Exchange

Features of specialised exchange surfaces

• large SA

• short diffusion path

• steep concentration gradient

• selectively permeable membranes

Gas exchange in Insects

• made from spiracles leading to trachea with tracheoles with fluid filled ends

• highly branched and thin for maximised diffusion

Gas Exchange in Fish

• gills covered by operculum flap with stacked filaments contains lamellae

• countercurrent blood and water flow with steep concentration gradient and large SA

Gas Exchange in Plants

• air spaces act as network for gas exchange

• mesophyll cells for large SA

• stomata open and close for diffusion

• waxy cuticle and stomata minimise water loss

Xerophyte Adaptations

• waxy cuticle

• rolled leaves

• hairy and small leaves

• water storage organs

Gas Exchange in Humans

• trachea leading to bronchi and highly branched bronchioles with alveoli ends

• contained in rib cage and intercostal muscles

• diaphragm underneath

• goblet cells in ciliated epithelium tissue secrete mucus to trap dust and microbes

• Alveoli Adaptations

• one cell thick

• large SA

• partially permeable

• surrounding capillaries for steep concentration gradient

• elastic and collagen fibres

Describe inspiration (breathing in)

1. external intercostal muscles contract

2. internal intercostal muscles relax

3. ribs move up and out

4. increased volume of thorax

5. diaphragm contracts and flattens

6. decreased pressure of thorax

7. atmospheric pressure > pulmonary pressure so air is forced in

Describe expiration (breathing out)

1. external intercostal muscles relax

2. internal intercostal muscles contract

3. ribs move down and in

4. decreased volume of thorax

5. diaphragm relaxes and domes

6. increased pressure of thorax

7. pulmonary pressure > atmospheric pressure so air is forced out

Function of Carbohydrase

• produced by salivary glands, pancreas and small intestine

• e.g. amylase breaks down maltose and maltase hydrolyses into a-glucose monomers

• same with lactose and sucrose

Function of Lipase

• produced by pancreas and small intestine

• breaks down lipids into fatty acids and monoglycerides

• lipids are emulsified by bile salts into micelles

Function of Protease

• produced by stomach, pancreas and small intestine

• endopeptidase = hydrolyse internal/mid chain peptide bonds

• exopeptidase = hydrolyse end chain peptide bonds

• dipeptidase = breaks dipeptides into amino acids