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AQA Biology 3

Exchange of materials B3.1
1. Osmosis
  1. The movement of water from a dilute solution to a more concentrated solution across a partially permeable membrane
    1. If cell uses up water in its chemical reactions, the cytoplasm becomes more concentrated. More water moves in by osmosis.
    2. If cytoplasm becomes too dilute because more water is made in chemical reactions, water leaves the cell by osmosis.
  2. Red Blood Cells
    1. If solution outside is more dilute than the cell contents, water will move into the cell by osmosis. The cell will swell and may burst.
    2. If the solution outside is more concentrated than the contents of the cell then the water will move out of the cell and may shrivel up
  3. Plants
    1. Water moves into the plant cells through osmosis
      1. Causes the vacuole to swell and press the cytoplasm up against the plant cell walls. Making the cell turgid.
        It keeps the leaves and stems of the plant rigid and firm therefore the plants need the surrounding area to have a higher concentration of water. than the cytoplasm
      2. If the surrounding area is more dilute the water would move out and the vacuole would shrivel up but not as much as the red blood cell because it has a strong cell wall
2. Active Transport
  1. The movement of particles from an area of low concentration to an area of high concentration against the concentration gradient
    1. ENERGY IS REQUIRED FROM RESPIRATION
  2. If a cell makes a lot of energy it can carry out a lot of active transport
  3. Root Hair Cells
    1. Mineral Ions
  4. Glucose
    1. Kidneys - reabsorption of glucose
    2. Small intestine (diffusion takes place, but not all substances work with the concentration gradient
3. Sports Drinks
  1. When you exercise you...
    1. Sweat
      1. Water + Mineral Ions
        If your body fluids become concentrated water will leave your cells by osmosis, cells become dehydrated and won't work as well
        If they are not replaced the balance is disturbed and the cells do not work as efficiently
    2. Release energy by respiration, using up sugar
      1. Needed for respiration
  2. REPLACE THE SUGAR USED IN RESPIRATION AND WATER + MINERAL IONS LOST IN SWEAT
    1. Evidence suggests that for normal levels of exercise water is at least as effective as sports drinks
4. Adaptations
  1. LARGE SURFACE AREA
  2. BEING THIN
    1. Provides a shorter diffusion path
  3. EFFICIENT BLOOD SUPPLY
    1. Moves the diffusing substances away and maintains a concentration gradient
  4. BEING VENTILATED
    1. Makes gaseous exchange more efficient by maintaining steep gradients
5. The Lungs
  1. Made up of alveoli
    1. Large surface area Most effective for diffusion of oxygen and carbon dioxide
    2. Rich blood supply, maintains concentration gradient in both directions
    3. Layer of cells between the air in the lungs and the blood in the capillaries is very thin - short diffusion path
6. Ventiating the lungs
  1. BREATHING IN
    1. Your intercostal muscles contract pulling your ribcage up and out
      1. Your diaphragm muscles contract, this flattens our diaphragm from it's normal domed shape
        Increases the volume of your thorax, and decreases the pressure- air moves into the lungs
  2. BREATHING OUT
    1. The intercostal muscles relax, your rib drops down and in again.
      1. Diaphragm relaxes and curves back up into your thorax
        Volume of thorax decreases, increasing the pressure inside your chest and forcing the air out
  3. BREATHING SYSTEM
    1. The lungs are in your thorax protected by your ribcage and separated from your diaphragm by your abdomen
The Gut
1. Food is broken down and molecules get turned into simple sugars, such as glucose, amino acids, fatty acids, and glycerol
  1. Need these products of digestion to provide fuel for respiration and the building blocks for growth and repair.
  2. Food molecules now small enough to pass freely through walls of the small intestine into the blood vessels
    1. DIFFUSION Steep concentration gradient
    2. lining of small intestine folded into thousands of tiny finger like projections known as VILLI (then microvilli)
      1. Increases surface area
      2. Good blood supply - carries digested food away as soon as it diffuses from one side to the other
        network of capillaries
  3. ACTIVE TRANSPORT
    1. Time since last meal gets longer you can have more dissolved food molecules in your blood than in your digestive system
      1. Glucose and other dissolved food molecules then move from the small intestine to the blood by active transport
In Plants
Transpiration
Transporting Materials B3.2
1. The Circulatory System and the Heart
  1. Made up of 3 parts: the pipes (blood vessels), the pump (the heart) and the liquid (the blood)
  2. Double Circulation
    1. One carries blood from your heart to your lungs and back. The other carries blood around the rest of your body and back again to the heart
    2. Arteries carry blood away from your heart to the organs of your body
    3. Blood returns to the heart through the veins
  3. Heart as a pump
    1. Walls of your heart are mosly muscle, muscle supplied with oxygen by the coronary arteries
      1. Valves make sure the blood flows in the right direction through the heart
  4. Blood enters the top chambers of your heart THE ATRIA
    1. The blood in the right atrium is from the VENA CAVA and is DEOXYGENATED blood from your BODY
      1. The atria contract together and force blood down into the VENTRICLES. Valves close to stop the bloos flowing backwards out of the heart
        The ventricles contract and force blood out of the heart
        The right ventricle forces deoxygenated blood to the lungs in the pulmonary artery
        The left ventricle forces out oxygenated blood to the body through the aorta
    2. The blood in the left atrium is from the PULMONARY VEIN is OXYGENATED blood from your LUNGS
2. Keeping the blood flowing

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	Created by anna.coughlan.12 almost 11 years ago