Structures and Functions in Living Organisms

Levels of Organisation
1. Organelles - Small organs in cells
2. Cells - Biological building blocks
3. Tissues - Groups of similar cells that do the same job
4. Organ - Made of different tissues that work together to do a specific job
5. Organ Systems - Multiple organs that work together
6. Organism - A living being made of multiple organ systems
Cell Structure
1. Nucleus - Controls the cell and contains DNA
2. Cytoplasm - Jelly-like substance in cells where reactions occur
3. Cell Membrane - Holds the cell in and allows certain particles in/out
4. Cell Wall (plant only) - Supports and protects the cell
5. Chloroplast (plant only) - Contains chlorophyll which enables photosynthesis to occur
6. Vacuole (plant only) - Contains water and sugars needed for cell growth
Nutrition
1. Photosynthesis is the conversion of sunlight into food for a plant
2. Water + Carbon Dioxide (+ energy) -> Oxygen + Glucose ¦¦¦ 6H2O + 6CO2 (+ energy) -> 6O2 + C6H1206
3. Limiting Factors - CO2 concentration, temperature and light intensity
  1. Lower CO2 concentration reduces the rate of photosynthesis
  2. Lower light intensity reduces the rate of photosynthesis
  3. Lower temperature reduces the rate of photosynthesis
4. Leaves are adapted for photosynthesis
  1. Upper epidermis is transparent to let light through
  2. Palisade cells are near the top of the leaf where there is the most light
5. Mineral ions are needed for growth
  1. Magnesium is needed for chlorophyll
  2. Nitrates are needed for amino acids
Transport
1. Blood = Red + White blood cells, platelets and plasma
2. Plasma carries CO2, digested food, urea, hormones and heat
3. Red blood cells are adapted to carry oxygen
  1. They are biconcave to increase surface area
  2. They have no nucleus to free up space for oxygen
  3. They contain haemoglobin which binds reversibly with oxygen (forming oxyhaemoglobin)
4. White blood cells provide immunity to disease
  1. If they detect a pathogen, they produce antibodies to destroy it
    1. Antibodies stick to pathogens making them easy to identify by phagocytes, which ingest the pathogens (phagocytosis)
    2. Antibodies cause pathogens to stick together making it easier for phagocytes to ingest them
    3. This also applies to weakened/dead strains, allowing for safe vaccinations
  2. After destroying a pathogen they produce memory cells which retain information about the pathogen so they can be destroyed more efficiently next time
5. Platelets help blood to clot. Clotting prevents blood loss and entry of microbes
6. You need to know the structure of the heart (4 chambers, blood vessels and valves)
  1. The heart beats faster (pumping more blood) during exercise or under the effect of adrenaline, to meet the body's demand for oxygen
7. Arteries carry blood AWAY from the heart at high pressure
8. Veins carry blood totheheart at low pressure
9. Capillaries link arteries and veins, and have thin walls to allow gas exchange with cells
10. In Plants
  1. Phloem transports sucrose and amino acids between parts of the plant that need them
  2. Xylem transports water and mineral ions from the roots to the leaves
    1. This is done by a process called transpiration, where water evaporates off the leaves to drag more up
      1. Humidity, wind speed, temperature and light intensity all affect the rate of transpiration positively (except humidity, which affects it negatively)
  3. Water is absorbed by root hair cells via osmosis
Respiration
1. Releases energy from food
2. Aerobic respiration requires oxygen, but is very efficient
3. Anaerobic respiration does not need oxygen but it is very inefficient and produces lactic acid in animals
4. Oxygen + Glucose -> Water + Carbon Dioxide (+ energy)
Gas Exchange
1. Ribs protect the lungs and heart
2. Intercostal muscles located between ribs expand and contract during breathing
3. Diaphragm contracts during inhalation to allow lungs to expand and take in air
4. Trachea = Windpipe - Connects mouth and lungs
5. Lungs made of bronchi (branches) which split into bronchioles, ending in alveoli
  1. Alveoli are tiny air sacs surrounded by capillaries which allows for gas exchange between blood and the lungs
    1. They have a large surface area in contact with the capillaries to maximise gas exchange
6. In Plants
  1. When the rate of photosynthesis exceeds the rate of respiration, there is a net release of oxygen. When the rate of respiration exceeds the rate of photosynthesis, there is a net release of carbon dioxide.
  2. Net exchange of oxygen and carbon dioxide depends on light intensity.
  3. The stomata are pores on the underside of leaves. They open and close to let water and oxygen out, and carbon dioxide in.
Movement of Substances in Cells
1. Diffusion is the net movement of particles from an area of high concentration to low concentration, down the concentration gradient
2. Osmosis is the net movement of water particles from an area of high concentration to low concentration, down the concentration gradient, across a selectively permeable membrane
3. Active Transport is the net movement of particles from an area of low concentration to high concentration, against the concentration gradient. It is an active process and requires energy.
4. The surface-area-to-volume ratio, temperature and concentration gradient all affect the rate of movement
Nutrition Continued
1. A balanced diet needs appropriate proportions of proteins, carbohydrates, lipids, vitamins, minerals, water and fibre
  1. Starches give long-lasting energy Sugars give short bursts of energy
  2. Proteins are needed for amino acids, which are needed for growth and repair
  3. Fats are a store of energy and also provide insulation and protection
  4. Vitamin A strengthens the immune system
  5. Vitamin C protects cells and helps blood clotting
  6. Vitamin D helps regulate calcium and phosphate levels and strengthens bones
  7. Calcium helps blood clotting and strengthens bones
  8. Iron helps make red blood cells
  9. Water is needed for hydration
  10. Fibre is needed for a healthy alimentary canal
2. Energy needs vary depending on age, activity level and pregnancy.
3. You need to know the structure of the alimentary canal (digestive system)
4. Peristalsis is the movement of ring muscles to push food along the gut
5. Bile is made by the liver and stored in the gall bladder. It neutralises stomach acid and emulsifies lipids
6. The intestines have very large amounts of villi, which have a large surface area and produce digestive enzymes, to absorb products of digestion efficiently

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