biology, topic 2: genes and health

(spec 2.1) describe the anatomical adaptations that maximise gas exchange in mammals

• alveoli are used as an exchange surface for gas

• many alveolar mean they have a large surface area that maximises gas exchange

• alveolar are made up of squamous tissue so have a short distance for gasses to diffuse across, so more oxygen is taken in and more carbon dioxide is released faster

• the network of blood capillaries surrounding the alveolar maintain the concentration gradient while also increasing the surface area

(spec 2.1) give the formula for flick’s law

rate of gas exchange= surface area × concentration gradient / thickness of diffusion surface

(spec 2.1) explain how each of these factors would alter the rate of gas exchange:

• increased thickness due to thicker mucus

• reduction in the concentration gradient

• damage to alveoli resulting in a reduction in number

• increased thickness of diffusion surface decreases the rate of gas exchange as gasses are diffusing at a slower rate

• less oxygen is diffused into the blood and less carbon dioxide is diffused into the alveolar as the areas of concentration become similar

• reduction in surface area so rate of gas exchange decreases as less gas exchange occurs at a time

(spec 2.1) explain the role in goblet cells in the respiratory system

• goblet cells produce mucus which is released into the airways

• the mucus then traps any inhaled dust and pathogens in the lungs

• the mucus is then removed by the cilia

(spec 2.1) explain the role of ciliated epithelial cells in the respiratory system

• ciliated epithelial cells have cilia attached on the surface

• cilia are hair-like structures that sweep mucus backwards and forwards and move the mucus out the lungs

• they keep the lungs clean from excess mucus which can effect the respiratory system

(spec 2.2) describe the structure and properties of phospholipids

• phospholipids are made of a glycerol and phosphate head (hydrophilic) and two fatty acid tails (hydrophobic)

• phospholipids can join together to form a phospholipid bilayer in cell membranes

(spec 2.2) explain why phospholipids for a bilayer in cell membranes

• the hydrophilic glycerol and phosphate head remains in the aqueous environment staying on the outside of the bilayer

• the hydrophobic fatty acid tails remain inside, away from the aqueous environment

(spec 2.2) list the other components of cell membranes and give a function for each one

• glycolipids and glycoproteins: involved in cell to cell signalling, act as antigens and are receptors for hormones

• channel and carrier proteins: transport polar/charged/ionic substances through the membrane

• cholesterol: maintains membrane fluidity so that the components can move around in the membrane

• phospholipid bilayer: transports very small and non-polar substances through the membrane

(spec 2.2) draw a labelled diagram of a cell membrane

(spec 2.2) why is the cell membrane called a fluid mosaic

• the components of the membrane are constantly moving in a fluid manner (fluid)

• the cell membrane has many components that work together (mosaic)

(spec 2.2) explain how the level of cholesterol affects membrane fluidity

• decrease: at high temperatures phospholipids spread apart, cholesterol fits into the gaps between the phospholipids limiting movement

• increase: at low temperatures phospholipids tend to clump together, cholesterol inserts itself between the phospholipids to prevent them becoming tightly packed

(spec 2.2) explain how unsaturated and saturated phospholipid tails affects membrane fluidity

• saturated: straight chains mean the phospholipids can pact tightly reducing fluidity

• unsaturated: kinks in the fatty acid chain provides a less tightly packed structure, providing more space and increasing fluidity

(spec 2.2) give reasons why the three-layer protein lipid sandwich theory of a membrane was rejected as a model

• couldn’t explain how the hydrophilic and hydrophobic regions could be stable in an aqueous solution

• the model suggested a static and rigid structure but fluorescent antibody tagging showed that membrane proteins are mobile

• the model suggested that proteins were only on the surface but freeze-fracture evidence proved the existence of integral proteins