- energy in a cell is stored in the chemical bonds between atoms, and this energy is released when the bonds are broken
- some of the energy that is released does work for the cell, and the rest is given off as heat
- catabolism is the process by which molecules are broken down and the energy is released
Two types of catabolism
- fermentation: the breakdown of sugars that occurs in the absence of oxygen
- cellular respiration: the breakdown of sugars that occurs in the presence of oxygen
- carbohydrates, fats, and proteins can all be broken down to release energy in cellular respiration
- glucose is the primary nutrient fuel molecule that is used in cellular respiration to release energy
- the standard way of representing that process of cellular respiration shows glucose being broken down in the following reaction
- the breakdown of glucose is exergonic-that is, energy is given off in this reaction, in the form of ATP
- this ATP is used to power all cellular activities
- ATP is released as energy when enzymes in the cell transfer are one of its three phosphate groups to another molecule
- ADP can be recycled to ATP
- when electrons are transferred from one reactant to another, the reactions are called redox-reaction and oxidation-reduction reaction
- electrons "fall" from organic molecules to oxygen during cellular respiration
- cellular respiration is a redox process that transfers hydrogen, including electrons with high potential energy, from sugar to oxygen
- the "fall" of electrons during respiration is stepwise, via NAD+ and an electron transport chain
Process of Cellular Respiration:
- there are 3 main stages of respiration: glycolysis, the Krebs cycle, and the electron transport chain and oxidative phosphorylation
Q. In the following redox reaction, which compound is oxidized and which is reduced?
A. C 4 H 6 O 5 is oxidized and NAD + is reduced. \
1. Select the correct sequence of steps as energy is extracted from glucose during cellular respiration.
a) glycolysis → citric acid cycle → acetyl CoA → electron transport chain
b) citric acid cycle → electron transport chain → glycolysis → acetyl CoA
c) glycolysis → acetyl CoA → citric acid cycle → electron transport chain
d) acetyl CoA → citric acid cycle → electron transport chain → glycolysis
e) electron transport chain → citric acid cycle → glycolysis → acetyl CoA
2. What is the correct general equation for cellular respiration?
a) C6H12O6 + 6 CO2 → 6 O2 + 6 H2O + ATP energy
b) 6 CO2 + 6 H2O + ATP energy → C6H12O6 + 6 O2
c) C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + ATP energy
d) 6 O2 + 6 H2O + ATP energy → C6H12O6 + 6 CO2
e) C6H12O6 + 6 H2O → 6 CO2 + 6 O2 + ATP energy
3. Which of the following processes takes place in the cytosol of a eukaryotic cell?
a) ATP production by ATP synthase
b) citric acid cycle
c) electron transport chain
e) acetyl CoA formation
4. In what organelle would you find acetyl CoA formation, the citric acid cycle, and the electron transport chain?
d) Golgi apparatus
5. Which statement describes glycolysis?
a) This process splits glucose in half and produces 2 ATPs for each glucose.
b) This process uses energy captured from electrons flowing to oxygen to produce most of the ATPs in cellular respiration.
c) This process produces some ATP and carbon dioxide in the mitochondrion.
d) This process converts pyruvic acid to acetyl CoA.
e) This process joins 2 pyruvic acid molecules into a molecule of glucose.
Answers: 1. c, 2. c, 3. d, 4. c, 5. a
Have a good rest of the weekend!