Metabolism Flashcards
What are the major metabolic roles of carbohydrates and their general chemical structure? Which carbohydrate is most common in a healthy human diet?
Energy source
[C(H20)]n
Classified according to number of monomers: monosaccharides, disaccharides, oligosaccharides and polysaccharides
Polysaccharides most common - complex carbohydrates that need to be broken down to be absorbed
Sucrose =
Lactose =
Maltose =
Glucose + Fructose = Sucrose
Galactose + Glucose= Lactose
Glucose + Glucose = Maltose
What are the important monosaccharides and how many C atoms do they contain?
Glucose, fructose and galactose - hexoses (6C)
What are 5 roles of lipids?
Fuels for cells (fatty acids/ketone bodies)
Energy storage (triglycerides)
Transport between tissues (cholesterol esters, triglycerides)
Structural components of cell membranes (phospholipids/cholesterol)
Chemical messengers (diglycerides)
What’s the structure of a steroid and why is cholesterol important?
4 ring like structures
Oestrogen, progesterone and testosterone are synthesised from cholesterol
What’re the major metabolic roles of amino acids?
Building blocks of proteins: Regulation - enzymes Transport - Hb/plasma proteins Protection - antibodies Contraction - actin and myosin Structure - keratin Energy - proteins can be broken down when needed
Explain the roles of biological membranes and membrane transporter proteins in the regulation of metabolism
Membrane transporter proteins allow control of substances entering a cell - glucose cannot readily pass through membrane so relies on GLUT1-GLUT5 transmembrane proteins
GLUT1 - highest affinity so in brain and RBCSs
GLUT2 in pancreatic B-cells after food
GLUT4 - fat storage
SGLT1 & SGLT2 are co-transporters in intestine and kidney
What tissues are these substrates essential for: Glucose Fatty acids Ketones Amino acids
Glucose - brain and RBCs
Fatty acids - all tissues but neurones
Ketones - synthesised in liver and used in other tissues, back up energy for brain
Amino acids - glutamine used in fast dividing cells (cancer, enterocytes)
Describe anaerobic ATP formation through glycolysis
Reactions in cytosol converting 1 glucose molecule into 4x ATP and 2x Pyruvates (3C molecule) and 2 NADH
Outline fatty acid oxidation
Fatty acids metabolised by B-oxidation where 2C atoms are removed from each end of the fatty acid chain to form acetyl-CoA, which enters the Krebs cycle
Reaction keeps happening, generating more acetyl Co-A molecules and shortening the fatty acid chain
Outline amino acid transamination, deamination and urea synthesis
Transamination: NH2 group transferred from amino acid to keto acid to make a different amino acid
Deamination: amino acid loses NH2 group to become a keto acid, NAD+ converted to NADH to generate ATP
Urea synthesis: in the liver, NH4 reacts with CO2 to form urea and H20
Outline the TCA cycle and its roles
Energy production: converts oxoloacetate (4C) into citrate (6C) generating 1 ATP molecule per cycle
Products:
2 CO2, 1 ATP, 1 FADH, 3 NADH + H+ (electron carriers)
Describe the electron transport chain and oxidative phosphorylation
Series of redox reactions on inner mitochondrial membrane - proton gradient to drive synthesis of ATP by chemiosmosis
NADH and FADH2 > NAD+ and FAD
e- move from higher energy level to lower, releasing energy which is used to pump further H+ ions out to establish electrochemical gradient
e- transferred to O2 to form H20
1 ATP synthesised from 3H+ flowing through ATP synthase (ADP + Pi -> ATP)
How are monosaccharides classified?
By how many C atoms they contain: triode, tetrose, pentose, hexose
Londer chain monosaccharides (pentoses, hexoses) form cyclic molecules
How are disaccharides formed?
By a reaction between 2 monosaccharides, producing water and a glycosidic bond
What are the 4 important poly/oligosaccharides?
Glycogen (branched polymer of glucose)
Starch (from diet in plant sources)
Dextrin (breakdown product of starch and glycogen)
Cellulose (in diet from plant sources but not digestible)
Outline fatty acids
Hydrocarbon chains of various lengths: long chain>12C and very long chain if >22C
Can be saturated or unsaturated (double bond)
What’s the molecular structure of triglycerides?
Glycerol + 3 fatty acid chains
What’s the difference between cis and trans fatty acids?
Type of stereoisomerism around the double bond (in unsaturated fatty acids only)
Cis fatty acids (have a kink by the bond) pack less closely together = cause membranes to be more fluid
What are modified lipids? What’s an important feature of them?
Phosphate group + fatty acid chain bound via glycerol or sphingosine
Amphiphatic = polar and non-polar ends for membrane structure
How are ketone bodies formed? What’s their breakdown product?
Small 4C fatty acids formed by oxidation of fatty acids in the liver (during fasting)
Acetone is exhaled
Why are ketone bodies dangerous in diabetes?
Excessive formation of ketone bodies in the liver cause blood levels to dangerously rise
Brain will use ketone bodies as an energy source
= diabetic ketoacidosis
What type of metabolic processes use and produce ATP?
Anabolic uses ATP (energy stored in high-energy bond is released)
Catabolic processes produce ATP (energy from oxidation stored in bond)
Outline the relevance of glucose and fatty acid interactions?
Fatty acids can be formed from glucose
Excess glucose stored as lipid/triglycerides in white adipose tissue, but this can only be metabolised as fatty acid
Spillover of triglyceride storage into ectopic tissues has pathological consequences (skeletal, cardiac muscle, liver)
What are the 5 different passive glucose transporters and the 2 using facilitated transport?
GLUT1 - GLUT5 passive
GLUT5 specialised to transport Fructose in the intestine
SGLT1 - SGLT2 active (in kidney and co-transport Na+)
What is glucose phosphorylated by once inside the cell?
Hexokinase
Tissues with low affinity GLUTs express low affinity Hexokinases (liver, pancreatic B-cells)
What’s the Warburg effect?
Cancer cells use glucose anaerobically even when O2 present = use glucose at a very high rate
How can Acetyl CoA be formed?
From pyruvate
From lipids (fatty acids undero B-oxidation to acetyl coA)
From amino acids
What’re the effects of proton uncoupling?
H+ influx can be uncoupled from ATP synthase by UCP1
Dissipation of the proton gradient releases heat = non-shivering thermogenesis in brown adipose tissue
