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Guyton > Unit 13 > Flashcards

Unit 13 Flashcards

1
Q

What is the structure of ATP?

A

Adenine
Ribose
3 x phosphate radicals

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2
Q

What are the final products of CHO metabolism? Which is present in the largest quantity?

A

Glucose - 80%
Fructose
Galactose

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3
Q

What happens to fructose and galactose following absorption from the GIT?

A

Mostly converted to glucose in the liver

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4
Q

How is the liver able to convert other monosaccharides into glucose?

A

Large quantity glucose-6-phosphatase

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5
Q

How is glucose transported into cells in the a) GIT, b) kidneys, c) peripheral tissues

A

A and B - sodium glucose co-transport
C - facilitated diffusion

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6
Q

What happens to glucose following entry into a cell? What enzyme is involved? How does the process differ in the liver/kidneys?

A

Phosphorylated by hexokinase (glucokinase in liver)
Reversible in liver (not in other cells) - liver cells have glucose phosphatase

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7
Q

Describe glycogenesis

A

Glucose ==> glucose-6-phosphate ==> glucose-1-phosphate ==>uridine diphosphate glucose ==> glycogen

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8
Q

Describe glycogenolysis

A

Glycogen ==> glucose-1-phosphate ==> glucose-6-phosphate ==> glucose

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9
Q

In glycolysis, which enzyme is responsible for converting glycogen into glucose-1-phosphate?

A

Phosphorylase

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10
Q

How is phosphorylase activated?

A

Epinepherine
Glucagon

Both promote cAMP production

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11
Q

Where is glucagon released?

A

Alpha cells of pancreas

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12
Q

Describe glycolysis

A

Glucose ==> 2x pyretic acid

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13
Q

What are the net ingredients and products of glycolysis?

A

Glucose + 2 ADP + 2 P ==> 2 pyruvic acid + 2 ATP + 4H

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14
Q

What happens to the pyruvic acid formed in glycolysis? What else is formed in this reaction?

A

Concerted to acetyl-CoA
2 pyruvic acid + 2 CoA ==> 2 acetyl-CoA + 2CO2 + 4H

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15
Q

What happens following acetyl-CoA formation? Where does this reaction take place?

A

Acetyl degraded to CO2 and H in the CAC
Matrix of mitochondria

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16
Q

What is the net result of the CAC?

A

2 Acetyl CoA + 6 H20 + 2 ADP ==> 4CO2 + 16H + 2CoA + 2ATP

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17
Q

How many hydrogen ions are produced per glucose molecule?

A

24

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18
Q

What happens to the H ions produced during CHO metabolism?

A

20 pair with NAD+
4 pass directly into oxidative process

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19
Q

What happens to H+ produced during CHO metabolism?

A

Oxidative phosphorylation

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20
Q

Briefly describe oxidative phosphorylation

A

H split into H+ and e-
e- + H2O => OH-
H+ + OH- => H2O + ATP

21
Q

Where is ATP produced in the oxidative phosphorylation
process?

A

ATP synthetase - H+ passes down concentration/electrical gradient in mitochondria through ATPase molecule

22
Q

How much ATP is formed per glucose molecule metabolised?

A

38

23
Q

How is the rate of glycolysis controlled?

A

ATP and citrate inhibit phosphofructokinase - presently glycolytic pathway
ADP enhance phosphofructokinase
Once all ADP used, further ATP cannot be formed

24
Q

Describe anaerobic glycolysis

A

If quantities of pyruvic acid and NADH become excessive, combine with one another to form lactic acid

25
Q

What happens to lactic acid formed during anaerobic glycolysis?

A

Converted back to pyruvic acid and NADH once oxygen is available again

26
Q

What is the alternative pathway of glucose metabolism? Where does it occur? Why is it important?

A

Pentose phosphate pathway
Liver and adipose
Releases NADP - can be used for fat synthesis

27
Q

Briefly describe gluconeogenesis

A

Amino acids and glycerol portion of fat combined to form glucose

28
Q

What stimulates gluconeogenesis?

A

Reduced cellular CHO and low BG
ACTH secreted = ^cortisol
Mobilises proteins

29
Q

What promotes hydrolysis of stored fat?

A

1 - alpha-glycerophosphate - glucose breakdown product - maintains glycerol portion of triglycerides. When reduced glucose availability - insufficient quantity
2 - hormone sensitive lipase activated

30
Q

What is the function of a) chylomicrons and b) lipoproteins?

A

a) Transport lipids from GIT to tissues
b) Transport lipids between tissues

31
Q

What are the 4 types of lipoproteins? How do they differ in composition?

A

VLDLs - high concentration triglycerides, moderate cholesterol and phospholipids
IDLs - some triglycerides removed
LDLs - almost all triglycerides removed
HDLs - high concentration protein, smaller concentration cholesterol/phospholipids

32
Q

Where are lipoproteins formed?

A

The liver

33
Q

Which tissues cannot use fatty acids for energy?

A

Brain and RBCs

34
Q

Briefly, how are triglycerides used to produce energy?

A

Triglyceride hydrolysed
Glycerol - converted to glycerol-3-phosphate - enters glycolytic pathway
Fatty acids - degraded and oxidised in mitochondria - converted into acetyl CoA - beta oxidation

35
Q

What limit the rate of utilisation of ketone bodies?

A

Oxaloacetate - product of CHO metabolism needed to bind to acetyl-CoA before it can be processed in the CAC

36
Q

Why are fats poorly synthesised in diabetes?

A

Little cellular glucose:
- little acetyl-CoA and NADPH available for fat synthesis
- reduced availability of alpha glycerophosphate

37
Q

What prevents fat metabolism when excess CHO is available?

A
  • Excess CHO = excess alpha-glycerophosphate - binds FFA in form of stored triglycerides
  • Excess CHO = excess acetyl-CoA and low quantities FFA - favours FFA formation
  • Acetyl-CoA-carboxylase - controls rate of acetyl CoA => malonyl CoA for FA synthesis. Activity accelerated in presence of CAC intermediates
38
Q

What hormones are most important in promoting fat utilisation?

A

Ep/NEp => activate hormone sensitive lipase
Cortisol and glucocorticoids => activate HSL
GH => => activate HSL
Thyroid hormone - overall increase in metabolism

39
Q

What process allows amino acids to be used for energy?

A

Deamination

40
Q

Draw a liver lobule

A

pg 872

41
Q

What substances encourage hepatic growth?

A

Hepatocyte growth factor
TNF
IL-6

42
Q

What substances terminate hepatic growth?

A

Transforming growth factor beta

42
Q

How does the liver contribute towards CHO metabolism?

A

Glycogen storage
Conversion of galactose/fructose to glucose
Gluconeogenesis
Formation of chemical compounds from intermediate products of CHO metabolism

42
Q

What is the respiratory quotient for the metabolism of CHO?

A

1.0

42
Q

What is the respiratory quotient for the metabolism of protein?

A

0.8

43
Q

What is the respiratory quotient for the metabolism of fat?

A

0.7

43
Q

What is the respiratory quotient?

A

Ratio or CO2 output to O2 usage

44
Q

Where are the hunger and satiety centres located?

A

Hypothalamus

Guyton (10 decks)

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