BSC Metabolism Flashcards
what are the 3 sections of the small intestine, their lengths, and characteristic features
1- duodenum, 10-12 inches, pyloric valve, arcs around head of pancreas, ends at duodenojejunal flexure/ junction
2- jejunum, 8ft, from duodenum to ileum
3- ileum, 12 ft, joins large intestine at ileocecal valve
what are the roles of the duodenum and ileum
d- receives stomach contents, pancreatic juice, and bile
i- regulates flow of contents
what do plicae circulares/ villi/ microvilli do
absorbs nutrients, electrolytes, and water in small intestine, NEEDS TO BE MAXIMAL SURFACE AREA
what happens to diet glucose
- most of it is absorbed into bloodstream as glucose formed by hydrolysis of dietary starch and disaccharides
- others are converted into glucose in the liver
what are carbohydrates/ sugars/ saccharides the precursor for
1- glycogen for storage
2- ribose & deoxyribose in nucleic acids
3- galactose for synth of lactose in milk
what are the 3 major carbohydrates and list examples for each category
1) monosaccharides, glucose, galactose, fructose
2) disaccharides, sucrose (gl & fr), lactose (ga &gl), and maltose (2xgl)
3) polysaccharides, glycogen stored in skeletal muscle (meat), starch, fiber (cellulose)
how do you regress from polysaccharide to disaccharide? from disaccharide to monosaccharide?
- poly to di: salivary amylase and pancreatic amylase
- di to mono: disaccharidases in small intestine and brush border enzyme near microvilli
how are glucose, galactose, and fructose absorbed into cells? how do they leave?
- glucose and galactose: SGLT1, secondary active transport thru Na+ dependent cotransporter, high luminal [ ] against gradient
- fructose: GLUT5, facilitated diffusion via glucose transporter
- all leave through GLUT2 into capillaries
what happens when lactose is tolerated vs not tolerated
tolerated: lactase breaks down lactose to glucose and galactose -> normal poopie
not tolerated: lactase not present, only water, bacteria results and ferments -> gas, organic acids, osmotically active molecules irritation and motility -> back to more bacteria
what do insulin and glucagon do
insulin: stores fuel
glucagon: creates fuel by breaking down
what are the 4 fates of glucose
1) metabolized into pyruvate/ lactate via glycolysis
2) metabolized in the pentose phosphate pathway
3) stored as glycogen in the liver and skeletal muscle
4) stored as triglyceride in adipose tissue
what are the processes involved with metabolizing glucose into pyruvate/ lactate
glycolysis, krebs/tca/citric acid cycle, etc
what are the processes involved with metabolizing using the pentose phosphate pathway
glycolysis- alternate route: HMP -> glutathione
what are the processes involved with storing glycogen in the liver and skeletal muscle
glycogenesis
what are the processes involved with storing triglyceride in adipose tissue
fatty acid synthesis
what are the important features of glycolysis
- 10 enzymatic rxns
- occurs in cytosol
- anaerobic (but w/ O2 can make 5 ATP in ETC)
- aerobic, undergoes oxidative degradation in mitochondria to acetyl CoA
- result sin 2 ATP and 2 NADH
- 1 glucose = 2 pyruvate
what happens if glycolysis takes place in an anaerobic setting? what is another situation where this would occur
- converts to lactate
- w/ cells that have no mitochondria like RBCs
what is the process of pyruvate undergoing oxidative degradation during glycolysis
1) carboxyl group removed from pyruvate, releases CO2
2) NAD+ reduced to NADH
3) acetyl group transferred to coenzyme A -> acetyl CoA
what are the important features of krebs cycle? alternate names for this process?
