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ACVIM Generals Revision MS > Metabolism > Flashcards

Metabolism Flashcards

1
Q

What is the basic reaction by which food is converted to ATP?

A

Oxidation

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2
Q
  1. Which enzyme(s) are responsible for initial glucose phosphorylation after entry into the cell?
  2. Which enzyme reverses this reaction?
A
  1. Glucokinase - liver

Hexokinase - other tissues

  1. Glucose-6-phosphatase
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3
Q

GLYCOGENESIS

A

glucose 6-phosphate is converted to glucose-1-phosphate and then uridine diphosphate glucose before becoming glycogen.

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4
Q

Which is the important enzyme involved in glycogenolysis?

A

Glycogen phosphorylase

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5
Q

How many moles of ATP are formed from a single mole of glucose?

A

38

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6
Q

What is the end product of the glycolytic pathway?

A

Two pyruvic acid molcules

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7
Q

How many ATPs are formed from glycolysis?

A

4 are formed but 2 are required in the initial phosphorylation of glucose so the net gain is two ATP

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8
Q

What vitamin is acetyl-CoA a derivative of?

A

Vitamin B5 - patothenic acid

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9
Q

What is the net reaction of the CAC following the processing of one molecule of glucose?

A
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10
Q

What is the starting molecule of the CAC?

A

Oxaloacetate

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11
Q

Which vitamin is required to form NADH?

A

Nicotinamide (vitamin B3)

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12
Q

What group of enzymes splits hydrogen from substrates in glucose breakdown pathways?

A

Dehydrogenases

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13
Q

What group of enzymes splits away CO2 in the various glucose breakdown pathways?

A

Decarboxylases

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14
Q

What is oxidation vs. reduction?

A

Oxidation = removal of electrons

Reduction = addition of electrons

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15
Q

What is the role of cytochrome oxidase in the electron transport chain?

A

To reduce oxgen by combining it with H20.

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16
Q

Summarise ATP formation during the breakdown of glucose

A
  1. Glycolysis - formation of net 2 ATP
  2. CAC - 2 ATP
  3. 24 hydrogens produced from the above, which are then oxidised in the mitochondrial chemiosmotic mechanism.

= 38 ATP molecules

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17
Q

What is the importance of the enzyme phosphofructokinase in the glucose metabolic pathway?

A

It is involved in the formation of fructose 1,6-diphosphate (early stage in glycolysis).

PPK can be inhibited by ATP and this represents a feedback mechanism by which cellular energy metabolism is regulated.

Citrate also inhibits PPK

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18
Q

What are the most common fatty acids present in human triglycerides?

A
  1. Stearic acid
  2. Oleic acid
  3. Palmitic acid
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19
Q

What is the plasma T½ of a chylomicron?

A

Approz. 1h

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20
Q

What is the role of lipoprotein lipase and where is it located?

A

Its role is to release triglycerides from chylomicrons so that they can diffuse into cells.

Location = capillary wall (particularly of adipose tissues)

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21
Q

What is the role of apoliprpteins (e.g. Apo E and Apo B) in lipid metabolism?

A

They mediate clearance of chylomicron remnants from the blood by the liver.

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22
Q

Which type of lipoproteins transport TG to the following:

  1. Adipose tissue
  2. Liver
A
  1. VLDL transport TG to adipose tissue
  2. IDL transported to liver in an ApoE mediated process and LDLs are trasported by ApoB mediated transport
23
Q

What are the liver’s roles in fat metabolism?

A
  1. Generation of energy from triglycerides
  2. Synthesis of fatty acids from carbodydrates +/- amino acids
  3. Production of other lipid compounds e.g. cholesterol and phospholipids from fatty acids
24
Q

Which molecule is required to transport fatty acids into the mitochondria prior to beta-oxidation?

A

Carnitine

Carnitine is a derivative of lysine

25
Q

What are the end products of each cycle of beta-oxidation of fatty acids?

A

Acetyl-CoA and 4H+

26
Q

How is acetoacetic acid formed chemically?

A

2xacetyl-CoA + H2O

27
Q

What ketones are detected by a urine dipstick pad?

A

Predominantly acetoacetate and acetone

28
Q

What are the three main steps in TG synthesis from excess carbohydrate?

