Summary Edexcel GCE A level biology B Detailed Notes
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Course
A level Biology
Institution
Hi there; I was once an A-level student just like you all, these notes helped me achieve an A* in biology, in addition, I also took human biology (with a grade of 9) and biology in GCSE therefore I was able to link all 3 subiects for better understanding of certain topics.
It includes:
- In-d...
RESPIRATION IN CELLS
→ CELLULAR RESPIRATION IS THE PROCESS BY WHICH ENERGY FROM THE BONDS IN THE
FOOD IS TRANSFERRED TO ATP.
RESPIRATORY SUBSTRATES
→ THE SUBSTANCE THAT IS BROKEN DOWN DURING RESPIRATION IS KNOWN AS
RESPIRATORY SUBSTRATE.
THERE ARE MANY RESPIRATORY SUBSTRATES:
- GLUCOSE: RELEASE UPTO 30.5 KJ/g
- CARBOHYDRATES: RELEASE 15.8 KJ/g
- LIPIDS: RELEASE 39.4 KJ/g
→ THE FATS WILL BE BROKEN DOWN INTO FATTY ACIDS AND GLYCEROL. AFTER
THIS 2 MAIN PROCESSES TAKE PLACE
● BETA OXIDATION: FATTY ACIDS WILL BE BROKEN DOWN IN THE CYTOSOL (IN
PROKARYOTES) AND IN MITOCHONDRIA (IN EUKARYOTES) TO PRODUCE
ACETYL COENZYME (CoA) WHICH ENTERS KREBS CYCLE AFTER WHICH.
● PHOSPHORYLATION:
LIPIDS TEND TO FIRST BREAK DOWN INTO FATTY ACIDS AND THEN THEY
TEND TO REACT WITH ACETYL COENZYME A TO ENTER THE KREBS CYCLE.
THUS ONLY IF THERE IS AN OXIDISED CoA THEN THE LIPIDS WILL BE ABLE
TO RESPIRE.
LIPIDS WILL ONLY RESPIRE IN AEROBIC CONDITIONS; THIS IS BECAUSE IN
ANAEROBIC RESPIRATION THE PYRUVATE WILL BE USED TO REOXIDISE
THE NADH COENZYME BACK TO NAD RATHER THAN MOVING ON TO KREBS
CYCLE.
ALSO, OXYGEN WILL NOT BE AVAILABLE IN ANAEROBIC RESPIRATION SO IT
WOULD NOT ACT AS AN ELECTRON ACCEPTOR.
THEREFORE THE COENZYMES (FAD, NAD) THAT GOT REDUCED WILL NOT
BE ABLE TO GET OXIDISED BACK.
THIS WILL RESULT IN COENZYME A NOT BEING THERE TO BIND TO THE
FATTY ACIDS
- PROTEINS: THEY RELEASE 17 KJ/g
→ THEY ARE BROKEN DOWN INTO AMINO ACIDS. AFTER WHICH 2 MAIN PROCESSES
TEND TO TAKE PLACE:
● DEAMINATION: IT IS THE REMOVAL OF AN AMINO GROUP FROM A MOLECULE
AND IT REPLACED BY A KETONE.
ENZYMES THAT CATALYSE THIS REACTION ARE CALLED DEAMINASES.
TAKES PLACE IN THE LIVER
● TRANSAMINATION: A CHEMICAL REACTION THAT TRANSFERS AN AMINO
GROUP TO A KETO ACID TO FORM NEW AMINO ACIDS
,→ THE DIFFERENCE IN THE ENERGY RELEASED BY EACH RESPIRATORY SUBSTRATE IS
DUE TO THE DIFFERENT AMOUNT OF HYDROGEN ATOMS PRESENT IN EACH ONE OF THEM.
THE MORE HYDROGEN ATOMS PRESENT TO REDUCE THE COENZYMES, MORE IS THE
ENERGY THAT CAN BE GENERATED IN THE ELECTRON TRANSPORT CHAIN.
THAT IS WHY WE SEE THAT LIPIDS WILL PRODUCE ABOUT DOUBLE THE ENERGY
CARBOHYDRATES TEND TO PRODUCE, THAT IS BECAUSE THEY TEND TO CONTAIN
DOUBLE THE AMOUNT OF HYDROGEN.
→ RESPIRATION QUOTIENT IS THE RATIO OF THE VOLUME OF CARBON DIOXIDE
PRODUCED TO THE VOLUME OF OXYGEN USED IN THE SAME PERIOD.
IF THE VALUE OF RQ IS GREATER THAN 1; THEN ANAEROBIC RESPIRATION HAS TAKEN
PLACE
IF THE VALUE OF RQ IS 1; THEN AEROBIC RESPIRATION HAS TAKEN PLACE.
FORMS OF CELLULAR RESPIRATION
→ RESPIRATION CONSISTS OF 4 MAIN PARTS:
- GLYCOLYSIS
- LINK REACTION
- KREBS CYCLE
- OXIDATIVE PHOSPHORYLATION (THE ELECTRON TRANSPORT CHAIN)
AEROBIC RESPIRATION
→ TAKES PLACE IN THE PRESENCE OF OXYGEN
→ TAKES PLACE IN MITOCHONDRIA
→ COMPLETE OXIDATION OF GLUCOSE TAKES PLACE
→ NET ATP PRODUCED = 31 MOLECULES
→ WHEN ENERGY IS NEEDED THE 3RD PHOSPHATE BOND IN ATP WILL BE BROKEN DOWN
(HYDROLYSIS REACTION) BY THE ENZYME ATPase TO PRODUCE ADP AND PHOSPHATE
GROUP.
30.5KJ OF ENERGY WILL BE RELEASED DURING THIS HYDROLYSIS.
