Chapter 16 (Cellular Respiration) Flashcards
What is ATP
- Phosphorylated nucleotide
- Universal energy currency
- Short term energy molecule
- Large molecule so can’t diffuse across cell membranes.
Definition of oxidation?
Removal of hydrogen ions
Addition of oxygen
loss of electrons
definition of Reduction
Addition of hydrogen ions
Removal of oxygen
Gain of electrons
Definition of dehydrogenation
Removal of hydrogen ions
Definition of decarboxylation
Removal of carbon dioxide
Product has one less carbon atom within it.
Definition of phosphorylation
Addition of of a phosphate group
sometimes involves kinase
What is decarboxylase
Enzyme that removes carboxyl group from molecule. (carries out decarboxylation)
by hydrolysis, releasing CO2
Occurs in link reaction and krebs cycle
What is dehydrogenase
Enzyme that removes hydrogen atoms from molecules.
Passes hydrogen atoms to another molecule.
(dehydrogenation reaction)
Occurs in link reaction, krebs cycle and E transport chain.
What is a kinase
Enzyme that adds a phosphate group to a molecule.
Often involves ATP (as phosphate group donor)
What are coenzymes
An additional molecule required by some enzymes to enable their function. (Non-protein organic molecules which bind to enzyme’s active site.)
Required by many dehydrogenases to accept/donate hydrogen atoms removed by the enzyme.
Examples of coenzymes
NAD
FAD
CoA
What does NAD do
Hydrogen carrier produced in body.
Nicotinamide part accepts pair of hydrogen atoms, so NAD becomes red NAD, so it can then donate pair of hydrogen atoms - Becomes oxidised
What does FAD do
Acts as hydrogen carrier, so FAD becomes red FAD when it accepts hydrogen atoms. It becomes oxidised when it donates hydrogen atoms.
What does CoA
Organic molecule consisting of adenosine ( adenine + ribose), 3 phosphates, cysteine and Pantothenic acid ( Vit B)
Carries 2 carbon fragments.
Glycolysis info
NET INCREASE COME BACK TO
In cytosol
each stage requires specific enzyme to increase rate of reaction.
Function - to split glucose (hexose 6C) into 2 trioses (3C)
Input: Glucose, 2ATP, NAD, enzymes
Output: 2 Pyruvate, 4ATP, 2 red.NAD
What is the purpose of ATP
To supply energy to drive metabolic reactions and other processes inside cells
Examples of uses of ATP
Bioluminescence
Endocytosis
Active Transport
Muscle contraction
Spindle fibre formation in mitosis + meiosis
Anabolic reactions, eg, protein synthesis, semi-Conservative replication
Maintenance of internal stable body temperature
BEAMSAM
Properties of ATP
- Small
- Water soluble (easily transported around the cell)
- Easily hydrolysed and reformed
- Bonds between adjacent phosphates are easily broken
Why is ATP called the ‘universal energy currency’
UNIVERSAL
-Found in ALL eukaryotes and prokaryotes
ENERGY CURRENCY
- can be hydrolysed to release small quantities of energy
- ATP ADP + Pi is reversible
- Terminal phosphate group is hydrolysed to release energy
- Energy can be passed to other molecules
- It has a high turnover and acts as an immediate energy donor.
How is ATP formed
During respiration (both aerobic and anaerobic) by the phosphorylation of ADP
How is ATP used
Hydrolysed to release energy that is then used in metabolic reactions inside ALL living cells.
Benefit of the hydrolysis of ATP
Enables energy to be released in small quantities
If all the chemical potential energy from glucose was released in one go, this would release lots of heat which would denature enzymes and cause cell metabolism to stop.
What is the role of a phosphatase
CHECK SPELLING
Responsible for removing a phosphate from a protein
What is substrate-level phosphorylation
Direct phosphorylation of ADP with an inorganic phosphate
does not involve electron transport chain
accounts for 10% of ATP production in aerobic respiration.
What is oxidative phosphorylation
CHECK WHAT THEY WANT FOR THIS ON!!!
ATP is generates from the oxidation of red. NAD and red. FAD, and the subsequent transfer of electrons and pumping of protons.
