs in the duodenum and jejunum

Glycosidase enzymes involved are attached to the brush border membrane of the epithelial cells lining these regions.

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16
Q

What are the major disaccharide giestion enzymes?

A

Lactase, glycoamylase and sucrase/isomaltase

17
Q

What does a low activity of Lactase cause?

A

Reduced ability to digest the lactose present in milk products - lactose intolerance.

18
Q

Define Glycolysis

A

Central pathway in the catabolism of all sugars. Has 10 enzyme-catalysed steps that occur in the cell cytoplasm

19
Q

What is the function of Glycolysis?

A 
Makes ATP
Makes NADH
Makes molecules for anabolism
No loss of CO2
Glucose oxidised to Pyruvate
Involves substrate level phosphorylation
Exergonic
NET ATP = 2
20
Q

Which steps of Glycolysis are irreversible?

A

1 (Hexokinase, Glucokinase in the Liver), 3 (Phosphofructokinase-1) & 10 (Pyruvate Kinase)

21
Q

How is Lactic acid/Lactate produced?

A

Pyruvate is reduced to lactate by the enzyme lactate dehydrogenase (LDH). In Anaerobic respiration.
LDH increases NAD+ concentrations under anaerobic conditions for Glycolysis to proceed

22
Q

What happens to Lactate?

A

Released into the circulation where it is converted back to Pyruvate and oxidised to CO2 (heart muscle) or converted to glucose (liver)

23
Q

How is Lactate controlled?

A

Usually amount used = amount made

Once >5mM exceeds renal threshold and effects buffering capacity of the plasma = Lactic acidosis

24
Q

Define Galactosaemia

A

Individuals are unable to utilise galactose obtained from the diet because a lack of Galactokinase or Galactose 1-phosphate uridyl transferase

25
Q

How can you tell which enzyme is absent in Galactosaemia?

A

Kinase enzyme - rare, characterised by accumulation of galactose in tissues.
Transferase - more common serious as galactose and Galactose 1-Phosphate (which is toxic to the liver) accumulate in tissues.

26
Q

What does accumulation of Galactose cause?

A

Reduction to Galactitol (aldehyde group reduced to alcohol group) by the activity of the enzyme aldose reductase.
Depletion of NADPH
Cross-linking of lens proteins by S-S bond formation cannot be stopped - cataracts.
Glucomas can occur

Metabolism II (16 decks)

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