→ ATP CAN BE THEN FORMED FROM ADP AND PHOSPHATE GROUP THROUGH
PHOSPHORYLATION REACTION CATALYSED BY ATPase ENZYME. THIS NEEDS 30.5 KJ
WHICH IS SUPPLIED BY RESPIRATION.
,ANAEROBIC RESPIRATION
→ TAKES PLACE IN THE ABSENCE OF OXYGEN
→ TAKES PLACE IN THE CYTOPLASM
→ INCOMPLETE OXIDATION OF GLUCOSE TAKES PLACE
→ NET ATP PRODUCED = 2 MOLECULES.
→ ANAEROBIC RESPIRATION IN MAMMALS:
→ ANAEROBIC RESPIRATION IN PLANTS AND FUNGI:
INVESTIGATING FACTOR AFFECTING THE RATE OF RESPIRATION
RESPIRATION RATE IS THE RATE AT WHICH AN ORGANISM CONVERTS GLUCOSE TO
CARBON DIOXIDE AND WATER.
WE CAN MEASURE IT BY MEASURING THE RATE OF OXYGEN CONSUMPTION BY THE
ORGANISM.
1. RESPIROMETER
→ WE TEND TO MEASURE THE CHANGE IN GAS VOLUME IN A
CLOSED SYSTEM.
→ WE USE SODA LIME, THE CO2 IN THE TEST TUBES WILL BE
ABSORBED AS IT IS PRODUCED. THUS, ANY CHANGE IN THE
VOLUME WILL BE DUE TO OXYGEN CONSUMPTION.
→ WE CAN USE ANIMALS LIKE: WOODLICE, INSECT LARVAE,
WORMS (THIS IS BECAUSE THEY’RE SMALL AND READILY
AVAILABLE)
FOR PLANTS WE TEND TO USE GERMINATING SEEDS
FOR MICROORGANISMS WE USE YEAST
→ PROCEDURE:
- THE SCREW SLIP IS CLOSED DURING THE
EXPERIMENT TO SEAL THE APPARATUS TO AVOID LOSS OF GAS.
IT CAN BE OPENED BETWEEN EXPERIMENTS TO EQUALISE THE PRESSURE
AND REPLENISH THE GASES IN THE TEST TUBE
- WE TEND TO USE 2 TEST TUBES:
THE EXPERIMENTAL TUBE; WHICH WILL CONTAIN THE ORGANISM WE ARE
STUDYING
CONTROL CHAMBER WILL NOT CONTAIN THE ORGANISM RATHER IT WILL
HAVE GLASS BEADS THAT OCCUPY THE SAME VOLUME AS THE ORGANISM
(IF WE ARE GOING TO USE GERMINATED PLANTS THEN WE ADD BOILED
SEEDS TO THE CONTROL TUBE).
, THE CONTROL CHAMBER WILL ELIMINATE FACTORS LIKE TEMPERATURE
AND PRESSURE, BECAUSE BOTH THE CONTROL AND EXPERIMENTAL TUBE
WILL BE AFFECTED EQUALLY BY THEM.
- BOTH THE TUBES WILL BE CONNECTED WITH A CAPILLARY GLASS TUBE
KNOWN AS MANOMETER. IT WILL BE FILLED WITH A COLOURED LIQUID THAT
MOVES IN RESPONSE TO CHANGES IN PRESSURE.
BECAUSE THE VOLUME OF GAS WILL DECREASE IN THE EXPERIMENTAL
TUBE, THE PRESSURE IN IT WILL DECREASE. SINCE THE CONTROL TUBE IS
AT HIGHER PRESSURE, THE LIQUID WILL BE PUSHED TOWARDS THE
EXPERIMENTAL TUBE.
- THE EXPERIMENTAL TUBE WILL ALSO HAVE A SYRINGE WHICH WILL BE
USED TO RETURN THE COLOURED LIQUID TO WHERE IT WAS. THE VOLUME
OF AIR PUMPED INTO THE EXPERIMENTAL TUBE FOR THE COLOURED LIQUID
TO RETURN TO ITS ORIGINAL POSITION IS THE VOLUME OF OXYGEN
CONSUMED DURING THIS TIME PERIOD.
OR WE CAN CALCULATE THE DISTANCE MOVED BY THE FLUID IN THE
MANOMETER AND FIND THE VOLUME USING πr2l
2. DYES
3. GAS SYRINGE METHOD
INVESTIGATING THE SITE OF ATP SYNTHESIS
→ SINCE MITOCHONDRIA IS CONSIDERED THE MAIN SITE FOR ATP SYNTHESIS, WE CAN
BREAK OPEN CELLS AND OBTAIN MITOCHONDRIA (THROUGH CENTRIFUGATION). WE
SUPPLY IT WITH OXYGEN AND GLUCOSE, AND SEE IF ATP WILL BE PRODUCED.
→ THE PROCESS OF ELECTRON TRANSPORT CHAIN TENDS TO TAKE PLACE IN THE (INNER
MEMBRANE) OF THE MITOCHONDRIA.
UNDER OBSERVATION USING ELECTRON MICROSCOPE, WE SEE THAT THE INNER
MEMBRANE IS DIVIDED INTO CRISTAE WHICH HELPS INCREASE ITS SURFACE AREA.
→ WE CAN ALSO SEE THAT THE INNER MEMBRANE IS COVERED WITH CLOSELY PACKED
STALKED PARTICLES (OXYSOMES) AND AFTER SEPARATING THE STALKED PARTICLES
FROM THE INNER MEMBRANE, WE CAN SEE THAT ONLY ATP SYNTHESIS TAKES PLACE
THERE.
THEREFORE THE STALKED PARTICLES ARE THE MAIN SITE OF ATP PRODUCTION IN THE
MITOCHONDRIA.
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