1. Chapter 27 Nutrition and Metabolism

2. Overview: Nutrition and Metabolism
Nutrition: food (nutrients) humans eat
Malnutrition— a deficiency of food, vitamins, and minerals
Categories of nutrients
Macronutrients— nutrients needed in large amounts (bulk nutrients)
Macromolecules such as carbohydrates, fats (lipids), and proteins
Water
Macrominerals
minerals needed in large quantity
for example, sodium, chloride, and calcium
Micronutrients— nutrients needed in very small amounts
Vitamins
Microminerals (trace elements)
minerals such as iron, iodine, zinc, that are needed only in very small quantities

3. Metabolism Metabolism: “use of food” the use of nutrients
a process made up of many chemical processes
Catabolism- breaks food down into smaller molecular compounds and releases two forms of energy— heat and chemical energy
Anabolism— a synthesis process
Occur constantly
Chemical energy released by catabolism must be transferred to ATP, which is used in the cells

4. Chemical Energy in Food
How much energy is in food?
When 1 gram of glucose (C6H12O6) is burned in the presence of oxygen, 3811 calories are released.
What is a calorie? A calorie is the amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius.
On a food label Calories (with a capital “C”) represent kilocalories. 1 kilocalorie = 1000 calories.
Cells use the energy in glucose by slowly releasing it.

5. Carbohydrates Dietary sources of carbohydrates Complex carbohydrates
Polysaccharides— starches
found in vegetables and grains
glycogen is found in meat
Cellulose
a component of most plant tissue
passes through the digestive system without being broken down
Fiber, “roughage”

6. Carbohydrates Disaccharides— found in refined sugar
must be broken down before they can be absorbed
Monosaccharides— found in fruits
move directly into the internal environment without being processed directly
Glucose
carbohydrate most useful to the human cell
can be converted from other monosaccharides

7. Know for test!

8. Carbohydrates
Carbohydrate metabolism— human cells catabolize most of the carbohydrate absorbed and anabolize a small portion of it
Glycolysis— the first process of carbohydrate catabolism
of a series of chemical reactions (Figure 27-3)
Glycolysis occurs in the cytoplasm of all human cells
An anaerobic process— provides cells with energy under conditions of inadequate oxygen
It breaks down chemical bonds in glucose molecules and releases about 5% of the energy stored in them
It prepares glucose for the 2nd step in
catabolism: the citric acid cycle
Produces 2 pyruvic acid, 2 (net) ATP,
and 2 NADH!

9. FYI!

10. Carbohydrate metabolism
Citric acid cycle
formerly called Krebs cycle after Sir Hans Krebs, who discovered this process
By the end of the reactions of the citric acid cycle, two pyruvic acids have been broken down to 6 carbon dioxide, 6 NADH, 2 FADH2 and 6 water molecules (Figures 27-4 and 27-5)

11. FYI!

12. Know for test!

13. DING! The magical world of electron transport!
What purpose is the NADH and FADH2?
Electron transport chain (or system) in the mitochondria
These molecules are very HIGH ENERGY!
In the mitochondria, for every:
NADH  3 ATP
FADH2  2 ATP

14. Carbohydrate metabolism
Electron transport chain (ETC) (Figure 27-6)
NADH and FADH2 removed during CAC enter a chain of molecules that are embedded in the inner membrane of the mitochondria
As electrons move down the chain, they release small bursts of energy to pump protons between the inner and the outer membrane of the mitochondrion
Protons move down their concentration gradient and across the inner membrane, driving ATP-synthase
Oxidative phosphorylation— the joining of a phosphate group to ADP (di) to form ATP (tri) by the action of ATP synthase

15. Must understand the concept but not the names of the proteins (except ATP synthase)

16. ATP Synthase

17. Carbohydrate Metabolism
The anaerobic pathway- Lactic Acid Fermentation
Without O2
a pathway for the catabolism of glucose
transfers energy to ATP using only glycolysis
Converts NADH back to NAD+
paying the “oxygen debt”- Box 27-4

18. Oxygen uptake during and after exercise

19. Glucose Use Glycogenesis
Glucose join together  strand of glucose beads = glycogen
a process that operates when the blood glucose level increases above the midpoint of its normal range (Figures 27-11)
Glycolysis—the first process of carbohydrate catabolism
in cytoplasm of all human cells
An anaerobic process
It breaks down chemical bonds in glucose molecules and releases about 5% of the energy stored in them
It prepares glucose for the second step in catabolism—the citric acid cycle

20. Control of Glucose Metabolism
Hormonal and neural devices maintain homeostasis of blood glucose concentration
Insulin
secreted by beta cells in pancreas
decreases blood glucose level
Glucagon
Secreted by alpha cells in pancreas
Breaks down glycogen only in liver 
increases blood glucose level
Epinephrine
hormone secreted in times of stress by adrenal medulla
Breaks down glycogen in liver AND muscles  increases blood glucose level

21. Control of Glucose Metabolism
Adrenocorticotropic hormone (ACTH)
stimulates adrenal cortex to increase its secretion of glucocorticoids
Glucocorticoids accelerate gluconeogenesis
Gluconeogenesis is the formation of new glucose from proteins and fats
Increases blood glucose levels
Growth hormone
Made by pituitary
increases blood glucose level by shifting from carbohydrate to fat catabolism

23. Carbohydrate Metabolism
Hormones that cause the blood glucose level to rise are called hyperglycemic
Insulin is hypoglycemic because it causes the blood glucose level to decrease

25. Lipids Dietary sources of lipids Triglycerides
the most common lipids
Composed of a glycerol subunit that is attached to 3 fatty acids
Phospholipids— an important lipid found in all foods
Cholesterol— an important lipid found only in animal foods
Used in cell membrane
Dietary fats
Saturated fats contain no double bonds
Unsaturated fats contain some double bonds

