1 Exchange And Transport Systems Flashcards
1
Q
Describe the relationship between size and surface area to volume ratio.
A
- if organism has large volume, its surface area is relatively small, this makes it harder for it to lose heat from its body.
- if organism is small its relative surface area is large, so heat lost more easily. This means smaller organisms need relatively high metabolic rate in order to generate enough heat to stay warm.
2
Q
What 3 things to organisms exchange with the environment.
A
- oxygen
- waste products
- heat
3
Q
Describe adaptations in organisms to aid exchange.
A
- animals with high SA:volume ratio tend to lose more water as evaporates from their surface. Some small dessert animals have kidney structure adaptations so that produce less urine to compensate.
- to support high metabolic rates, small organisms living in cold regions need to eat large amounts of high energy foods.
- larger organisms living in hot regions find hard to keep cool as heat loss relatively slow. Elephants developed large flat ears to increase SA, allowing them to lose more heat.
4
Q
Describe adaptations of gas exchange surfaces, shown by gas exchange across body surface of singe-celled organism.
A
- singe-celled organisms absorb and release gases by diffusion through outer surface.
- have relatively large surface area, thin surface and short diffusion pathway, so no red for gas exchange system.
5
Q
Describe adaptations of gas exchange surfaces, shown by gas exchange in tracheal system of an insect.
A
- air enters trachea through pores on surface called spiracles.
- oxygen diffuses down concentration gradient along trachea
- trachea branch off into smaller tracheoles with thin, permeable walls and go to individual cells, means oxygen diffuses directly into respiring cells
- carbon dioxide from cells moves down its own concentration gradient towards spiracles to be released.
6
Q
Describe adaptations of gas exchange surfaces, shown by gas exchange across gills of fish.
A
- filaments and lamellae have big surface area, increases efficiency of diffusion
- lamellae have lots of blood capillaries and thin surface layer of cells so short diffusion distance.
- blood flows through lamellae in one direction, water flows over in opposite direction. (Counter-current system)
- maintains high concentration gradient between water and blood.
- concentration of oxygen in water always higher than that in blood, so as much oxygen as possible diffuses from water into blood.
7
Q
Describe adaptations of gas exchange surfaces, shown by gas exchange by the leaves of dicotyledonous plants.
A
- main gas exchange surface is surface of mesophyll cells in leaf. Well adapted as have a large surface area.
- mesophyll cells are inside leaf. Gases move in and out through stomata.
- stomata can open to allow exchange of gases, and close to prevent water loss.
- guard cells control opening and closing of stomata. Water enters Guard cell making it turgid which opens stomata, plant gets dehydrated guard cells lose water become flaccid and closes stomata.
8
Q
How do insects control water loss.
A
- if insects losing too much water, they close their spiracles.
- also have waterproof waxy cuticle all over body and tiny hairs around spiracles, both of which reduce evaporation.
9
Q
Describe the adaptations of xerophytes for controlling water loss
A
- stomata sunk in pits that trap moist air, reducing the concentration gradient of water between leaf and air. This reduces amount of water diffusing out of leaf and evaporating away.
- layer of hairs on epidermis, trap moist air around stomata.
- curled leaves with stomata inside, protecting them from wind.
- reduced number of stomata, so fewer places for water to escape.
- waxy, waterproof cuticles on leaves and stems reduce evaporation.
10
Q
Describe the structure of the human gas exchange system.
A
- air enters trachea
- trachea splits into 2 bronchi, 1 bronchus leading to each lung
- each bronchus branches off into bronchioles
- bronchioles end in alveoli.
- rib cage, intercostal muscles and diaphragm work together to move air in and out.
11
Q
Explain gaseous exchange in the alveoli.
A
- huge number of alveoli in lungs, so big surface area for exchanging O2 and CO2
- alveoli surrounded by network of capillaries
- O2 diffuses out of alveoli across alveolar epithelium (Only 1 cel thick,short diffusion pathway )and capillary epithelium, and into haemoglobin in blood
- CO2 diffuses into alveoli from blood, and is breathed out.
12
Q
Describe inspiration.
