Respiration Flashcards
what is respiration?
respiration is the controlled release of energy from organic compounds to form ATP.
What are the two types pf respiration?
Aerobic and Anaerobic respiration
what is Aerobic respiration?
requires oxygen and produces carbon dioxide, water and much ATP
what is anaerobic respiration?
takes place in the absence of oxygen and produces lactate (in animals)or ethanol and carbon dioxide (in plants and fungi) but only little ATP in both cases
which type of respiration produces little ATP?
Anaerobic rspiration
what stage do both anaerobic and aerobic respiration share?
What differs?
Glycolysis
the stages after glycolysis differ
where is the main site of aerobic respiration?
the mitochondria
what are three biological processes need energy for?
- active transport,
- cell division
- muscle contraction
- protein synthesis
- DNA replication
Draw and label the mitochondrion?
explain why the mitochondrion in a body cell has more cristae than the mitochondria in a less metabolically active cell?
- cristae are folds of the inner mitochondrial membrane which increases the surface area
- this provides a greater surface area for the electron transport chain , which produces ATP
- ATP is needed in larger amounts in muscle cells for muscle contractions
What are the four stages in Aerobic respiration and where does each stage of respiration occur?
glycolysis - cytoplasm
link reaction - mitochondrial matric
Krebs cycle - mitochondrial matric
Oxidative phosphorylation
what is glycolysis?
the splitting of the 6-carbon glucose molecule into two molecules of 3-carbon pyruvate.
how can glycolysis be split again into 4 other stages?
- phosphorylation of glucose into glucose phosphate
- splitting of the phosphorylated glucose
- oxidation of triose phosphate
- the production of ATP
Draw and describe the full process of glycolysis?
- glucose is made more reactive by the addition of two phosphate groups (phosphorylation). the phosphate molecules come from the hydrolysis of two ATP molecules to form ADP. This provides the energy to activate glucose and lowers the activation energy for the enzyme controlled reactions that follow.
- each glucose phosphate molecule is split into 3-carbon molecules known as triose phosphate
- Triose phosphate is oxidised as hydrogen is removed from each of the two triose phosphate molecules and is transferred to a hydrogen-carrier molecule known as NAD to form reduced NAD (reduction)
- enzyme-controlled reactions convert each triose phosphate into another 3-carbon molecule called pyruvate. in the process two molecules of ATP are regenerated from ADP
what are the total products gained from glycolysis and where do they go?
- 2 x pyruvate –> to matrix
- net gain of 2 ATP –> used for energy
- 2x NADH –> to oxidative phosphorylation
What is meant by a net gain of 2 ATP?
four molecules of ATP produced, but two were used up in the initial phosphorylation of glucose
what can glycolysis be used to prove, explain how?
Evolution - glycolysis is a universal feature of every organism and therefore provides indirect evidence for evolution
The link reaction and the Krebs cycle
Title
what is the link reaction?
3 carbon pyruvate molecule enter into a series of reactions which lead to the formation of acetylcoenzyme A, a 2-carbon molecule
how are pyruvate molecules transported from the cytoplasm to the mitochondrial matrix?
the pyruvate molecules produced in the cytoplasm are actively transported into the matrix of the mitochondria.
explain what happens to pyruvate during the link reaction?
- the pyruvate is oxidised to acetate. in this reaction, the 3 carbon pyruvate loses a carbon dioxide molecule (decarboxylation) and two hydrogens. these hydrogens are accepted by NAD to form reduced NADH. which is later used to produce ATP
- the 2 -carbon acetate combines with a molecule Coenzyme A to produce a compound called acetylcoenzyme A
What is the link reaction also referred to as?
oxidative decarboxylation
how many times does the link reaction occur?
twice for two molecules of pyruvate/ per glycolysis
what are the total products of the link reaction per glucose molecule?
- 2 acetylcoenzyme A
- 2 co2 released
- 2 reduced NAD
what is the overall equation for the link reaction?
pyruvate + NAD + CoA —> acetyl CoA + reduced NAD + CO2
Wo was the Krebs cycle named after?
Hans Krebs
What is the Krebs cycle also known as?
the citric acid cycle, or TCA cycle.
what is the Krebs cycle?
the introduction of acetylcoenzymeA into a cycle of oxidation-reduction reactions that yield some ATP and a large quantity of reduced NAD and FAD
explain what happens int he Krebs cycle?
