Biology csec

• Photosynthesis:

  • Process by which green plants convert carbon dioxide and water into glucose using sunlight energy absorbed by chlorophyll in chloroplasts
  • Chemical equation: 6CO2 + 6H2O + Sunlight > C6H12O6 + 6O2
• Transpiration:

  • Process of water movement through a plant and its evaporation
• Glucagon:

  • Hormone secreted by the pancreas to keep blood glucose levels constant
  • In diabetes, the pancreas is unable to produce sufficient glucagon or insulin
• Arthritis:

  • Caused by the wear and tear of a joint over time
  • Results in joint pain or stiffness
• Drugs:

  • Chemical substances that affect the body's functioning
  • Many drugs are used medically to improve health
  • Abuse of drugs can lead to addiction and harm
  • Withdrawal from drugs can cause withdrawal symptoms
• The nucleus is the control center of the cell, containing genetic material (DNA) that determines an organism's characteristics.
• Chromosomes are thread-like structures made up of DNA and proteins found inside the nucleus.
• Genes are segments of DNA that contain instructions for making specific proteins or controlling other genes.
• Mitochondria generate ATP through aerobic respiration, providing energy for cellular processes.
• Proteins are large molecules made up of amino acids that perform various functions within cells.
• Protein synthesis involves the production of proteins based on the information encoded in genes.
• Chloroplasts contain chlorophyll and carry out photosynthesis, converting light energy into chemical energy.
• Enzymes are specialized proteins that catalyze chemical reactions in living organisms.
• Lysosomes break down waste materials within cells.
• Antibodies are proteins produced by immune system cells that recognize and neutralize foreign invaders such as bacteria and viruses.
• Digestion breaks down food into a form that is useful for body activities
• Digestion occurs in the alimentary canal, which spans from the mouth to the anus
• Digestion begins with the mechanical breakdown of food followed by the chemical breakdown of food molecules
• Mechanical digestion involves breaking up large pieces of food into smaller pieces
• Importance of mechanical digestion:

  • Increases the surface area of food for digestive enzymes to act on, making chemical digestion quicker and easier
  • Makes food easier to swallow
• Mechanical digestion starts in the mouth and is mainly carried out by the teeth
• Chemical digestion breaks down large, usually insoluble, food molecules into small, soluble molecules by hydrolysis
• During hydrolysis, bonds within large food molecules are broken down by the addition of water molecules
• Hydrolysis is catalyzed by digestive enzymes
• Transpiration is the evaporation of water through the stomata of leaves. This creates a pull from the roots upwards to the leaves called the transpiration pull, which is the main force that transports water up the stem to the leaves. • Light, humidity, temperature, wind speed and water availability are factors affecting rate of transpiration. • Plants which live in extremely dry environments have special adaptations to control their transpiration rate and conserve water.
• Xylem


  • Transports water and dissolved minerals from the roots to the other parts of the plant
  • Provides mechanical support to the plant
• Xylem vessels and tracheids

  • Consist of elongated cells arranged end to end
  • Have no protoplasm and end walls to form a continuous hollow tube
  • Lignin is deposited on the cell walls
• Xylem vessels


  • Form a continuous hollow tube which allows easy flow of water with no resistance
  • Lignified cell walls prevent collapse of the xylem vessel
• Water uptake by plants

  1. Water enters root hair cells by osmosis

  2. Minerals are absorbed into root hair cells by diffusion or active transport

  3. Water enters xylem vessels
• Vascular tissue in plants

  Consists of xylem and phloem
• Xylem and phloem


  • Arranged differently in the roots, stem and leaves
• Phloem


  Transports organic nutrients such as sugar and amino acids from leaves and storage organs to other parts of the plant
• Phloem tissue


  • Composed of companion cells and sieve tube elements
  • Sieve tube elements lack the cell structures needed to carry out many metabolic processes, they rely on the companion cells for their survival
• Sieve tube elements


  1. Arranged to form a continuous column

  2. Have little protoplasm

  3. Have sieve plates containing pores so that there is less resistance to the flow of liquid within them
• Xerophytes


  Plants which live in extremely dry environments
• Plants take in water by the roots
• Adaptations of xerophytes to control transpiration rate and conserve water

  • Deep roots to reach water far underground
  • Shallow spreading roots to collect occasional rainfall
  • Leaves reduced to spines to reduce surface area for transpiration
  • Less stomata present on the leaves to reduce transpiration rate
  • Rolled leaves, leaf hairs and stomata sunk in pits to trap moist air and slow diffusion of water vapour from the stomata
  • Waxy leaf cuticle that is impermeable to water
  • Stomata closed at midday when transpiration rate would be the highest
  • Storage of water in succulent tissues
• Excessive transpiration is harmful to the plant, but it is also important because: ▫ it creates a transpiration pull which carries water and minerals from the roots to the stems and leaves; ▫ water transported to the leaves is used for photosynthesis and it replaces water lost by the cell and keeps cells turgid; ▫ evaporation of water from the leaves has a cooling effect on the plant.
• We need a heart to pump blood around the body. The heart is a “ double pump” (blood enters twice). The right side of the heart pumps blood to the lungs and the left side pumps blood to the rest of the body. The Septum separates the two halves of the heart.
• The human heart is made up of specialized muscles called cardiac muscle that can contract and relax independent of nervous stimulation, about 70 times a minute for up to a hundred years and does not experience fatigue.