2) Structure and functions in living organisms - respiration + gas exchange

Question 1

Respiration

Answer 1

-a chemical reaction carried out in all living organisms
-energy released from glucose in the presence of oxygen (aerobic) or the absence of oxygen (anaerobic)
-produce carbon dioxide and water
-energy in the form of ATP

Question 2

Organisms need energy for

Answer 2

-Chemical reactions to build larger molecules from smaller molecules
-Muscle contraction to allow movement
-Keeping warm (to maintain a constant temperature suitable for enzyme activity)

Question 3

ATP

Answer 3

-energy transferred via the molecule ATP (Adenosine Triphosphate)
-produced in respiration in the mitochondria
-required for living processes to occur within cells and organisms

Question 4

Aerobic respiration

Answer 4

-oxygen needed
-complete breakdown of glucose
-produces carbon dioxide and water
-a lot of energy released

Question 5

Anaerobic respiration

Answer 5

-oxygen not needed
-incomplete breakdown of glucose
-a little energy released
Products:
-animal cells: lactic acid
-yeast: carbon dioxide and ethanol

Question 6

Aerobic respiration equation

Answer 6

glucose + oxygen –> carbon dioxide + water
C6H12O6 + 6O2 –> 6CO2 + 6H2O

Question 7

Anaerobic respiration in animals

Answer 7

-mainly takes place in muscle cells during vigorous exercise
-muscles have higher demand for energy
-our bodies can only deliver so much oxygen to muscle cells for aerobic respiration
-when oxygen runs out, glucose is broken down without it, producing lactic acid
-glucose has not been fully broken down, there is still energy stored within the bonds of lactic acid molecules
-lactic acid needs to be removed

Question 8

Effect of lactic acid in muscles

Answer 8

-lactic acid can build up in muscles, causing pain and tiredness
-needs to be removed as it lower pH of cells and can denature enzymes

Question 9

Oxygen debt

Answer 9

-after exercise, you continue to breath deeply and quickly for a short period
-excess post-exercise oxygen consumption
-during this time, the lactic acid reacts with oxygen to form carbon dioxide and water
-released the rest of the energy originally in the glucose

Question 10

Anaerobic respiration in plants and fungi

Answer 10

-in yeast cells: fermentation
glucose –> alcohol + carbon dioxide
-important in making bread and brewing

Question 11

Investigating respiration

Answer 11

1. Measure out 10 cm3 of hydrogencarbonate indicator into 3 boiling tubes
2. Put in a layer of cotton wool
3. Place 10 germinating seeds in tube A
4. Place 10 boiled/dead seeds in tube B
5. Place 10 glass beads in tube C
6. Seal each tube with a rubber bung
7. After 3 hours, observe the colour of the indicator

A: yellow - seeds are respiring
B: orange - dead seeds - no CO2
C: orange - no living material

Question 12

Investigating respiration: Hydrogencarbonate indicator

Answer 12

-normal CO2 levels: orange
-high: yellow
-low: purple

Question 13

Investigating respiration: production of heat

Answer 13

1. Flask A with the germinating seeds
2. Flask B with the dead seeds
3. Make sure the cotton wool is plugging the top of each flask
4. Hold the thermometer in place with the cotton wool
5. Invert the flask
6. Record the initial temperature
7. After 4 days, record the final temperature

A - increase in temp - respiration is exothermic
B - remain room temp

Question 14

Role of diffusion in gas exchange - single celled organisms

Answer 14

-can exchange gases sufficiently by simple diffusion through the cell membrane as there is a short diffusion distance
-O2 diffuses in for respiration
-CO2 diffuses out

Question 15

Role of diffusion in gas exchange - multicellular organisms

Answer 15

Have exchange surfaces and organ systems that maximise the exchange of materials (lungs, gills)
-Large SA increases rate of transport
-barrier separating two regions is as thin as possible - short diffusion distance for substances to move across

Question 16

Gas exchange during respiration - plants

Answer 16

glucose + oxygen –> carbon dioxide + water
-O2 diffuses down the conc gradient from a high (outside) to a low conc (inside) - cells use O2 in respiration so the conc is always low inside respiring cells
-CO2 diffuses down the conc gradient from a high (inside) to low conc (outside)

Question 17

Gas exchange during photosynthesis - plants

Answer 17

carbon dioxide + water –light/chlorophyll–> glucose + oxygen
-CO2 diffuses down the conc gradient from high (outside) to low conc (inside) - cells use CO2 in photosynthesis so the conc is low in photosynthesizing cells
-O2 diffuses down the conc gradient from a high (inside) to low conc (outside)

Question 18

Adaptation of leaves for gas exchange

Answer 18

-thin - short diffusion distance
-flat - large SA:vol
-many stomata - allow movement of gases in and out of the air spaces inside the leaf to maintain a steep concentration gradient

Question 19

Internal adaptations of leaves for gas exchange

Answer 19

-air spaces - allow gas movement around loosely packed mesophyll cells
-stomata - open in sunlight to allow gas movement in and out of the leaf
-Thin cell walls - gases to move into the cells easily
-Moist air which gases can dissolve into for easier movement into and out of cells
-close contact between the cells and the air spaces - efficient

Question 20

Role of stomata in gas exchange - open

Answer 20

-water moves (by osmosis) into the guard cells causing them to become turgid
-allows gases to diffuse in and out of the leaf through the stomatal pore
-tend to open when there is plenty of water and sunlight

Question 21

Role of stomata in gas exchange - close

Answer 21

-guard cells lose water (by osmosis) to the neighbouring epidermal cells and they become flaccid
-prevents any diffusion into or out of the leaf
-tend to close due to low water availability or low sunlight