The movement of electrons down an electron transport chain and ATPSynthase and Chemiosmosis.
(process of oxidation in a series of redox reactions)
Benefits of cristae in mitochondria
Inner membrane folded into cristae
Inc SA to inc no. of electron transport carrier proteins, to inc pumping of protons into the intermembrane space, inc chemiosmosis, inc rate of ATP production
Impermeable to protons
what does the matrix of mitochondria do
- contains enzymes for LR + KC
- contains enzymes for oxidation of fatty acids
- contains lipid droplets
- contains DNA plasmid
What does the plasmid do in mitochondria
Has genes that code of proteins in the ETC
Has genes that code for proteins required to make mitochondrial ribosomes.
What does the mitochondrial envelope do
Forms the intermembrane space to enable protons to accumulate to generate proton motive force that leads to ATP production via chemiosmosis.
Separates krebs cycle and OP from rest of cell.
Definition of respiratory substrate
An organic molecule that can be broken down in respiration to produce ATP
Why do different respiratory substrates produce different amounts of ATP
Different RS contain different amounts of hydrogen
Higher the number of H+ that can be pumped into IMS, the greater the PMF.
So greater no. ATP molecules produced
Info on carbohydrate as a respiratory substrate
- Glycogen/amylose/amylopectin can be hydrolysed (break glycosidic bonds) to glc.
- Other monosaccharides can be respired, eg, frc + gal are converted to glc, then respired.
Examples of respiratory substrates
Carbohydrates
Proteins
Lipids
Info on protein as a respiratory substrate
- excess amino acids are deaminated: removal of amine group -> urea via ornithine cycle.
- Remainder of molecule is converted to glycogen/lipids for energy storage.
- During starvation, proteins can be hydrolysed ( breaking peptide bonds) to release aa.
- Some are converted to pyruvate/acetate and enter Krebs cycle.
- other enter Krebs cycle directly.
Info on lipids as respiratory substrates
Triglycerides are hydrolysed (breaking ester bonds) to 3 fatty acids + 1 glycerol.
Glycerol is converted to glc and respired
Fatty acids broken down during B-oxidation to release acetyl groups
each acetyl group can join with CoA to form aCoA and enter Krebs cycle.
What two cells can only respire glc.
Mature RBC (no mitochondria, so not aa or fatty acids can be respired as no LR or KC occurs)
Human brain cell. ( aa or fatty acids can’t cross the blood-brain barrier)
What is a respiratory quotient
The ratio of the volume of carbon dioxide produced by a respiring organism to that of oxygen consumed by an organism, tissue or cell in a given period of time. INDICATES TYPE OF RESPIRATORY SUBSTRATE BEING USED IN RESPIRATION
Formula for respiratory quotient
RQ= volume of CO2 evolved/ volume of O2 taken up
UNITS OF BOTH GASES = SAME
TIME PERIOD OVER WHICH EACH GAS IS EVOLVED + TAKEN UP = SAME
overall = no units.
RQ for carbohydrates (aerobic)
1
RQ for lipids (aerobic)
0.7 - 0.72
RQ for proteins (aerobic)
0.8 - 0.9
RQ for anaerobic conditions
Infinite
why do lipids and proteins have a lower RQ than carbohydrates
More energy is needed to oxidise them compared to CBH.
What could cause changes in the RQ of an animal
- Different availability of different substrates
- Different availability of different oxygen levels.
Respirometers using gas syringe
SET UP CONTROL
Acclimatise sugar solution + buffer solution in water bath and when added dried yeast using clean graduated syringe, immediately add bung. Ensure gas syringe set to zero. Place in water bath at 25 degrees. stop watch.
at regular time intervals, record volume of Co2 in syringe for 10 mins.
Repeat
calculate mean volume of CO2 produced for each minute.
calculate SD, plot graph with error bars.
Gradient = rate of respiration.
Adaptations for gas syringe respirometers
- Different respiratory substrates
- Different temperatures
- Anaerobic vs. aerobic respiration.
- Different pH
what does a respirometer do
used to measure rate of respiration in a living organism by measuring rate of exchange of oxygen/carbon dioxide.
Possible errors when using gas syringe method
- Failure to acclimatise sugar solution/yeast suspension/buffer solution to appropriate temps.
