AQA BIOL1 Extended Responses

Amylase

(starch to maltose)

Maltase

(maltose to glucose)

Hydrolysis

(of glycosidic bond)

Glucose moves in with sodium into the epithelial cell

Via carrier protein

Sodium removed from epithelial cell by active transport (sodium potassium pump)

Into blood

This maintains a low concentration of sodium in epithelial cell which maintains the concentration gradient of sodium between the lumen and the epithelial cell

Glucose moves into the blood

By facilitated diffusion

Cholera bacterium is prokaryotic, epithelial cell from the small intestine is eukaryotic.

Cholera bacterium does not have a nucleus, epithelial cell from the small intestine does.

Cholera bacterium has no membrane bound organelles, epithelial cell from the small intestine does.

Cholera bacterium has small ribosomes only.

Cholera bacterium has a cell wall, epithelial cell from the small intestine does not.

Cholera bacterium has a flagellum, epithelial cell from the small intestine does not.

Pros:

Small objects can be seen

TEM has a higher resolution

Cons:

Can't look at living cells as species must be in a vacuum

Must be a very thin specimen

Preparation may create artefact

Does not produce a colour image

SAN initiates heartbeat

By sending out a wave of electrical activity

AVN delays

Allowing atria to empty before ventricles contract

AVN sends wave of electrical activity down bundle of His

Causing ventricles to contract from base up

Atheroma: fatty deposits in the walls of arteries, often associated with high cholesterol levels in the blood.

If an atheroma breaks through the lining of the blood vessel the rough surface formed can cause a blood clot to form.

This blood clot can break off and block the coronary artery

This reduces the oxygen and glucose supply to the heart

This means the heart muscle is unable to respire and so it dies

Facilitated diffusion from a high concentration to a low concentration (down a concentration gradient)

Lipid-soluble materials pass through phospholipid bilayer

Water moves by osmosis from a region of high water potential to a region of low water potential

Active transport is the movement of a substance from a region of low concentration to a region of high concentration (against the concentration gradient)

Active transport involves proteins

Active transport requires energy in the form of ATP

Alveoli walls folded to provide a large SA

Many capillaries provide a large SA

Therefore fast diffusion

Epithelium is thin so short distance between alveoli and blood

So short diffusion pathway

Ventilation and circulation maintain diffusion gradient

Bacteria transmitted in droplets

Bacteria engulfed by phagocytes

Bacteria encased in tubercle

Bacteria are dormant

If immunosupressed, bacteria replicate

Bacteria destroy alveoli

This leads to fibrosis

Damage leads to decrease in SA of lungs and increases diffusion distance

Activation allows bacteria to enter blood and spread to other organs

Emphysema causes the alveoli to break down and the alveolar walls to thicken

This means there is a smaller SA and longer diffusion pathway

Loss of elastic tissue in the lungs

This makes it more difficult to expel air

Less air leaves lungs so air is not replenished

Less oxygen enters blood so less oxygen reaches tissues

Less ATP produced