bio

• Digestive system


  To digest food and absorb the nutrients obtained from digestion
• Pancreas and salivary gland


  Glands which produce digestive juices containing enzymes
• Stomach


  Produces hydrochloric acid - which kills any bacteria present and provides the optimum acidic pH for the protease enzyme to function
• Small intestine


  The site where soluble food molecules are absorbed into the bloodstream
• Liver


  Produces bile (stored in the gallbladder) which emulsifies lipids and allows the lipase enzyme to work more efficiently
• Large intestine


  Absorbs water from undigested food, producing faeces
• Enzymes


  Act as biological catalysts which speed up the rate of biological reactions (the breakdown of food) without being used up
• Enzyme shape


  Enzymes have a specific active site which is complementary to their substrate
• Metabolism


  The sum of all the reactions in a cell or an organism
• Types of metabolic reactions catalysed by enzymes

  • Building larger molecules from smaller molecules
  • Changing one molecule to another
  • Breaking down larger molecules into smaller molecules
• Lock and key hypothesis

  The shape of the enzyme active site and the substrate are complementary, so can bind together to form an enzyme-substrate complex
• Temperature effect on enzymes

  Up to a certain point, increasing temperature increases enzyme action, as molecules have a higher kinetic energy. Above a certain temperature, the shape of the active site is altered and the enzyme becomes denatured, so it can no longer catalyse the reaction. The optimum temperature is around 37°
• pH effect on enzymes

  The optimum pH for most enzymes is 7 (apart from proteases in the stomach). If the pH is too extreme, the shape of the active site may be altered and the enzyme may no longer work
• Epidermal tissue


  • Covers the entire plant
  • Has a waxy cuticle which helps reduce water loss from the leaf surface
• Locations of enzyme production

  • Carbohydrases: amylase - salivary gland and pancreas; maltase - small intestine
  • Proteases: pepsin - stomach; others - pancreas and small intestine
  • Lipases: pancreas and small intestine
• Role of carbohydrases


  Break down carbohydrates into monosaccharides and disaccharides. Amylase breaks down starch into maltose, and maltase breaks down maltose into glucose
• Role of proteases


  Break down proteins into amino acids
• Role of lipases


  Break down lipids into fatty acids and glycerol
• Use of digestion products

  They are used to build bigger molecules such as carbohydrates and proteins. Glucose is used as a substrate in respiration
• Palisade mesophyll tissue


  • Contains lots of chloroplasts which allows photosynthesis to progress at a rapid rate
• Bile production and storage

  Bile is made by the liver and stored in the gallbladder
• Role of bile


  Bile is an alkaline substance which neutralises the hydrochloric acid secreted by the stomach. Bile emulsifies lipids to form droplets - this increases the surface area for the lipase enzyme to work on
• Heart


  An organ that pumps blood around the body
• Spongy mesophyll tissue


  • Has lots of air spaces which allow gases (including oxygen and carbon dioxide) to diffuse in and out
• Circulatory system


  Carries oxygen and other useful substances to bodily tissues, and removes waste substances
• Double circulatory system


  1. One pathway carries blood from the heart to the lungs - where the gaseous exchange of oxygen and carbon dioxide takes place

  2. One pathway carries blood from the heart to the tissues
• Blood flow from right ventricle


  The lungs
• Blood flow from left ventricle


  Body tissues
• Importance of double circulatory system

  It makes the circulatory system more efficient - for example, oxygenated blood can be pumped around the body at a higher pressure by the left ventricle
• Chromosomes


  DNA molecules combined with proteins that contain genes which provide the instructions for protein synthesis
• Gene


  A section of DNA which codes for a protein
• Xylem


  • Made up of dead cells which form a continuous hollow tube - allows the movement of water and mineral ions from the roots to the leaves
  • Strengthened by lignin - makes the vessel strong and waterproof
  • Has bordered pits - allow minerals to be transported to specific places
• The nucleus of human body cells contains 46 chromosomes
• The nucleus of gametes contains 23 chromosomes
• Arrangement of chromosomes in body cell nucleus

  Arranged in pairs - 46 chromosomes form 23 pairs
• Cell cycle


  1. Replication of DNA and synthesis of organelles

  2. Mitosis

  3. Division of cell
• Heart chambers


  4 - right atrium, right ventricle, left atrium, left ventricle
• Eukaryotic cells


  Plant and animal cells
• Mitosis


  • Produces identical cells which all have the same genetic information
  • Produces additional cells for growth and repair
• Differences between eukaryotic and prokaryotic cells

  • Prokaryotic cells are much smaller than eukaryotic cells
  • Eukaryotic cells contain membrane bound-organelles and a nucleus containing genetic material, while prokaryotes do not