Download Learning Objectives Chapter 2 Biochem [10-30

Jimmy Kimber
LECOM – Seton Hill OMS1
Biochemistry Chapter 2: Fed or Absorptive State
Learning Objectives
1. Briefly describe digestion/absorption of carbohydrates, proteins, fats
Carbohydrates: converted to monosaccharides:
- Sucrose converts sucrose to glucose and fructose
- Lactase converts lactose to glucose and galactose
- Starch is digested by salivary α-amylase and then pancreatic α-amylase
Proteins: cleaved to amino acids by proteases
- Stomach secretes pepsin
- Pancreas secretes trypsin, chymotrypsin, elastase, and carboxypeptidases that act in the
lumen of the small intestine
- Absorbed by intestinal epithelium and released to hepatic portal vein
Fats:
- Emulsified by bile salts
- Pancreatic lipase converts to fatty acids, 2-monoacylglycerols
- Interact with bile salts to form micelles, absorbed into intestinal epithelium, resynthesized
- Packaged with proteins, phospholipids, cholesterol as chylomicrons, released in lymph
2. What are the roles of insulin, glucagon?
Insulin: secreted from pancreas in response to high-=carbohydrate meal, carries the message
that dietary glucose is available and can be used and stored
Glucagon: carries the message that glucose must be generated from endogenous fuel stores
3. What is the fate of glucose in the liver?
-
Oxidized to ATP generating pathways to meet immediate energy needs: oxidized to
pyruvate  acetyl CoA  TCA cycle
Converted to Glycogen: maximum of 200-300g
Converted to triacylglycerols: occurs as liver glycogen stores begin to fill; liver does not store
triacylglycerols but packages them with proteins phospholipids and cholesterol into VLDLs
4. What happens to glucose in peripheral tissues?
-
Oxidized for energy
Used by all tissues
Stored as glycogen (particularly in muscle)
Insulin stimulates transport of glucose into muscle and adipose
5. Describe glucose metabolism in: Brain/neural tissue, RBCs, muscle, adipose
Brain: dependent on glucose, oxidized via glycolysis and TCA cycle to CO2 and H2O. Glucose is
the only major fuel, and it is a precursor of neurotransmitters
RBCs: glucose is the only fuel used (lack mitochondria), anaerobic glycolysis
Jimmy Kimber
LECOM – Seton Hill OMS1
Muscle: use glucose from the blood or from own glycogen stores; convert glucose to lactate
through glycolysis or oxidize it to CO2 and H2O. Muscle also uses other fuels from the blood like
fatty acids
Adipose tissue: Insulin stimulates transport of glucose into adipose cells. Adipocytes oxidize
glucose for energy and use glucose as the source of glycerol moiety of triacylglycerols they
store.
6. Describe the 2 lipoproteins and how they are cleared
Chylomicrons: formed in the intestinal epithelial cells from the products of dietary
triacylglycerols; remnants cleared from the body by the liver
VLDL: synthesized in the liver; remnants cleared by the liver, or they form low-density
lipoprotein (LDL) which is cleared by the liver or by peripheral cells.
When they pass through blood vessels in adipose tissue, triacylglycerols are degraded to fatty
acids and glycerol. Fatty acids enter the adipose and combine with glycerol produced from
blood glucose.
7. What is the fate of amino acids in the fed state?
Travel from intestine to liver in the hepatic portal vein. Liver uses them for synthesis of serum
proteins and for biosynthesis of nitrogen-containing compounds. Liver may oxidize AAs or
convert them to glucose or ketone bodies and dispose of nitrogen as urea.
AAs released by protein breakdown enter the same pool of free AAs in the blood as AAs in the
diet.
8. What are 2 patterns of fat distribution?
Android (apple shape): occurs more frequently in men; storage of fat in and on the abdomen
and upper body; carries higher risk of hypertension, cardiovascular disease, hyperinsulinemia,
diabetes mellitus, gallbladder disease, stroke, cancer of breast and endometrium.
Gynecoid (pear shape): occurs more frequently in women; storage of fat around breasts, hips,
and thighs
9. Why is lower body fat more difficult to lose?
Upper body fat deposition tends to occur by hypertrophy of existing cells. Lower body fat
deposition occurs by hyperplasia, differentiation of new fat cells.
10. How is waist to hip ratio measured? MUAMC?
Waist-to-hip: waist circumference divided by hip circumference. Average for men is 0.93
women is 0.83. Waist circumference may correlate better with intra-abdominal fat and
associated risk factors.
Mid Upper Arm Muscle Circumference: arm circumference (cm) – (3.14 x skin fold thickness
(mm)/10) reflects caloric adequacy and muscle mass.