26. Lipids Lipoproteins and fatty acids are transported in the blood
95% of lipids are in the form of lipoproteins
Consists of lipids + protein
Formed in the liver
Blood contains 3 types of lipoproteins
very low density
Low Density (LDL)
High Density (HDL)
Cholesterol lipoproteins associated with heart disease

27. Proposed Functions of Lipoproteins
Some people have very few LDL receptors on the surface of their cells and cannot store excess cholesterol inside the cell so it accumulates in the blood
High levels of LDL leads  high risk of atherosclerosis (“hardening” of the arteries)  high risk for heart attack or stroke

28. Proposed Functions of Lipoproteins
High HDL levels  low risk of atherosclerosis
HDL binds to the surface of a cell and stimulates the release of cholesterol which HDL takes to the liver for excretion
High LDL (>180mg)- lots of cholesterol is being delivered
High HDL (>60mg)- lots of cholesterol is being removed

29. Omega-3 fatty acids
An essential fatty acid- our body is unable to produce polyunsaturated fats so we must eat them in order to obtain them
Fish contain this fat in their cell membranes
This is what causes fish from very cold areas to be oily and not freeze
“fish oil”
Examples: salmon, herring, trout

30. Lipids Lipid metabolism Lipid catabolism Lipid anabolism
beta-oxidation  acetyl-CoA  citric acid cycle
Lipid anabolism
lipogenesis
Control of lipid metabolism is through the following hormones:
Insulin
Growth hormone
ACTH
Glucocorticoids

31. Proteins Sources of proteins 20 different amino acids
The body synthesizes amino acids from other compounds in the body
Only about half of the necessary types of amino acids can be produced by the body
the rest are supplied through diet—found in both meat and vegetables

32. Proteins
Protein metabolism— anabolism is primary, and catabolism is secondary
Protein anabolism— process by which proteins are synthesized by ribosomes
Protein catabolism— deamination takes place in liver cells and forms an ammonia molecule, which is converted to urea and excreted in urine, and a keto acid molecule, which is oxidized or converted to glucose or fat
Protein balance— rate of protein anabolism balances rate of protein catabolism
Nitrogen balance— amount of N taken in = N out thru protein catabolic waste
Two kinds of protein or nitrogen imbalance:
Negative nitrogen balance
protein catabolism exceeds protein anabolism
more tissue proteins are catabolized than are replaced by protein synthesis
Positive nitrogen balance
protein anabolism exceeds protein catabolism
Control of protein metabolism— achieved by hormones

34. This may have certain things you do NOT need to know for the test!

35. Vitamins Vitamins organic molecules necessary for normal metabolism
many attach to enzymes and help them work or have other important biochemical roles
The body does not make most of the necessary vitamins
they must be obtained through diet
Body stores fat-soluble vitamins (D,A,K, and E)
Taken up in the small intestine
These molecules are predominantly non-polar
Body does NOT store water-soluble vitamins
These molecules are predominantly polar

36. Vitamins- do NOT memorize locations

37. Minerals Minerals inorganic elements or salts found in the earth
Attach to enzymes and help them work and function in chemical reactions
Essential to the fluid/ion balance of internal fluid environment
Are involved in many processes in the body such as muscle contraction, nerve function, hardening of bone, etc.
Too large or too small an amount of some minerals may be harmful
Recommended mineral intakes may vary over the lifespan

38. Metabolic Rates
Metabolic rate means the amount of energy released by catabolism
Metabolic rates are expressed in two ways:
Number of kilocalories (C) of heat energy expended per hour or per day
As normal or as a percentage above or below normal
Basal metabolic rate— rate of energy expended under basal (base) conditions
Factors:
Size Body composition
Sex Age
Thyroid hormone Body temperature
Drugs other factors

39. Metabolic Rates
Total metabolic rate- the amount of energy used over time
Main determinates:
Basal metabolic rate
Energy used to do skeletal muscle work
Thermic effect of foods
Energy balance and weight— the body maintains a state of energy balance
Body maintains weight when the total calories in the food ingested equals the total metabolic rate
Body weight increases when energy input exceeds energy output
Body weight decreases when energy output exceeds energy input
In starvation, carbohydrates are used up first, then fats, then proteins (Figure 27-32)

43. Mechanisms for Regulating Food Intake
Hypothalamus plays a part in food intake
Feeding centers in hypothalamus exert primary control over appetite
Appetite center
Cluster of neurons in hypothalamus when stimulated, increases appetite
Orexigenic effects— factors that trigger appetite
Satiety center
Group of neurons in the hypothalamus that, if stimulated, brings about decreased appetite
Anorexigenic effects— factors that suppress appetite (anorexia is loss of appetite)

44. Anorexia Nervosa
Self-induced weight loss, negative perception of body image, and changes in their body due to nutritional depletion
Predominantly in young, single females, and may be inherited.
Abnormal menstruation, amenorrhea, and a lowered BMR
Associated disorders are:
Osteoporosis
Depression
Brain abnormalities

45. The Big Picture: Nutrition, Metabolism, and the Whole Body
Every cell in the body needs the maintenance of the metabolic pathways to stay alive
Anabolic pathways build the various structural and functional components of the cells
Catabolic pathways convert energy to a usable form and degrade large molecules into subunits used in anabolic pathways

46. The Big Picture: Nutrition, Metabolism, and the Whole Body
Cells require appropriate amounts of vitamins and minerals to produce structural and functional components necessary for cellular metabolism
Other body mechanisms operate to ensure that nutrients reach the cells