Metabolism Overview (Crash Course Book) Flashcards
TCA cycle: Definition Location Cell site Functions
Cyclical series of 8 reactions that oxidise 1 Acteyl CoA completely to 2 CO2.
Generates energy: directly as ATP or in form of reducing equivalents (NADH, FAD2H)
Aerobic: absence/deficiency O2 = total/partial inhibition of cycle
Catabolic (oxidation of substrates) & anabolic (synthetic reactions)
All cells that contain mitochondria
All enzymes free in mitochondrial matrix
Except succinate DH (in inner mitochondrial membrane)
Final common pathway for oxidation of carbs, fat, protein
(Glucose, FAs, aa’s all metabolised to Acetyl CoA or other cycle intermediates)
Produce energy: directly as ATP or as reducing equivalents (NADH or FAD2H, oxidised by ETC). Each turn of cycle = 10ATP
Provides substrates for ETC
Cycle intermediates: Source of biosynthetic precursors, regulatory effects on other pathways (e.g. Citrate inhibits PFK-1)
Oxidative phosphorylation:
Definition
Location
Cell site
Process in which ATP is formed as electrons are transferred from NADH & FAD2H to molecular oxygen, via a series of electron carriers to make up the electron transport chain
All cells that contain mitochondria
Inner mitochondrial membrane
Glycogen: Location of stores Functions of each Size of stores/how long they last Hormonal control
Liver:
Maintains BG conc (esp btw meals/early stages of fasting)
Can be used as fuel by any tissue
12-24hr store
Glucagon/adrenaline promote glycogenolysis
Insulin promotes glycogenesis
Muscle: Fuel reserve for musc contraction Store cannot leave musc (lacks glucose 6 phosphatase) More then liver glycogen store Adrenaline promotes glucogenolysis Insulin promotes glycogenesis
Glycogenesis:
Location
Cell site
Liver & muscle
Cell cytoplasm
Pentose phosphate pathway: Definition Location Cell site Functions
Provides an alternative route for metabolism of glucose
No ATP directly consumed or produced
Instead, produces reducing power in form of NADPH
(Like NADH, is a high-energy molecule, but instead of transferring e- to ETC to make ATP, used for reductive synthetic reactions)
Liver, lactating mammary glands, adipose, adrenal cortex, rbc’s
Cell cytoplasm
Generation of NADPH (for reductive biosynthetic reactions e.g. FA & cholesterol synthesis)
In rbc’s: NADPH used to regenerate reduced form of antioxidant glutathione (protects cell against damage from ROS)
Production 5C ribose sugars for nucleotide/nucleic acid synthesis
Lipogenesis/Fatty Acid synthesis:
Definition
Location
Cell site
A cyclical series of reactions in which a molecule of FA is built up by sequential addition of 2C units, derived from Acetyl CoA, into a growing FA chain
Not a reversal of the degradative pathway
Liver, adipose, lactating mammary glands, kidney (small amt)
Cytoplasm
Lipolysis/Fatty Acid breakdown:
Definition
Location
Cell site
Molecule of fatty acid is degraded by sequential removal of 2C units, producing Acetyl CoA, which can be (beta) oxidised to CO2 & H2O by TCA
Many tissues esp Liver & muscle
(Brain, rbc’s adrenal medulla unable to oxidise FAs; lack enzymes needed)
Cholesterol synthesis:
Definition
Location
Cell site
A 27C steroid molecule that is derived from Acetyl CoA
Liver (main site) Most tissues (except rbc's)
Cell cytoplasm (although some enzymes in the ER)
Ketogenesis:
Definition
Cell site
Functions
Ketone bodies formed from acetyl CoA
Arising mainly from beta oxidation of FAs
Liver mitochondria
Provide an alternative fuel for cells (produced at low levels all the time)
Produced in sig quantities during stress states (e.g. Starvation, strenuous exercise, uncontrolled diabetes)
Provides an alternative fuel for the brain during starvation: FAs cannot cross blood brain barrier; ketone bodies are soluble
Transamination:
Definition
Cell site
Functions/ process
Converts one amino acid into another
Fully reversible reactions (amino grp not released)
Cytoplasm & mitochondria
Aminotransferases (transaminases) catalyse transfer of amino group (NH3+) from amino acid to keto acid (alpha ketoglutarate, pyruvate, oxaloacetate)
New amino acid & keto acid are formed (glutamate for alpha ketoglutarate)
Deamination:
Definition
Cell site
Functions/ process
Removes amino group
Reversible reaction
Mitochondria
Glutamate DH removes amino group, leaving C skeleton:
Ammonia formed enters urea cycle
C skeletons (ketoacids) are glycolytic & TCA cycle intermediates
Urea cycle:
Definition
Location
Cell site
5 reactions that synthesise organic compound urea from 2 inorganic compounds (CO2 & NH4+)
Urea contains 2 nitrogen atoms: one from ammonia (from breakdown of aa’s) & one from aspartate
Cycle uses a carrier molecule which is regenerated
Liver hepatocytes
1st 2 reactions: mitochondria
Last 3 reactions: cytoplasm
Gluconeogenesis: Definition Location Cell site Functions/ process
The production of glucose from non-carbohydrate sources:
Glycerol, lactate, amino acids
For starvation longer than 12hrs or during prolonged exercise
Liver (prolonged starvation: also in kidney cortex)
Cytoplasm (except 1st step: mitochondria)
Maintains BG conc
Glycolysis: Definition Location Cell site Where its important (& functions)
Sequence of 10 reactions that breaks down 1 molecule of glucose (6C) into 2x3C molecules of pyruvate.
Sequence involves net generation of 2 ATP & NADH.
Provides energy & intermediates for other metabolic pathways
Can produce ATP under either aerobic or anaerobic respiration
All cells
Cytoplasm
RBCs: lack mitochondria, so glycolysis their only energy producing pathway
Exercising skeletal musc: when oxidative metab cant keep up with increased energy demand
Brain: glucose main fuel