- 2 carbon compounds acetylcoenzymeA from the link reaction combines with 4 -carbon molecule (Oxaloacetic acid) to produce a 6 carbon molecule
- the coenzyme A is released and recycled back to the link reaction
- in a series of reactions this 6 carbon molecule (Citric Acid) loses carbon dioxide (decarboxylation) and hydrogen (dehydrogenation) to give a 5-carbon (α keto - glutaric acid) molecule, then a 4 carbon molecule
- a single molecule of ATP produced as a result of substrate-level phosphorylation ( a phosphate group is directly transferred directly from a donor molecule to ADP)
- the 4 carbon molecule which has bee regenerated can now combine with a new molecule of acetylcoenzyme A to begin the cycle again
What is produced during the Krebs cycle per glucose molecule?
- 2 ATP
- 6 reduced NAD
- 2 reduced FAD
- 4x CO2
What is the importance of the Krebs cycle in cells of organisms?
- it breaks macromolecular into smaller ones - pyruvate is broken down into carbon dioxide
- it produces hydrogen atoms that are carried by NAD to the electron transfer chain and provide energy for oxidative phosphorylation. this leads to the production of ATP that provides metabolic energy for the cell
- it regenerates the 4 carbon compound molecule that combines with acetylcoenzyme A which would otherwise accumulate
- it is a source of intermediate compounds used by the cells in the manufacture of other important substances such as fatty acids, amino acids and chlorophyll
what is oxidative phosphorylation?
the use of electrons, associated with reduced NAD and FAD, released from the Krebs cycle to synthesise ATP with water produced as a By-product
what is the main site of oxidative phosphorylation?
The inner membrane and the mitochondrial matrix
what is contained within the inner folded membrane (cristae’s)
here are enzymes and other proteins involved in oxidative phosphorylation (OP) and hence ATP synthesis
- where is a lot of mitochondria found?
- give some examples
- what do they carry out?
in metabolically active cells - such as muscle, liver and epithelial cells (which carry out active transport)
what is the role of the cristae in the mitochondria specifically for respiration?
the mitochondria in these cells have more densely packed cristae which provide a large surface area of membrane incorporating enzymes and other proteins involved in OP
what is involved during Oxidative phosphorylation?
- transfer of electrons
- electron carrier molecules
- electron transfer chain
describe the full process of the oxidative phosphorylation/ electron transfer chain ?
- the reduced NAD and FAD are oxidised donate it’s electrons and hydrogen atoms they are carrying to the first molecule (protein) in the electron transfer chain
- the electrons then pass along a chain of electron transfer carrier molecules in a series of oxidation-reduction reactions.
- as the electrons flow along the chain, the energy they release causes the active transport of protons across the inner mitochondrial membrane and into the inter-membranal space
- the concentration of protons is now higher in the intermembrane space. this forms an electrochemical gradient.
- these protons move down the electrochemical gradient, Via ATP synthase. this makes ATP from ADP + Pi (chemiosmosis)
- at the end of the chain (in the mitochondrial matrix) the electrons combine with these protons and oxygen to form water. oxygen is the final acceptor of electrons in the electron transfer chain.
what is the importance of oxygen in respiration at acting as the final acceptor of hydrogen atoms produced in glycolysis and the Krebs cycle.
without it’s role in removing hydrogen ions at the end of the chain the hydrogen ions (protons) and electrons would ‘back up’ along the chain and the process of respiration will come to a halt
the more energy released in a single step , the more ….?
of it is released as heat and the less there is available for more useful purposes
why is it more of an advantage if energy is released a little at a time?
more of it can be harvested for the benefit of the organism . for this reason, the electrons carried by NAD and FAD are not transferred in one explosive step. instead they are passed along a series of electron transfer carrier molecules. each of which is at a slightly lower energy level. the electrons therefore move down an energy level gradient. the transfer of electrons down this gradient allows their energy to be released gradually and therefore more usefully.
what other substances can be oxidised by cells to release energy?
both lipids and proteins may in certain circumstances be used as respiratory substrates, without first being converted to carbohydrates.
before lipids are used to release energy they need to be hydrolysed first?
- before being respired, lipids are fist hydrolysed to glycerol and fatty acids. the glycerol is then phosphorylated and converted to triose phosphate which enters glycolysis pathway and subsequently the Krebs cycle. the fatty acid component is broken down into 2-carbon fragments which are converted to acetyl coenzyme A . this then enters the Krebs cycle
What are alternative respiratory substrates?
sugars (e.g glucose) are not the only respiratory substrate
- both proteins and lipids as well
Explain how the respiration of lipids goes?
the oxidation of lipids produces 2 carbon fragments of carbohydrates and many hydrogen atoms. the hydrogen atoms are used to produce ATP during oxidative phosphorylation. for tis reason lipids release more than double the energy of the same mass of carbohydrate
explain how the respiration of proteins go?
protein is first hydrolysed to its constituent amino acids. these have their amino group removed (deamination) before entering the respiratory pathway at different points depending on the number of carbon atoms they contain. 3 carbon compounds are converted to pyruvate, while 4 and 5 carbon compounds are converted to intermediates in the Krebs cycle.
explain the effect of cyanide on respiration?
