Chapter 10

• Biochemical processes

  are chemical processes that occur in all cells

  • biochemical reactions result in products needed by cells
• Metabolism

  Is the sum of all the biochemical reactions in an organism, this can be divided into two types of reactions

  • Anabolic reactions: involve the synthesis (building up) of complex molecules from simpler ones (e.g. photosynthesis), requiring energy to form new chemical bonds
  • Catabolic reactions: involve the breakdown of complex molecules into simpler ones (e.g. cellular respiration), releasing energy breaking chemical bonds
• Organelles: compartments within a cell, each with a specific function

  Membrane-bound organelles: create specialised environments for different tasks

  Compartmentalisation: allows multiple activities to happen simultaneously under different conditions
• Biochemical reactions: involve breaking and forming chemical bonds in molecules with reactants turning into products

  • Exergonic reactions release energy (Catabolic)
  • Endergonic reaction require energy (Anabolic)
• ATP -> (Adenosine Triphosphate) is the main energy carrying molecule in cells, used in both energy-releasing (exergonic) and energy-consuming (endergonic) reactions
• ATP

  • Light is captured by producers through photosynthesis -> it is converted to chemical energy stored in bonds of organic molecules
  • Cellular respiration in producers and consumer release this energy to make ATP
• ATP structure

  composed of adenosine, a sugar group (ribose) and three phosphate groups.
• when energy is needed, ATP's last phosphate bond breaks, releasing energy, leaving ADP (adenosine diphosphate)

  ADP can convert back into ATP by adding a phosphate group through phosphorylation -> this cycle efficiently transfers energy between cellular reactions
• NADH and FADH2 act as coenzymes during cellular respiration, helping transfer energy but ATP is the most important energy carrier

  • these molecules help transport energy during aerobic respiration respiration process in mitochondria
• Photosynthesis is a crucial biochemical process in producers that uses light energy to transform carbon dioxide and water into glucose.
• Chloroplast

  Photosynthesis takes place in chloroplasts, organelles that contain the pigment chlorophyll, which captures light energy

  • chloroplasts have an outer and inner membrane
  • inside the stroma contains enzymes, suspended within it is the thylakoid membrane system, where light energy is absorbed
• Process of photosynthesis is divided into:

  Light-dependent stage (occurs in thylakoid membranes)

  Light-independent stage (occurs in the stroma)
• Light-dependent stage (light reaction)

  • it happens in thylakoid membranes
  • chlorophyll absorbs light, energising electrons which is splitting water molecules into oxygen (released as byproduct, hydrogen ions, and electrons)
  • ATP and NADPH are formed which provide energy and reducing power for the next stage
• Light-independent stage (Calvin Cycle)

  • occurs in the stroma of the chloroplast
  • using the ATP and NADPH produced in the light-dependent stage, carbon dioxide is converted into glucose -> this process is anabolic and stored energy in glucose
  • chloroplast convert glucose molecules to sucrose or starch in daylight hours
  • at night, cells convert starch to sucrose to transport to other cells in leaves, stems, and roots that lack chloroplasts
• Photosynthesis word equation

  Carbon dioxide + water → glucose + oxygen (in the presence of sunlight and chlorophyll)
• Factors that affects the rate of photosynthesis

  Photosynthesis is affected by abiotic factors such as:

  • light intensity
  • carbon dioxide concentration
  • temperature
• Limiting factor: restricts a rate of a reaction
• Light intensity

  Plants use chlorophyll to absorb sunlight and convert into chemical energy, light from the Sun fuels reactions that transform CO2 and water into glucose and oxygen -> without light photosynthesis cannot proceed

  • as light increases, photosynthesis increases until a maximum rate is reached -> where the plant's chlorophyll is fully saturated
• Carbon dioxide concentration

  Carbon dioxide and water are the reactants that are converted into glucose -> if there is a limited availability of carbon dioxide then the rate of reaction slows

  • higher concentration of carbon dioxide increase the rate of photosynthesis until saturation occurs
• Temperature 


  Enzymes catalyse the reactions that take place during photosynthesis -> enzymes are proteins that is affected by temperature, which makes temperature a limiting factor for photosynthesis

  • photosynthesis is enzyme-driven and enzymes function optimally at specific temperatures
  • too high or low temperatures can inhibit enzyme activity, reducing the rate of photosynthesis
• Explain the interdependence of photosynthesis and aerobic respiration.

  Photosynthesis produces glucose and oxygen which are used in aerobic respiration to generate ATP. Aerobic respiration produces carbon dioxide and water, which are used in photosynthesis