Exchange Of Substances Flashcards

Question

Mass flow hypothesis of phloem

Answer 1

A

Hydrolysis of large, insoluble biological molecules into smaller, soluble molecules which can be absorbed across the cell membrane of the epithelial cells of the illeum.

Answer 2

A

-Food is broken up by teeth (mechanical digestion) then mixed with saliva containing salivary amylase which hydrolysed glycosidic bonds in starch to produce maltose.
-In the stomach salivary amylase is denatured due to the acidic pH
-in the illeum, pancreatic amylase dither hydrolysed starch into maltose.
-maltose is hydrolysed into glucose by membrane bound maltase embedded in the epithelial cells of the illeum.
-Glucose is absorbed into the illeum

GLYCOSIDIC BONDS ARE HYDROLYSED

Answer 3

A

-Na+ is actively transported out of the epithelial cells and into the blood (requires ATP)
-Creates a concentration gradient of Na⁺ between the ileum and the epithelial cell.
-Na+ and glucose (or amino acids) enter the epithelial cells from the ileum via facilitated diffusion through complementary co-transporter proteins.
-These co-transporter proteins have two binding sites: one specific for Na⁺ and one for glucose or an amino acid.
-Na+ moves into the cells down its concentration gradient and glucose/amino acids move into the cell against their concentration gradient.
-amino acids enter the blood via facilitated diffusion.

Answer 4

A

-Endopeptidase hydrolyse internal peptide bonds within the polypeptide chain. This increases the surface area for the next enzyme.
-Exopeptidase hydrolyse peptide bonds at the terminal ends of the polypeptide chain, producing dipeptides and single amino acids.
-Dipetidase are embedded in the csm of the epithelial cells and hydrolyse peptide bonds between dipeptides to produce amino acids.

Answer 5

A

-Bile is released into the small intestines and emulsifies lipids to increase SA for faster hydrolysis action of lipase into monoglycerides and fatty acids.
-Bile salts mix with glycerol, fatty acids and monoglycerides to form micelles.
-Micelles make fatty acids soluble in water and bring them to the surface of the epithelial cell membrane. This mainatains a higher concentration relative to the epithelial cells.
-Fatty acids enter the epithelial by simple diffusion (micelles don’t cross csm)
-At SER fatty acids and glycerol are recombined into triglycerides.
-At the Golgi, triglycerides are modified into chlyomicrons and packaged into vesicles (chlyomicrons are water soluble and can be carried by the blood)
-Chlyomicrons are transported into a lymph vessel via exocytosis and then enter the blood.

Answer 6

A

-As an object gets larger, its surface area to volume ratio decreases.
-Larger multicellular organisms have specialised exchange systems because they have smaller surface area to volume ratios, and so need more complex systems in order to carry out efficient exchange of gases and absorption of nutrients. This is shown by Ficks law.
-Ficks law states: Diffusion rate =
SA x concentration gradient / diffusion distance or pathway
-Because smaller organisms have larger smaller SA:volume ratios, they lose more heat. To compensate they have to increase metabolic activity such as through respiration, which produces heat, allowing organisms to maintain body temperature.
-Single celled organisms carry out gas exchange through simple diffusion because they have a large enough SA:volume ratio to meet their gas exchange needs through simple diffusion across their short pathway.

Answer 7

A

-Oxygen enters the insect through spiracles and into the trachea
-Spiracles close
-Oxygen diffuses down the concentration gradient through tracheae into tracheoles where gas is directly delivered to respiring tissue.
-Tissue use oxygen, reducing concentration inside insects, so oxygen diffuses down the concentration gradient into the insect from the air.
-CO2 moves in the opp direction.
-Tracheae are kept open by chitin

Tracheoles are adapted because:
-Highly branched, increase SA
-Thin walls, short diffusion pathway
-Supply directly to tissue, SDP

-Abdominal pumping is when insects contract muscles, pumping CO2 out and oxygen through the tracheal system.

-To reduce waterloss:
-Exoskeleton, covered by waterproof cuticle which is impermeable to water.
-Spiracles close
-Small hairs around spiracles trap water and reduce WP gradient.

Answer 8

A

-Water carrying oxygen enter mouth
-Gills contains projections called filaments made up of lamellae which contain capillaries and are the site of gas exchange.
-Most oxygen is removed as water passes through the lamellae and enters capillaries.
-Water containing little oxygen leaves gill opening (operculum).

Gill adaptations:
-many filaments with many lamellae, large SA for diffusion
-thin epithelium for short diffusion pathway between water and blood

-Counter current flow: water and blood flow in opposite directions, which maintains a constant concentration gradient of oxygen so that the oxygen concentration is always high in water, along the entire length of the gill lamellae.

Answer 9

A

Inhalation:
-External IM contract, pulling rib cage up and out. Diaphragm contracts and flattens.
-Increases thoracic cavity volume.
-pressure in lungs is lower than atmospheric pressure.
-Air flows down pressure gradient into lungs.

Exhalation:
-External IM relax, pulling rib cage down and in. Diaphragm relaxes and moves up/domes.
-Internal intercostal muscles contract (forced exhalation).
-decreases thoracic cavity volume.
-pressure in lungs is higher than atmospheric pressure.
-Air flows down pressure gradient out of lungs.

-Antagonistic interaction between internal and external IM

-Pulmonary ventilation rate (total volume air moved into lungs in 1 minuite) = tidal volume (volume of air taken in each breath) x breathing rate (number of breaths taken a minuite)