Bio B2 - Organisation

• What features do plants and animals cells have in common?


  Nucleus - contains DNA and controls cell activity

  Cytoplasm - Contains enzymes where most chemical reactions occur

  Cell membrane - holds cell together and controls what goes in/out

  Ribosomes - make proteins

  Mitochondria - Where most energy is released in respiration
• What features do only plant cells have?

  Cell Wall - made of cellulose, makes cell stronger/rigid

  Chloroplasts - contain chlorophyll (makes leaf green), photosynthesis occurs here

  Vacuole - cell sap
• What features does a yeast cell have?

  Yeast is microorganism (single celled) which has a cell wall and membrane, nucleus and cytoplasm
• What features does a bacterial cell have?

  Single celled. contains cell wall and membrane, cytoplasm, but doesn't have a nucleus, genetic material floats in cytoplasm
• What is diffusion?

  The spreading out of particles (dissolved substances or small molecules) from a high concentration to a low concentration, bigger difference, faster diffusion rate. E.g. oxygen needed for respiration diffuses through the cell membrane
• What are specialised cells?

  Cells that carry out a specific function
• How are palisade leaf cells specialised?

  They are adapted for photosynthesis:

  - Many Chloroplasts; crammed at the top, near to light, faster rate

  - Large surface area allow large absorption of CO2
• How are guard cells specialised?

  Adapted to open and close stomata:

  - Lots of water, guard cells become turgid, makes stomata open so gases can be exchanged and vice versa (close to stop too much water vapour escaping)

  - Close at night to save water
• How are red blood cells specialised?

  Adapted to carry oxygen:

  Concave shape gives larger surface area, more room for O2

  Packed with haemoglobin (absorbs it)

  No nucleus
• How do cells become specialised?

  Differentiation happens during the development of multicellular organisms.
• What is a tissue?

  Group of similar cells that work together to carry out a certain function
• What is the muscular tissue?

  Contracts to move whatever its attached to
• What is glandular tissue?


  Makes and secretes chemicals such as hormones or enzymes
• What is epithelial tissue?

  Covers parts of the body (e.g. skin)
• What is an organ?

  Group of different tissues which work together to perform a certain function
• How does the stomach work?

  Muscular tissue will move the stomach wall to church food

  Glandular tissue makes digestive juices to break down and digest foods

  Epithelial tissue covers the inside and outside the stomach
• What is an organ system?

  Several organs working together for a particular function
• How does the digestive system work?

  - Glands such as pancreas and salivary glands produce digestive juices

  - Stomach and small intestine digest food

  - Liver produces bile

  - Small intestine absorbs soluble food molecules

  - Large intestine absorbs water from undigested foods, leaving faeces

  
• What organs are present in plants?

  Stems, roots and leaves
• How do tissues in the leaf work?

  Mesophyll tissue - where most photosynthesis occurs

  Xylem and Phloem - Transport water, mineral ions around plant

  Epidermal tissue - covers the whole plant
• What is the equation for photosynthesis?

  Carbon dioxide + water ----> Oxygen + glucose
• How does photosynthesis work?

  Chlorophyll absorbs sunlight and uses energy to convert CO2 and water into glucose and O2 (by product). Water reaches the cell through the xylem

  
• What is a limiting factor?

  A factor that is stopping photosynthesis from happening any faster e.g. light, temperature and carbon dioxide levels
• When is light a limiting factor?

  When there isn't enough of it (so mainly at night), light provides the energy for photosynthesis, so up to a certain point, increasing light will increase the rate of photosynthesis. after a certain point, it is no longer a limiting factor

  
• When is carbon dioxide a limiting factor?

  Higher CO2, quicker rate but like light, this only works till a certain point then it no longer becomes a limiting factor and therefore increase will make no difference to the rate

  
• When is temperature a limiting factor?

  Higher temperatures increase the rate of photosynthesis as enzymes work better at higher temperatures HOWEVER, if the temperature gets to 45°C or over, the enzymes will denature and photosynthesis wont be able to occur

  
• How can the ideal conditions for photosynthesis be artificially created?

  Greenhouses:

  - Trap Sun's heat to make sure temp. isn't limiting (heaters/ventilation used depending on season)

  - Artificial light used (lamps)

  - Increase CO2 using paraffin heaters

  - Keeping plants enclosed also makes it easier to keep them pest/disease free, add fertilisers for minerals

  - Expensive, but if done correctly, more crop=profit
• How do plants use glucose?

  - Respiration (energy released allows conversion from glucose to other useful substances

  - Making cell walls (converted into cellulose)

  - Making proteins (Glucose + nitrate ions make amino acids)

  - Stored in seeds as lipids

  - Stored as starch (insoluble) in roots, stems and leaves for when photosynthesis isn't happening as much e.g. winter
• What physical factors may affect an organism?

  - Temperature

  - Light

  -Water

  - Oxygen/CO2

  - Food/nutrients
• How are quadrats used?

  Study distribution of small organisms

  - Place qaudrat randomly in certain area, count organisms within that area, repeat in same areas, repeat in different areas, calculate average/mean
• How are transects used?

  Study distribution of organism along a line (closer to hedge or middle of field etc)

  - Mark out line using tape measure, collect data along line (organisms touching line or using quadrats placed along line)
• What makes collecting environmental data reliable/valid?

  Reliability: Large sizes (more representative) and random samples (reproducible)

  Validity: Control other variables to ensure correlation is due to factor being investigated
• What are proteins?

  Chains of amino acids which are folded into unique shapes. They can act as:

  - Enzymes (biological catalysts which increase speed of reactions)

  - Structural components of tissues such as muscles

  - Hormones

  - Antibodies
• How do enzymes work?

  Each enzyme has a unique shape that fits onto a substance in a reaction, this unique shape means that each enzyme can only catalyse one type of reaction because the substance must fit its shape. Substance then splits.

  Enzymes in the body work best at 37°C, too hot and the bonds break, enzyme becomes denatured

  Optimum pH is generally 7, too high/too low and it denatures (pepsin works best at pH 2, good for acidic condition of stomach)

  
• What are digestive enzymes?

  Enzymes that break down large molecules such as starch, protein and fats into smaller ones such as sugars, amino acids etc
• What is amylase?

  It converts Starch into sugars, produced in salivary glands, pancreas and small instestine
• What is protease?

  Converts proteins into amino acids in stomach (pepsin), pancreas and small intestine
• What is lipase?

  Converts lipids (fats and oils) into glycerol and fatty acids in the pancreas and small intestine
• What is bile?

  Produced in the liver and stored in the gall bladder till its released into the small intestine. The hydrochloric acid in the stomach passes into food which reaches the small intestine, however the pH is too acidic for the small intestine, bile (alkaline) neutralises it so enzymes can work

  Also emulsifies/breaks down fat so it is digested quicker
• How are enzymes used in the home?

  Proteases and lipases used in biological detergents and washing powders to remove food/blood stains as they break down the matter. They are more effective at low temperatures compared to other detergents