AQA Biology 3

AQA Biology 3

1. Exchange of materials B3.1

   • Osmosis
     • The movement of water from a dilute solution to a more concentrated solution across a partially permeable membrane
       • If cell uses up water in its chemical reactions, the cytoplasm becomes more concentrated. More water moves in by osmosis.
       • If cytoplasm becomes too dilute because more water is made in chemical reactions, water leaves the cell by osmosis.
     • Red Blood Cells
       • 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.
       • 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
     • Plants
       • Water moves into the plant cells through osmosis
         • 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
         • 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
   • Active Transport
     • The movement of particles from an area of low concentration to an area of high concentration against the concentration gradient
       • ENERGY IS REQUIRED FROM RESPIRATION
     • If a cell makes a lot of energy it can carry out a lot of active transport
     • Root Hair Cells
       • Mineral Ions
     • Glucose
       • Kidneys - reabsorption of glucose
       • Small intestine (diffusion takes place, but not all substances work with the concentration gradient
   • Sports Drinks
     • When you exercise you...
       • Sweat
         • 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
       • Release energy by respiration, using up sugar
         • Needed for respiration
     • REPLACE THE SUGAR USED IN RESPIRATION AND WATER + MINERAL IONS LOST IN SWEAT
       • Evidence suggests that for normal levels of exercise water is at least as effective as sports drinks
   • Adaptations
     • LARGE SURFACE AREA
     • BEING THIN
       • Provides a shorter diffusion path
     • EFFICIENT BLOOD SUPPLY
       • Moves the diffusing substances away and maintains a concentration gradient
     • BEING VENTILATED
       • Makes gaseous exchange more efficient by maintaining steep gradients
   • The Lungs
     • Made up of alveoli
       • Large surface area Most effective for diffusion of oxygen and carbon dioxide
       • Rich blood supply, maintains concentration gradient in both directions
       • Layer of cells between the air in the lungs and the blood in the capillaries is very thin - short diffusion path
   • Ventiating the lungs
     • BREATHING IN
       • Your intercostal muscles contract pulling your ribcage up and out
         • 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
     • BREATHING OUT
       • The intercostal muscles relax, your rib drops down and in again.
         • Diaphragm relaxes and curves back up into your thorax
           • Volume of thorax decreases, increasing the pressure inside your chest and forcing the air out
     • BREATHING SYSTEM
       • The lungs are in your thorax protected by your ribcage and separated from your diaphragm by your abdomen

2. The Gut

   • Food is broken down and molecules get turned into simple sugars, such as glucose, amino acids, fatty acids, and glycerol
     • Need these products of digestion to provide fuel for respiration and the building blocks for growth and repair.
     • Food molecules now small enough to pass freely through walls of the small intestine into the blood vessels
       • DIFFUSION Steep concentration gradient
       • lining of small intestine folded into thousands of tiny finger like projections known as VILLI (then microvilli)
         • Increases surface area
         • Good blood supply - carries digested food away as soon as it diffuses from one side to the other
           • network of capillaries
     • ACTIVE TRANSPORT
       • Time since last meal gets longer you can have more dissolved food molecules in your blood than in your digestive system
         • Glucose and other dissolved food molecules then move from the small intestine to the blood by active transport

3. In Plants

4. Transpiration

5. Transporting Materials B3.2

   • The Circulatory System and the Heart
     • Made up of 3 parts: the pipes (blood vessels), the pump (the heart) and the liquid (the blood)
     • Double Circulation
       • 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
       • Arteries carry blood away from your heart to the organs of your body
       • Blood returns to the heart through the veins
     • Heart as a pump
       • Walls of your heart are mosly muscle, muscle supplied with oxygen by the coronary arteries
         • Valves make sure the blood flows in the right direction through the heart
     • Blood enters the top chambers of your heart THE ATRIA
       • The blood in the right atrium is from the VENA CAVA and is DEOXYGENATED blood from your BODY
         • 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
       • The blood in the left atrium is from the PULMONARY VEIN is OXYGENATED blood from your LUNGS
   • Keeping the blood flowing