Organisms exchange systems

Question 1

Surface area to volume ratios in animals

Answer 1

-specialised exchange systems are needed as larger organisms have lower surface area to volume ratios
-in single celled organisms substances can easily enter the cell as the distance is much smaller
-

Question 2

metabolic rate and demand

Answer 2

-an organisms metabolic rate is the amount of energy expended by an organism in a specific time period.
-metabolic demand is therefore how much oxygen is needed by an organism to respire enough to maintain the metabolic rate

-general rule as the mass of an organism increases the higher the metabolic rate as they need greater oxygen delivery as more respiration is needed

Question 3

Mammalian gas exchange -

Answer 3

Nasal cavity- air enters the nasal cavity
1) large surface area with good blood supply which allows for air to be warmed to body temp
2) hairy lining which secretes mucus trapping dust and bacteria to protect lungs from infection and irritation
3) moist surfaces to increase humidity of the air to reduce evaporation in the lungs

Trachea - main airways to the lungs
1) wide tube supported by incomplete rings of cartilage to prevent the airways from collapsing
2)lined with ciliated epithelial cells and goblet cells which secrete mucus to trap microorganisms and ciliated epithelial cells beta and move mucus upwards away from the lungs

Bronchus- trachea splits into 2 bronchi
1) Incomplete cartilage

Bronchioles-
1) they are small and have no rings of cartilage
2) walls contain smooth muscles and when the muscles contract the bronchioles constrict and when relaxed dilate which changes amount of air entering the lungs
3) lined with flattened epithelium which make some gas exchange possible

Alveoli - tiny airsacs which carry out main gas exchange
1) thin flattened epithelium with collogen and elastic fibres allows it to stretch when air enters
2) elastic recoil
3) one cell thick

Question 4

Adaptations of the alveoli

Answer 4

1) large surface area
2) thin layers of one cell thick allows for a shorter diffusion distance
3) good blood supply maintaining a steep concentration gradient between blood and alveoli
4) blood is slowed as they travel through pulmonary capillaries to allow for greater diffusion distances
5) the diffusion distance is shortened as blood cells are flattened against capillary walls
6) good ventilation maintains steep concentration gradient
7) inner surface covered in lung surfactant helping prevent the loss of water as oxygen dissolves in water before diffusing into blood

Question 5

Ventilation

Answer 5

-air movement in and out of the lungs is a result of pressure changes in the chest cavity
-gases move from region of high to low pressure

Question 6

Inspriation

Answer 6

-active process
1) diaphragm contracts and lowers
2) external intercostal muscles contract moving ribs upwards and outwards
3)volume of thorax increases
4) pressure of thorax decreases
5) pressure in thorax is now lower than atmospheric pressure
6) air is drawn into the lungs
7) equalises air inside and outside of lungs

Question 7

Expiration

Answer 7

-passive process
1) the diaphragm relaxes moving into a domed shape
2) external intercostal muscles relax moving ribs downwards and inwards
3) the elastic fibres in the alveoli return to the normal length
4) volume of thorax decreases
5) pressure of thorax decreases
6) pressure of the thorax is now higher than atmospheric pressure
7) air moves out of the lungs
8) until air is equalised inside and outside

Can be active if the internal intercostal muscles contract pulling ribs down hard and fast whilst abdominal muscles contract pushing the diaphragm up increasing pressure rapidly

Question 8

Measuring lung capacity

Answer 8

• a spirometer is used to measure lung volume
  -person breathes in and out of an airtight chamber causing it to move up and down producing a trace in a graph

Question 9

Tidal volume

Answer 9

volume of air we inhale and exhale at every breath at rest which will increase according to oxygen demand

Question 10

Vital capacity

Answer 10

the max amount of air that can be inhaled and exhaled in a breath (strongest inhalation and exhalation)

Question 11

Inspiratory and Expiratory reserve volumes

Answer 11

Inspiratory- the maximum volume of air that can be inhaled on top of the tidal volume

Expiratory- the maximum volume of air that can be exhaled on top of the normal tidal volume

Question 12

Residual volume

Answer 12

-volume of air left in your lungs after strongest exhalation

Question 13

Total lung capacity

Answer 13

vital capacity + residual volume

Question 14

Breathing Rhythms

Answer 14

-pattern will change according to the demands of the body
-breathing rate = breaths per min
-ventilation = total volume of air inhaled in a minute
tidal x breathing rate

