2.8 (Energy Metabolism) Flashcards
Define “cell respiration.”
- Cellular respiration is a series of metabolic reactions that convert biochemical energy from organic molecules into adenosine triphosphate (ATP), and then release waste products.
- the controlled release of energy from organic compounds in cells to form ATP
State the reaction for cellular respiration.
- Cellular respiration is the chemical reaction in which glucose and oxygen are turned into water, carbon dioxide, and ATP energy. In the reaction, glucose and oxygen are reactants, while water, carbon dioxide, and energy (ATP) are products.
- 6O2 + C6H12O6 —> 6CO2 + 6H2O +ATP
- Aerobic uses O2 to completely break down glucose in the mitochondria for a larger ATP yield
- Anaerobic involves partial breakdown of glucose in the cytoplasm for a small yield of ATP
State the types of organic compounds used in cellular respiration by animals and plants.
The main organic compound used for cellular respiration is the carbohydrate glucose, although lipids and proteins can also be used if glucose is not readily available to the cell.
State three example uses of cellular energy.
- synthesizing large molecules like DNA, RNA, proteins
- pumping of molecules or ions across the membrane via active transport
- moving thing inside the cell (chromosomes, vesicles, protein fibers)
Outline energy transfer in the formation and use of ATP.
- Energy is released when a phosphate group is removed from ATP in a hydrolysis reaction.
- The reverse reaction (which is what happens in cellular respiration) regenerates ATP and requires energy input.
State three reasons why cellular respiration must be continuously performed by all cells.
- ATP can not be stored for later use.
- ATP can not be transferred from cell to cell.
- When ATP is used in cells, heat energy is released. This heat energy can not be reused and will be lost to the environment.
Define “anaerobic respiration”
- the breakdown of glucose without using oxygen that occurs in the cytoplasm of the cell and produces a small yield of ATP
- Anaerobic respiration is a type of cellular respiration that does not use oxygen.
List three situations in which anaerobic respiration is useful.
In-depth
- Anaerobic respiration can act as a backup when cellular oxygen is depleted. For example, when muscle cells use up oxygen faster than it can be replenished, the cells start to perform anaerobic respiration in order to keep muscles moving.
- Anaerobic respiration is used when ATP is needed quick, because anaerobic respiration is more rapid than aerobic respiration.
- Anaerobic metabolism allows microbes to inhabit low-oxygen or oxygen-free environments which allows them to exploit an otherwise empty habitat.
Simple
- Short but rapid bursts of ATP production is needed
- When oxygen supplies run out in respiring cells
- Environments that are deficient in oxygen (ex. waterlogged soil)
Compare anaerobic respiration in yeasts and humans.
Yeast and plants
- In-depth
- First, in glycolysis, glucose is broken down to pyruvate and NADH and ATP are created.
- Then, in alcohol fermentation, pyruvate is converted to ethanol. Carbon dioxide is released and NADH is recycled into NAD+.
- The reaction nets two molecules of ATP.
- Simple
- In yeast and plants, glucose is converted to ethanol and carbon dioxide. Both forms are toxic in excess, therefore must be removed or kept at small quantities
Human
- In-depth
- First, in glycolysis, glucose is broken down to pyruvate and NADH and ATP are created.
- Then, in lactic acid fermentation, pyruvate is converted to lactic acid. NADH is recycled into NAD+.
- The reaction nets two molecules of ATP.
- Simple
- In humans, glucose is converted to lactic acid, which usually in a dissolved form known as lactate
Compare the total amount of ATP made from anaerobic and aerobic respiration.
- Anaerobic respiration produces a net of 2 ATPs per molecule of glucose.
- Aerobic respiration produces up to 38 ATPs per molecule of glucose.
State the location of aerobic respiration.
Aerobic respiration occurs in the cell mitochondria.
Outline how anaerobic respiration in yeast is used in baking.
- Anaerobic respiration in yeast is used during brewing and bread-making:
- glucose → ethanol + carbon dioxide
Outline how anaerobic respiration in yeast is used in ethanol production.
Ethanol is the alcohol found in alcoholic drinks like beer and wine. In bread-making, bubbles of carbon dioxide gas expand the dough and help the bread rise.
State the condition in which humans would perform anaerobic respiration.
- When exercising at high intensity, cell demand will exceed available supplies of O2. Muscle cells will start breaking down glucose anaerobically to supply ATP rapidly for a short period of time.
- Red blood cells do not have mitochondria, so anaerobic respiration always happens
Outline production of lactate in humans during anaerobic respiration.
- In lactic acid fermentation NADH produced in glycolysis transfers its electrons directly to pyruvate, generating lactate as a byproduct.
- There is a limit to the concentration of lactate that the body can tolerate, which limits how much and how long anaerobic can be performed. We often feel a burn in our body when that happens.
- Afterwards, the lactate must be broken down which involved the use of oxygen that builds up during a short period of anaerobic respiration called the Oxygen Debt
