Unit 13 Flashcards
What is the structure of ATP?
Adenine
Ribose
3 x phosphate radicals
What are the final products of CHO metabolism? Which is present in the largest quantity?
Glucose - 80%
Fructose
Galactose
What happens to fructose and galactose following absorption from the GIT?
Mostly converted to glucose in the liver
How is the liver able to convert other monosaccharides into glucose?
Large quantity glucose-6-phosphatase
How is glucose transported into cells in the a) GIT, b) kidneys, c) peripheral tissues
A and B - sodium glucose co-transport
C - facilitated diffusion
What happens to glucose following entry into a cell? What enzyme is involved? How does the process differ in the liver/kidneys?
Phosphorylated by hexokinase (glucokinase in liver)
Reversible in liver (not in other cells) - liver cells have glucose phosphatase
Describe glycogenesis
Glucose ==> glucose-6-phosphate ==> glucose-1-phosphate ==>uridine diphosphate glucose ==> glycogen
Describe glycogenolysis
Glycogen ==> glucose-1-phosphate ==> glucose-6-phosphate ==> glucose
In glycolysis, which enzyme is responsible for converting glycogen into glucose-1-phosphate?
Phosphorylase
How is phosphorylase activated?
Epinepherine
Glucagon
Both promote cAMP production
Where is glucagon released?
Alpha cells of pancreas
Describe glycolysis
Glucose ==> 2x pyretic acid
What are the net ingredients and products of glycolysis?
Glucose + 2 ADP + 2 P ==> 2 pyruvic acid + 2 ATP + 4H
What happens to the pyruvic acid formed in glycolysis? What else is formed in this reaction?
Concerted to acetyl-CoA
2 pyruvic acid + 2 CoA ==> 2 acetyl-CoA + 2CO2 + 4H
What happens following acetyl-CoA formation? Where does this reaction take place?
Acetyl degraded to CO2 and H in the CAC
Matrix of mitochondria
What is the net result of the CAC?
2 Acetyl CoA + 6 H20 + 2 ADP ==> 4CO2 + 16H + 2CoA + 2ATP
How many hydrogen ions are produced per glucose molecule?
24
What happens to the H ions produced during CHO metabolism?
20 pair with NAD+
4 pass directly into oxidative process
What happens to H+ produced during CHO metabolism?
Oxidative phosphorylation
Briefly describe oxidative phosphorylation
H split into H+ and e-
e- + H2O => OH-
H+ + OH- => H2O + ATP
Where is ATP produced in the oxidative phosphorylation
process?
ATP synthetase - H+ passes down concentration/electrical gradient in mitochondria through ATPase molecule
How much ATP is formed per glucose molecule metabolised?
38
How is the rate of glycolysis controlled?
ATP and citrate inhibit phosphofructokinase - presently glycolytic pathway
ADP enhance phosphofructokinase
Once all ADP used, further ATP cannot be formed
Describe anaerobic glycolysis
If quantities of pyruvic acid and NADH become excessive, combine with one another to form lactic acid
What happens to lactic acid formed during anaerobic glycolysis?
Converted back to pyruvic acid and NADH once oxygen is available again
What is the alternative pathway of glucose metabolism? Where does it occur? Why is it important?
Pentose phosphate pathway
Liver and adipose
Releases NADP - can be used for fat synthesis
Briefly describe gluconeogenesis
Amino acids and glycerol portion of fat combined to form glucose
What stimulates gluconeogenesis?
Reduced cellular CHO and low BG
ACTH secreted = ^cortisol
Mobilises proteins
What promotes hydrolysis of stored fat?
1 - alpha-glycerophosphate - glucose breakdown product - maintains glycerol portion of triglycerides. When reduced glucose availability - insufficient quantity
2 - hormone sensitive lipase activated
What is the function of a) chylomicrons and b) lipoproteins?
a) Transport lipids from GIT to tissues
b) Transport lipids between tissues
What are the 4 types of lipoproteins? How do they differ in composition?
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
Where are lipoproteins formed?
The liver
Which tissues cannot use fatty acids for energy?
Brain and RBCs
Briefly, how are triglycerides used to produce energy?
Triglyceride hydrolysed
Glycerol - converted to glycerol-3-phosphate - enters glycolytic pathway
Fatty acids - degraded and oxidised in mitochondria - converted into acetyl CoA - beta oxidation
What limit the rate of utilisation of ketone bodies?
Oxaloacetate - product of CHO metabolism needed to bind to acetyl-CoA before it can be processed in the CAC
Why are fats poorly synthesised in diabetes?
Little cellular glucose:
- little acetyl-CoA and NADPH available for fat synthesis
- reduced availability of alpha glycerophosphate
What prevents fat metabolism when excess CHO is available?
- 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
What hormones are most important in promoting fat utilisation?
Ep/NEp => activate hormone sensitive lipase
Cortisol and glucocorticoids => activate HSL
GH => => activate HSL
Thyroid hormone - overall increase in metabolism
What process allows amino acids to be used for energy?
Deamination
Draw a liver lobule
pg 872
What substances encourage hepatic growth?
Hepatocyte growth factor
TNF
IL-6
What substances terminate hepatic growth?
Transforming growth factor beta
How does the liver contribute towards CHO metabolism?
Glycogen storage
Conversion of galactose/fructose to glucose
Gluconeogenesis
Formation of chemical compounds from intermediate products of CHO metabolism
What is the respiratory quotient for the metabolism of CHO?
1.0
What is the respiratory quotient for the metabolism of protein?
0.8
What is the respiratory quotient for the metabolism of fat?
0.7
What is the respiratory quotient?
Ratio or CO2 output to O2 usage
Where are the hunger and satiety centres located?
Hypothalamus
