Unit 5 summary notes

• Kreb's cycle


  1. Acetyl CoA combines with oxaloacetate (4 carbon compound) to form citrate (6 carbon compound)

  2. Decarboxylation of citrate to release 1 CO2 and 1 NADH

  3. Citrate will be converted to 5 carbon compound

  4. Decarboxylation of 5 carbon compound to release 1 CO2 and 1 NADH

  5. 5 carbon compound will be converted to oxaloacetate

  
• • FAD is reduced by electrons from 4 carbon compound to give 1 FADH
  • NADH will be produced
  • 2 ATP will be produced
  • Then regeneration of oxaloacetate for cycle to continue

  
• Multiply the products x2
• Glycolysis


  1. Phosphorylation of glucose using 2 ATP

  2. Giving us 2 trios phosphate

  3. 2 trios phosphate are oxidized giving us 2x pyruvate

  4. Then NAD will be reduced to give us 2x NADH and 2x ATP

  
• Linked reaction


  1. Decarboxylation of 2x pyruvate (1 carbon atom are removed in the form of CO2) so 2x molecules of CO2 are produced

  2. Giving us 2x acetate

  3. 2x NAD will be reduced by hydrogen from pyruvate giving us 2x NADH

  4. 2x Acetate combines with coenzyme A to form 2x acetyl CoA

  
• Role of oxygen in aerobic respiration


  • Oxygen is needed in oxidative phosphorylation
  • Oxygen act as final electron acceptor
  • Reduced to water for regeneration of NAD and FAD
• Oxidative phosphorylation


  1. H atoms released from NADH and FADH

  2. H atoms splits into protons and electrons

  3. Electron pass across ETC releasing energy

  4. Energy is used to pump protons from mitochondrial matrix into the intermembrane space

  5. To create proton gradient

  6. Hydrogen ions diffuse back into the matrix by chemiosmosis through ATP synthase

  7. Phosphorylation of ADP to form ATP

  8. Oxygen act as final electron acceptor

  9. Oxygen is reduced to water (oxygen, protons and electrons)

  
• Lactate fermentation


  1. Regeneration of NAD is achieved by pyruvate from glycolysis

  2. Glycolysis produces 2 pyruvate, 2 NADH and 2 ATP

  3. 2 pyruvates will be reduced to convert it to 2 lactate

  4. Then oxidation of NADH to be regenerated

  
• Animals break down lactate

  1. Converting it to pyruvate

  2. Liver cells convert lactate back to glucose

  
• Why anaerobic respiration produces less ATP
• Oxygen debt


  • After stopping exercise oxygen consumption increase to breakdown lactate produced from anaerobic respiration
  • Lactate/lactic acid lowers the pH of blood
  • Breathing rate increases to transport lactate to the liver to be broken down

  
• Respiratory substrates


  • Glucose
  • Lipids
  • Proteins
• Glycerol


  Phosphorylated and enter glycolytic pathway as GALP

  
• Fatty acids


  Hydrocarbon chains are broken down, two carbons are broken at a time to produce acetyl CoA, then it will enter the matrix to be used in Kreb's cycle

  
• Proteins


  Deamination takes place in liver to remove amine group, remaining organic part is converted into pyruvate or acetyl CoA (depending on R groups), then enters Kreb's cycle, used in case of starvation
• Respiratory quotient (RQ)


  • RQ = Carbon dioxide produced / Oxygen used
  • RQ of glucose= 1
  • RQ of triglyceride= 0.7
  • RQ of proteins= 0.9
  • RQ 1 or less than 1 is aerobic, RQ more than 1 is mixture, very low RQ values are in photosynthetic organisms

  
• Tendons


  Attaches a muscle to a bone, no elastic fibers, so they don't stretch when the muscle contract, so the bone is moved
• Ligaments


  Attaches a bone to bone/holds bone together, have elastic fibers, so bones can move at the joint without dislocation, have collagen to provide strength
• Antagonistic pairs


  Muscles work in pairs called antagonistic pairs, they work opposite to each other, when one contract the other relax, as muscles pull but never push
• Muscle contraction


  Sarcoplasmic reticulum contains calcium ions, calcium ions binds to troponin, cause the movement of the tropomyosin, which exposes the binding site of myosin head on the actin filament, forming actomyosin cross bridges, myosin head changes its shape pulling the actin filament, ATP attaches to myosin head breaking actomyosin cross bridges, actin filament slide causing the sarcomere to shorten, this is called sliding filament theory

  
• Sarcomere


  Made up of actin (thin filament) and myosin (thick filament), I band= formed of actin only, A band= formed of actin and myosin, H zone= formed of myosin only

  
• Muscle structure


  • Muscle fibres are made from: Myofibrils, each myofibril is made from sarcomeres, sarcolemma (cell surface membrane), sarcoplasm (cytoplasm), mitochondria and sarcoplasmic reticulum

