1. Integration of Metabolism in Energy, Protein and Lipids

2. Metabolism
A term referring to all chemical reactions necessary to maintain life. Substances are constantly being broken down and built up.
Catabolism: complex structures broken down into simpler ones (digestion)
Anabolism: larger molecules are built from small ones (like AA’sproteins)

3. The Nutrient Pool Contains all organic building blocks cell needs:
to provide energy
to create new cellular components
6 categories of nutrients
Carbohydrates
Lipids
Proteins
Vitamins
Minerals
Water
Lipids release 9.46 C/g
Carbohydrates release 4.18 C/g
Proteins release 4.32 C/g

4. Carbohydrates Dietary sources Predominately plants
Sugars – fruits, honey, milk, candy, soda
Starch – grains, legumes, root veggies
Cellulose – veggies

5. Carbohydrates, cont. Uses in the body
Glucose is a major fuel to make ATP
Carbohydrate digestion yields fructose and galactose, liver converts them to glucose before circulation
*when glucose is in excess, it is converted to glycogen or fat and stored for later use*

6. Lipids Dietary sources Saturated fats Unsaturated fats
Animal products (meat & dairy) & coconut, palm,etc.
Unsaturated fats
Seeds, nuts, most veggie oils
Storage as triacylglycerol (TAG) in adipose tissues
Glycogen (branched polymer α-D-glucose) found in Liver, MM.
More TAG (give 9 kcal/g ) > glycogen in body strorage

7. Brown fat had a small molecule, more blood vessels, low ATP produced and make more EN than White fat (Birth animal)
Wild animal had lean meat (low marbling) and more PUFA ( >30% total FA vs. 12% in domestic animal )
FUFA in wild ani. made unfavour meat from FUFA-phospholipids form.

8. Lipids, cont. Dietary fats help the body absorb fat-soluble vitamins
triglycerides are the major EN source for liver cells & skeletal muscle
Cholesterol is not used as an EN source. It is a precursor to bile salts, steroid Hormones, and other essential functional molecules
Non ruminant fat intake and fat in body found in the same proportion (Unsat --> Unsat, Sat Sat)
Ruminant always had biohydrogenation in rumen.

9. Glycogen & Lactic cycle ( Cori cycle)
Insulin moving glucose to glycogen (storage in liver, mm)
Glucagon activate glycogenolysis for glucose in Liver, and Lactic in MM.

10. Proteins Dietary sources Primarily animal products (eggs, milk, meat)
Legumes, nuts, & cereals are nutritionally incomplete because they are low in one or more essential AA’s

11. Proteins, cont. Uses in the body Hormonal controls
Structural materials (collagen, elastin, keratin)
Functional proteins (enzymes, hemoglobin, H’s)
Hormonal controls
Anabolic hormones accelerate protein synthesis
i.e. growth hormone, sex hormones, adrenal glucocorticoids, etc.

12. Adequacy of caloric intake
Proteins, cont.
Adequacy of caloric intake
For protein synthesis you must have adequate intake of carb’s & fats for ATP production
If not…dietary & tissue proteins are used for En

13. Energy Yield of Aerobic Metabolism
For 1 glucose molecule processed, cell gains 36 molecules of ATP:
2 from glycolysis
4 from NADH generated in glycolysis
2 from TCA cycle (through GTP)
28 from ETS

14. Carbohydrate Synthesis and Breakdown
Gluconeogenesis - the synthesis of glucose from noncarbohydrate precursors:
lactic acid, glycerol, & AA’s
Stores glucose as glycogen in liver and skeletal muscle
Glycogenesis - the formation of glycogen from glucose
Glycogenolysis - Is the breakdown
of glycogen to glucose
Figure 25–7

15. Lipolysis
Breaks lipids down into pieces that can be converted to pyruvic acid & channeled directly into TCA cycle
Hydrolysis splits triglyceride into component parts:
1 molecule of glycerol & 3 fatty acid molecules
Different enzymes convert fatty acids to acetyl- CoA (beta-oxidation)

16. Fat & Glucose in Non Ruminant

17. Fat & Glucose in Ruminant

18. 3 Energy Benefits of Beta-Oxidation
For each 2-carbon fragment removed from fatty acid, cell gains:
12 ATP from acetyl-CoA in TCA cycle
5 ATP from NADH
Cell can gain 144 ATP molecules from breakdown of one 18-carbon fatty acid molecule
3. Fatty acid breakdown yields about 1.5 times the energy of glucose breakdown

