2.8 Cell respiration Flashcards
Glucose
-This is the preferred energy source for brain cells and is broken down in muscle cells for energy.
-Glucose is the most widely used source of energy in living organisms.
Define cellular respiration
The gradual and controlled release of energy by breaking down organic compounds to produce ATP ( A denosine T ri P hosphate).
What is the purpose of enzymes in cellular respiration?
They that control the process to ensure that energy is produced when it is required.
Diagram of overview of cellular respiration in a cell
What are the three main processes of cellular respiration?
-Glycolysis
-The Krebs cycle
-The electron transport chain
What do the three main processes of cellular respiration do?
They generate energy in the form of ATP.
What is ATP?
-A molecule that carries energy within the cell.
-It can be compared to a currency that is used to pay for different biochemical processes such as movement of substances, contraction of muscles and synthesis of large molecules.
Diagram showing the structure of ATP
Where does glycolysis take place?
In the cytoplasm
Where do the Krebs cycle and oxidative phosphorylation (and electron transport chain) take place?
In the mitochondria.
Within the mitochondria, where does the Krebs cycle occur?
In the matrix
Within the mitochondria, where is the electron transport chain located?
On the inner membrane of the mitochondrial envelope.
Function of ATP
-ATP fuels most of our body’s energy needs.
-ATP from cell respiration is immediately available as a source of energy in the cell.
-Without it we would not be able to move, think, digest food, conduct nerve signals or breathe.
-Energy is produced when ATP is hydrolysed.
-It should be noted that this same energy was generated during respiration and stored in the energy-rich phosphate bond of ATP.
Diagrm showing the hydrolysis of ATP to produce energy
Why do we breathe in oxygen?
To support aerobic respiration.
When oxygen (O 2 ) is present, aerobic respiration can yield ___
Far more ATP than under anaerobic conditions, as most of the energy contained in a glucose molecule can be harvested and converted into ATP.
What is the main reason for the increased ATP production in aerobic respiration?
-That during aerobic respiration, all the four steps of cellular respiration are completed (in anaerobic respiration only glycolysis is completed).
-The reason for this increased yield is that 6-carbon glucose is systematically and gradually broken down to 6 CO 2 molecules.
-Each step yields potential energy, which can be converted into ATP in the electron transport chain.
3 key facts about aerobic respiration
1) It requires oxygen
2) It gives a large yield of ATP from oxidation of glucose
3) It occurs in the cytoplasm and mitochondria
Equation to show aerobic cell respiration
Which method of respiration is more efficient?
-It is much more efficient to respire aerobically than anaerobically.
-That is why long distance runners try to maintain an aerobic speed.
-If they use up the available oxygen, their muscles will start anaerobic respiration, producing much less energy.
Diagram showing the comparison between anaerobic and aerobic respiration.
When describing cell respiration you should mention that ___
-It produces ATP molecules.
-You should avoid using descriptions such as ‘energy production’ as it is too vague and does not explain the main purpose of respiration.
What is the function of ATP molecules?
They provide energy for biochemical processes such as pumping molecules across membranes.
Where is the electron transport chain located in the diagram of a mitochondrion below?
-C
-C represents the inner mitochondrial membrane (folded into cristae) where the electron transport chain takes place.
Sequence showing the end product of the anaerobic respiration pathway in humans
glucose → lactate
Equation for aerobic respiration
glucose + oxygen → carbon dioxide + water + large amount of energy
Which type of respiration produces the most energy?
Aerobic
What is cell respiration called when it takes place without oxygen?
Anaerobic respiration
Where does anaerobic respiration occur only and why?
In the cell cytoplasm as it involves only glycolysis (to be able to complete the other steps, oxygen is required).
What are the two main types of anaerobic respiration?
Alcoholic and lactic fermentation
Diagram showing the different uses of yeast
Explain why yeast can be used to produce different foods
-Yeast respires anaerobically to produce ethanol and CO 2 when fermenting raw ingredients to make beer, wine or bread.
