CAPE Biology Unit 2 Notes (2)

CAPE BIOLOGY UNIT TWO MANUAL

MODULE ONE – BIOENERGETICS AND CONSERVATION

This module contains four topics:

  1. PHOTOSYNTHESIS AND ATP SYNTHESIS
  2. CELLULAR RESPIRATION AND ATP SYNTHESIS
  3. ENERGY FLOW AND NUTRIENT CYCLING
  4. ECOLOGICAL SYSTEMS, BIODIVERSITY AND CONSERVATION

TOPIC 1: PHOTOSYNTHESIS AND ATP SYNTHESIS

1.1: Relate the structure of a dicotyledonous leaf, a palisade cell and a chloroplast to their roles in the process of photosynthesis

  • Photosynthesis is a process where AUTOTROPHS (or producers) take in inorganic molecules and produce organic substances, such as CARBOHYDRATES.
  • These carbohydrates contain trapped energy that the organism can release and use from a molecule called ATP. This process of releasing energy is called RESPIRATION.
  • ATP (Adenosine Triphosphate)
    • Functions as the intracellular energy currency in all organisms.
    • Contains:
    • A nitrogenous base (adenine)
    • A ribose sugar
    • Three inorganic phosphate groups (Pi)
    • Energy is released when the bonds between these groups are broken.
Basics of Photosynthesis
  • Photosynthetic organisms contain either CHLOROPLASTS (in plants) or light-capturing pigment CHLOROPHYLL in membranes (in phytoplankton).
  • Chemical equation for photosynthesis in green plants:
    6CO2+6H2O<br/>ightarrowC6H12O6+6O26CO_2 + 6H_2O <br /> ightarrow C_6H_{12}O_6 + 6O_2
  • Photosynthesis involves both light-dependent and light-independent reactions.
    • Light-dependent reactions:
    • Light energy is used to break bonds of water molecules (PHOTOLYSIS), producing OXYGEN as a by-product.
    • HYDROGEN molecules combine with CARBON DIOXIDE to form GLUCOSE.
    • Light-independent reactions occur in the STROMA of the chloroplast.
Internal Structure of a Dicotyledonous Leaf
  • Upper Epidermis:
    • Thin, transparent cells coated with waxy cuticle.
    • Function: Limits water loss, protects against insects and microbes, transparent for sunlight absorption.
  • Lower Epidermis:
    • Thin layer interspersed with GUARD CELLS forming stomata.
    • Function: Stomata control gas exchange and transpiration.
  • Spongy Mesophyll:
    • Loose, irregular packing with air spaces for gas exchange.
  • Palisade Mesophyll:
    • Cylindrical cells with numerous chloroplasts for light absorption.
    • Large vacuoles maintain chloroplast positioning for light access.
    • Adjacent to VASCULAR BUNDLES supplying water via XYLEM.
The Chloroplast
  • Double-membraned organelles composed of THYLAKOIDS arranged in stacks known as GRANA.
  • THYLAKOID LUMENS store H+ ions for ATP production.

1.2: Explain the process of photophosphorylation with respect to photosynthetic electron transport

  • Photophosphorylation Definition:
    • Simple concept of using light to