exchange and transport systems

Question 1

what 2 main things increase the efficiency of gas exchange surface?

Answer 1

-large surface area
-thin so they have a short diffusion pathway

Question 2

how does gas exchange happen in a single celled organism?

Answer 2

-through their cell surface membrane
-have a large surface area : volume ratio and a short diffusion pathway

Question 3

what is the structure of a fish’s gills and how are they adapted to gas exchange?

Answer 3

-made of lots of thin plates called gill filaments which increase the surface area
-filaments are covered in lots of tiny structures called lamellae which increase the surface area more
-the lamellae have lots of blood capillaries and a thin surface layer of cells to speed up diffusion

Question 4

what is counter-current flow in fish?

Answer 4

-blood flows through the lamellae in one direction and over them in the opposite direction
-maintains steep concentration gradient between the water and the blood

Question 5

what would happen if there was parallel flow of blood and water in a fish?

Answer 5

-the diffusion gradient would only be maintained across part of the length of the gill lamellae

Question 6

describe the two types of fish in terms of how they ventilate.

Answer 6

cartilaginous fish- (mainly shark and rays) have no ventilation system so have to keep swimming for oxygenated water to flow over their gills

bony fish- use a ventilation mechanism

Question 7

why do plants need gas exchange?

Answer 7

-they need carbon dioxide for photosynthesis which produces o2 as a waste gas
-they need o2 for respiration which produces co2 as a waste gas

Question 8

how does gas exchange happen in plants?

Answer 8

-it happens on the surface of the mesophyll cells in the leaf
-gases move in and out through special pores in the epidermis called stomata
-the opening and closing of the stomata is caused by guard cells

Question 9

describe the gas exchange system in insects.

Answer 9

-there are air filled pipes called tracheae
-air moves into the tracheae through pores on the surface called spiracles
-the tracheae branch off into smaller tracheoles which have thin, permeable walls and go to individual cells
-carbon dioxide from the cells moves down its own concentration gradient towards the spiracles to be released into the atmosphere
-they use rhythmic abdominal movements to move air in and out of the spiracles

Question 10

how do insects control water loss?

Answer 10

they close their spiracles using muscles

they also have a waxy, waterproof cuticle all over their body and tony hairs around their spiracles which reduce evaporation

Question 11

how do plants control water loss?

Answer 11

water enters the guard cells which makes them turgid, meaning the stomatal pore opens
if the guard cell loses water and becomes flaccid, they close

Question 12

what are xerophytes?

Answer 12

plants that are specially adapted to life in warm, dry or windy environments

Question 13

what are some adaptations of xerophytes?

Answer 13

-stomata are sunk into pits to trap water vapour, reducing the concentration gradient of water between the leaf and the air, reducing evaporation from the leaf

-a layer of ‘hairs’ on the epidermis to trap water vapour around the stomata

-curled leaves with the stomata inside, protecting them from win

-reduced number of stomata minimising water loss

-thicker waxy, waterproof cuticles on the leaves and stems to reduce evaporation

Question 14

what is the general structure of the human gas exchange system?

Answer 14

-air enters the trachea as you breath in
-the trachea splits into two bronchi, one leading to each lung
-each bronchus branches of into smaller tubes called bronchioles
-bronchioles have lots of small air sacs called alveoli on the end of them
-the ribcage, intercostal muscles and diaphragm work together to move air in and out

Question 14

write out the stages of inspiration.

Answer 14

1. air is sucked in through the mouth
2. the rib cage moves upwards and the external intercostal muscles and the diaphragm contract, pushing down organs underneath
3. the volume of the thoracic cavity increases and the pressure decreases
4. air flows down the pressure gradient into the thoracic cavity
5. inspiration is an active process and requires energy

Question 15

write out the stages of expiration?

Answer 15

1. the external intercostal muscles and diaphragm relax, causing all displaced organs underneath to move back into place
2. the volume of the thoracic cavity decreases and the pressure increases above atmospheric pressure
3. air is forced down a pressure gradient and out of the lungs
4. it is a passive process- doesn’t require energy

Question 16

what is the structure of the alveoli?

Answer 16

-microscopic air sacs which are surrounded by a network of capillaries
-walls are made from a single layer of thin, flat cells called alveolar epithelium (walls of the capillaries are made from capillary endothelium)
-walls contain a protein called elastin which helps them recoil to their normal shape after inhaling and exhaling air

Question 17

draw a flow chart of the movement of air to the blood.

Answer 17

trachea - bronchi - bronchioles - alveoli - alveolar epithelium - capillary endothelium - blood

Question 18

what are the four measures of lung function?

Answer 18

tidal volume - volume of air in each breath

ventilation rate - number of breaths per minute

forced expiratory volume - maximum volume of air that can be breathed out in one second

forced vital capacity - maximum volume of air it is possible to breathe forcefully out of the lungs after a really deep breath

Question 19

describe what these tuberculosis is.

Answer 19

tuberculosis
-caused by bacteria
-forms small, hard lumps known as tubercles
-infected tissue within the tubercles dies and the gaseous exchange surface is damaged so tidal volume decreases
-common symptoms include: persistent cough, shortness of breath, coughing up blood, chest pains

Question 20

describe what fibrosis is.

Answer 20

fibrosis
-the formation of scar tissue in the lungs which can be the result of an infection or exposure to substances like asbestos
-scar tissue is thicker and less elastic meaning they are unable to hold as much air as normal, tidal volume is decreased
-symptoms include: shortness of breath, dry cough, chest pain, fatigue and weakness

Question 21

describe what asthma is.

Answer 21

-respiratory condition where the airways become inflamed and irritated
-during an asthma attack, the smooth muscle lining the bronchioles contracts and a large amount of mucus is produced causing constriction of the airways
-air flow in and out of the lungs is reduced
-symptoms include: wheezing, tight chest, shortness of breath

Question 22

describe what emphysema is.

Answer 22

-caused by smoking or long term exposure to air pollution
-foreign particles in the smoke become trapped in the alveoli causing inflammation and attracts phagocytes
-the phagocytes produce an enzyme that breaks down elastin meaning the alveoli can’t recoil as usual
-symptoms include: shortness of break, wheezing and an increased ventilation rate as they try to increase the amount of air reaching their lungs

Question 23

what are some restrictions on tobacco and smoking?

Answer 23

• in 2003, a ban was imposed on advertising tobacco based products
  -as of October 2008, health warnings are mandatory on smoking packets
  -in 2007, workplaces and public areas such as pubs and restaurants were made smoke free to reduce second hand smoke
  -in 2015, smoking was banned in cars carrying under 18s

Question 24

what are some ethical issues around dissections?

Answer 24

-morally wrong to kill animals just for dissections
-animals are not always kept in humane conditions when they are raised