Quick revision Flashcards
Explain aerobic respiration
-Process of large energy release by splitting glucose into CO2 and H2, which forms H2O
-Energy released is used to phosphorylate ADP to ATP, to provide energy for biological processes
-4 stages: glycolysis, link reaction, krebs cycle, oxidative phosphorylation
-Products from first 3 stages are used in 4th stage to produce many ATP
-Coenzymes (NAD, FAD) are used to transfer H from one molecule to the next
Explain glycolysis
-Occurs in cytoplasm
-Glucose (6C) is phosphorylated using 2x ATP, 2x Phos added to sides of glucose
-Splitting of 1x glucose (6C) into 2x triose phosphate (3C), 1Phos on side of 3C
-Phosphorylation occurs again, 2x Phos on both sides of both triose phosphate
-Triose Phosphate is oxidised to form 2x Pyruvate (3C) (phosphate is removed from molecule)
-2x NAD + H -> reduced NAD and 2x ADP +Pi -> ATP
-Net: 2 ATP produced, 2x Pyruvate + H2O, 2x NADH + 2H
Explain link reaction
-Occurs in matrix of mitrochondria, active transport via transport protein across mitochondrial envelope, using H ion.
-Occurs twice for every glucose molecule since 2x Pyruvate is made
-Decarboxylation and dehydrogenation of 3C is catalysed by pyruvate dehydrogenase
-Dehydrogenation occurs: 1x NAD -> Reduced NAD
-Pyruvate is decarboxylated from 3C -> 2C (Acetyl), lost carbon is in CO2 form
-Acetyl combines with coenzyme A to form acetyl-CoA
-Net: 2x acetylCoA goes into krebs, 2x CO2 is waste
-Net: 2x Reduced NAD is formed
Explain krebs cycle
-Occurs in matrix of mitrochondria and occurs twice (since 2 acetylcoa)
-Coenzyme A released from Acetyl
-Acetyl (2C) reacts with acetate (4C) to form citrate (6C)
-Dehydrogenation occurs on Citrate (6C), producing reduced NAD
-Decarboxylation occurs, CO2 wasted, citrate becomes 5C
-Dehydrogenation occurs on 5C, producing reduced NAD
-Decarboxylation occurs again on 5C, CO2 wasted, becomes 4C
-substrate level phosphorylation occurs, 1x ADP + Phos -> ATP
-4C combines with CoA temporarily
-Dehydrogenation occurs twice on 4C, reduced FAD and reduced NAD produced
-A new 4C is produced (oxaloacetate is regenerated allowing cycle to repeat)
-Net: 3x reduced NAD, 1x reduced FAD, 2x CO2, 1x ATP (ONE ACETYL)
Explain oxidative phosphorylation
-Inner mitochondria membrane is an ETC and ATP synthase
-Reduced NAD and reduced FAD transfers 2 high energy electrons into the ETC becoming unreduced
-Electrons move down the ETC, reducing and oxisiding ETC proteins
-Electron moves and energy is lost which is taken by ETC proteins to pump protons from matrix into intermembrane space - proton conc gradient increases here
-Protons move down the gradient into the ATP synthase. The energy from movement is used to create ATP whilst pushing protons into matrix. - This is chemiosmosis
-In the matrix, at end of ETC, electrons combine with 1/2oxygen and 2H to produce H2O
-Oxygen is named the final electron acceptor
Explain anaerobic respiration
-Respiration without oxygen
-Only glycolysis occurs
-Lactate fermentation occurs in animals and produces lactate
-After glycolysis occurs, reduced NAD is converted into NAD and lactic acid is produce
-Glycolysis produces a net of 2 ATP which can keep biological processes going
-Lactic acids needs to be broken down by
-Converting it back to pyruvate to go into krebs cycle
-Liver cells converting it into glucose to be respired or stored
Explain rod cells
-Type of photoreceptor which gives information in black and white
-Rod cells contain light-sensitive rhodopsin pigment
-Rhodopsin is made of retinal and opsin chemical joined together
-In the dark, your rods aren’t stimulated
-Na ions are pumped out of rod cell via active transport
-Na ions diffuse back in through open sodium channels
-This makes the inside slightly more negative then the outside, creating a depolarised membrane
-This triggers neutransmitter release which inhibit the bipolar neurone
-Bipolar neurone cannot fire an A.P to send information to the optic nerve thus to the brain
-In light, rod cells are stimulated
-Light energy breaks/bleaches rhodopsin into retinal and opsin
-Causing Na ion channels to close, preventing Na ions in and Na ions actively transporting out
-Na ions build up on outside, inside is much more negative - the cell membrane becomes hyperpolarised
-When the rod cell is hyperpolarised, neutransmitters release is inhibited preventing its inhibition of the bipolar neurone therefore an A.P is sent to the optic nerve and to the brain
Explain photoreceptors
-Photoreceptors called phytochromes detect light, found in many plant parts e.g leave, seet, root
-Phytochromes control many responses
-Phytochromes are molecules that absorb light, exist in 2states, Pr and Pfr which absord light at 660nm and 730nm respectively
-Phytochromes change state when exposed to different light concentrations
-Pr quickly converts to Pfr in red light
-Pfr quickly converts to Pr when exposed to FR light (or slowly when in darkness)
-Daylight contains more Fr so more Pr converted to Pfr than vice versa
-Differing amount of phytochrome types regulate transcription of genes
-High Pfr levels stimulate flowering
