T5 - Energy for biological Processes Flashcards
State what is meant by the term cellular respiration
A series of chemical reactions that release chemical potential energy from organic molecules eg glucose to make ATP
What is the function of ATP?
Source of energy for metabolic reactions such as:
Muscle contraction
Active transport e.g. of mineral ions into root hair cells
Secretion (exocytosis)
Endocytosis
Anabolic reactions (building large molecules) e.g. Protein synthesis
DNA replication
Mitosis (cell division)
Activation of chemicals
What does ATP stand for?
Adenosine Triphosphate
Describe the structure of ATP
Adenine base bonded to a ribose molecule, which is bonded to three phosphate
Describe how energy is released from ATP.
ATPase catalyses the hydrolysis of ATP into ADP and Pi (inorganic phosphate) by lowering the activation energy required to break the bonds between the phosphate groups.
Explain why respiration is considered an exergonic reaction
It releases energy to the environment.
It also releases heat, so is exothermic.
How much energy is released when ATP is hydrolysed into ADP?
30.6 kJ
Explain why ATP is considered the “universal energy currency of
cells”
ATP is useful as an energy carrier (currency) because;
● it cycles – there is a rapid turnover of ATP within cells.
● it “ ” the energy released from respiration into small manageable amounts that will not damage cells or be wasted.
● it releases energy instantly in a single reaction.
● it is universal - found in all organisms
Contrast aerobic respiration with anaeroic respiration
Aerobic respiration occurs in the presence of oxygen, anaerobic occurs when oxygen is absent.
Aerobic produces a much higher yield of ATP than anaerobic respiration.
Aerobic produces CO and H O as waste products, whereas anaerobic produces lactate (animals) or ethanol (plants) as waste products.
List the different stages of of aerobic respiration and where they occur
Glycolysis in cytoplasm, link reaction and Kreb’s cycle in the matrix of mitochondria, and oxidative phosphorylation on the inner membrane of mitochondria.
State the location of glycolysis
Cytoplasm
What are redox reactions?
Reduction and oxidation reactions
What happens when a molecule gets reduced (reduction)?
It gains hydrogen atoms or electrons
What happens when a molecule gets oxidised (oxidation)?
It loses hydrogen atoms or electrons
What is glycolysis?
Metabolic pathway that converts glucose into pyruvate
Where does the glucose required for glycolysis come from?
Glucose comes directly from blood or breakdown of glycogen stores in muscle/liver cell
Describe how glucose is converted to pyruvate
Describe glycolysis
Outline the stages in glycolysis
● Glucose is phosphorylated into hexose bisphosphate using the energy released from hydrolysis
● Hexose bisphosphate is unstable so splits into two glycerate 3-phosphate (GP) molecules.
● Each GP is oxidised by removal of 2 hydrogen atoms by dehydrogenase to form pyruvate
● The hydrogen atoms are transferred to 2 NAD to form 2 NADH (and 2 H+) molecules.
● The energy released by oxidation of GP produces a net gain of 2 ATP molecules by substrate level phosphorylation
Explain the significance of the phosphorylation of glucose
Phosphorylation is the addition of phosphate by ATP. Glucose is stable.
Phosphorylation of glucose produces hexose bisphosphate, which is unstable, so more easily splits into two GP molecules.
What happens to the phosphate groups used to phosphorylate glucose later on in glycolysis?
The phosphate groups are used to phosphorylate ADP to reform ATP
State what is meant by substrate level phosphorylation
The addition of phosphate to ADP directly from substrate using the energy from a coupled reaction e.g. oxidation of GP
State the role of NAD in glycolysis and explain its significance
NAD is a coenzyme
It is needed to accept hydrogen atoms from oxidised GP.
Reduced NAD (NADH) transfer electrons from glycolysis to the electron transport chain which results in ATP production
Name the enzyme that removes hydrogen atoms from GP
Dehydrogenase
What is the role of dehdrogenase enzyme in glycolysis?
Catalyses the oxidation of GP by removing 2 hydrogen atoms
List the products of glycolysis
2 pyruvate
2 NADH
Net gain of 2 ATP
How many carbon atoms are in one molecule of pyruvate?
3
State location of the link reaction and the Kreb’s cycle
Matrix of mitochondria
State what is meant by the term decarboxylation
Removal of a carboxyl group (CO2)
State what is meant by the term dehydrogenation
Removal of hydrogen atoms
State what is meant by the term oxidation
Loss of hydrogen
State what is meant by the term reduction
Gain of hydrogen
Describe what happens to pyruvate in the link reaction
● Pyruvate is decarboxylated by pyruvate decarboxylase which removes a carboxyl group.
● Pyruvate is oxidised to form acetate by pyruvate dehydrogenase which removes 2 hydrogen atoms and transfers them to NAD+.
Describe the link reaction
● Pyruvate is decaroboxylated by pyruvate decarboxylase which removes a carboxyl group.
● CO2 is released as a waste product
● Pyruvate is completely oxidised to form acetate by pyruvate dehydrogenase which removes 2 hydrogen atoms.
● The 2 hydrogen atoms are transferred to NAD+, forming reduced NAD (NADH)
●Acetate is combined with coenzyme A (CoA) to form acetyl CoA)
What happens to the acetyl CoA produced in the link reaction?
It is actively transport into the mitochodrial matrix where it enters the Kreb’s cycle.
How many carbon atoms are in acetyl CoA?
2
How many CO and NADH molecules are produced by the link reaction per glucose molecule?
2 x CO2
2 x NADH
Explain the role of the Krebs cycle.
