Respiration 5.7 Flashcards
What is respiration?
Respiration is the process that occurs in all living cells and releases the energy stored in organic molecules like glucose.
What is energy immediately used for?
Energy released is immediatly used to synthesise molecules of ATP from ADP and inorganic phosphate (pi)
What happens when ATP is hydrolysed?
The hydrolysis of ATP releases energy needed to drive biological processes
What are biological processes ATP drives?
ATP need processes:
- active transport
- endocytocis and exocytosis
- synthesis of large molecules like proteins
- DNA replication
- Cell division
- movement
- activation of chemicals
What is metabolism?
Metabolism is all the chemical reactiosn that take place in living cells
What are anabolic reactions?
Anabolic reactions are metabolic reactions where large molecules are synthesises from smaller molecules (making large molecules from small molecules)
What are catabolic reactions?
Catabolic reactions are metabolic reactions involving the hydrolysis of large molecules from smaller ones (breaking down of large molecules to small)
Does respiration create or release energy?
Respiration releases energy from respiratory substrates
Why is ATP referred to as the universal energy currency?
ATP is the universal energy currency as it occurs in all living cells and is a source of energy that can be use by cells in small amounts
What is the structure of ATP?
ATP structure: Adenosine -nitrogenous base adenine -5 carbon sugar ribose 3 phosphate groups ( Tri phosphate)
What are the 2 mains bonds in ATP?
Bonds:
- phosphodiester between CH2 group o ribose and the first P on the phosphate group
- Phosphoanhydride bond between the phosphate groups
Discuss the stability of ATP
ATP is relatively stable when in solution in cells and can be easily moved from place to place in a cell BUT is readily hydroylysed by the enzymes catalysis
Hydrolysis of ATP releases heat. Why is this not wasteful/inefficient?
The heat released helps keep the organisms warm and enables their enzyme catalyses reactions to proceed at or near optimum rate
What does glycolyis make?
Gylcolysis produces:
- 2 Pyruvate
- 2 reduced NAD
- 2 ATP
Where does gycolysis occur?
Glycolysis occurs in the cytoplasm
What is the series of reactions of respiration?
- glycolysis
- link reaction
- krebs cycle
- oxidative phosphorylation
What is pyruvate converted to in anaerobic conditions?
In anaerobic condtions pyruvate is converted to ;lactate or ethanol
What is the structure of NAD?
NAD:
- adenosine attached to a ribose attached to a phosphate
- nicotinamide attached to a ribose attached to a phosphate
- both phosphates are joined
What is NAD?
NAD is a non protein molecules that helps dehydrogenase enzymes to carry out oxidative reactions
Where does reduced NAD carry the proteins and electrons?
Reduced NAD carries protons and electrons to the cristae of mitochondria and delivers them to be used in oxidative phosphorylation.
What is nictotinamide?
Nicotinamide is vitamin B12
Define glycolysis
Glycolysis is the first stage of respiration and is a 10 stage metabolic pathway that converts glucose to pyruvate. It is a biochemical pathway that occurs in the cytoplasm of all living organisms that respire
How many reactions happen in gycolysis?
Gylocysis is a 10 stage metabolic pathway
Briefly summarise Gylycolysis
Glycolysis:
- glucose (6c)
- Glucose-p (6c)
- Hexose bisphosphate (6c)
- 2 x triose phosphate (3c)
- 2 x pyruvate
What stage of gylcolysis does ATP and reduced NAD gte made?
4 ATP are made from ADP +p and 2 reduced NAD are made form 2 NAD in the oxidation of triose phosphate to pyruvate
What is the first big stage of Gycolysis?
Phosphorylation of glucose to hexose bisphosphate
Glucose is a stable hexose sugar so needs to be activated before spiltting into 3 carbon compounds
- One ATP is hydrolysed and the released phosphoryl group is added to the glucose
- Another ATP molecule is hydrolysed and the phosphoryl is added again to make hexose bisphosphate
In the first stage of glycolysis what does the ATP do other than activating the hexose sugar?
The ATP also prevents it from being transported out of the cell
What is the second stage of gycolysis?
The second stage is where hexose bisphosphate is split into 2 triose phosphate molecules each made of three carbons
What is the final stage of gycolysis
Oxidation of triose phosphate to pyruvate:
This is anaerobic but involves oxidation
1. dehydrogenase enzymes aided by NAD remove hydrogens from triose phosphate
2. the 2 NAD molecules accept the hydrogen ions and become reduced
3. 2 molecules of NAD are reduced for every molecule of glucose undergoing the process
4. 4 molecules of ATP are made for every 2 triose phosphate molecules undergoing oxidation
Define dehydrogenation
Dehydrogenation is the removal of hydrogen atoms from a substrate molecule
Define decarboxylation
Decarboxylation is the removal of a carboxyl group from a substrate molecule
What is substrate level phosphorylation?
Substrate level phosphorylation is the production of ATP from ADP and Pi during glycolysis and the krebs cycle
Where does the link reaction occur and how does the pyruvate get there?
The link reaction occurs in the mitochondrial matrix. The pyruvate is actively transported via a specific pyruvate-H+ symport ( a symport is a transport protein that transports two ions or molecules in the same direction)
What are the stages of the link reaction?
The link reaction
- pyruvate dehydogenated and decarboxylatrd by pyruvate dehydrogenase
- The decarboxylation and hydrogenation of pyruvate produces an acetyl group
- the acetyl group combines with coenzyme a (CoA) to come acetyl CoA
- NAD gets reduced
- Acetyl CoA transports the acetyl group to the krebs cycle
What is the equation summarising the link reaction?
Link reaction
2 pyruvate + 2 NAD + 2 CoA——–
2CO2 + 2 reduced NAD + 2 acetyl CoA
Where dos the krebs cyelce take place?
The krebs cycle takes place in the mitochondrial matrix
What arew the products of the krebs cycle?
The krebs cycle products:
- 6 reducced NAD
- 2 reducced FAD
- 4 carbon dioxide
- 2 ATP
What are the procuts od the link reaction?
Products of the link reaction
- 2 reducded NAD
- 2 carbon dioxide
Describe of the Krebs cycle
Krebs cycle
- Acetyl group + oxaloacetatae = citrate (6c)
- citrate decarboxylated and dehydrogenated making a 5c compound, CO2 and reduced NAD
- 5c compound decarboxylated + dehydrogenated to make 4c compound, 1 CO2, 1 reduced NAD
- 4c temp combines with and released from CoA + substrate level phosphorylation makes 1 ATP
- 4 c is dehydrogenated producing another 4c compound + 1 reduced FAD
- Isomerase catalyses rearrangement of 4c molecule + hydrogenation to regenerate a molecule of oxaloacetate
How many turns of the Krebs cycle are there for each glucose molecule?
For each glucose molecule there are 2 turns of the Krebs cycle
Simply describe main parts of each stage of the Krebs cycle
Krebs cycle:
- citrate formed
- 5c moleule made from citrate
- 5c turned into 4 c compound
- 4c compound + CoA
- 4c compound makes new 4c compound
- rearrangement regenerates oxaloacetate
Are the krebs cycle and link reaction anaerobic or aerobic?
The krebs cycle and link reaction are aerobic as they will not happen in the absence of oxygen
What are three other substrates for aerobic respiration other than glucose?
- fatty acids broken down into many molecules of acetate
- glycerol converted to pyruvate
- amino acids are deaminated and can enter the krebs cycle directly or change to acetyl CoA or pyruvate
What is the only stage of respiration that does not make ATP?
The only stage of respiration that does not make any ATP is the link reaction