combined chapters carbohydrate, lipid, and protein metabolism
TRANSCRIPT
Combined Combined ChaptersChapters
Carbohydrate, Lipid, and Protein Metabolism
Metabolism | # 2 of 43
Stage 1: Digestion of Carbohydrates
• In the mouth, salivary amylase hydrolyzes a-glycosidic bonds in polysaccharides to give smaller polysaccharides (dextrins), maltose, and some glucose.
• In the small intestine, pancreatic amylase hydrolyzes dextrins to maltose and glucose.
• The disaccharides maltose, lactose, and sucrose are hydrolyzed to monosaccharides.
• The monosaccharides enter the bloodstream for transport to the cells.
Metabolism | # 3 of 43
Summary of carbohydrate digestion in the human body.
Metabolism | # 4 of 43
Section of the small intestine, showing its folds and the villi that cover the inner surface of the folds.
Metabolism
© Ed Reschke / Peter Arnold, Inc.
Metabolism | # 5 of 43
Glycolysis: Splitting Sugar
• In Stage 2, the metabolic pathway called glycolysis degrades glucose (6C) obtained from digestion to pyruvate (3C)
Metabolism | # 6 of 43
Glycolysis: Energy-Investment
In reactions 1-5 of glycolysis:• Energy is used to add phosphate
groups to glucose and fructose• Glucose is converted to two
three-carbon molecules
Metabolism | # 7 of 43
Glycolysis: Energy-Production
• In reactions 7 and 10, the hydrolysis of triose phosphates generates four ATP molecules
Metabolism | # 8 of 43
Step 1: Formation of Glucose 6-phosphateStep 2: Formation of Fructose 6-Phosphate
O
OH
HHH
OH
H
OH OH
H
OP
O
OH
OHO
OH
HHH
OH
H
OH OH
H
OH
O
OH
HHH
OH
H
OH OH
H
OP
O
OH
OH
O
OH
H
OH
OH
H
H
O OHP
O
OH
OH
Step 1Hexokinase
Step 2
phosphoglucoisomerase
ATP ADP
Metabolism | # 9 of 43
Step 3: Formation of Fructose 1,6-bisphosphateStep 4: Formation of Triose Phosphates
O
OH
H
OH
OH
H
H
O OP
O
OH
OH
P
O
OH
OHO
OH
H
OH
OH
H
H
O OHP
O
OH
OH
ATP ADP
Step 3
phosphofructokinase
Aldolase
Step 41
2
34
5
6
1
2
3
4
5
6C C
CO
C
CH2
OH
H
OH
OH
H
H
O OP
O
OH
OH
P
O
OH
OH
CH2
C
CH2
O
O
OH
P
O
OH
OH
+
CH
CH
CH2
O
OH
O P
O
OH
OH
dihydroxyacetonephosphate glyceraldehyde 3-phosphate
Metabolism | # 10 of 43
Step 5: Isomerization of Triose Phosphates
CH2
C
CH2
O
O
OH
P
O
OH
OH
+
CH
CH
CH2
O
OH
O P
O
OH
OH
CH
CH
CH2
O
OH
O P
O
OH
OH
Step 5
Triosephosphate isomerase
2
By the end of Step 5, we have:
1. Used two molecules of ATP so we can
2. Break Glucose (6C) into 2 3C units of glyceraldehyde 3-phosphate
Metabolism | # 11 of 43
Step 6: Formation of 1,3-BisphosphoglycerateStep 7: Formation of 3-Phosphoglycerate
+ 2NAD+ +2Pi
Glyceraldehyde 3-phosphate dehydrogenase
+ 2NADH + 2H+
Step 6
2 2
O O-
OH
O P
O
OH
OH
O O
OH
O P
P
O
OH
OH
O
OH
OH
Step 7
phosphoglycerokinase
2ADP 2ATP
2 2
Metabolism | # 12 of 43
Step 8: Formation of 2-PhosphoglycerateStep 9: Formation of Phosphoenolpyruvate
C
CH
CH2
O O-
O
OH
P
O
OH
OH
O O-
OH
O P
O
OH
OH
C
C
CH
O O-
O
H
P
O
OH
OH
C
CH
CH2
O O-
O
OH
P
O
OH
OH
Step 8
Step 9
phosphoglyceromutase
enolase
2 2
2 2
+2H2O
Metabolism | # 13 of 43
Step 10: Formation of Pyruvate
C
O O-
C
CH3
O
C
C
CH
O O-
O
H
P
O
OH
OH
2 2
pyruvate kinase
2ADP 2ATP
By the end of Step 10, we have:
1. Generated 4 ATP molecules (2 net)
Metabolism | # 14 of 43
Glycolysis: Overall Reaction
• Glycolysis generates 2 ATP and 2 NADH• Two ATP are used in energy-investment to add phosphate
groups to glucose and fructose-6-phosphate• Four ATP are formed in energy-generation by direct
transfers of phosphate groups to four ADP.
