Topic 2: Organisation

• Levels of organisation in organisms

  • Cell
  • Tissue
  • Organ
  • Organ system
• Cell

  Smallest structural and functional unit of an organism
• Tissue

  Group of cells with a similar structure and function
• Organ

  Group of tissues performing specific functions
• Organ system

  Group of organs performing specific functions
• Digestion

  Breaking down large, insoluble molecules in food into smaller, soluble molecules that can be absorbed into blood
• Enzyme

  A type of protein molecule that acts as a biological catalyst, speeding up reactions in organisms without being used up or changed
• Enzymes

  • Each type catalyses a specific reaction
• How enzymes work (lock and key theory)

  1. Substrate binds to enzyme active site because shapes are complementary

  2. Chemical reaction occurs (such as bonds in substrate broken to produce smaller molecules)

  3. Products released from the unchanged enzyme
• Metabolism

  The sum of all the reactions in a cell or the body, different enzymes catalyse specific metabolic reactions
• Enzymes and their functions

  • Lipase breaks down lipids into fatty acids and glycerol, produced in the pancreas and small intestine, acts in small intestine
  • Carbohydrase (such as amylase) breaks down carbohydrates into simple sugars (such as starch into glucose), produced in salivary glands, pancreas and small intestine and acts in mouth and small intestine
  • Protease breaks down proteins into amino acids, produced in the stomach, pancreas and small intestine, and acts in stomach and small intestine
• Fatty acids and glycerol are used to build new lipids in the body once absorbed
• Amino acids are used to build new proteins in the body once absorbed
• Bile

  Produced in the liver, stored in the gallbladder, and released into the small intestine
• Enzyme denaturation

  Active site changes shape (such as due to too high temperature or too high or low pH) so substrate no longer binds and reaction can no longer be catalysed
• Natural resting heart rate control

  A group of cells located in the right atrium act as a pacemaker by sending regular electrical impulses
• Structure of veins

  • Valves to prevent backflow of blood
  • Large lumen so less resistance to blood flow
• Structure of capillaries

  • One cell thick and thin walls so short diffusion distance
  • Narrow lumen so blood moves slowly, more time for diffusion
• Adaptations of white blood cells

  • Can produce antibodies and engulf pathogens (phagocytosis)
• Cause of coronary heart disease (CHD)

  1. Layers of fatty material build up inside coronary arteries, narrowing them and reducing blood flow

  2. Resulting lack of oxygen or glucose for the heart
• Healthy heart valves

  Prevent backflow of blood in the heart
• Consequences of faulty heart valves

  1. Valve doesn't open fully which restricts blood flow, or valve develops a leak so backflow of blood occurs

  2. So less blood containing oxygen pumped around body

  3. So less aerobic respiration and less energy released

  4. So more anaerobic respiration which produces lactic acid

  5. Causing tiredness or muscle fatigue or increased breathing rate
• Treatments for heart failure

  • Heart transplant
  • Artificial heart
• Health

  The state of physical and mental well-being
• Risk factors

  An aspect of a person's lifestyle or substances in a person's body or environment that have been shown to be linked to an increased rate of disease
• The main risk factor for Type 2 diabetes is obesity
• Effect of alcohol on the liver and brain function

  1. Breakdown of alcohol by liver cells produces toxic substances causing cirrhosis (scarring) leading to liver failure

  2. Neurons in brain damaged
• How are tumours (and cancers) formed

  Growth of abnormal cells due to changes in cells that lead to uncontrolled growth and division
• Differences between benign and malignant tumours

  • Malignant tumours are cancerous, invade neighbouring tissues, and spread to different parts of the body
  • Benign tumours are not cancerous, do not invade neighbouring tissues, and stay in one place
• Structure of palisade mesophyll tissue

  • Many chloroplasts so lots of chlorophyll to maximise light absorption for rapid photosynthesis
• Structure of spongy mesophyll tissue

  • Many large air spaces so large surface area for rapid diffusion of gases such as carbon dioxide and oxygen
• Function of xylem tissue

  Transport water and dissolved mineral ions from roots to leaves
• The root, stem and leaf system

  Transports substances around a plant
• Transpiration

  1. Evaporation of water from cells inside leaves

  2. Diffusion of water vapour out of leaves through stomata
• Factors affecting transpiration rate

  • Increasing light intensity, temperature, or air flow increases transpiration rate
  • Increasing humidity decreases transpiration rate
• Translocation

  Movement of dissolved sugars (such as sucrose) through phloem (up and down) from leaves (made in photosynthesis) to rest of plant for immediate use or storage