19. Free Fatty Acids (FFAs)
Are lipids that can diffuse easily across cell membranes
In blood, are generally bound to albumin (most abundant plasma protein)
Are an important energy source:
during periods of starvation when glucose supplies are limited
Liver cells, cardiac muscle cells, skeletal muscle fibers, etc. metabolize free fatty acids

20. Proteins The body synthesizes 100,000 to 140,000 proteins:
each with different form, function, and structure
All proteins are built from the 20 amino acids

21. Protein Metabolism Cellular proteins are recycled in cytosol:
peptide bonds are broken
free amino acids are used in new proteins
If other energy sources are inadequate:
mitochondria generate ATP by breaking down amino acids in TCA cycle
Not all amino acids enter cycle at same point, so ATP benefits vary

23. 3 Factors Against Protein Catabolism
Proteins are more difficult to break apart than complex carbohydrates or lipids
A by-product, ammonium ion, is toxic to cells
Proteins form the most important structural and functional components of cells

24. Protein Synthesis
The body synthesizes half of the amino acids needed to build proteins (Nonessential AA’s)
amino acids made by the body on demand
10 essential AA’s:
8 not synthesized: isoleucine, leucine, lysine, threonine, tryptophan, phenylalanine, valine, and methionine
2 insufficiently synthesized: arginine and histidine

25. Summary: Pathways of Catabolism and Anabolism
Figure 25–12

26. Metabolic Interactions
Body has 2 patterns of daily metabolic activity:
absorptive state
postabsorptive state

27. The Absorptive State
Is the period following a meal when nutrient absorption
most excess metabolites will be converted to fat for storage if not used in anabolism
carbs-->liver to covert to glu-->released to blood or makes & stores glycogen & makes fat to release to blood for storage by adipocytes
triglycerides-->FA’s + glycerol-->sk mm, liver cells, & adipocytes use FA’s as primary E source-->most FA’s & glycerol re-enter adipose tissue & reconvert to triglycerides for storage
AA’s-->some to liver for deamination to keto acids-->Kreb’s for ATP formation or conversion to liver fat stores; liver uses some AAs for plasma protein synthesis but most go into general circulation for uptake by other body cells to use for anabolism

28. The Postabsorptive State
When nutrient absorption is not under way (fasting state)
Primarily catabolic to maintain blood glucose levels w/in normal range b/t meals
glycogenolysis in liver can maintain blood glu levels for ~ 4 hrs
glycogenolysis in skeletal mm - glucose cannot be released to blood as w/liver (lacks all necessary enzymes) but…partial oxidation to pyruvic acid (or lactic acid) occurs-->goes to liver for conversion back to glucose & is released to blood
lipolysis in adipose tissue & liver -->leads to glycerol-->liver converts to glucose & releases to the blood
catabolism of cellular protein - primary source of blood glucose w/fasting (glycogen stores are depleted)-->AAs are deaminated & coverted to glucose in liver & are released to blood

29. Glucose for Energy enzymes break apart glucose – yielding energy
inadequate supply of carbohydrates
ketone bodies (fat fragments) are an alternate energy source during starvation
excess ketones can lead to ketosis: imbalance of acids in body

30. Protein Metabolism protein turnover
constant making and breaking of proteins
frees amino acids to “amino acid pool”
can be used to make body proteins
nonessential amino acids can be made from other amino acids

31. amino acid pool Excreat of nitrogens and made available for energy
deamination
make fat
amino acids are deaminated, nitrogen is excreted, carbon is converted to fat and stored
protein-rich foods can cause weight gain

32. Feasting and Fasting

33. Feasting and Fasting

34. Fasting several hours after a meal, glucose is used up
protein is used for energy
shift to ketosis
suppresses appetite
hormones slow metabolism
eventually starvation

35. Regulatory Hormones on Metabolism
Table 25–1

36. Basal Metabolic Rate (BMR)
Is the minimum resting energy expenditure:
Involves monitoring respiratory activity
Energy utilization is proportional to oxygen consumption

37. Hormonal Effects Thyroxine: Cholecystokinin (CCK):
controls overall metabolism
Cholecystokinin (CCK):
suppresses appetite
Adrenocorticotropic hormone (ACTH):
Leptin:
released by adipose tissues
binds to CNS neurons that suppress appetite

38. Heat Production BMR estimates rate of energy use
Energy not captured is released as heat:
serves important homeostatic purpose

39. Thermoregulation The body produces heat as by-product of metabolism
Increased physical or metabolic activity generates more heat
Body controls heat gains and losses to maintain homeostasis