- Failure to reset gas syringe to zero between repeats
- Failure to insert bung quickly enough at start ( CO2 escape)
- Parallex errors when reading meniscus on gas syringe.
Possible limitations when using gas syringe method.
- Seal may not be obtained between flask + bung enabling CO2 to escape. (USE VASELINE)
- Different samples of yeast suspension may have different no. of yeast cells (ENSURE SUSPENSION IS STIRRED THOROUGHLY BEFORE TAKING SAMPLE)
- Supply of oxygen may be used up towards end of investigation (USE LARGER VOLUME CONICAL FLASK TO HOLD MORE AIR ABOVE SUGAR SOLUTION + YEAST SUSPENSION)
Sources to obtain glucose for Glycolysis?
In animals
Glycogen
- found in liver cells and skeletal muscle cells.
- insoluble
Many branches - many terminal ends - quickly and easily hydrolysed to release glc.
Sources to obtain glucose for glycolysis?
In plants
Amylose
- unbranched polysaccharide, soluble
Amylopectin
-Branched polysaccharide, insoluble.
Where does the link reaction occur
Mitochondrial matrix
What does the link reaction initially require
Pyruvate to have been actively transported from the cytosol to the matrix through the mitochondrial envelope.
Coenzyme A
Type of reactions involved during link reaction
Oxidation
Reduction
Decarboxylation
Type of reactions involved during link reaction
Oxidation
Reduction
Decarboxylation
-> Oxidative decarboxylation
What is CoA made up from
Cysteine (aa) Pantothenic acid (vitamin B5) Adenosine triphosphate (ATP)
Why can’t the link reaction occur in the cytosol
No CoA in the cytosol
Where does the Krebs cycle take place
Mitochondrial matrix
affected by [s],[E], temp, pH, [I] as it is a series of enzyme-controlled reactions.
Where does oxidative phosphorylation occur
On cristae of mitochondria
Definition of chemiosmosis
Movement of ions across a semipermeable membrane, down their electrochemical gradient.
What is oxidative phosphorylation
The combined effect and outcome of both the ETC and chemiosmosis
What does oxygen do in ETC
Oxygen acts as the final electron acceptor
O2 accepts protons and is reduced to form water
4H+ + 4e- +02 –> H20. BALANCE
Enables ETC to continue, which enables chemiosmosis to continue, which inc ATP production.
What is the proton motive force
Proton concentration and electrical gradient together.
What is the principle of anaerobic respiration
- ## Molecules other than oxygen are used as electron acceptors (as no oxygen available)
What is the principle of anaerobic respiration
- Molecules other than oxygen are used as electron acceptors (as no oxygen available)
- occurs only in skeletal muscles
ensures cell can produce some ATP in times of oxygen stress, eg after vigorous exercise. - enables glycolysis to continue to ensure 2 ATP is made per glc.
What is meant by ‘yeast is a facultative anaerobe’
Yeast is an organism that makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation if oxygen is absent.
Why is the net gain of ATP actually less than the theoretical gain
ATP is used to:
- Actively transport pyruvate into the matrix
- Shuttle hydrogen from Red NAD produced in glycolysis into the matrix
- Pump protons into the inter membrane space.
- some protons leak across the mitochondrial membrane, reducing the proton motive force.
Why is the net gain of ATP actually less than the theoretical gain
ATP is used to:
- Actively transport pyruvate into the matrix
- Shuttle hydrogen from Red NAD produced in glycolysis into the matrix
- Pump protons into the inter membrane space.
- some protons leak across the mitochondrial membrane, reducing the proton motive force.
Similarities between anaerobic respiration in skeletal muscle cells and anaerobic respiration in yeast cells?
- Incomplete breakdown of glucose
- No oxygen required
- NAD, ATP products
- low efficiency
How are electrons carried from the Krebs cycle to ETC…
Electrons carried via reduced NAD, and Reduced FAD..
Why is the ATP yield in anaerobic respiration smaller?
Only glycolysis occurs - No LR, K cycle, OP..
Glucose not fully broken down and so still contains chemical potential energy.
no oxygen to act as final oxygen acceptor, so ETC stops - no OP.