-The CO 2 produced by yeast is used to make bread rise, while the ethanol is evaporated away during baking.
-Bread made without yeast would be very flat.
Describe anaerobic respiration in humans
-Although we breathe air (and thus oxygen) during strenuous exercise, our muscle cells may use up all the available oxygen.
-Nonetheless, the muscle cells still need ATP to continue the exercise.
-Without oxygen, the muscle cells start to respire anaerobically and are able to produce a very small amount of ATP, which allows the power of muscle contractions to be maximised in the absence of oxygen.
-During anaerobic respiration, animals produce lactate (also known as lactic acid).
-This can lead to soreness in the muscles.
The soreness in muscles was once believed to be cause by ___
A buildup of lactic acid, but more recent research has shown that this pain is caused by microscopic damages to the muscle fibres.
Diagram showing two anaeronic pathways compred to the aerobic pathway
Which genereates more ATP: aerobic or anaerobic respiration?
Aerobic respiration
Word equation for lactic acid fermentation
Glucose → lactate + 2 ATP molecules
What is the difference between lactate and lactose?
Lactate is an acid, while lactose is a disaccharide
Word equation for alcoholic fermentation
Glucose → ethanol + carbon dioxide + 2 ATP molecules
Where in the cell does anaerobic respiration take place?
In the cytoplasm
How much ATP does anaerobic respiration produce?
2 ATP molecules
In yeast, what does anaerobic respiration produce?
Alcohol and CO 2
In animal muscle cells, what does anaerobic respiration produce?
Lactate
What is the net yield of ATP produced by anaerobic respiration in yeast?
2 ATP molecules
What is a respirometer?
A simple apparatus that can measure the rate of respiration
What does aerobic cell respiration use and produce?
It uses oxygen and produces carbon dioxide and water
We can measure the consumption of oxygen as an indication of the ___
Respiration rate
Diagram showing how a respirometer can be used to measure the respiration rate of living organisms
What happens in Tube A of the respirometer (look at diagram)
-In Tube A, the organism to be tested (or germinating seed) is positioned, and the tap is closed.
-The organism starts respiring, consuming O 2 and producing CO 2 and H 2 O.
-The alkaline solution at the bottom of Tube A will absorb the CO 2.
What happens in Tube B of the respirometer?
Tube B is the control where no O 2 is used or CO 2 produced because no living organism is present.
What is the capillary that connects the two tubes of the respirometer?
A manometer
Explain what will happen in the respirometer
The reduction in oxygen in Tube A will reduce the pressure in Tube A and will move the coloured liquid in the manometer in the direction of Tube A, providing an indirect measurement of the oxygen consumed, allowing the rate (amount of oxygen consumed per time unit) to be calculated.
Why is it important to set up the respirometer in a water bath?
This ensures that the temperature does not affect the pressure and hence, the volume of air in the system
What can a respirometer be used for?
-A respirometer can give us a good idea of the respiration rate of germinating seeds, a resting animal or a moving animal, and it allows us to compare different species.
-It can measure the influence of temperature or, for example, sleep, on respiration.
Diagram showing different methods of measuring the respiration rate in living organisms
What is the role of an alkaline solution in the respirometer?
To absorb carbon dioxide
Suggest ethical limitations when using animals in an experiment
-Will the animals suffer pain?
-Will they have to be removed from their natural habitat?
-Could you use plants instead?
What happens if anaerobic respiration in muscles continues for more than 2 minutes?
-Hydrogen ions increase in the blood
-Lowers pH of blood
What is the advantage of anaerobic respiration in muscles during periods of intense activity?
-An intense activity e.g. sprinting requires rapid and powerful muscle contractions over a short time
-Anaerobic respiration can be used to supply ATP during intense exercise
-Small amounts of ATP can be produced quickly without the need for oxygen