A
- external intercostal + diaphragm muscles contract
- causing rib cage to move upwards and outwards and diaphragm to flatten, increasing volume of thoracic cavity
- as volume of thoracic cavity increases, lung pressure decreases
- air flows from area of high pressure to low pressure so air flows down trachea into lungs
- inspiration is an active process, requires energy.
13
Q
Describe expiration.
A
- external intercostal + diaphragm muscles relax
- rib cage moves downwards and inwards and diaphragm becomes curved again
- volume of thoracic activity decreases causing air pressure to increase
- air forced down pressure gradient and out of lungs
- normal expiration is passive process, doesn’t require energy.
14
Q
What occurs during digestion.
A
Large biological molecules are hydrolysed to smaller molecules that can be absorbed across cell membranes.
15
Q
Explain how carbohydrates are broken down by amylase and membrane-bound disaccharidases.
A
- enzyme amylase catalysed conversion of starch into smaller sugar maltose. Involves hydrolysis of glycosidic bonds in starch.
- amylase produced by salivary glands and by pancreas.
- membrane-bound disaccharidases are enzymes that are attached to cell membranes of epithelial cells lining the ileum. They help to break down disaccharides into monosaccharides, involves hydrolysis of glycosidic bonds.
- monosaccharides transported across cell membranes of ileum epithelial cells via specific transporter proteins.
16
Q
Explain how lipids are broken down by lipase.
A
- enzyme lipase catalysed breakdown of lipids into monoglycerides and fatty acids. Involves hydrolysis of ester bonds in lipids.
- lipases made in pancreas. Work in small intestine.
- bile salts produced by liver and emulsify lipids, means they cause lipids to form small droplets.
- several small lipid droplets have bigger surface area than single large droplet, so formation of small droplets greatly increases surface are of lipid that’s available for lipases to work on.
- once lipid has been broken down, monoglycerides and fatty acids stick with bile salts to form tiny structures called micelles.
17
Q
Why are micelles important in absorption of lipids.
A
- micelles help to move monoglycerides and fatty acids towards epithelium.
- because micelles constantly break up and reform they ‘release’ monoglycerides and fatty acids, allowing them to be absorbed- whole micelles no taken up across epithelium.
- monoglycerides and fatty acids are lipid-soluble so can diffuse directly across epithelial cell membrane.
18
Q
Explain how proteins a broken down by endopeptidases and exopeptidases.
A
- endopeptidases act to hydrolyse peptide bonds within a protein.
- exopeptidases act to hydrolyse peptide bonds at the ends of protein molecules. They remove single amino acids from proteins.
- dipeptidases are exopeptidases that work specifically on dipeptides. They act to separate the 2 amino acids that make up a dipeptide by hydrolysing the peptide bonds between them. Located in cell-surface membrane of epithelial cells in small intestine.
19
Q
Explain co-transport mechanisms for the absorption of amino acids and of monosaccharides.
A
- glucose absorbed by active transport with sodium ions via a co-transporter protein. Galactose absorbed in same way using same co-transporter protein
- fructose absorbed via facilitated diffusion through different transporter protein.
- sodium ions actively transported out of epithelial cells into ileum. They then diffuse back into cells through sodium-dependent transporter proteins in epithelial cell membranes, carrying amino acids with them.
20
Q
What are the haemoglobin’s.
A
A group of chemically similar molecules found in many different organisms. Haemoglobin is a protein with a quaternary structure.
21
Q
Explain how haemoglobin is different in different organisms.
A
- organisms living in environments with low concentration of oxygen have haemoglobin with higher affinity for oxygen than human human haemoglobin, dissociation curve to left of human one.
- very active organisms that have high oxygen demand have haemoglobin with a lower affinity for oxygen than human haemoglobin, dissociation curve to right of human one.
22
Q
Describe the effect of carbon dioxide on the dissociation of oxyhaemoglobin.
A
- when cells respire they produce CO2 with raises partial pressures of CO2.
- this increases rate of oxygen unloading i.e. the rate at which oxyhaemoglobin dissociates to form haemoglobin and oxygen. So dissociation curve shifts right.
- saturation of blood with oxygen is lower for a given partial pressure of O2, meaning more oxygen being released.
- this called Bohr effect.