Question 15

Lung diseases

Answer 15

-decrease surface area of the lungs and reduce oxygen uptake

Question 16

Gas exchange in insects

Answer 16

-need to balance need for exchanging gases with reducing water loss
-have tough exoskeleton and small surface area to volume ratio to reduce loss of water so cannot use body surface to diffuse respiratory gases

1) Spiracles small openings in the thorax and abdomen let air in and out to minimise water loss
2) Sphincters open and close spiracles
3) tracheae supported by chitin to stop collapsing
4) tracheae divide into smaller tracheoles which extend through the entire body
5) at end of each tracheole is tracheal fluid which allows gases to dissolve and diffuse into cells

Question 17

Adaptations in the structure of an insects gas exchange system

Answer 17

Tracheoles -
Thin walls which reduces the diffusion distance
Highly branched increasing the surface area
Contain tracheal fluid which allows gases to diffuse to tissues faster and can be withdrawn into body fluid to increase surface area of tracheole exposed to air

Muscles-
Can pump body and force air in/out which maintains a concentration gradient

Spiracles-
Can be opened or closed to prevent water loss and keep waterproof

Question 18

Methods used by insects when oxygen demand is high and when flying

Answer 18

-anerobic respiration will occur and lactic acid will be produced which is soluble this means that the water potential of cells is lowered and water moves from cells into tracheoles via osmosis the volume of water is then reduced and more air enters
-mechanical pumping of abdomen changes volume of insects body and pressure in tracheae
-air reservoirs which inflate/deflate air sacs

Question 19

Gas Exchange in fish -

Answer 19

-small surface area to volume ratio but impermeable membrane so gases are unable to diffuse through skin
-4 pairs of gills supported by a bony arch
-gill filaments contain lamellae which take part in gas exchange
-projections are held apart in water
-ventilation is required to maintain continuous unidirectional flow

-flow of water over the gills and the blood are co current so flow in opposite directions this is so there is always a higher concentration of oxygen in the water so it diffuses into the blood along the whole length of the lamellae
-concentration gradient is maintained as blood is always in contact with water that has higher dissolved oxygen concentration
-facilitates maximum possible gas exchange

Question 20

Leaves

Answer 20

Waxy Cuticle – Waterproof layer in the top and bottom of the leaf

Upper Epidermis – Layer of tightly packed cells at the top of the leaf

Palisade Mesophyll – a layer of cylindrical cells adapted to photosynthesis by having many chloroplasts

Spongey Mesophyll – a layer of irregular shaped cells with a vast network of air spaces for gas exchange

Xylem – tissue which transports water and minerals through the plant
Phloem – tissue which transports dissolved sugars through the plants

Lower epidermis – a layer of tightly packed cells at the bottom of the leaf

Guard Cells – cells either side of the stomata which control the opening and closing of the stomata

Stomata – pores found on the bottom of the leaf which allow gas exchange
Photosynthesis occurs in the palisade Mesophyll tissue. Photosynthesis requires carbon dioxide which diffuses into the leaf via the stomata due to the concentration gradient between the leaf and the air outside the leaf. Stomata are able to close at night to reduce water loss (water evaporates out of the stomata in transpiration when stomata are open). Oxygen produced in photosynthesis is able to diffuse out of the leaf due to the concentration gradient of oxygen on and out of the leaf.

Question 21

Gas Exchange in plants

Answer 21

1) Guard cells are turgid and the stomata remain open allowing air to enter the leaf.
2) the air spaces in the spongey mesophyll allows co2 to rapidly diffuse into cells
3) the co2 is quickly used up in photosynthesis maintaining the concentration gradient
4) no active ventilation is required as the thinness of the plants tissues and stomata helps create and short diffusion pathway

Question 22

Xerophytes

Answer 22

Plants with adaptations to limit water loss as they cannot reduce S:A ratio as they need sunlight for photosynthesis

1) thick waxy cuticle
2) rolled up leaves - protects the lower epidermis which contains the stomata as it traps a region of still air which becomes saturated with water vapour so there is no concentration gradient for water to leave the cell e.g marram grass
3) hairy leaves - traps still air making gradient shallower and less air loss
4) sunken stomata - trap still moist air reduce water potential gradient
5) reduced surface area of leaves to be like needles so water loss is reduced but needs to balanced against the need for water. Plants carry out photosynthesis in stem e.g cacti

