L-6 Energy Balance and Metabolism I Flashcards
describe the energy production
- oxidation; make ATP
1) proteins
2) Carbs
3) fats
describe the energy utilization
consume ATP
- active ion transport
- muscle contraction
- synthesis of molecules
- cell division and growth
describe the delta G
- std free energy difference
= difference in free energy when 1 mole of each reactant is converted to 1 mole of each product at 1 atm pressure at 25 degrees C
what becomes the final common pathway for the transport of almost all the carbs to the tissue cells?
glucose
T/F: galactose, glucose, and fructose are all interconvertible
true
what two hexoses can be converted to fructose-6-phosphate to enter the glycolytic pathway?
galactose and glucose
describe the two type of glucose uptake
via active sodium-glucose co-transport and facilitated transport
where does sodium-glucose co-transport occur? describe it
GI tract and renal tubules
- active transport of sodium provides energy for absorbing glucose against a concentration gradient
where does facilitated transport occur? describe it
most tissues
- only transported from higher to lower concentration
- presence of insulin increases glucose transport x10
- phosphorylation of glucose prevents diffusion out of cell
in what tissues can the phosphorylation be reversed?
- phosphorylation can be reversed in liver, renal, and intestinal cells
what 3 important enzymes are involved in glycogenesis and glycogenolysis? what do they do?
- glucokinase - transfers phosphate from ATP
- phosphatase (removes phosphate)
- phosphorylase (catalyzes production of glucose-1-phosphate from glycogen)
what factors can activate phosphorylase?
- epinephrine (from adrenal medulla)
- glucagon (from alpha cells of pancreas)
what are the effects of phosphorylase?
- promotes conversion of glycogen to glucose
- glucose can then be released into blood
in glycolysis, what are the end products?
- 2 pyruvic acid
- 4 hydrogens (released via dehydrogenase)
- 2 ATP (net)
what are the end products of converting pyruvate to acetyl-CoA?
- 2 Acetyl-CoA
- 4 Hydrogen
- 2 CO2
describe the citric acid cycle and its end products
- occurs in the mitochondrial matrix
- 16 H’s
- 2 ATPs
- 4 CO2
what is the net reaction of the citric acid cycle?
2 Acetyl-CoA + 6H20 + 2ADP –> 4 CO2 + 16 H + 2 CoA + 2 ATP
where does oxidative phosphorylation occur?
mitochondrial cristae
what is the fate of hydrogen atoms from previous cycles?
- note that hydrogens are removed in pairs
- one member of each pair becomes a H ion
- the other member combines with NAD+ –> NADH
what is the fate of electrons removed from H ions?
- enter ETC
what are the major components of the ETC?
- flavoprotein
- several ion sulfide proteins
- Ubiquinone (Q)
- cytochrome A3 (cytochrome oxidase) // located on inner membrane; can give up two electrons to oxygen
number of ATPs formed per glucose molecule:
- glycolysis: 2 ATP
- CAC: 2 ATP
- oxidative phosphorylation: 34 ATP
what is the max number of ATPs per glucose molecule?
38 ATP
what is the efficiency?
66%
456,000/686,000 = 66%
what is the pentose phosphate pathway?
the ppp is a cyclical pahtway in which one molecule of glucose is metabolized for each revolution of the cycle
describe some details about it
- for every 6 molecules of glucose that enter the pathway, 5 molecules of glucose are resynthesized
what is this pathway used for?
mostly used for the synthesis of fats and other substances
-
Where are the hydrogens generated from this pathway bound to?
NADP+ instead of NAD+
what can be used for the synthesis of fats from carbohydrates? NADP or NAD?
NADP+ (as NADPH)
how is glucose broken down when theres an excess of glucose in liver?
PPP; producing excess NADPH
what does this NADPH participate in?
- in the conversion of Acetyl-CoA into fatty acid chains
- glucose is preferentially stored as glycogen until the storage cells (liver and muscle) are saturated
- excess glucose is then converted into fat (liver and fat cells) and stored in fat cells
describe what happens when triglyceride absorption occurs from intestinal lumen
- most triglycerides are digested into monoglycerides and fatty acids
- intestinal epithelial cells resynthesize these into triglycerides that enter the lymph as chylomicrons
- apoprotein B is adsorbed to the chylomicron surfaces
how are chylomicrons transported to the venous system?
via the thoracic ducts
what tissues are chylomicrons especially removed from (from their blood)?