A
  1. Formation of melanyl-CoA from acetyl-CoA by acetly-CoA carboxylase
  2. The above starts to form a fatty acid which is elongated by the addition of succusive acetyl-CoA molecules using NADPH and H+
  3. Glycerol is synthesised from alpha-glycerophosphate (a product of glycolysis)
29
Q

Which phospholipid is choline required for the syntehsis of?

A

Sphingomyelin (amoung others)

30
Q

Which phospholipids is inositol involved in the synthesis of?

A

Cephalins

31
Q

List 5 main processes phospholipids are required for

A
  1. Formation of cell membranes
  2. Formation of lipoproteins
  3. Nervous development/funciton (sphinomyelin)
  4. Thromboplastin formation (cephalin)
  5. Chemical reactions - donation of phosphate radicals
32
Q

Which enzyme is responsible for cholesterol synthesis?

A

3-hydroxy-3-methylglutaryl CoA reductase

33
Q

Which enzyme is required for the transformation of one amino acid into another?

A

Aminotransferase (aka. transainase)

34
Q

Which amino acids can be used in transamination?

A

Asparaginine
Aspartic acid
Glutamine

35
Q

Which vitamin is important in the formation of transaminases?

A

Vitamin B6 - pyroxidine

36
Q

What are the main amino acids found in the urea cycle?

A

Ornithine
Citrulline
Arginine - this is actually the only one on the list of the 20 amino acids in the human body.

37
Q

What are Kupffer cells?

A

Reticuloendothelial cells of the liver (macrophages).

38
Q

The presence of which compoud in the liver allows storage of iron?

A

Apoferritin + Fe –> ferritin

39
Q

Explain the formation and excretion of bilirubin

A
40
Q

Where are the feeding and satiety centres of the hypothalamus located?

A

Feeding centre = lateral nuclei

Satiety centre = ventromedial nuclei.

41
Q

What are the main neurons in the arcuate nucleus of the hypothalamus that result in increased/decreased hunger signals?

A
  1. Increase: agouti-related protein (AGRP) and neuropeptide Y producing neurons
  2. Decrease: proopiomelanocortin (POMC) and cocain-amphetamine related transcript (CART) neurons -these produce alpha-MSH.
42
Q

Which MCRs are most important in the regulation of feeding behaviours?

What is the effect of activation of these receptors?

A

MCR-3 and MCR-4

MCR-3 is present on POMC/CART (increases activity) and NYP/AGRP (decreases activity) neurons

MCR-4 is presnt in the paraventricular nucleas of the hypothalamus

These effects all act to decrease appetite.

43
Q

Where is MCR-4 activated with regards to its role in energy expenditure?

A

The PVN of the hypothalamus is where the MCR-4 receptor is present and to some degree it is present int the nucleus tractus solitarius.

44
Q

What is thought to be the role of AGRP in hunger signalling?

A

It antagonises the MCR-4 receptor.

45
Q

Which neurotransmitter is released to increase hunger? Which receptor does it act on?

A

Neuropeptide Y (NYP), the NYP1

46
Q

Ways in which leptin may impact on energy storage

A

Inhibition of the feeding centre and stimulation of the satiety centre

Increase production of CRH (an anorexigenic hormone)

Increase sympathetic tone (increasing BMR)

Decrease insulin production (reducing energy storage)

47
Q

What is the enzyme that activates the vitamin K dependent co-facotors?

Bonus = what is the action of this enzyme?

A

Carboxylase epoxidase

Carboxylates glutamic acid residues on inactive coagulation factors. (II, VII, IX, X, C, S, Z)

48
Q

How much of bodily iron (as a fraction) is in the form of haemoglobin?

A

2/3

49
Q

Michaelis-Menten equation

A
50
Q

Which area of the hypothalamus detects temperature changes?

A

Temperature sensitive neurons in the anterior pre-optic area

51
Q

Which area of the hypothalamus integrates temperature sensing afferents?

A

The posterior hypothalamus

52
Q

Where in the brain is the motor centre for shivering located?

A

Dorsomedial hypothalamus next to the wall of the third ventricle

53
Q

Which interleukin is important in increasing the hypothalamic set point in fever?

A

IL-1

ACVIM Generals Revision MS (32 decks)

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