Question 23

Anatomy of the human digestive system

Answer 23

Salivary glands- secretions from the salivary gland into the mouth contains amylase
Oesophagus- thick muscle walls push the food down by peristalsis
Stomach- muscular bag that churns food and its inner layer produces enzymes. Function is too store and digest food which primarily digests protein and has glans producing enzymes to hydrolyse protein
Liver - produces bile which emulsifies fat making it easier to digest and neutralises stomach acid
Pancreas - secretes pancreatic juice which contains proteases, lipases and amylases
Small Intestine - ileum is a long muscular tube and food is digested by enzymes secreted by walls of enzymes and by glands. Adapted to absorb products of digestion by having villi and micro villi
Large intestine - where water is absorbed mostly from the secretion of many digestive glands
Rectum - final section of the intestine that stores the faeces before egestion from the anus

Question 24

Small intestine adaptations

Answer 24

1) contain villi to increase the surface area for diffusion
2) Epithelial cells contain microvilli to further increase surface area
3) Epithelial wall is very thin to reduce diffusion distance
4) They are well supplied with blood vessels so blood can carry away absorbed nutrience to maintain the concentration gradient
5) villi contain muscle meaning they can move and mix the contents of the ileum maintaining the concentration gradient

Question 25

Carbohydrate Digestion

Answer 25

-digestion of carbohydrates takes place in the mouth and small intestine 1) Amylase is made in the salivary glands and breaks glycosidic bonds to form maltose (disaccharides) 2) In the pancreas amylase is secreted into the small intestine and breaks glycosidic bonds to form maltose 3) Small intestine contain disaccharidases in the cell membrane of epithelial cells so maltase hydrolyses maltose into alpha glucose 4) this allows for the absorption of the monosaccharide straight from epithelial cell into the blood and villi have a high SA for disaccharidases increasing monosaccharide absorption

Question 26

Absorption of carbohydrates

Answer 26

1) Glucose carrier proteins are also present on the cell surface membrane of an epithelial cell 2) Sodium ions and glucose molecules are co-transported into the cell via facilitated diffusion 3) Glucose molecules can then diffuse across cell and into the capillary via facilitated diffusion down a concentration gradient 4) The concentration of sodium ions is maintained by sodium ions being actively transported out of epithelial cell into the blood via a sodium potassium pump

Question 27

Digestion of proteins

Answer 27

1) Lumen of the stomach where hydrochloric acid denatures the proteins and reveals the polypeptide chain 2) Endopeptidases secreted by the lining of the stomach (e.g pepsin due to having opimum pH) hydrolyse the peptide bonds within a large chain to create smaller chains with more terminal ends 3)bExopeptidases in the small intestine secreted by the pancreas hydrolyse the terminal peptide bonds to remove individual amino acids and create smaller poly peptide chains 4) Dipeptidases found on the cell membrane of epithelial cells hydrolyse dipeptides creating amino acids that are bale to travel across the membrane

Question 28

Absorption of amino acids

Answer 28

1) specific amino acid co-transport proteins are found on the cell-surface membrane of the epithelial cell and amino acids facilitating diffuse into cell with a sodium ion 2) amino acids then diffuse across the epithelial cell into the blood via facilitated diffusion 3) concentration of sodium ions in maintained via a sodium potassium pump

Question 29

Lipid Digestion

Answer 29

Emulsification- 1) in the stomach solid lipids are turned into fat droplets by bile salts which are stored in the gallbladder and secreted by the liver 2) combine with lipid and help brake large globules by emulsifying them into smaller droplets 3) makes them more soluble and increases the speed of lipases by increasing the surface area of lipids that can be exposed to enzymes Digestion- 1)Occurs in the lumen of the small intestines 2) lipases are produced in the pancreas and then secreted into the small intestine 3) lipases hydrolyse the ester bonds in a triglyceride and form fatty acids and a monoglyceride Micelles are formed which consist of bile salt, monoglycerides and fatty acids which aid the transport of the molecules to the epithelial cell

Question 30

Absorption of Lipids

Answer 30

1)Micelles hit the cell and break down and the fatty acids and monoglycerides are able to simply diffuse across the cell membrane 2) short fatty acid chains can then diffuse straight into the blood 3) longer fatty acid chains and monoglycerides are made back into triglycerides in the endoplasmic reticulum by combining glycerol with a monoglyceride 4) Inside the Golgi body the triglycerides bind with cholesterol and proteins e,g lipoproteins 5) Chylomicrons are formed and hold the non-polar triglycerides inside away from aqueous environment 6)Transported out of epithelial cell via exocytosis and enter lacteals 7) will eventually end up in the blood where they will be hydrolysed by an enzyme in the endothelial cells of the blood capillary and here they diffuse into cells

