extended responses

• Describe the main structural features of the cell membrane

  Phospholipid bilayer - phosphate and glycerol heads and fatty acid tails.

  Channel and carrier proteins are embedded in the membrane.

  Cholesterol in the membrane - to maintain membrane consistency.

  Glycolipids - attached to phosphate head. Cell signalling and recognition.

  Protein channel - all the passage of large molecules such as glucose and amino acids across the membrane.

  Protein carrier - each protein carrier is specific to the molecule it moves.
• Diffusion

  • The movement of substances from an area of high concentration to an area of low concentration.
  • So that particles are evenly distributed.
• Osmosis

  • The movement of water
  • from a region of low solute concentration to a region of high solute concentration.
  • passive process
• Facilitated diffusion

  • the movement of a substance from a region of high concentration to a region of low concentration
  • passive process
  • through the use of a carrier or transport protein
• Active transport

  • the movement of a substance against the concentration gradient
  • requires ATP/energy
  • through the use of carrier or transport proteins.
• Endocytosis

  • cell membrane surrounds solid/liquid particles and engulfs material
  • in small membrane-bound vesicles
• exocytosis

  • contents os vesicle are expelled out through the cell membrane
  • vesicle fuses with membrane and contents passed to exterior
• Explain the similarities and differences between aerobic

  and anaerobic respiration.

  Similarities

  • both start with glucose
  • both use glycolisis
  • occurs in the cytoplasm
  • both produce ATP
  • both produce pyruvate

  Differences

  Aerobic respiration

  • pyruvate transported to h mitochondria
  • further oxidized to CO2 and water (in Krebs cycle)
  • produce more ATP
  • can use other compounds for energy - ATP - amino acids

  Anaerobic respiration

  • produces lactic acid
  • produces less ATP - 2
• Outline the functions of vitamins and minerals ni the body.

  Functions of vitamins

  • act as co-enzymes for enzyme activity
  • incorporated into chemical structures
  • immune function - vitamins A, C, D

  Functions of minerals

  • building of structures like teeth and bones
  • transfer of nerve impulses
  • transport of oxygen
• Name the disease caused by the lack of one of these in the diet and the foods needed to be added as a good source of these.

  Vitamin deficiencies

  • vitamin C - scurvy - citrus fruits
  • vitamin D - rickets - milk and fish

  Mineral deficiencies

  • calcium - brittle bones - milk and dairy products
  • iron - anemia - meat and green leafy vegetables
• Explain the need for, and mechanism of, ventilation of the lungs.

  The need for ventilation

  • humans are large and have a small surface area to volume ratio
  • so need a ventilation system to increase the surface area available for receiving oxygen
  • removal or excretion of carbon dioxide

  the mechanism of ventilation

  • diaphragm contracts
  • intercostal muscles contract
  • decreasing air pressure in the lungs
  • air rushes down the pressure gradient
  • the converse of the above causes exhalation
  • elastic recoil of the lungs helps with exhalation.
• State the differences between ventilation and gas exchange.

  Ventilation

  • movement of air
  • movement in and out of the lungs
  • an active process
  • involves flow along air passages

  Gas exchange

  • movement of carbon dioxide and oxygen
  • happens when oxygen or carbon dioxide moves from the alveoli to the bloodstream or vice versa.
  • passive process of diffusion.
• Compare the structure of the three types of blood vessels and explain how their structure relates to their function.

  Arteries

  • smooth muscle
  • small lumen
  • very elastic
  • pump blood under high pressure from the heart

  Veins

  • Less muscular
  • large lumen
  • valves resent preventing backflow
  • carry blood under low pressure to the heart

  capillaries

  • 1 cell thick
  • no muscle
  • very small microscopic lumen
  • allows diffusion to transport substances from the plasma into tissues
• Pathway taken by a red blood cell through the heart

  1. Red blood cell enters the right atrium

  2. Right atrium contracts and blood forces the AV valve open

  3. Red blood cell is in the right ventricle

  4. Right ventricle contracts and blood forces semi lunar valve open

  5. Red blood cell is in the pulmonary artery

  6. Artery goes to the lungs where gas exchange occurs and the oxygen combines with haemoglobin

  7. Red blood cell is in the pulmonary vein

  8. Going back to the heart

  9. Red blood cell is in the left atrium

  10. Left atrium contracts and blood forces the bicuspid valve open

  11. Red blood cell is in the left ventricle

  12. Contracts and the blood forces the semi lunar valve open and blood flows into the aorta
• Structure of the nephron

  1. Glomerulus

  2. Glomerular capsule

  3. Proximal convoluted tubule

  4. Loop of Henle

  5. Distal convoluted tubule

  6. Collecting duct
• Glomerulus


  • A collection of capillaries
  • Filtration of substances through the capillaries
• Glomerular capsule


  • A double-walled cup that surrounds the glomerulus
  • Collects filtrate and directs it to the proximal convoluted tubule
• Proximal convoluted tubule


  • A winding tube where the filtrate enters from the capsule
  • All glucose from the drink is reabsorbed here
• Loop of Henle


  • Two straight tubules with a hairpin bend
  • Reabsorption of water in the descending loop
  • Absorbance of salts in the ascending loop
• Distal convoluted tubule


  • Highly coiled and empties into the collecting duct
  • Salt and water reabsorbed
• Collecting duct


  Has many distal convoluted tubules emptying filtrate into it
• The components of the electrolyte drink are reabsorbed as it travels through the structures of the nephron
• Describe the microscopic mechanism that allows muscles to contract.

  • calcium influx
  • causes myosin heads to form cross-bridges with actin
  • pulls myosin towards the middle of the sarcomere
  • sarcomere shortens and Z lines move closer together
  • ATP is required for the shortening of muscle fibres
• Fibrous or immovable

  • fibrous connective tissue joins the bones, so there is very little or no movement
  • an example is sutured in the skull and teeth in the jaw
  • the bones are fused together to make a solid joint to protect the brain or ensure the teeth don't come loose and fall out.
• Cartilaginous or slightly moveable

  • held in place with cartilage which may flex slightly with movement between adjacent bones
  • example: between the vertebrate
  • allows for some movement between the bones to maintain the structure but to move slightly under pressure
• Synovial or freely movable

  • allow for a range of large movements limited by the surrounding tendons, ligaments and muscles; have articulating surfaces that easily slide over one another.
  • example: ball and socket - hip and shoulder
  • movements such as walking or picking up objects. movements are determined by the location controlled by voluntary muscles to bring about coordinated