Section 3 Flashcards
Name 3 reasons why large multicellular organisms cant use their body for exchange
- small SA : vol
- diffusion too slow
- need for water proofing
Describe the specialised exchange system in insects
The tracheal system. Air enters through open spiracles, then trachea and tracheoles. Oxygen diffuses into the surrounding cells used in respiration and carbon dioxide diffuses out. This maintains a concentration gradient. The carbon dioxide then enters the tracheoles and trachea and finally is forced out the spiracles by the help of abdominal pumping.
How do tracheoles provide a good exchange surface?
. Many highly branched so provides short diffusion distance
. Many small branched provides large surface area
. Respiration of muscle cells maintains conc grad for o2 and co2
. thin walls so short diffusion
Describe and explain counter current flow system
Water high in oxygen and blood low in oxygen flow in opposite directions to maintain a diffusion gradient for o2 and co2. So its maintained along the entire lamellae. This means more oxygen is diffused into blood so more aerobic respiration which therefore means more muscle contraction.
How do gills provide a good exchange surface?
. thin lamellae are well supplied with capillaries provide short diffusion distance
. lots of gill filaments with lots of lamellae provides large surface area
. counter current flow maintains diffusion gradients
Explain the digestion of starch
. salivary glands in mouth produce amylase which hydrolyse starch into maltose
. in the duodenum amylase is produced which hydrolyses more starch into maltose
. in the ileum maltase is produced which hydrolyses maltose into alpha glucose
Describe the digestion of lipids
. in the duodenum lipids are emulsified by bile salts into smaller lipid droplets
. pancreas then secretes lipase in duodenum which hydrolyses lipid droplets into monoglycerides and fatty acids
. these then form micelles
Describe lipid absorption
. micelles bring monoglycerides and fatty acids to ileum epithelial cells
. they diffuse into cell and get formed into triglycerides at SER
. at Golgi app cholesterol and protein are added to produce chylomicrons
. leave cell via exocytosis into lymphatic capillary
Describe protein digestion
. in stomach endopeptidase hydrolyses peptide bonds between peptide chains in the middle producing a series of shorter peptide chains
. in the duodenum exopeptidase and endopeptidase is secreted by pancreas. Exopeptidase hydrolyses peptide bonds between terminal amino acids
. in the ileum membrane-bound dipeptidase hydrolyses dipeptides into amino acids
How is the ileum adapted to be a good exchange surface?
. large surface area for more carrier/channel proteins for facilitated diffusion- cotransporters for co-transport
. ileum folded has villi which each epithelial cell has microvilli so larger surface area
. thin layer of epithelial cells lining each villus each close to a capillary provides short diffusion distance
. Circulation of blood flow maintains a concentration gradient
Describe the absorption of glucose via co-transport (or amino acids)
. Na+ ions actively pumped out of epithelial cell via a Na+K+ pump
. this lowers conc of Na+ ions inside cell creating a concentration gradient for Na+ to enter
. Na+ diffuse into cell via N+ glucose co-transporters down a conc gradient which carry glucose too ( go down a Na+ gradient)
. Glucose diffuses out of cell into the blood stream
What are the components of the right side of the heart?
Vena Cava
Right atrium
Atrioventricular valve
Right ventricle
Semi-lunar valve
Pulmonary artery
What are the components of the left side of the heart?
Pulmonary vein
Left atrium
Atrioventricular valve
Left ventricle
Semi-lunar valve
Aorta
What are two advantages of the septum?
. separates deoxygenated blood and oxygenated blood
. means left side maintains a higher pressure than right
Describe the cardiac cycle
Atrial systole:
AV open because atrium higher pressure than ventricle. Both atria contract and blood is forced into ventricles.
Ventricular systole:
AV closed because ventricle higher pressure then atrium and ventricles contract. Semi-lunar valves open as blood forced into arteries.
Diastole:
Atria and ventricles relax
Semi-lunar valve closed because artery pressure is higher than ventricle. AV open.
Compare the properties of arteries and veins structurally
Arteries have a thicker muscular layer than veins to control the volume of blood whereas veins have a relatively thin muscle wall.
Arteries have a thicker elastic layer to maintain blood pressure whereas veins have a relatively thin elastic wall as pressure is much lower.
Arteries have thicker walls so can withstand higher pressure so therefore have a smaller lumen whereas veins have thin walls as pressure is a lot lower so their lumen may appear to be in a irregular shape.
Veins have valves to prevent backflow due to low pressure whereas arteries do not have valves as they can maintain a constant blood pressure throughout so no backflow occurs.
Explain the structure of a capillary
One cell layer thick (endothelium cells).
Lumen is extremely narrow so RBC only just fit through- maximises diffusion due to slowed blood flow.
Compare the structure of arterioles and capillaries.
Arterioles have a thicker muscular layer than arteries to help restrict blood flow into capillaries whereas capillaries do not have a muscular layer.
Arterioles have an elastic layer which is thinner than arteries as pressure is a little lower whereas capillaries do not have an elastic layer as they are only one cell thick.
Arterioles have a thicker wall than capillaries as capillaries only consist of one cell thickness.
Both arterioles and capillaries do not have valves.
Describe the structure of haemoglobin
4 polypeptide chains- each chain is bound to a group called haem which contains Fe2+. Each Fe2+ combines with one oxygen.
One molecule of haemoglobin can combine with 4 oxygen molecules.
What is oxyhaemoglobin and what type of reaction is it.
Oxyhaemoglobin is when oxygen and haemoglobin bind together during a reversible reaction so the oxygen can be released again at respiring muscles and tissues.
Describe the relation to partial pressure and affinity of haemoglobin
At low partial pressures of oxygen, haemoglobin has a low affinity for oxygen.
At the lungs, haemoglobin has a high affinity for oxygen so binds.
At tissues, haemoglobin has a low affinity for oxygen so unloads.