- occurs in mitochondria
- doesn’t use O2 but will stop w/o it
- forms: NADHx6, FADH2x2, GTPx2, waste- CO2
- needs B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid)
- TCA (tricarboxylic acid), citric acid cycle
describe the important features of ETC
- inner mitochondrial membrane
- requires lots of O2
- converts NADH to NAD+ : generates 2.5 ATP& FADH2 to FADH generates 1.5 ATP
- ATP synthase enzyme is key and what creates the H+ gradient to produce ATP
- 4 complexes
what are the important features of the alternate route of glycolysis
- HMP
- not ATP instead NADPH and pentoses important for ribose (RNA, DNA, and making proteins)
- instead of glucose becoming pyruvate
- occurs in cytosol, thus all cells
- key enzyme: G6DP NEEDED
what is NADPH used for
- donates electrons (reducing agent) in anabolic rxns to make fatty acids and cholest. in liver and adipose tissue/ mammary glands/ synth steroids
- indirectly eliminates toxic oxygen radicals
what is glutathione and what are its states
major endogenous antioxidant produced by all cells
- participates directly in neutralizing free radicals
- maintains vitamin c& e in reduced forms
- reduced state- GSH, oxidized state- GSSG
what are important features about glycogenesis
stores glucose in liver/ skeletal muscle for a rainy day
compare and contrast liver hepatocytes and skeletal muscle in glycogenesis
liver
- glucokinase, stores 350-400 g of glucose
skeletal muscle
- hexokinase, stores 100g of glucose
BOTH use glycogen synthase (stim. by insulin) as key enzyme and if no room, stored as fat
describe important features of fatty acid synthesis
- synth. from acetyl-CoA
- mainly in adipose tissue and liver
- pathways between cytosol and mitochondria
what are the 3 types of lipids and their roles
1) triglycerides- energy
2) phospholipds- plasma cell membrane, made of nitrogen compound, phosphate group, glycerol, and FA tails
3) cholesterol- building block of steroid hormones, travels in blood as LDL, HDL, used for plasma cell membrane
what are the 6 stages of digestion/ absorption of lipids and relevant details of each step
1) emulsification: lipophilic and hydrophobic fat globule undergoes lecithin/ bile acid to become droplet
2) pancreatic lipase: hydrolyzes 1st and 3rd FA from triglycerides
3) colipase: is a co-enzyme that helps pancreatic lipase
4) micelles: lipids -> micelles coated w/ bile acid
5) chylomicrons- resynth’d and packaged triglyceride, cholesterol, and phospholipids, how intestinal cells absorb
6) lacteals: lymphatic capillary of the villus chylomicrons packaged into secretory vesicles and released from basal cell membranes into lacteal
what is lipemia and when does it occur
w/in 1 hour of eating a fatty meal, chylomicrons are active in capillary endothelium.
- FAs into adipocytes and hepatocytes
- clears in a few hours
- contain lipoprotein lipase
what are the types of lipoproteins and relevant features
- synth by small intestine
1) chylomicrons
2) VLDL
3) IDL
4) LDL, bad cholesterol transports from liver to tissues
5) HDL, good cholesterol transports excess tissues to liver
what type of TG and cholesterol/ phospholipid content do VLDLs have?
high TGs, moderate C/P
what type of TG and cholesterol/ phospholipid content do IDLs have?
moderate TGs, moderate C/P
what type of TG and cholesterol/ phospholipid content do LDLs have?
low TGs, high C/P
what type of TG and cholesterol/ phospholipid content do HDLs have?
low TGs, low C/P
what are the treatments for high LDL?
statins
1) fluvastatin (lescol)
2) lovastatin (altoprev, mevacor)
3) atorrastatin (lipitor)
4) pitavastatin (livalo)
5) pravasttin (pravachol)
6) rosuvastatin (crestor)
7) simvastatin (zocor)
what are the 2 modes of cholesterol de novo synthesis
dietary and synth by liver hepatocytes (amt determined by genetics)
describe FA beta- oxidation
- mitochondrial aerobic process
- FA -> acetyl- CoA -> krebs (NADH, FADH2, GTP) -> ETC uses NADH, FADH2, ATP!
- liver, skeletal muscle, and heart
describe important features of ketone metabolism
- synth in mitochondria of liver hepatocytes
- ocurrs when fasting, oxaloacetate depletes in liver b/c gluconeogenesis -> impedes entry of acetly- CoA in Krebs
- acetyl CoA accumulates -> liver converts to ketone bodies -> peripheral tissues (brain, skeletal muscle, kidneys -> acetyl CoA -> ATP via Krebs and ETC
describe glucuneogenesis
- synth glucose from non carb sources such as AAs (not leucine/ lysine), lactate, and glycerol
- occurs primarily in liver hepatocytes
- occasionally in epithelial cells of kidneys and small intestine
- complex! NOT a reversal of glycolysis
describe glycogenolysis
- occurs during fasting state in liver and skeletal muscle
- muscle provides G6P and begins glycolysis
- liver breaks down glycogen into glucose preventing hypoglycemia
- in both locations glucose is produced and fat is broken down
what is the connection between glycogenolysis and gluconeogenesis
keeps you sustained in case liver and skeletal muscle run out of glycogen
describe the cori and alanine cycles
- involve gluconeogenesis in the liver and glycolysis in the muscle
- cori: glucose -> pyruvate -> lactate in muscle -> blood -> liver, converted to pyruvate 0> gluconeogenesis -> glucose release and travels back to muscle
- alanine: cori but pyruvate is transaminated after pyruvate then released into blood. in the liver-> transaminated back. xs alanine becomes urea
how are AAs collected for energy
- clear off brush border w/ aminopeptidases and proteases using active pancreatic enzymes
- facilitated diffusion (GLUT5)
how are AAs used for energy
1) gluconeogenesis (except leucine and lysine
2) ketone body (leucine and lysine)
3) directly fed into krebs
can AAs be converted to TGs? how?
yes, krebs
can AAs be broken down into waste
yes, amino groups cleaved into urea
- all urea synth in liver
- urea build up in blood leads to renal disease such as hepatic coma/ hepatic encephalopathy and azotemia and uremia which is TOXIC