Glucose + 2ADP + 2Pi + 2NAD+
2Pyruvate + 2ATP + 2NADH + 4H+
Metabolism | # 15 of 43
Carbohydrate Metabolism
Metabolism | # 16 of 43
Regulation of Glycolysis
• Reaction 1 Hexokinase is inhibited by high levels of glucose-6-phosphate (feedback)
• Reaction 3 Phosphofructokinase, an allosteric enzyme, is inhibited by high levels of ATP and activated by high levels of ADP and AMP
• Reaction 10 Pyruvate kinase, another allosteric enzyme is inhibited by high levels of ATP or acetyl CoA
Metabolism | # 17 of 43
Pathways for Pyruvate
When oxygen is present in the cell, pyruvate from glycolysis is decarboxylated to produce acetyl CoA (enters TCA cycle) and CO2
• Pyruvate + HS-CoA + NAD+ acetyl CoA + CO2 + NADH + H+
Metabolism | # 18 of 43
Lactate Formation
When oxygen is not available, pyruvate is reduced to lactate, which replenishes NAD+ to continue glycolysis
• Pyruvate + NADH + H+ lactate + NAD+
Metabolism | # 19 of 43
Lactate in Muscles
Under anaerobic conditions (strenuous exercise):• Oxygen in the muscles is depleted• Lactate accumulates in the muscles• Muscles tire and become painful• Rest is needed to repay the oxygen debt and to
reform pyruvate in the liver
Metabolism | # 20 of 43
Fermentation
Fermentation:• Occurs in anaeobic microorganisms such as yeast• Decarboxylates pyruvate to acetaldehyde, which is
reduced to ethanol.• Regenerates NAD+ to continue glycolysis
• Pyruvate + NADH + H+ ethanol + NAD+ + CO2
Metabolism | # 21 of 43
All three of the common fates of pyruvate from glycolysis provide for the regeneration of NAD+ from NADH.
Metabolism | # 22 of 43
Structural relationships among glycerol and acetone and the C3 intermediates.
Carbohydrate Metabolism
Metabolism | # 23 of 43
Entry points for fructose and galactose into the glycolysis pathway.
Note: Glycolysis functions in the cytosol.
Metabolism
Metabolism | # 24 of 43
The dihyroxyacetone phosphate-glycerol 3-phosphate shuttle.
Cytosolic NADH can not cross mitochondrial membrane.
Shuttle brings cytosolic electrons into mitochondria in form of mitochondrial FADH2
NADH SHUTTLE
Metabolism | # 25 of 43
The processes of glycogenesis, storage of glucose and glycogenolysis, liberating glucose, are contrasted.
Carbohydrate Metabolism
Metabolism | # 26 of 43
The Cori Cycle
Cori Cycle
Metabolism | # 27 of 43
Metabolism
Metabolism | # 28 of 43
Carbohydrate Metabolism
A diabetic giving himself a blood glucose test.
Saturn Stills / SPL / Photo Researchers
Metabolism | # 29 of 43
The events that must occur before triacylglycerols can reach the bloodstream through the digestive process.
Lipid Metabolism
Metabolism | # 30 of 43
Chylomicron, a type of lipoprotein
Lipid Metabolism
Metabolism | # 31 of 43
Structural characteristics of the adipose cell.
Lipid Metabolism
Metabolism | # 32 of 43
Fatty acids are transported across the inner mitochondrial membrane in the form of acyl carnitine.
Lipid Metabolism
Metabolism | # 33 of 43
Reactions of the fatty acid spiral for an 18:0 fatty acid.
Metabolism | # 34 of 43
Lipids cont’d
Metabolism | # 35 of 43
Summary of protein digestion in human body.
Protein Metabolism
Metabolism | # 36 of 43
Protein Metabolism
Metabolism | # 37 of 43
Possible fates for amino acid degradation products.
Protein Metabolism
Metabolism | # 38 of 43
Key compounds in the transamination / oxidative deamination process include three keto acid/amino acid pairs.
Protein Metabolism
Metabolism | # 39 of 43
The four-step urea cycle.
Metabolism | # 40 of 43
Fates of the carbon skeletons of amino acids.
Protein Metabolism
Metabolism | # 41 of 43
The starting materials for the biosynthesis of the 11 nonessential amino acids.
Protein Metabolism
Metabolism | # 42 of 43
Metabolism | # 43 of 43
Human body response to feasting, fasting, and starving.