  
• Types of muscle fibres

  • Slow twitch fibre: More myoglobin, high capillary density, contract slowly, long period, more ATP (aerobic respiration), less glycogen
  • Fast twitch fibre: Less myoglobin, Less capillary density, contract more rapidly, short period, less ATP (anaerobic respiration), more glycogen
• Homeostasis


  Maintenance of conditions inside the body near the constant level, by negative feedback mechanism
• Negative feedback mechanism


  Mechanism that returns a change away from normal value to normal value, keeping a constant value
• Homeostasis in case of increase in temperature

  • Vasodilation: Arterioles in skin gets wider, so more blood flow near the skin surface, so more heat lost to surroundings
  • Increasing sweat production: So more heat loss by water evaporation from skin surface
  • Hair erector muscle relaxes: So they lie flat reducing layer of insulation
  • Decreased adrenalin production: Decrease in respiration so less heat generated
  • Inhibition of shivering: So less heat generated
• Homeostasis in case of decrease in temperature

  • Vasoconstriction: Arterioles in skin gets narrower, so less blood flow near the skin surface, so less heat lost to surroundings
  • Decreasing sweat production: So reduce heat loss by reducing water evaporation from skin surface
  • Hair erector muscle contract: So trap layer of warm air
  • Increased in adrenalin production: Increase in respiration so more heat generated
  • Shivering involve muscle contraction, so heat generated and absorbed by blood
• Control temperature by negative feedback mechanism

  Change in temperature away from normal value act as a stimulus, detected by thermoreceptors in skin/hypothalamus, sending impulses to hypothalamus, hypothalamus act as a thermoregulatory center, hypothalamus send nerve impulses to effector, temperature returns back to normal by homeostasis
• Transcription factors


  Control/involved in transcription of genes, proteins acting as chemical messenger, TF binds to DNA at promoter, activators increase rate of transcription and repressor decrease rate of transcription
• Peptide hormones


  They can't cross the cell membrane, they bind to specific receptors on the cell surface membrane causing a change in the shape of the receptor, resulting in the formation of a second messenger inside the cell, second messenger activates number of different enzymes, second messenger (Cyclic AMP) bind to other chemical which pass into the nucleus and act as DNA transcription factors

  
• Steroid hormones


  They are lipid soluble so they pass through phospholipid bilayer, then act as internal messenger itself, hormone bind to receptors inside the cell and form hormone receptor complex and passes into the nucleus, hormone receptor complex act as TF regulatory gene expression
• Similarities between endocrine and nervous system

  • Both involve chemicals, both involve cell signalling, both involve signal molecule binding receptor
• Differences between endocrine and nervous system

  • Communication: By hormones vs By nerve impulses, Nature of communication: Chemical vs Electrical impulses, Mode of transmission: Blood vs Neurones/nerve cell, Transmission speed: Slower vs Faster, Duration: Long lasting vs Short lived, Effects: Wide spread vs Localised

  
• Excretion is the removal of toxic substance, waste products of metabolic reactions and the removal substances found in excess out of the body
• Deamination


  Break down of excess amino acids in liver, to remove amine group (NH2) forming ammonia so ammonia combine with CO2 in urea cycle forming urea

  
• Ornithine cycle


  2NH3 + CO2 forming CO (NH2)2 + H2O, Urea

  
• Function of the kidney


  • Excretion, removal of urea from the body, Osmoregulation, control water potential of the blood that passes through them by ADH

  
• Ultra-filtration


  The blood comes in the afferent arteriole under high pressure, the efferent arteriole has a smaller diameter than afferent arteriole, building up a pressure in the glomerulus forcing fluid out of the glomerulus through capillary pores into Bowman's capsule, basement membrane act like a selective barrier, the wall of the capsule is made up of special cells called podocytes, the foot like extensions form gaps known as slit pores, molecules will pass through slit pores into Bowman's capsule
• PCT


  • Microvilli: increase surface area for absorption of sodium ions and glucose, Mitochondria: to produce ATP for active transport of NA+ out of cells, Tight junctions: formed between adjacent cells so that fluid can't pass between cells, Folded basal membrane: with many transport proteins (sodium pump), Carry co transporters
• Selective reabsorption


  Sodium ions pumped out of the cells into blood against concentration gradient using ATP, so sodium ions will diffuse into PCT cells through sodium co transport from the filtrate down concentration gradient, glucose and amino acids enter PCT by secondary active transport, glucose, amino acids, vitamins, and hormones are reabsorbed completely by active transport, some sodium ions can also be reabsorbed by active transport, chloride ions can also leave by diffusion, the co transport of solutes into the cytoplasm of epithelial cells increase concentration of the cytoplasm, so water moves by osmosis down water potential gradient from filtrate in the PCT lumen into the epithelial cell cytoplasm through the epithelial cell membrane, which in turn enters the blood by osmosis