Question 22

Gas exchange in the day - plants

Answer 22

-plants both respire and photosynthesize
-rate of photosynthesis > rate of respiration
-net diffusion of carbon dioxide into the plant
-net diffusion of oxygen out of the plant

Question 23

Gas exchange at night - plants

Answer 23

-only respire
-net movement of oxygen into the plant
-net diffusion of carbon dioxide out of the plant

Question 24

Gas exchange at low light intensities - plants

Answer 24

-rate of photosynthesis = rate of respiration
-no net movement of oxygen or carbon dioxide in either direction

Question 25

Practical: The Effect of Light on Gas Exchange in Plants

Answer 25

1. Measure out 20 cm3 hydrogencarbonate indicator into 4 boiling tubes, label and put cotton wool into each
2. -Tube A - No leaf (control tube)
   -Tube B - Leaf
   -Tube C - Leaf, in aluminium foil to block out light
   -Tube D - Leaf, wrap in gauze to allow partial light
3. Put a bung into the top of each tube
4. Leave all 4 tubes in the light for 30 minutes

A - red - normal CO2 levels
B - purple - pho>res - less CO2
C - yellow - respiring/ no pho - more CO2
D - red - pho = res - normal CO2

Question 26

Thorax structures

Answer 26

-rib
-intercostal muscles
-diaphragm
-trachea
-bronchi
-bronchioles
-alveoli
-pleural membranes

Question 27

Rib function

Answer 27

Bone structure that protects internal organs - lungs

Question 28

Intercostal muscle function

Answer 28

Muscle between the ribs which control their movement causing inhalation and exhalation

Question 29

Diaphragm function

Answer 29

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 30

Trachea function

Answer 30

Windpipe that connect the mouth and nose to the lungs

Question 31

Bronchi function

Answer 31

Large tubes branching off the trachea with one bronchus for each lung

Question 32

Bronchioles function

Answer 32

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

Question 33

Alveoli function

Answer 33

Tiny air sacs where gas exchange takes place

Question 34

Pleural cavity function

Answer 34

The fluid filled space between the pleural membranes which reduces friction and allow the lung to move freely

Question 35

Prevention of pathogens/particles in the lungs

Answer 35

-cilia and mucus
-passages down to the lungs are lined with ciliated epithelial cells
-cilia cells have tiny hairs on the end of them that beat and push mucus up the passages towards the nose and throat where it can be removed
-mucus traps particles, pathogens, dust, prevents them from getting into the lungs and damaging cells there

Question 36

Intercostal muscles and diaphragm - inhalation

Answer 36

-The diaphragm contracts and flattens
-The external set of intercostal muscles contract to pull the ribs up and out
-increases the volume of the chest cavity (thorax)
-decrease in air pressure inside the lungs relative to outside the body
-Air is drawn in

Question 37

Intercostal muscles and diaphragm - exhalation

Answer 37

-The diaphragm relaxes it moves up into its domed shape
-The external set of intercostal muscles relax so the ribs drop down and in
-decreases the volume of the chest cavity (thorax)
-increase in air pressure inside the lungs relative to outside the body
-Air is forced out

Question 38

Alveoli adaptations

Answer 38

-small size - large SA:Vol
-large number - around 700 million - more gas exchange
-one cell thick - short diffusion pathway
-thin film of moisture on alveoli walls - gases dissolve in water, making diffusion path smaller
-good blood supply - constant supply of blood high in carbon dioxide, low in oxygen

Question 39

Chemicals in cigarettes

Answer 39

-tar - carcinogen
-nicotine - addictive substance
-carbon monoxide - permanently binds to hemoglobin, forming carboxyhemoglobin in blood, reducing the ability to carry oxygen, resulting in a light headed feeling

Question 40

Effects of smoking

Answer 40

-bronchitis
-emphysema
-lung cancer
-coronary heart disease

Question 41

Bronchitis

Answer 41

-smoking destroys cilia, reducing their number
-mucus not removed and bacteria in the mucus can cause infection in the bronchus
-reduces airflow to the lungs

Question 42

Emphysema

Answer 42

-wall of alveoli are broken down, reduces surface area for gas exchange
-person carries less oxygen in their blood
-reduces ability to do exercise

Question 43

Lung cancer

Answer 43

-carcinogens in tar can cause cells in the lungs to mutate and become cancerous
-tumor can form in the lung and spread to other tissues in the body
-tumors take resources which would normally go to the tissues they are in

Question 44

Coronary heart disease

Answer 44

-cholesterol is deposited in the artery wall, causing a plaque to form
-makes the wall swell, reduces the artery lumen
-makes blood flow more difficult and increases blood pressure
-reduces the oxygen and glucose which goes to the tissues relying on the artery
-tissues can eventually die
-if this happens in a coronary artery (carry blood to the heart), it can result in a heart attack

Question 45

Practical: effect of exercise on breathing

Answer 45

1. Work out student A’s breathing rate at rest - Count their number breaths for 15 seconds and multiply by 4
2. Repeat several times to calculate an average
3. Student A should then exercise for a set time (at least 4 minutes)
4. Immediately after exercising, count the breaths taken in 15 seconds and multiply by 4 to obtain the breathing rate per minute
5. Compare the result to the breathing rate to work out change
6. Repeat this last step every minute after exercise for 5 minutes
7. Repeat the process for student B

Question 46

Practical: effect of exercise on breathing - analysis

Answer 46

-frequency of breathing increases when exercising
-as muscles are working harder and aerobically respiring more and they need more oxygen to be delivered to them (and carbon dioxide removed) to keep up with the energy demand
-If they cannot meet the energy demand they will also respire anaerobically, producing lactic acid

-after exercise has finished, breathing rate remained elevated - repaying oxygen debt