1. CARBOHYDRATE METABOLISM
Dr. Madushani Silva
(MBBS) North Colombo Teaching Hospital – Ragama

2. Metabolism
Metabolism is all the chemical reactions that occur in an organism

3. Anabolism Performance of structural maintenance and repairs
Support of growth
Production of secretions
Building of nutrient reserves

4. Catabolism
Breakdown of nutrients to provide energy (in the form of ATP) for body processes
Nutrients directly absorbed
Stored nutrients

5. Cellular metabolism
Cells break down excess carbohydrates first, then lipids, finally amino acids if energy needs are not met by carbohydrates and fat
Nutrients not used for energy are used to build up structure, are stored, or they are excreted

6. Cells and Mitochondria
Cells provide small organic molecules to mitochondria
Mitochondria produce ATP used to perform cellular functions

7. Carbohydrate Metabolism
Primarily glucose
Fructose and galactose enter the pathways at various points
All cells can utilize glucose for energy production
Glucose uptake from blood to cells usually mediated by insulin and transporters

8. Liver is central site for carbohydrate metabolism
Glucose uptake independent of insulin
The only exporter of glucose

9. Cellular Respiration

10. Cellular Respiration
Is a series of reactions where fats, proteins, and carbohydrates, mostly glucose, are broken down to make CO2, water, and energy.

11. Cellular Respiration
Cellular Respiration uses oxygen and glucose to produce
Carbon dioxide, water, and ATP.

12. Cellular Respiration
Glucose
Oxygen gas
Carbon dioxide
Water
Energy

13. How efficient is cell respiration?
Energy released from glucose banked in ATP
Energy released from glucose (as heat and light)
Gasoline energy converted to movement
100%
About 40%
25%
Burning glucose in an experiment
“Burning” glucose in cellular respiration
Burning gasoline in an auto engine

14. Cellular Respiration
The Stages of Cellular Respiration Cellular respiration has two stages.
Glycolysis
Aerobic and Anaerobic Respiration

15. Cellular Respiration
Glycolysis The first stage of cellular respiration is called glycolysis.
Aerobic and Anaerobic Respiration aerobic respiration
(in the presence of oxygen)
anaerobic respiration
(in the absence of oxygen) 12

16. Glycolysis General Outline Glucose Pyruvic Acid No Oxygen Anaerobic
Transition Reaction
Fermentation
Krebs Cycle
ETS
36 ATP

17. General Outline of Aerobic Respiration
Glycolysis
Transition Reaction
Krebs Cycle
Electron Transport System

18. Overview of Aerobic Respiration

19. Cellular Respiration Stage One: Breakdown of Glucose
Glycolysis Glucose is broken down to pyruvate during glycolysis, making some ATP. 13

20. Glycolysis
Sequence of reactions that converts glucose into pyruvate

21. 1 1 2 3 4 5 6 7 8 9 10

22. Energy Balance Sheet for the Oxydation of Glucose via Glycolysis
Gains:
4 ATP
2 pyruvate
2 NADH + H+
Losses:
2ATP
Glucose
Phosphate
NAD+ (recycled)
Net Gain:
+ 2 ATP
Mitochondria for further oxidation via the TCA/Krebs cycle

24. Cellular Respiration Stage Two: Production of ATP
Krebs Cycle The Krebs cycle is a series of reactions that produce energy-storing molecules during aerobic respiration.
Electron Transport Chain During aerobic respiration, large amounts of ATP are made in an electron transport chain. 14

25. The Fate of PYRUVATE Taken into mitochondria Broken down to ACETATE
CO2 produced
Binds to large protein Coenzyme A to produce acetyl Coenzyme A

28. The TCA or KREBS CYCLE
CO2
NADH & FADH
2 more ATP

31. 3rd alternative pathway… Electron Transport Chain
Mitochondria and
O2 needed
Uses NADH and FADH produced in previous reactions
To make more ATP

32. NADH
FAHD

33. What is NADH?? FADH??
ENERGY CARRIER!
Same for FADH
Carrier to…?

35. Electron Transport System
ETS (cytochrome chain) is a series of reduction/oxidation reactions
Enzymes embedded in mitochondrial membranes

36. ETS makes
how much ATP??

38. cytoplasm
mitochondria

40. Fermentation in the Absence of Oxygen
Fermentation When oxygen is not present, fermentation follows glycolysis, regenerating NAD+ needed for glycolysis to continue.
Lactic Acid Fermentation In lactic acid fermentation, pyruvate is converted to lactate. 15

41. Fermentation

42. Glycogenolysis
The process by which glucose is released from the liver

43. Fate of Glucose Synthesis and breakdown occur at all times
Fed state
Storage as glycogen
Liver
Skeletal muscle
Storage as lipids
Adipose tissue
Fasted state
Metabolized for energy
New glucose synthesized
Synthesis and breakdown occur at all times
regardless of state...
The relative rates of synthesis and breakdown change

44. THE LIVER
The liver is an important organ in blood glucose homeostasis

45. Blood glucose homeostasis
-THE LIVER
After feeding (stores some excess glucose as glycogen)
In the fasted state (through glycogenolysis and gluconeogenesis, maintains blood glucose levels)

46. THE LIVER The hepatic uptake and output of glucose is controlled by:
the concentration of key intermediates, and
The activity of enzymes.

