Exchange and Transport Systems Flashcards
What features increase the rate of movement of molecules across surfaces?
-large SA:V ratio
-very thin
-selectively permeable
-molecules can be moved away to keep the concentration gradient steep
Calculating SA:V
(surface area/volume):1
Describe and explain the relationship between an organism’s size and SA:V ratio.
The larger the organism the smaller the surface area to volume ratio, so the more heat they lose, the the higher the metabolic rate
Explain gas exchange in single-celled organisms
-Relatively large surface area, a thing surface and short diffusion distance (oxygen can take part in reactions as soon as it diffuses into the cell)- no need for specialised gas exchange system
Explain gas exchange in fish
(conc of oxygen in air<conc of oxygen in water)
-gills made of lots of thin plates called gill filaments giving a large SA for gas exchange therefore increased rate of diffusion
-gill filaments covered in lamellae (tiny structures) increasing the SA even more
-lamellae have lots of blood capillaries and a thin surface layer of cells to speed up diffusion between the water and the blood
counter-current system:
-blood flows through lamellae in one direction and water flows over them in the opposite direction
-means that water with a high oxygen concentration always flows next to blood with a lower oxygen concentration
-steep conc gradient maintained
-as much oxygen as possible diffuses from water into blood
-diffusion along length of lamellae
Explain gas exchange in dicotyledonous plants.
-mesophyll cells (in leaf) have a large SA
-gases move in and out through stomata
-guard cells control opening and closing of stomata and therefore water loss
Explain how the structure of plants helps them to limit water loss.
-hairs on epidermis trap water vapour round the stomata reducing the water potential gradient
-thick waxy cuticle reduces evaporation
-curled leaves protect stomata from wind that would otherwise increase the rate of diffusion and evaporation
-stomata in pits to trap water vapour reduce the water potential gradient
-reduced number of stomata- fewer places for water to escape
Explain gas exchange in insects.
-terrestrial insects have trachea (microscopic air-filled pipes) that branch off into smaller tracheoles which have thin permeable walls and go into individual cells
-air moves into trachea through pores on the surface called spiracles- oxygen diffuses directly into respiring cells
-air moves in and out of spiracles using rhythmic abdominal movements
How are insects adapted for efficient gas exchange?
-tracheoles have thin walls-short diffusion distance
-highly branched-short diffusion distance therefore large exchange surface area
-trachea provide tubes full of air- fast diffusion
-fluid in end of tracheoles that moves out during exercise- faster diffusion through air to gas exchange surface
-body can be moved by muscles to move air-maintains diffusion gradient for oxygen
What are the different ways respiratory gases can move in and out of the tracheal system in insects?
-along diffusion gradient- oxygen in, carbon dioxide out
-mass transport-muscle contraction squeezes trachea
-end of tracheoles filled with water- allow water and thus air to be drawn in due to a lowered water potential from lactate (product of anaerobic respiration)
Explain the advantage for larger animals having a specialised system that facilitates oxygen uptake.
-larger organisms have a smaller surface area to volume ratio
- specialised system overcomes long diffusion pathway
-faster diffusion
Describe the gross (not microscopic) structure of the human gas exchange system.
-the trachea have cartilage rings that strengthen it and prevent it from collapsing
-trachea divided into bronchi, bronchioles then alveoli
Describe what happens during inspiration.
ACTIVE
-The volume of our thoracic cavity increases and pressure decreases as the external intercostal muscles and diaphragm contract whilst the internal intercostal muscles relax
Describe what happens during expiration.
PASSIVE
-The volume of the thoracic cavity decreases and pressure increases as the internal intercostal muscles contract whilst the external intercostal muscles and diaphragm relax
Describe and explain how the lungs are adapted to allow rapid exchange of oxygen between air in the alveoli and blood in the capillaries around them.
-constant blood supply maintains concentration gradient so oxygen can rapidly diffuse into blood
-thin walls of blood capillaries create short diffusion distance
-flattened epithelium so short diffusion distance so fast diffusion
-ventilation maintains concentration gradient so fast diffusion
-many alveoli-large SA
Define digestion.
The hydrolysis of large insoluble molecules into smaller soluble molecules.
Describe starch digestion.
-amylase
-hydrolyses
-glycosidic bonds
-starch broken down into maltose
-maltase
-hydrolyses
-maltose to glucose
Explain how digestion of starch in the small intestine leads to an increase in the concentration of glucose in the blood.
-starch hydrolysed by amylase, then maltase
-produces glucose
-facilitated diffusion of glucose across the epithelium into the blood
Describe the processes involved in the absorption of the products of starch digestion.
-sodium ions removed from epithelial cell by active transport/sodium-potassium pump
-into blood
-maintaining low concentration of sodium ions in epithelial cell
-glucose moves in with sodium ions into epithelial cell
-via facilitated diffusion through a co-transport protein
-glucose moves into blood
-by (facilitated) diffusion
Describe protein digestion.
-endopeptidases hydrolyse the peptide bonds between the amino acids in the centre of the polypeptide
-increasing the SA, creating more ends for exopeptidases
-exopeptidases hydrolyse the peptide bonds between the terminal amino acids of the polypeptides
-this creates dipeptides and single amino acids
-membrane-bound dipeptidases hydrolyse the peptide bonds between the amino acids in these dipeptides
