HL Bio: Unit 3.1 - Cell Respiration

ATP

Distributes energy within a cell

• ATP is a nucleotide since it contains all the nitrogen containing base, the five-carbon sugar and the phosphate group 

  • Not the same as normal RNA and DNA nucleotide

  • It is made of a…

    • Ribose = the five-carbon sugar

    • Adenine = Nitrogen base

    • Triphosphate group:

When energy is being taken from an ATP molecule what changes

• Only carbons on the triphosphate are hydrolyzed off the adenine and ribose remain unchanged during the production of ADP and AMP

Pi

The Inorganic phosphate

Properties of ATP

• It is soluble in water 

• Stable at pH levels close to neutral (7)

• Cannot pass freely through the phospholipid bilayer - cannot diffuse out of the cell (controlled movement)

• Third phosphate group can easily be removed and reattached 

  • Hydrolysis and condensation reactions 

• Hydrolysis of ATP to ADP can release a small amount of energy 

• Higher chemical potential energy than ADP 

Processes using ATP

1. Synthesizing Macromolecules

   • Anabolic reactions linking monomers into large polymers - an endothermic reaction so it requires ATP energy 

2. Active Transport

   • Pumping ions against their concentration gradient requires ATP 

   • Causes reversible changes in the conformation of the pump protein

3. Movements

   • Cells require energy from ATP for movement 

     • Components within the cells like chromosomes moving to their poles or cytokinesis

     • Locomotion as well - phagocytes or sperm cells 

Role of hydrogen in the release of energy in cells

• Redox Reaction → Oxidation = loss of electrons (or hydrogen) and Reduction = Gain of electrons (hydrogesn

Hydrogen Ion properties

• H+ → ion/ proton, they don’t move well through membranes

• They are polar and the inside of the membrane is nonpolar 

Electron Carries

Substances that can accept and lose electrons REVERSIBLY 

• Linking oxidation and reduction in cells 

Cell respiration uses what electron carries

• use NAD and FAD as it’s main electron carrier 

  • NAD starts by having a positive charge and then when oxidation occurs it is reduced to NADH

    • Gains two electrons and one proton from the hydrogen 

  • Glycolysis produces around 36 ATP and FAD and NAD support 32 of those

  • They are randomly produced in the cytoplasm → Only used in the ETC tho 

phosphorylation

Processes converting ADP and phosphate back into ATP

1. Cell Respiration

2. Chemosynthesis

3. Photosynthesis

Gas Exchange

• the use of oxygen and then the production of carbon dioxide → Transverse the plasma membrane independently by simple diffusion

  • Necessary or else there is a harmful excess of carbon dioxide 

  • Cell respiration is required or else gas exchange can’t occur since it creates the gradient for simple diffusion

Two types of cellular respiration

1. Aerobic

2. Anearobic

Both have the same goal of producing atp

Aerobic Cell respiration

• Oxygen is an electron acceptor in redox reaction (gain)

• Carbohydrates, lipids and amino acids are used after deamination 

• Carbon dioxide and water are the waste products

• Higher yield of ATP → Around 30 molecules per glucose

• Initially in the cytoplasm and then in the mitochondria where it uses the oxygen

• Forming polymers like proteins and DNA

Anaerobic Cell Respiration

no oxygen needed 

• Unique Qualities

  • Other substances act as the oxygen acceptor in oxidation reaction 

  • Only uses carbohydrates

  • Carbon dioxide and either lactate or ethanol are the waste products 

    • NO WATER

  • Lower yield of only 2 ATP

• All reactions occur in the cytoplasm - no oxygen 

  • In humans this can occur when enough oxygen is not reaching the body eg in a short distance run or an adrenaline rush moment

    • Only produced for a short amount of time for maximization

Lactic Acid

• A waste product of anaerobic respiration in muscles 

  • Can only be tolerated at a certain concentration 

  • Can be broken down when oxygen is again available 

Oxygen Debt:

 Amount of time to recuperate the amount of oxygen needed to break down the Lactic Acid

Aerobic Respiration: Process

Glycolysis → Link Reaction → Kreb Cycle →  ETC

Anaerobic Respiration Respiration

Glycolysis → Fermentation

• Requires oxygen for the link reaction so lack of oxygen forces it to stay in the cytoplasm 

Variables affecting cellular respiration rate

1. Metabolic rate of cell:

   • Varying in their energy demand based on their location 

2. Size of the organism

   • Smaller organism have a higher rate to account for heat loss - since more is able to come out 

3. O₂ Concentration

4. Temperature and pH

   • This process is enzyme controlled so it requires optimal levels for it to happen

5. Respiratory Substrates

   • As substrate increase the rate does as well 

6. CO₂ Concentration

   • Can lower the pH so rate will increase to get rid of it