Respiration Flashcards
why do we need to respire?
we need energy for biological processes
Why do plants need energy?
active transport (uptake of minerals from roots) DNA replication photosynthesis protein synthesis cell division
Why do animals need energy?
maintaining body temperature muscle contraction active transport DNA replication cell division protein synthesis
Outline glycolysis
- splitting of one molecule of glucose (6C) into 2 smaller molecules of pyruvates (3C)
- occurs in cytoplasm
- first stage in aerobic and anaerobic respiration
- itself is anaerobic process as requires no 02
Explain glycolysis
- 2 stages: phosphorylation and oxidation
- in phosphorylation, 1 molecule of glucose (6C) is phosphorylated by adding 2 phosphate groups from 2 ATP molecules forming one molecule of hexose bisphosphate (6C) and 2 molecules of ADP.
- Hexose bisphosphate is unstable and splits further into 2 smaller molecules of triose phosphate (3C)
- In oxidation, the 2 triose phosphates each lose a hydrogen ion which is collected by NAD forming reduced NAD.
- 2 ATP molecules are formed from each triose phosphate from being directly converted into a pyruvate.
What are the products of glycolysis?
- 2 reduced NAD - go to oxidative phosphorylation
- 4 ATP - used for energy
- 2 pyruvates - actively transported to matrix for link reaction
How much ATP is produced in glycolysis?
4 ATP but net gain of 2 as 2 were used up in phosphorylation
Outline link reaction
- occurs in matrix
- requires 02
- conversion of pyruvate into acetate
Explain link reaction
- pyruvate (3C) is decarboxylated as 1 Carbon is removed in the form of CO2
- NAD collects H+ion from the pyruvate forming a reduced NAD molecule and acetate (2C)
- Acetate combines with coenzyme A forming acetyl coenzyme A
What are the total products of link reaction and why?
- 2 pyruvates produced form glycolysis so link reaction occurs twice for each glucose molecule
- 2 acetyl coenzyme A - go to krebs cycle
- 2 reduced NAD - oxidative phosphorylation
- 2 C02 - released as waste
Outline Krebs cycle
- occurs in matrix
- occurs twice for each glucose molecule as 2 pyruvates so 2 acetates
Explain krebs cycle
Co-enzyme drops acetate off at the krebs cycle and go back to link reaction to be reused
- acetate (2C) combines with oxaloacetate (4C) forming citrate (6C)
- citrate undergoes decarboxylation and dehydrogenation as it loses 1 C in form of CO2 and 1 H atom which is collected by NAD forming 1 reduced NAD and a 5 carbon compound.
- 5carbon compound undergoes decarboxylation as it loses 1 C in form of CO2 and dehydrogenation as 2 NAD and 1 FAD collect 3 H atoms forming 2 reduced NAD and 1 reduced FAD. ATP is also formed by substrate level phosphorylation which is where a phosphate groups is being directly transferred from one intermediate compound to ADP
- oxaloacetate is now formed
What are the products of krebs cycle per cycle?
- 1 ATP - for energy
- 3 reduced NAD - oxidative phosphorylation
- 1 reduced FAD - oxidative phosphorylation
- 2 CO2 - waste
- coenzyme A - regenerated for next use in link reaction
- 1 oxaloacetate - regenerated for next use in krebs cycle
outline electron transport chain
- process where energy carried by electrons from coenzymes is used to make ATP
- occurs in inner mitochondrial membrane
Explain electron transport chain
- reduced FAD and NAD are oxidised making FAD and NAD so H atoms are released which are split into electrons and protons (H+ ions)
- 3 electron carriers make up electron transport chain which is located in inner mitochondrial membrane which folds into cristae so an increased SA maximises respiration
- electrons move along the electron transport chain losing energy at each carrier
- carriers use the energy to pump protons across the membrane into inter membrane space from matrix
- proton concentration is higher in inter membrane space so electrochemical gradient formed
- protons move down electrochemical gradient via ATP synthase into matrix
- movement of protons back into the matrix drives synthesis of ATP from ADP and P (I)
- at end of chain, protons, electrons and 02 combine to form water
- 02 is final electron acceptor
What is chemiosmosis
process of ATP production driven by movement of protons across membrane due to electrons moving down electron transport chain
What is anaerobic respiration?
- no 02 needed
- no link reaction, krebs cycle, electron transport chain
What are the 2 types of anaerobic respiration?
alcoholic fermentation
lactate fermentation
What are the similarities between the 2 types?
- both have glycolysis as first stage which produces pyruvates
- both occur in cytoplasm
What are the differences between the 2 types?
- both differ in what happens to pyruvates
- both differ in which organisms they occur in as alcoholic occurs in plants and yeast where as lactate occurs in mammals and bacteria
Explain lactate fermentation
- glycolysis occurs and pyruvates are formed
- reduced NAD gives H ion to pyruvate forming NAD and lactate
- NAD is regenerated for use in glycolysis so it can occur with little 02
Why is lactate fermentation useful?
- small ATP yield formed for some biological processes
- cells can tolerate high lactate levels and resulting low ph levels for short time periods
What happens to the lactate after formed?
- too much can be toxic so removed from cells and into the blood
- liver removes lactate from blood and converts it into glucose via gluconeogenesis
Explain alcoholic fermentation
- glycolysis occurs so pyruvate formed
- decarboxylated as 1 C removed in form of CO2
- ethanal formed
- reduced NAD gives h ion to ethanol forming ethanol and NAD
- NAD regenerated for use in glycolysis
Why does anaerobic respiration always produce lower ATP yield than aerobic?
- always lower
- anaerobic only has 1 energy releasing stage which is glycolysis
- aerobic has 3 so more ATP made but they require 02
What is a respiratory substrate?
- it is any biological molecule that can be broken down in respiration to release energy
- they all have different energy values
Name some respiratory substrate?
proteins, lipids and carbs
- proteins and lipids enter respiration in krebs cycle
