Thom1-Carbohydrates Flashcards
What do most carbons from our diet get converted into?
AcetylCoA (oxidized in the TCA cycle)
What causes ketoacidosis?
- Excessive production of ketone bodies
- Diabetes ketoacidosis symptoms include: polydipsia (excessive) thirst, polyuria, fatigue, & blurred vision
What is ATP & what is the structural basis of the its high phosphoryl transfer potential?
- Universal currency of free energy
- High phosphoryl transfer potential results from structural differences between ATP & its hydrolysis products: –> Hydrolysis products are more stable bc of electrostatic repulsion, resonance hybridization, and stabilization due to hydration
- Energy is stored in phosphoanhydride bonds
How does ATP drive metabolism?
- Phosphoryl transfer potential is an important form of cellular energy transformation (flow of phosphoryl groups from high-E phosphate donors to low-E phosphate acceptors)
- ATP hydrolysis shifts equilibrium of coupled reactions
What are oxidants and reductants?
-Oxidant (oxidizing agent): become reduced, electron accepting molecule
-Reductant (reducing agent): become oxidized (dehydrogenated), electron-donating molecule -Transfer of: electrons, H-atoms, hydride ions
What is a reducing equivalent?
A single electron equivalent participating in an oxidation/reduction reaction
What are some major cofactors for redox reactions?
-Niacin (from vit-B3), nicotinamide, tryptophan
What is pellegra?
- Niacin vitamin deficiency
- Dementia, diarrhea, dermatitis
What are the 2 phases of respiration?
1) The oxidation of fuels
2) ATP generation from oxidative phosphorylation
What is the role of the respiratory chain?
It oxidizes reducning equivalents and acts as a proton pump.
How are metabolic pathways regulated (3 ways)?
1) Amounts of enzymes (protein synthesis, degradation)
2) Catalytic activity (feedback and allosteric inhibition)
3) Accessibility to substrate: hormonal control
Where do major metabolic pathways take place?
-Cytosol: glycolysis, pentose phosphate pathway, protein synthesis, FA synthesis, part of urea cycle, part of gluconeogenesis
-Mitochondria: krebs cycle, FA oxidation, acetylCoA formation, part of urea cycle, part of gluconeogenesis
-Lysosomes: degradation of complex macromolecules
-Nucleus: DNA & RNA synthesis
What are the major specialized functions of the liver?
1) FA synthesis (along w/fat cells)
2) Gluconeogenesis (along w/kidney)
3) HMP shunt (along with adrenal cortex, far cells)
4) AA synthesis & breakdown
5) Urea synthesis
6) Cholesterol synthesis
Where does FA oxidation not occur?
It does not occur in the brain and in RBCs
What are the types of receptors used for hormonal regulation?
1) Coupled to adenylate cyclase (2nd msn systems, glucagon, epinephrine)
2) With kinase activity (insulin-R)
3) Coupled to phosphatidyl inositol hydrolysis (epinephrine, GH)
4) Coupled to gated-ion channels (angiotensin II, GABA, acetylcholine)
5) Intracellular receptors (for transcription activation; steroids/Vit-D/retinoic acid/thyroxine)
What are glycans?
-Carbohydrates, compounds that usually contain and aldehyde or ketone group and hydroxyl groups.
What are isomers, enantiomers, epimers, anomers?
- Isomers: same chemical formula, different structure (glucose & fructose)
- Enantiomers: mirror images of each other
- Epimers: differ only in position of the hydroxyl group around asymmetric carbon (ex. glucose & mannose; glucose & galactose)
- Anomers: differ only in configuration around new asymmetric carbon
What is a reducing sugar?
-When oxygen on anomeric carbon is not attached to other structure, it can react with chemical reagents & become oxidized to carboxylic acid
What is the importance of the anomeric carbon?
- Cyclization of glucose produces a new asymmetric center at C1
- Anomers have a different configuration at this new asymmetric carbon
- alpha: OH below the ring
- beta: OH above the ring
What’s a glycosidic bond?
- Hydroxyl group on anomeric carbon of monosaccaride reacts with hydroxyl or amino group of another compound.
- N-glycosidic bond: sugar linked to N in asparagine side chain
- O-glycosidic bond: sugar linekd to O in serine’s side chain
What are some sugar derivatives?
- Sugar alcohol: lacks an aldehyde or ketone (ribitol)
- Sugar acid: aldehyde at C1 or OH at C6 is oxidized to carboxylic acic (gluconic acid)
- Amino sugar: amino gorup substitutes for a hydroxyl (glucosamine, N-acetylglucosamine)
How do plants and humans store glucose?
- PLANTS: store glucose as amylose or amylopectin, collectively called starch. Polymeric storage minimized osmotic effects. Also, cellulose (beta-1–>4 linkages).
- HUMANS: amylose is a glucose polymer with a(1–>4) linkages. Adopts helical conformation. the end wuth an anomeric C1 not involved in a bond is the reducing end.
How are carbohydrates digested?
1) a-amylase in the mouth (low pH in stomach stops action)
2) Pancreatic a-amylase breaks a(1–>4) linkages in the small intestine
3) Mucosal cell membrane-bound enzymes break down small polymers
How are simple CHOs transported across the intestinal epithelium?
-Several glucose transporters:
- Glut 1: most cells
- Glut 2: glucose, galactose, fructose (low affinity/high capacity)
- Glut 3: high affinity, basal
- Glut 4: muscle, adipose. Insulin dependent
- Glut 5: fructose (high affinity
- Faciitated diffusion (Glut 2/5)
- Secondary active transport (SGLT1)
