Carbohydrate metabolism Flashcards
Metabolism
the sum of processes of chemical changes in living cells by which energy and nutrients are provided for vital processes and activities and new materials are assimilated
Anabolism
the constructive part of metabolism involving synthesis
Catabolism
the destructive part of metabolism involving the release of energy and breakdown of complex materials
ATP
adenosine triphosphate
ADP
adenosine diphosphate
NADH
nicotinamide adenine dinucleotide
1 NADH = ___ ATP
3
FADH
flavin adenine dinucleotide
1 FADH = ___ ATP
2
GTP
guanosine triphosphate
1 GTP = ___ ATP
1
OIL RIG
oxidation is loss and reduction is gain (of electrons)
Reducing equivalent
transfer of one electron
Metabolism of CHO provides… (4)
- energy source (ATP)
- short term energy storage (glucose)
- long term energy storage (fatty acid precursors/glycogen
- amino acid precursors (C skeleton)
Characteristics of glycolysis
anaerobic
occurs in cytosol
Characteristics and other names for the krebs cycle
the krebs cycle is also called the TCA (tricarboxylic acid) cycle and the citric acid cycle
the krebs cycle is aerobic and occurs in the mitochondria
characteristics of oxidative phosphorylation
aerobic
occurs in the mitochondria
how much ATP does the priming stage of glycolysis use?
2 ATP
what are the key enzymes used in the priming stage of glycolysis
hexokinase
phosphofructokinase
hexokinase
removes a phosphate from ATP to make glucose-6-P
phosphofructokinase
takes a P from ATP to make fructose 1,6-P
what is the end product of the priming stage of glycolysis?
2 molecules of glyceraldehyde 3-P
what is important about fructose 1,6-P?
it is so unstable it tears itself apart into glyceraldehyde 3-P and dihydroxyacetone-P
how many carbons are in glyceraldehyde 3-P
3
What is the end product of the production stage of glycolysis
two glyceraldehyde 3-Ps are converted to two 1,3 bisphosphoglycerates, then to phosphophenolpyruvate and finally via pyruvate kinase to pyruvate
How much ATP is produced per glucose in the production stage of glycolysis
4
What is the net gain of ATP after the production stage of glycolysis
2
How much NADH is produced during the production stage of glycolysis?
2
What molecules are generated during the production stage of glycolysis?
4 ATP
2 NADH
(note that two ATPs are used in the priming stage)
What enzymes are used during the production stage of glycolysis?
pyruvate kinase converts phosphophenylpyruvate to pyruvate
what does -kinase mean?
the enzyme adds a phosphate to something
what is the overall product of glycolysis?
glucose is oxidized to 2 pyruvates
- uses 2 ATP
- generates 2 net ATP and 2 NADHs
What can happen to pyruvate after glycolysis?
pyruvate can be fermented anaerobically to VFAs or it can go to the krebs cycle (aerobic)
How are NADH and FADH turned into ATP
they are put through the electron transport chain
What is the overall product of the krebs cycle?
3 NADH
1 FADH2
1 GTP
After the ETS
12 ATP per acetyl CoA
What is produced during the krebs cycle per ONE pyruvate
3 NADH
1 FADH
1 GTP
12 ATP
what is the net amount of ATP that is produced after the krebs cycle from all preceding processes
38 ATP total at the end of this step
Where is the electron transport chain located?
The inner membrane of the mitochondria
What is the function of the ETC
synthesis of ATP
source of energy
What is oxidative phosphorylation?
caused by a multi enzyme complex located on the inner membrane
the inner membrane is impermeable to NAD+, NADH, ATP and ADP
this causes a proton motive force that drives ATP synthesis
Proton motive force
a buildup of protons in the intermembrane space that drives ATP synthesis down a concentration gradient
What is the main enzyme that drives ATP formation from ADP and P?
ATP synthase or F1F0ATPase
How does ATP synthase make ATP
the flow of protons through the intermembrane space drives synthesis
In the ETC, how many protons does NADH move?
10 protons
in the ETC, how many protons does FADH move?
FADH moves 6 protons
How many protons are needed in the ETC for one full turn?
10 protons
How many ATP are created from one full turn during oxidative phosphorylation?
3 ATP
Glucose, a 6 carbon molecule, enters the cytosol, which is anaerobic, and is oxidized to 2 ____ , yielding ___ net ATP and ___ NADH molecules
pyruvate, 2, 2
Each pyruvate is transported into the mitochondria, which is an _____ environment, and is converted to 2 ______, which yields _____
aerobic, acetyl CoA, 2 NADH
One acetyl CoA enters the krebs cycle at a time. For each turn of the krebs cycle, one ______ yields 3 _____, 1 _____ and 1 _____. Thus, for each molecule of glucose the krebs cycle turns _____ and yields 6______, 2 _____ and 2 _____
Acetyl CoA, NADH, FADH2, GTP, twice, NADH, FADH2, GTP
_____ and _____ enter oxidative phosphorylation. _______ yields 3 ATP and ______ yields 2 ATP. Oxidative phosphorylation regenerates ______ and ______ for glycolysis and the krebs cycle
NADH, FADH2. NADH, FADH2. NAD, FAD
Thus, 10 _____ from one molecule of glucose yields ____ ATP. Plus 2 ____ yields ____ ATP. Plus 4 _____ yields ____ ATP total.
NADH, 30. FADH, 4. ATP/GTP. 38
glucose oxidation is ____% efficient
42%
What happens to the ‘wasted’ energy in glucose oxidation?
heat and CO2
pyruvate can be fermented to…
lactic acid
fermentation of pyruvate serves this function
to regenerate NAD to continue glycolysis
Which metabolic process causes muscle soreness?
when LOTS of O2 is consumed during exercise, muscles revert to fermentation, generating lactic acid, which causes muscle soreness
How does alcohol alter metabolism?
Ethanol must be converted to acetaldehyde, then Acetyl CoA, using up valuable NAD. This prevents the krebs cycle from working and the acetyl coa is deposited as fat (beer belly)
Ruminants absorb very little glucose. What is their main energy source?
VFAs
How are VFAs absorbed?
they passively diffuse through the rumen wall
The VFA acetate enters the krebs cycle via
acetyl CoA
The VFA butyrate is converted to _______, then to ________
Ketones, Acetyl CoA
the VFA propionate enters the krebs cycle via _______
succinyl CoA
propionate can be converted to ________ and back to glucose
phosphenylpyruvate
What is the efficiency of VFA metabolism (per VFA)
1 glucose = 2 acetic acids + CO2 + CH4 = 62% efficient
1 glucose = 1 butyric acid + 2 CO2 = 78% efficient
1 glucose = 2 Propionic acids + 2 H2O = 109% efficient
Fuel sources in CHO metabolism
glucose, galactose, fructose - enter glycolysis
fats and proteins enter the krebs cycle
These two organs control blood glucose levels
liver and pancrease (glucagon and insulin)
Insulin is secreted from the pancreas. What does it do?
increases storage/uptake of glucose by cells
stimulate formation of glycogen by the liver
Glucagon is secreted from the pancreas. What does it do?
increases conversion of glycogen to glucose
stimulate conversion of amino acids to glucose
glucocorticoids and epinepherine both….
increase blood glucose
20% of a liver’s weight is _______
glycogen
glycogenesis
the production of glycogen
happens following a meal, mediated by INSULIN
glycogenolysis
breaking down of glycogen
mediated by GLUCAGON
gluconeogenesis
make glucose from non-carb sources
reverse glycolysis, basically
utilized most often in ruminants
propionate is often converted to _____ in ruminants
glucose
