Gas exchange

Question 1

using what process does gas exchange occur

Answer 1

-diffusion

Question 2

how do exchange surfaces and organs increase efficiency of exchange of materials

Answer 2

-large surface area
-short diffusion distance
-well-ventilated to maintain steep concentration gradients

Question 3

what happens in gas exchange in plants during respiration

Answer 3

-uptake of oxygen and release of CO2 needed
-Oxygen diffuses down the concentration gradient from a high concentration (outside the leaf) to a low concentration (inside leaf) (low concentration as used up in leaf)
-carbon dioxide diffuses down concentration gradient (inside leaf) from high concentration to low concentration (outside leaf)

Question 4

what happens in gas exchange in plants during photosynthesis

Answer 4

-when there is enough sunlight, plants photosynthesize
-uptake of CO2 and release of oxygen needed
-CO2 diffuses down concentration gradient from region of high concentration (outside leaf) to low concentration (inside leaf) (concentration low in leaf as it is used)
-oxygen diffuses down concentration gradient from high concentration (inside leaf) to a low concentration (outside leaf)

Question 5

pathway of CO2 from atmosphere to chloroplasts by diffusion

Answer 5

atmosphere -> air spaces around spongy mesophyll tissue -> leaf mesophyll cells -> chloroplasts

Question 6

adaptations of leaves to maximise gas exchange

Answer 6

Leaves:
-(thin which gives short diffusion distance)
-(flat to provide large surface area to volume ratio)
-(many stomata to allow movement of gases in and out of the air spaces by diffusion)
Internal structure:
-(moist air which gases can dissolve into for easier movement into and out of cells)
-(air spaces allow gas movement around loosely packed mesophyll cells)
-stomata in lower epidermis open in sunlight to allow gas movement in and out of the leaf
-thin cell walls allow gases to move into the cells easily
-close contact between cells and air spaces allows efficient gas exchange

Question 7

stomata

Answer 7

spaces found between two guard cells on the lower epidermis of the leaf

Question 8

guard cells

Answer 8

responsible for opening and closing of stomatal pore which controls gas exchange and water loss

Question 9

how do stomata open and close

Answer 9

Open:
-happens during day where there is water and sunlight
-water moves into guard cells by osmosis causing them to be turgid
-gases can diffuse in and out of the leaf
Close:
-happens during night where there is low water and low sunlight
-guard cells lose water by osmosis to neighbouring epidermal cells and become flaccid
-prevents diffusion in and out of leaf

Question 10

how does photosynthesis and respiration change from night to day in plants

Answer 10

Day time:
-more photosynthesis than respiration
-net diffusion of CO2 into plant and oxygen out of plant
Night time:
-respiration but no photosynthesis
-net diffusion of oxygen into plant and CO2 out of plant

Question 11

thorax

Answer 11

the part of the body which contains the heart and lungs within a rib cage

Question 12

ribs

Answer 12

bone structure that protects internal organs such as the lungs

Question 13

intercostal muscle

Answer 13

-muscles between ribs which controls their movement causing inhalation and exhalation

Question 14

diaphragm

Answer 14

-sheet of connective tissue and muscle at the bottom of the thorax that helps change the volume of the thorax to allow inhalation and exhalation

Question 15

trachea

Answer 15

-windpipe that connects the mouth and nose to the lungs

Question 16

larynx

Answer 16

-where air passes across here we are able to make sounds

Question 17

bronchi

Answer 17

large tubes branching off the trachea with one bronchus for each lungs

Question 18

bromchioles

Answer 18

-bronchi split to form smaller tubes called bronchioles in the lungs connected to alveoli

Question 19

alveoli

Answer 19

tiny air sacs where gas exchange takes place

Question 20

pleural cavity

Answer 20

-fluid filled space between the pleural membranes which reduces friction and allows the lungs to move freely

Question 21

what happens during inhalation

Answer 21

1. (diaphragm contracts) and (flattens)
2. (external intercostal muscles) contract, internal intercostal muscles relax
3. (rib cage moves up and out)
4. this increases (volume of the thorax)
5. decrease in (air pressure in lungs relative) to outside the body
6. (air is drawn in)

Question 22

what happens during exhalation

Answer 22

1. diaphragm relaxes and moves upwards back into
2. external intercostal muscles relax, internal intercostal muscles contract (forced exhalation)
3. ribs drop down and inwards
4. decreases volume of the chest cavity
5. increase in air pressure inside lungs relative to outside body
6. air is forced out

Question 23

how are alveoli adapted for gas exchange

Answer 23

1. good blood supply to capillaries with lots of CO2 and little oxygen, maintains concentration gradient
2. alveoli and capillaries around them have thin, single layers of cells to minimise diffusion distance
3. moist lining on surface of alveoli allows gas to dissolve for gas exchange, helps diffusion
4. capillaries provide blood supply close to alveoli, shorter diffusion distance
5. there is a large surface area of alveoli due to its multiple folds
6. ventilation maintains high levels of oxygen and low CO2 in alveoli, steep concentration gradient for diffusion

Question 24

mucus

Answer 24

-in trachea and bronchi
-stops harmful substances from entering the lungs and causing infections by trapping them
-cilia use hair to move mucus up and out the mouth

Question 25

what do harmful chemicals in cigarettes do smoking do

Answer 25

Nicotine:
-narrows blood vessels and increases heart rate -> increased blood pressure
-high blood pressure leads to blood clots forming in arteries
Carbon Monoxide:
-irreversibly binds to haemoglobin
-puts strain on breathing system as same amount of oxygen is needed
-circulatory system needs to pump blood faster, raises blood pressure, coronary heart disease and stroke
Tar:
-is a carcinogen linked to increased chances of cancerous cells developing in the lungs
-contributes do COPD

Question 26

bronchitis

Answer 26

-inflammation of the airways
-substances in smoke damage cilia
-mucus is not swept away from the lungs
-more mucus is produced due to irritation of smoke in the airways and tar, builds up
-results in ‘smokers cough’ irritation of airways and bacterial infections which inflames airways, blocking normal airflow and causing breathing difficulties

Question 27

emphysema

Answer 27

-the degeneration of alveoli
-the walls break down, decreasing the surface area for gas exchange and resulting in less oxygen in the blood
-mild exercise in severe cases cannot take place

Question 28

cancer as an effect of smoking

Answer 28

-substances in the tar of cigarettes called carcinogens
-causes cells to mutate and divide uncontrollably, forming a tumor
-often cause no pain in lungs and not identified before cancer spreads to rest of body

Question 29

effects of smoking (5)

Answer 29

1. emphysema
2. less surface area/ damage to alveoli
3. bronchitis
4. bacteria/infection
5. cilia damaged
6. more mucus
7. cancer
   8.tar

Question 30

what causes addiction in smoking

Answer 30

nicotine

Question 31

passive smoking

Answer 31

-non-smokers inhaling other people’s smoke are at risk of the effects of smoking

Question 32

ulcer

Answer 32

-smoking increases the acidity of the stomach and duodenum, leading to ulcers

Question 33

coronary heart disease as an effect of smoking

Answer 33

-blockage of the narrow coronary arteries of the heart
-leads to cardiac arrest
-smoking increases blood pressure and makes blood clots more likely so it increases the risk of a heart attack