Cyanide inhibits the 4th electron carrier and blocks the electron transport chain
what substances naturally produce cyanide?
Cyanides are naturally produced by certain bacteria, fungi, and algae
What is a fatal dose of cyanide?
A fatal dose for humans can be as low as 1.5 mg/kg body weight
What evidence is there to show the existence of chemiosmosis?
- The proton gradient across the inner membrane can be measured as there is pH gradient.
-Isolated ATP synthase enzymes can produce ATP using a proton gradient even if no electron transport is occurring. - Chemicals that block the ETC inhibit the formation of a proton gradient and prevent ATP synthesis.
How much ATP is made from using reduced enzymes (FAD +NAD)?
2.5 ATP from each reduced NAD
1.5 made from each reduced FAD
What is the total amount of ATP produced from all processes of respiration?
32 ATP’s
Why is aerobic respiration only 32% efficient?
- Some protons leak across the mitochondrial membrane, so not all are available to generate ATP via chemiosmosis.
- Some ATP is used up moving pyruvate into the mitochondria by active transport.
- Some ATP is used up moving hydrogen from reduced NAD made during glycolysis into the mitochondria.
- Some energy is lost as heat. This heat helps to maintain a suitable body temperature for enzyme-controlled reactions.
Anaerobic respiration
When does the anaerobic stage of respiration take place?
takes place in the absence of oxygen, neither the Krebs cycle nor the electron transfer chain can continue because soon all the FAD and NAD will be reduced. No FAD or NAD will be available to take up the H+ produced during the Krebs cycle and so enzymes will stop working. So leaves anaerobic respiration.
where does anaerobic respiration take place?
in the cytoplasm
Which stage occurs in both anaerobic and aerobic respiration?
Glycolysis
In order for glycolysis to continue, what must we need to happen?
it’s products of pyruvate and and hydrogen must be constantly removed. In particular the hydrogen must be released from the reduced NAD in order to regenerate NAD
Anaerobic respiration converts pyruvate to what in animals and plants?
- in animals pyruvate is converted into lactate
- in plants and microorganisms (e.g yeast), pyruvate is converted into ethanol and carbon dioxide
How does the above reactions occur?
By gaining Hydrogen from reduced NAD.
In plants, pyruvate loses a molecule of CO2 producing ethanal which accepts a hydrogen from reduced NAD to produce ethanol
which means that the NAD is..?
oxidised so that it can be reused in glycolysis and ensure more ATP is continued to be produced
Draw out the word equation to show anaerobic respiration in plants?
pyruvate + reduced NAD –> ethanol + carbon dioxide + oxidised NAD
when does lactate production usually occur?
most commonly in muscles as a result of strenuous activity. in these conditions oxygen may be used more rapidly than it can be supplied , therefore an oxygen debt occurs
Draw a word equation to show anaerobic respiration in animals?
pyruvate + reduced NAD –> lactate + oxidised NAD
Why can anaerobic respiration not continue infinitely?
- amount of ATP produced is not enough to maintain the process for long
and - Lactic acid and ethanol are both toxic/ acidic which decreases the pH and denatures proteins
what happens when oxygen is available again?
lactate produced is oxidised back into pyruvate. this can be further oxidised to release energy or be converted into glycogen
what does a build up of lactate cause?
cramps and muscle fatigue
why does the build up of lactic acid cause muscle fatigue?
- an increase in lactic acid results in a decrease in pH
- muscle contraction is dependent on enzymes/ proteins
- decreasing the pH can result in enzymes being denatured
- therefore, the proteins become non-functional
what are the similarities between alcoholic fermentation and lactate fermentation?
- both produce small amounts of ATP
- both regenerate oxidised NAD
what are the differences between alcoholic fermentation and lactate fermentation?
- lactate is formed by lactate fermentation, whereas ethanol is formed by alcoholic fermentation
- carbon dioxide is released during alcoholic fermentation, but not released by lactate fermentation
How much ATP is produced from anaerobic respiration?
only 2 ATP which makes it very inefficient
DONE
