Respiration C1.2

• What is a nucleotide?

  Nucleotides are the building blocks of nucleic acids. They consist of a nitrogenous base, a pentose and a phosphate group.
• What is ATP?


  ATP (Adenosine triphosphate) is a nucleotide, as it consists of a nitrogenous base, a pentose and three phosphate groups.

  It contains:

  Nitrogenous base- Adenine

  Pentose- Ribose

  Three phosphate groups, all negatively charged and in a chain
• What is the role of ATP?

  ATP is used for temporary storage of energy and energy transfer.
• What are the properties of ATP that optimise its function?

  Soluble in water, so can move through the cytoplasm to transfer energy

  Stable at pH close to neutral, like the cytoplasm, optimal for energy transfer

  Cannot pass freely through the phospholipid bilayer, so it cannot diffuse from the cell, and its movement and transfer of energy within the cell, between membrane-bound organelles can be controlled.

  The third phosphate group can be easily removed and reattached, through condensation or hydrolysis. Hydrolysing ATP to ADP and a phosphate releases a small amount of energy sufficient for many processes within the cell.

  - Soluble

  - Stable at neutral pH

  - Cannot pass through bilayer

  -Hydrolysis of third phosphate releases energy
• Why do cells need energy/what is ATP used for?

  ATP stores and transfers energy. Cells need energy for three main types of activity:

  Synthesising macromolecules (anabolic reactions)

  Active transport

  Movement
• Why do cells need ATP for anabolic reactions?

  Anabolic condensation reactions are endothermic, meaning that they require energy. One or more ATP molecules is used every time a monomer is linked to a growing polymer.

  Example: condensation
• Why do cells need ATP for active transport?

  Active transport is the process of particles moving from a high concentration to a low concentration, across a selectively permeable membrane. This requires energy from ATP, which is used to cause reversible changes in the conformation of a pump protein from a stable to less stable state. The reverse change does not require energy.

  Example: Nerves and nervous impulses
• Why do cells need ATP for movement?

  Components of cells are often moved, which requires energy from ATP. More ATP is needed when changing the shape of a cell, e.g. during cytokinesis. Locomotion for phagocytes also requires ATP, as does the contraction of muscle cells through actin and myosin filaments.

  Example: Chromosome movement
• What is a co-enzyme?

  Co-enzymes are non-protein organic compounds that facilitate enzyme reactions through cycling between loaded and unloaded form.
• Why is ATP a co-enzyme?

  ATP is a loaded co-enzyme that transfers chemical energy to enzymes, enabling them to reach the activation energy and triggering catalysis When ATP is hydrolysed, the terminal phosphate released, the coenzyme is in its unloaded form. The energy released through this reaction allows the enzyme to catalyse the reaction through reacting activation energy ATP= loaded ADP= unloaded
• How does the hydrolysis of ATP to ADP and a phosphate release energy?

  -37kj/mol of Chemical potential energy is within each covalent bond between the phosphates of the ATP molecule. It is so high because a lot of energy is required to keep negatively charged phosphates next to one another. When these bonds are hydrolysed, and the terminal phosphate is released forming ADP and a phosphate, the chemical potential energy is released and may be transferred to another store.
• Where is the energy that is required for the condensation of ADP and a phosphate to ATP sourced from?

  Cell respiration, through oxidisation of carbohydrates, fats or proteins

  Photosynthesis, where light energy is converted to chemical potential energy

  Chemosynthesis, where energy is released through oxidising inorganic substances like sulphides.
• What happens when a cell lacks sufficient ATP?

  If the small quantity of ATP within the cell at any given time is used up, then the processes within it that require energy stop. For example, neurons in the nervous system cannot convey impulses to the muscle cells to stop contracting, causing a cramp. Cells without ATP begin to degrade, leading to cell death. This cell death is usually prevented through the synthesis of ATP from ADP and phosphate at regular intervals.
• How is body temperature maintained?

  Energy transfers during interconversions aren't 100% efficient, and excess energy is transferred to heat. This maintains body temperature.
• What is respiration?


  It is defined as the controlled release of energy from the breakdown of organic compounds to release ATP
• How does respiration work?

  Respiration is the process of oxidising (losing electrons) carbon compounds, releasing energy that is then used to produce ATP from ADP and phosphate.

  It occurs in four stages:

  1) Glycolysis

  2) Link reaction

  3) Krebs cycle

  4) Electron transport chain

  Good Luck Krebs Etc
• Where are the carbon compounds for respiration sourced?

  The source of carbon compounds for respiration within humans is the food that they eat, and the source of carbon compounds for respiration within plants is the lipids or carbohydrates previously made through photosynthesis.
• What are the four stages of respiration?

  1) Glycolysis

  2) Link reaction

  3) Krebs cycle

  4) Electron transport chain

  Good Luck Krebs Etc
• How does respiration and gas exchange interact?

  For aerobic respiration gas exchange must occur, where oxygen enters cells and carbon dioxide exits them. Although gas exchange and respiration are independent processes, they are also interdependent.
• What are the possible substrates (carbon compounds) of respiration?