Question 31

Amylase

Answer 31

-hydrolyses carbohydrates -produced in salivatory glands and stomach -released in mouth and small intestine

Question 32

Maltase

Answer 32

-hydrolyses disaccharides -produced in the small intestine -released in the small intestine

Question 33

Endopeptidase

Answer 33

-hydrolyses proteins -produced in stomach and pancreas -released in stomach and small intestine

Question 34

Exopeptidase

Answer 34

- hydrolyses proteins -produced in the pancreas -released in the small intestine

Question 35

Dipeptidase

Answer 35

-hydrolyses dipeptides -produced in the small intestine -released in the small intestine

Question 36

Lipase

Answer 36

-hydrolyse lipids -produced in the pancreas -small intestine

Question 37

How does eating caecal droppings help rabbits digestion and absorption of protein

Answer 37

-More remaining undigested food is present -So more amino acids are absorbed -Because protein passes again through the stomach Ho

Question 38

How is the Golgi Body involved in the absorption of lipids

Answer 38

Modifies triglycerides by adding protein and cholesterol creating a chylomicron a vesicle that can pass through the cell membrane via exocytosis

Question 39

Describe how the structure of an insects gas exchange system provides cells with suffient oxygen and limits water loss

Answer 39

-spiracles can be opened/closed by sphincters to reduce water loss -structure contains highly branched tracheoles increasing the surface area to volume ratio -thin walls to decrease the diffusion distance -tracheole walls are permeable to oxygen -hairs around spiracles trap moist air -chitin is impermeable reducing water loss

Question 40

How does smoking damage the lungs

Answer 40

-inflammation -narrowed airways -lack of elasticity -scar tissue -mucus build up

Question 41

Explain the movement of oxygen into the gas exchange system of an insect when at rest

Answer 41

-oxygen enters through open spiracles and travel through tracheae and then into tracheoles where it is diffused into the blood down a concentration gradient and oxygen is used in respiration establishes a gradient so it can diffuse in.

Question 42

Suggest 2 reasons why the water uptake of a plant might not be the same as the rate of transpiration

Answer 42

-water used for the plants support -water used in hydrolysis and photosynthesis

Question 43

Describe and explain the mechanism that causes forced expiration

Answer 43

-Contraction of internal intercostal muscles -relax diaphragm -decrease volume of the thorax -air is pushed down the pressure gradient

Question 44

Suggest and explain how a reduced tidal volume affects exchange on co2 between blood and alveoli

Answer 44

-reduces amount of co2 diffused out of the blood due to less air being inhaled -lower amounts of co2 in the alveoli means there is a shallower concentration gradient in the blood so more co2 remains in the blood

Question 45

The volume of water passing over gills increases if the temperature increases explain why

Answer 45

-increased metabolism and respiration -less oxygen

Question 46

Describe and explain how the structure of the mammalian breathing system allows for effiecent uptake of oxygen into the blood

Answer 46

-alveoli have thin walls allowing for shorter diffusion distance -alveoli also have high surface are to volume ratio -blood cells in capillaries flatten against alveoli to help decrease diffusion distance -many capillaries which creates constant concentration gradient and also increased surface area -trachea is wide and held open by rings of cartilage allowing for good ventilation -cell membrane is permeable -capillary walls are also thin

Question 47

Describe how carbon dioxide reaches the mesophyll cells in a leaf

Answer 47

-enters via open stomata which is controlled by guard cells and diffuses into cell from a high to low concentration

Question 48

Describe and explain how the lungs are adapted to allow rapid exchange of oxygen between air and alveoli and blood

Answer 48

-large surface area to volume ratio as they have many alveoli present of which have thin folded walls with flattened epithelial cells decreasing diffusion distance -blood cells flatten -capillaries supply blood flow and also a large surface area -good ventilation

Question 49

Describe and explain two features of a cell specialised for absorption (2 marks)

Answer 49

1) microvilli to increase the surface area 2) large number of carrier and channel proteins 3) large number of mitochondria producing ATP for active transport

Question 50

Describe how oxygen in the air in the alveoli enters blood in capillaries (2 marks)

Answer 50

-oxygen will simply diffuse -across the squamous epithelium

Question 51

There is a one way flow of water over the gills of fish suggest one advantage of this (1 mark)

Answer 51

-less energy -continuous flow of water

Question 52

How does the removal of water from insects tracheoles increase the rate of diffusion (1 mark)

Answer 52

-greater surface area exposed to air -faster diffusion rate in gas