Biology PAPER 1

• Characteristics of living organisms

  Movement, Respiration, Sensitivity, Homeostasis, Growth, Reproduction, Excretion, Nutrition
• What is a eukaryotic cell?

  Cell with a nucleus and membrane bound organelles (multicellular)
• Structure of plant cell

  - contain chloroplasts for photosynthesis

  - have a cell wall made of cellulose

  - store carbohydrates as starch or sucrose
• Structure of animal cell

  - nucleus, membrane, cytoplasm, mitochondria, ribosomes, vacuole

  - no chloroplasts or cell wall

  - store carbohydrates as glycogen
• Structure of fungi cell

  - organised into mycelium made from thread-like structures called hyphae

  - cell wall is made of chitin

  - feed by extracellular secretion of digestive enzymes onto food and then absorb (saprotrophic)

  - store carbohydrates as glycogen

  - example is MUCOR or YEAST
• Example of protoctists


  Amoeba, Chlorella and Plasmodium
• Common features of prokaryotic organisms

  Bacteria: have a cell wall, membrane, cytoplasm, plasmids

  - do not have nucleus but instead a circular chromosome of DNA
• What does pathogen mean


  disease causing organism
• Structure and features of a virus

  - non living

  - extremely small

  - can reproduce only in living cells

  - have a protein coat

  - contain either DNA or RNA

  - examples: TMV, HIV, Influenza
• What does TMV do

  Causes discolouring of leaves in tobacco plants by preventing the formation of chloroplasts
• What does HIV cause

  AIDS
• What does the influenza virus cause?

  flu
• Levels of organisms (smallest to largest)

  Organelles, cells, tissues, organs and organ systems
• Function of the nucleus

  Contains DNA and genetic material of the organisms
• Function of cytoplasm


  Where chemical reactions take place
• Function of cell membrane


  Partially permeable membrane which controls substances that move in and out of the cell
• Function of cell wall


  Strengthens and protects the cell
• function of mitochondria


  cellular respiration
• Function of chloroplasts


  Site of photosynthesis
• function of ribosomes


  protein synthesis
• Function of vacuole


  Filled with cell sap which helps keep the cell turgid
• What are the chemical elements present in carbohydrates, proteins and lipids

  - carbon

  - hydrogen

  - oxygen

  - (nitrogen for PROTEINS)
• Describe the structure of Carbohydrates (starch and glycogen)

  Starch and glycogen are large, complex carbohydrates, which are made up of many smaller units called simple sugars
• Describe the structure of protein


  long chain of amino acids
• Describe structure of lipids

  Made from fatty acids and glycerol
• What are biological catalysts


  substances that speed up reactions but do not get used up themselves
• How does temperature affect enzyme activity? (Step by step)

  1. Temperature increases enzyme activity until it reaches optimum temperature

  2. After which the active site has changed shape and can no longer bind to the substrate

  3. Enzyme becomes denatured
• How can enzyme function be affected by changes in pH

  - all enzymes have an optimum pH at which they work best

  - if the pH becomes to low or too high, the active site changes shape and becomes denatured
• What does denatured mean

  When the active site changes shape so is unable to bind with the substrate, number of successful collisions decrease
• Describe diffusion


  - The net movement of molecules from an area of high concentration to an area of low concentration

  - passive process
• Describe osmosis in terms of water potential

  The net diffusion of water molecules along a concentration gradient across a PARTIALLY PERMEABLE MEMBRANE. From a HIGH TO LOW WATER POTENTIAL.
• If a cell is placed in a hypertonic (concentrated) solution, what will happen to the cell?

  - PLASMOLYSED and shrivelled cells

  - there is a higher water potential in the cell than the solution

  - water moves OUT of the cell by OSMOSIS
• If a cell is placed in a hypotonic (dilute) solution, what will happen to the cell?

  - TURGID or will burst if there is no cell wall (animal cell)

  - there is a higher water potential in the solution than in the cell

  - water moves IN the cell by OSMOSIS
• Describe active transport


  - The movement of molecules against a concentration gradient.

  - From low to high

  - CAN ONLY HAPPEN IN CELLS/LIVING ORGANISMS

  - requires energy
• What factors affect rate of movement of substances into and out of cells


  Surface area to volume ratio, distance, temperature, concentration gradient
• How does surface area affect the rate of diffusion?

  The larger the surface area, the faster the diffusion rate. This is because more particles can pass through at once
• How does distance affect the rate of diffusion?

  The shorter the distance the faster the rate of diffusion

  This is because particles need to move a shorter distance
• How does the concentration gradient affect the rate of diffusion?

  - the steeper the concentration gradient, the faster the rate of diffusion

  - more molecules so more successful collisions per unit time
• How does temperature affect diffusion

  - The higher the temperature, the faster the rate of diffusion

  - molecules have more KE so have more energy to move

  - MORE ENERGY MEANS MORE ACTIVE TRANSPORT
• Word equation of photosynthesis

  Carbon dioxide + water -> glucose + oxygen