  Lipids, carbohydrates and proteins may be used as substrates. Carbohydrates are optimal for respiration.
• What are triglycerides, in terms of their role as a substrate of respiration?

  Triglycerides produce more energy per gram as substrates of respiration, but are harder to digest and transport. The fatty acids are used in aerobic respiration, and the glycerol is used in anaerobic.
• What are proteins, in terms of their role as a substrate of respiration?

  Proteins produce around the same energy per gram as carbohydrates as substrates of respiration, but produces toxic nitrogenous waste (NH3)
• What are the products of aerobic respiration?

  Carbon dioxide and water
• What are the products of anaerobic respiration in humans?

  Lactate (lactic acid)
• What are the products of anaerobic respiration in yeast/fungi?

  Ethanol and Carbon dioxide
• How does oxidisation occur in aerobic respiration and why?

  Oxygen accepts electrons from Carbon during multiple stages of respiration. This oxidisation provides energy necessary to synthesise ATP from ADP and a phosphate.
• What is the yield of ATP in aerobic respiration?

  38 ATP molecules per glucose
• What is the process of aerobic respiration?

  Glycolysis:

  Breaks down glucose to pyruvate, releasing a small amount of ATP. Six carbons are converted into two lots of three carbons.

  Link reaction, Krebs cycle and ETC:

  Occurs in the mitochondria, the pyruvate is converted to carbon dioxide and water, releasing ATP. the oxygen allows the pyruvate to be broken down fully, allowing a higher ATP yield. Oxidisation of carbon also occurs, providing the energy necessary to synthesise ATP from ADP and a phosphate.
• What is lactate?


  Lactate is produced in human anaerobic respiration, which restricts how much anaerobic respiration can actually be done, as lactate cannot be maintained in large concentrations within the human body.

  After the muscle contractions anaerobic respiration is used for, the lactate must be broken down, requiring oxygen to do so. This may take some time, and the amount of oxygen required to do so is known as the oxygen debt.
• What is the yield of ATP for anaerobic respiration?

  2 ATP molecules per glucose
• What is the purpose of anaerobic respiration in humans?

  Supplies ATP rapidly, over a short time period, occurring in muscles in humans during short-distance running or other intense bursts of exercise
• What is the process of anaerobic respiration?

  Occurs within the cytosol, and only includes glycolysis. Oxidisation of carbon occurs without oxygen. Glucose is broken down into pyruvate, releasing a small amount of ATP. This is done through converting six carbons into two lots of three carbons.

  Without oxygen, the pyruvate molecules are fermented, producing lactic acid in animals and ethanol and carbon dioxide in plants and yeast
• What are some similarities between anaerobic and aerobic respiration?

  -Both release ATP

  -Both go through glycolysis

  -Both use carbon compounds as substrates
• What are some differences between anaerobic and aerobic respiration?

  - Anaerobic is less efficient than aerobic

  -Anaerobic yields 2 ATP molecules, while aerobic yields 38 ATP molecules

  -Anaerobic occurs in the cytoplasm, while aerobic occurs in the mitochondria and cytoplasm

  -Anaerobic does not require oxygen, while aerobic does

  -Anaerobic produces lactate or carbon dioxide and ethanol, while aerobic produces carbon dioxide and water

  -Anaerobic partially digests glucose, while aerobic fully digests it

  -Anaerobic respiration does not include a link reaction, the Krebs cycle or the ETC, while aerobic does.
• What are the variables that affect the rate of cell respiration?

  Temperature and pH (alters the functionality of respiratory enzymes and therefore reaction rates)

  Glucose and oxygen as respiratory substrates and their availability

  Inhibitors (prevent necessary enzyme-substrate interactions)
• How does temperature and pH influence the rate of cellular respiration?

  Low temperatures= low respiration rate as insufficient kinetic energy for collisions

  High temperature= low respiration rate as denaturation of enzymes necessary in the respiration cycle

  Respiration rates will be fastest at the enzyme's optimum pH
• How do substrates influence the rate of cellular respiration?

  Glucose levels determine the rate as it is the main respiratory substrates

  Increasing glucose increases rate until all glycolytic enzymes are saturated and the rate plateaus.

  Oxygen levels determine the rate of aerobic respiration as it is necessary for it.
• How do inhibitors influence the rate of cellular respiration?

  An inhibitor is a molecule that disrupts the normal reaction pathway between an enzyme and a substrate.

  Competitive inhibitors binds directly to the active site of the enzyme and prevent substrate interaction. Example: citrate

  Non-competitive inhibitors binds to a site other than the active site (known as an allosteric site) to prevent substrate interaction. Example: cyanide
• What is a competitive inhibitor?

  Competitive inhibitors binds directly to the active site of the enzyme and prevent substrate interaction. Example: citrate
• What is a non-competitive inhibitor?

  Non-competitive inhibitors binds to a site other than the active site (known as an allosteric site) to prevent substrate interaction. Example: cyanide