48. HORMONES
Insulin
Glucagon

49. Blood glucose homeostasis
Insulin
-Insulin is synthesized by the B (or β) cells in the pancreas.
-Glucose stimulates insulin release

50. Blood glucose homeostasis
Insulin
-Insulin is an anabolic hormone which
stimulates:
- glucose uptake by muscle and adipose tissue, and increases:
protein synthesis,
glycogen synthesis
lipogenesis.

51. Blood glucose homeostasis
Glucagon
-Glucagon is synthesized in the A (or α) cells of the pancreas.
-Inhibited by glucose and insulin
-Glucagon stimulates:
glycogenolysis and
gluconeogenesis (raising blood glucose concentrations).

52. PANCREASE

55. -Muscle has a higher rate of fuel utilization than other organs during exercise.
-The brain, kidney and intestine utilize a higher percentage of available glucose at rest.
-Alternative fuels are required during prolonged fasting or starvation

56. immediately after eating a meal…
High Blood Glucose
Glucose absorbed
Insulin
Pancreas
Muscle
Adipose
Cells
Glycogen
immediately after eating a meal…

57. Fate of Absorbed Glucose
1st Priority: glycogen storage
Stored in muscle and liver
2nd Priority: provide energy
Oxidized to ATP
3rd Priority: stored as fat
Only excess glucose
Stored as triglycerides in adipose

58. Glucose Utilization Adipose Glycogen Glucose Ribose-5-phosphate
Energy Stores
Glycogen
Glucose
Pentose Phosphate Pathway
Glycolysis
Ribose-5-phosphate
Pyruvate

59. Glucose Utilization Adipose Glycogen Glucose Ribose-5-phosphate
Energy Stores
Glycogen
Glucose
Pentose Phosphate Pathway
Glycolysis
Ribose-5-phosphate
Pyruvate

60. The importance of regulating blood glucose levels !

61. Glucose: Obligate fuel for CNS & RBC’s
CNS/Brain
Dependent on glucose as primary source of fuel
Uses ~120g glucose/day of total g/d
RBC
Dependent on glucose
Lack mitochondria

62. Anabolic in response to hyperglycemia
Liver
Stimulates glycogen synthesis, glycolysis, and fatty acid synthesis
Muscle
Stimulates glycogen synthesis

63. Anabolic in response to hyperglycemia
Adipose
Stimulates lipoprotein lipase resulting in uptake of fatty acids from chylomicrons and VLDL
Stimulates glycolysis for glycerol phosphate synthesis (precurser to triglycerides)

64. Figure 9-1 Role in insulin in lowering blood glucose

65. Catabolic, in response to hypoglycemia
Liver
Activates glycogen degradation, gluconeogenesis
Adipose
Stimulates lipolysis and release of fatty acids

66. Figure 9-2 Role of glucagon in increasing blood glucose levels

67. Diabetes- What is it?
Body is not producing or has lost sensitivity to insulin.
Insulin is a hormone that is needed to convert sugar, starches and other food into energy.
Insulin is produced in the body by the pancreas.

68. Vad happens to the carbohydrates from the food?
Stored sugar in the liver (glycogen)
Insulin from the pancreas
- - -
Fat/muscle cell
Carbohydrates from food

69. A healthy cell Blood Urine test shows vessel 0 0 Cell Insulin O2 CO2
Water
Energy
Glucose Ketones

70. Starvation Blood Urine test shows vessel 0 + Cell (Insulin) in liver
Fatty acids
Ketones
Glucose Ketones

71. Diabetes - lack of insulin
Cell
Blood
vessel
Urine test shows
in liver
Fatty acids
Ketones
Glucose Ketones

72. Type I Usually diagnosed in children and young adults.
Must take daily insulin shots to stay alive.
Type I accounts for 5-10% of the population with diabetes.

73. Type II The most common form of the disease.
Approximately 50% of men and 70% of women are obese at the time of diagnosis.
Nearing epidemic proportions, due to increase # of older Americans, greater occurrence of obesity and sedentary lifestyles.

74. Types of Diabetes
Secondary - a consequence from another disease. For example, pancreatitis or cystic fibrosis.
Gestational Diabetes- diabetes during pregnancy.
Impaired Glucose Tolerance- an intermediate between normal and diabetes.

76. Questions ?

77. Thank you