Kreb’s cycle completely oxidises acetyl CoA to release as much energy as possible to directly produce ATP and NADH so that ATP can be produced in the electron transport chain by oxidative phosphorylation.
Describe the stages of the Kreb’s cycle
● Acetyl CoA (2C ) adds its acetyl group to a 4C acid (oxaloacetate) to produce a 6C acid (citrate).
● CoA is released.
● The 6C acid is oxidised by a hydrogenase enzyme, which removes 2 hydrogen atoms and transfers them to NAD+, forming reduced NAD (NADH + H+).
● The 6C acid is decarboxylated by a decarboxylase enzyme, releasing CO2 and forming a 5C acid.
● The 5C acid is decarboxylated releasing another CO2
● The 5C is oxidised in a series of reactions to reform the initial 4C acid, producing 2 more NADH and FADH2
● During this stage ADP is phosphorylated to produce ATP by substrate-level phosphorylation.
Explain how the 4C compound changes its carbon atom number to 6C then 5C, and is then reformed during the Krebs cycle
The 4C compound is combined with the acetyl CoA, which is 2C, to form the 6C compound.
The 6C compound is decarboxylated to form the 5C compound.
The 5C compound is decarboxylated to reform the 4C compound.
Discuss the effect of a lack of Coenzyme A on the Krebs cycle
● Coenzyme A is needed to convert pyruvate to acetyl CoA.
● Acetyl CoA combines with the 4C compound at the start of the Krebs cycle to produce a 6C compound, which is used in subsequent reactions.
● Without CoA, acetyl CoA would not be produced and so the Krebs cycle would not continue.
● CO would not be produced as there would be no 6C compounds to decarboxylate.
● No NADH or FADH would be produced so the electron transport chain would stop, causing a fall in ATP production.
State the role of FAD and NAD in the Kreb’s cycle
● FAD and NAD are conezymes
● They accept hydrogen atoms from oxidised substrates.
● They transfer electrons from the Kreb’s cycle to the elctron transport chain, which results in ATP production.
State the number of ATP molecules that are made directly per ‘turn’ of the Kreb’s cycle.
1
State the number of reduced NAD molecules that are made directly per ‘turn’ of the Kreb’s cycle.
3
State the number of reduced FAD molecules that are made directly per ‘turn’ of the Kreb’s cycle.
1
State the number of reduced CO molecules that are made directly per ‘turn’ of the Kreb’s cycle.
2
State the number of ATP molecules that are made directly by the Kreb’s cycle per glucose molecule.
2
State the number of reduced NAD molecules that are made directly by the Kreb’s cycle per glucose molecule
6
State the number of reduced FAD molecules that are made directly by the Kreb’s cycle per glucose molecule.
2
State the number of reduced CO molecules that are made directly by the Kreb’s cycle per glucose molecule.
4
State the location of the electron transport chain
Inner mitochadrial membrane
State what is meant by the term oxidative phosphorylation
when ATP is produced in the presence of oxygen by the elctron transport chain and chemiosmisos
Name the last electron carrier in the electron transport chain
cytochrome oxidase
Name a coenzyme/hydrogen acceptor that links the kreb’s cycle to the ETC
NAD+ / FAD
state the role of oxygen in aerobic respiration
terminal electron acceptor in oxidative phosphorylation
forms water by accepting electrons from cytochrome oxidase and binding to hydrogen ions in matrix
What happens to NADH and FADH2 at the ETC
a dehydrogensae enzyme removes the hydrogen atoms from NADH and FADH2 so they are reoxidised
Explain the benefit of an electron transport chain instead of a single reaction
energy is released gradulaty
less energy is released as heat
Name the enzyme involde in chemiosmosis
ATP synthase
State the meaning of the term chemiososis
the production of ATP via use of energy vias use of energy released by the flow of hydrogen ions across the inner mitochondrial memebrane
Explain the high conc of h ions is mainted in the intermembrane space
the inner mitochondrial memebrane is impermable to h+ ions so the H+ can only diffuse back through the protien channel of atp synthase
Explain the benefit of the folding of the inner mitochondrial membrane
the inner mitochondrial memebrane is folded into cristea which allow a much greater number of electron chain carrier protiens and atp synthase to be packed into the mitochondrian. This increases the amount of ATP.
State the meaning of the term anearobic respiration
the partial breakdown of hexose/glucose to produce a limited yeild of ATP in the absence of osygen
State which part of respiration are anaerobic
glycolysis
Where in a cell does anearobic repiration occur
cytoplasm
How many ATP does anearobic respiration produce
2
State when anearobic respiration is useful
for short rapid bursts of ATP production eg during vigurous excersie
NAme the product of anearobic respiration in mammals
lactic acid
name the enzyme that reduces pyruvate into lactate
lactate dehydrogenase
where does the h atom coem from to reduce pyruvate
NADH
What is the role of NADH in anearobic respiration
NADH is used to reduce pyruvate rather than go to the ETC. NADH is oxidised to NAD which is reused in glycolysis to generate ATP
What effect does this product have on the blood
Lowers the pH
How does this affect the muscles
Reduces and eventually stops them contacting due to reduced nervous stimultion from CNS
Why does breathing rate remain high following exercise
Lactic acid produced, more oxygen needed to oxidise lactate into pyruvate whihc can then taken into the mitochondra inot the krebs cycle
Name the enzyme that removes CO2 from pyruvate to form ethanal in plants
pyruvate decarboxylase
Name the enzyme that reduces ethanal into ethanol
ethanl dehydrogenase
where does the hydrogen atom come from to reduce ethanal
NADH
which name is given to anearobic respiration in yeast
Fermentation
NAme the product of anearobic respiration in plants
Ethanol
