Which statements about bronchioles are correct?
1 - they have ciliated cells
2 - they have goblet cells
3 - they have muscle tissue
1 and 3 only
Which characteristic of the human gaseous exchange surface and the lungs maintains the necessary concentration gradients for carbon dioxide and oxygen?
Good ventilation of the lungs
Which tissues may be found in bronchioles?
Ciliated epithelium
Elastic fibres
Smooth muscle
What would be seen in an electron micrograph of a bronchus wall?
1 - cartilage cells
2 - ciliated cells
3 - exocytotic vesicles
1, 2 and 3
What 3 features increase the efficiency of gaseous exchange in the alveoli?
- The blood capillaries and alveoli have a large total surface area
- The blood flow is slowed as it passes through the pulmonary capillaries
- The walls of the alveoli and capillaries are very thin
Describe exhalation in a mammal
Ribcage moves downwards and inwards
External intercostal muscles relax
Diaphragm relaxes
Describe inhalation in mammals
Ribcage moves upwards and outwards
External intercostal muscles contract
Diaphragm contracts
Bony fish absorb dissolved oxygen from the water using gills. Water is passed through the buccal cavity and over the gill lamellae. The oxygen saturation of the blood and water changes as the water passes over the gills.
Describe the way oxygen is transferred into the blood at the gills.
Blood and water flow in countercurrent system
with a constant concentration gradient between them
Describe how you could test a food sample for the presence of starch
- Add iodine
- Blue-black colour indicates that starch is present
Describe the role of enzymes in the breakdown of starch in the mouth
Amylase
Breaks down starch into maltose
Explain how digestion of starch in the small intestine causes an increase in the blood glucose concentration
- Starch is hydrolysed by amylase to produce maltose
- Maltose is hydrolysed by maltase to produce glucose
- Glucose small enough to cross the wall of small intestine into the blood
Describe the process by which glucose is absorbed from the small intestine into the blood
- Via carrier/channel proteins
- Sodium is removed from epithelial cells by active transport of the sodium-potassium pump
- Maintains a low concentration of of sodium in the epithelial cells
- Glucose is co-transported with sodium into epithelial cells
- Glucose moves into the blood
- By facilitated diffusion
Gallstones are small stones, usually made up of cholesterol, that form in the gallbladder.
When the gallstones block the pancreatic duct, digestion of starch is affected.
Explain why
- Less amylase can enter the small intestine
- Less starch is digested in the small intestine
When the pancreatic duct is blocked, amylase can be released into the bloodstream.
Explain why this is not dangerous for the body.
- Amylase is specific to starch
- There is no starch in blood/cells/tissues
When the pancreatic duct is blocked, protease enzymes can be released into the bloodstream.
Explain why this is dangerous for the body.
- Enzymes could digest the body’s own proteins
e.g carrier/channel proteins, antibodies
Describe how proteins are digested in the small intestine
- Peptide bonds are hydrolysed
- Endopeptidases break polypeptides into smaller peptide chains
- Exopeptidases remove terminal amino acids
- Dipeptidases hydrolyse dipeptides into amino acids
Lipids form droplets and micelles during digestion.
Explain the advantage of this
- Droplets increase surface area for lipase action
- So faster hydrolysis of lipids
- Micelles carry fatty acids and glycerol into intestinal epithelial cells through the phospholipid bilhar
Explain how the Golgi apparatus is involved in the digestion of lipids
- Modifies/processes triglycerides
- Combines triglycerides with proteins
- Packages lipids for exocytosis by forming vesicles
Describe the role of membrane-bound dipeptidases and explain why they are important in digestion
- Hydrolyse peptide bonds to release amino acids
- Allow amino acids to cross the plasma membrane
Describe the roles of exopeptidases and endopeptidases in protein digestion
Exopeptidases: hydrolyse peptide bonds at the ends if a polypeptide
Endopeptidases: hydrolyse internal peptide bonds within a protein
Some mammals such as rabbits eat their own semi-digested droppings.
Suggest how this action helps mammals to digest and absorb protein
- More protein can be broken down
- So more amino acids can be absorbed
- Because proteins pass through the stomach/small intestine again
The epithelial cells lining the small intestine are specialised for the absorption of glucose.
Explain how adaptions of this lining allow rapid absorption of glucose
- Microvilli provide a large surface area
- Many mitochondria produce ATP for active transport
- Contain carrier proteins for active transport of sodium and glucose
- Contain channel protein for facilitated diffusion
- Contain membrane-bound enzymes to digest disaccharides