- adipose tissue
- skeletal muscle
- heart
what do these last three tissues synthesize?
- lipoprotein lipase, which:
= is transported to surface of capillary epithelial cells
= hydrolyzes chylomicron triglycerides, releasing fatty acids and glycerol
some more fun facts about neutral fats
- fatty acids can be used for fuel or again synthesized into triglycerides
- 50% of the plasma fatty acid is replaced every 2-3 minutres
- therefore, all normal energy requirements of the body can be provided by the oxidation of fatty acids without using carbs or proteins as an energy source
under what conditions is there an increase in utilization of fat for energy?
- starvation
- diabetes mellitus
what type of lipoprotein is synthesized by intestinal cells/
chylomicrons
what kinda lipoproteins are synthesized by the liver?
- very low density lipoproteins (VLDLs)
- intermediate DLs
- low DLs
- High DLs
describe the lipid transport in the blood via VLDLs
- high concentration of triglycerides and moderate amounts of cholesterol and phospholipids
- transport lipids mainly from liver to adipose tissue
LDLs
- high concentration of cholesterol and moderate concentration of phopsholipids
HDLs
- high concentration of proteins and low concentration of cholesterol and fatty acids
what are the principal functions of the liver in lipid metabolism?
text***
under what conditions do large quantities of triglycerides appear in the liver?
text***
what are triglycerides hydrolyzed into? (in regards to energy source)
- into fatty acids and glycerol, which are transported in blood to tissue
what two type of cells dont use fatty acids for energy?
brain cells and RBCs
what is glycerol converted to?
G3P
what are fatty acids converted to? and where?
Acetyl-CoA; in mito
via what process? elaborate
via beta-oxidation
- carnitine is used as a carrier molecule into the mitochondria
- Acetyle CoA enters the citric acid cycle by binding to oxaloacetic acid
- hydrogens enter the chemoismotic oxidative system
what are the products from beta-oxidation of one molecule of stearic acid?
- 9 ACA molecules
- 146 molecules of ATP
what happens to fatty acids in liver not used for metabolism?
releases many ACAs
- 2 ACAs condense to form acetoacetic acid
- some of the acetoacetic acid is converted to: b-hydroxybutyric acid and acetone
T/F: acetoacetic acid is a keto acid
True
what are considered ketone bodies?
- acetoacetic acid
- beta-hydroxybutyric acid,
- acetone
what happens to ketone bodies during ketosis?
- diffuse back into cells and are converted into ACA
how does ketosis occur/
if concentration of ketone bodies increase above normal in blood
what conditions favor ketosis?
- starvation
- diabetes
- diet composed almost entirely of fat
how many steps are involved in synthesis of fatty acids? what do they involve?
2;
- involves malonyl-CoA
- NADPH
why is fat synthesis important?
- more fat can be stored in tissues than carbs
- weight-for-weight, fat contains about 2.5x the energy of carbs
why are fats poorly synthesized during insulin insufficiency?
text
why are carbs preferred over fats for energy?
text
describe the development of atherosclerotic plaque
- damage to vascular endothelium
- circulating monocytes and LDLs accumulate at injury site
- monocytes
describe damage to vascular endothelium
- incr the expression of adhesion molecules
- decreases release of NO and other substances that prevent adhesion of macromolecules and cells
describe monocytes
- cross endothelium
- enter intima
- become macrophages
describe macrophages
- ingest lipoproteins
- become foam cells
- form visible fatty streaks
describe fatty streaks
- grow larger
- coalesce
surrounding fibrous and smooth muscle tissues
- proliferate
- form large plaques
descirbe the large plaques
- may occlude lumen
- may become sclerotic or fibrotic
- may become calcified
what are the basic causes of atherosclerosis?
- increased LDLs
- familial hypercholesterolemia (defective LDL receptors)
note about HDLs
they may be able to absorb cholesterol crystals that are beginning to be deposited in arterial walls
