Transport in Mammals

Question 1

Define Surface area

Answer 1

The total number of cells in direct contact with the surrounding environment

Question 2

Define Volume

Answer 2

The total 3D space occupied by metabolically active tissue

Question 3

What is the relationship between surface area and volume

Answer 3

As organisms get bigger, their volume and surface area increase both increase, but the volume increases much more than the surface area, as many cells are not in contact with the surrounding environment

Question 4

What is ficks law

Answer 4

Rate of diffusion is directly proportional to the surface area multiplied by the concentration gradient, divided by the diffusion distance

Question 5

What are the features of exchange surfaces that aid passive and active transport

Answer 5

-Large surface area
-moist surface into which the respiratory gases dissolve
-short diffuaion path
-diffusion gradient for both CO2 and O2
-permeable to O2 and CO2

Question 6

How do the alveolus maintain an effective exchange surface

Answer 6

-LARGE SURFACE AREA- 600 MILLION PER LUNG

-small distance- EACH ALVEOLUS IS 1 CELL THICK

-CONCENTRATION GRAIDENT- constant ventilation replaces the air

Question 7

How does red blood cells maintain an effective exchnage surface

Answer 7

-LARGE SURFACE AREA- biconcave disc shape

-SMALL DISTANCE- no nucleus- packed with haemoglobin- ensures distance to haemoglobin molecule is short

-CONCENTRATION GRADIENT- constant movement through the lungs and tissue causes gas exchange in and out of the cell

Question 8

How does a root hair cell maintain an effective exchange surface

Answer 8

-LARGE SURFACE AREA- extension of the cell wall

-SMALL DISTANCE- thin cell membrane and fully permeable cell wall

-CONCENTRATION GRADIENT- oxygen enters and is used by respiration- active transport allows ion entry

Question 9

How do capillaries maintain an effective exchange surface

Answer 9

LARGE SURFACE AREA- long

-SMALL DISTANCE- thin cell membrane

-CONCENTRATION GRADIENT- constant blood supply

Question 10

How do leaves maintain an effective exchange surface

Answer 10

-LARGE SURFACE AREA- surface area of leaves are 200 metres squared- Surface area of spongy mesophyll cells is 6000 metres squared

-SMALL DISTANCE- gases diffuse straight into leaf cells

-CONCENTRATION GRADIENT- wind replaces air around leaves

Question 11

How is mass flow brought about

Answer 11

Pressure differences

Question 12

What is Compensation Point

Answer 12

-When the rate of respiration equals the rate of photosynthesis and there are no changes in Carbon Dioxide levels

Question 13

What happens when there are high light intensity levels

Answer 13

The rate of photosynthesis is greater than the rate of respiration, and more Carbon Dioxide is taken in by the plant

Question 14

What happens when there are low light intensities

Answer 14

When there is little/ no light, the rate of respiration is greater than the rate of photosynthesis, and more Carbon dioxide is given out by the plant

Question 15

Mesophytic leaf adaptions for gas exchange

Answer 15

-Thin- large SA:V and short diffusion distance
-Moist- allows gases to dissolve
-Spongy Mesophyll- contains air spaces and cells are loosely arranged- provides a large SA over where gases can dissolve- unhindered path to the palisade layer for Photosynthesis
-Stomata- allow diffusion of gases in and out
-Air spaces- spongy mesophyll- unhindered access for gases to the palisade layer

Question 16

What is the purpose of Surfactant

Answer 16

Surfactant secreting cells in the alveolar wall secrete surfactant which reduces the surface tension of the water molecules in the layer of moisture coating the alveoli
-prevents the alveoli collapsing

Question 17

What is the purpose of macrophages

Answer 17

They originate from monocytes- found in the alveoli
-they protect against infection by carrying out phagocytosis

Question 18

Describe Inspiration

Answer 18

-External intercostal muscles contract
-ribs move up and out
-width of thorax increases, causing the volume to increase
-diaphram contracts and moves down
-depth of thorax increases top to bottom

The volume of the thorax increases, causing the pressure between the pleural surfaces to decrease The lungs expand to fill the thoracic cavity. Air pressure in the alveoli is less than atmospheric and air is forced in by the higher external atmospheric pressure

Question 19

Explain Expiration

Answer 19

-Internal intercostal muscles contract
-ribs move down and in
-width of thorax decreases, causing volume to decrease
-diaphram relaxes and moves up, returning to dome shape
-depth of thorax decreases

Volume of the thorax decreases, causing air pressure in the alveoli to be more than atmospheric pressure, therefore air is forced out. The natural elasticity of the lungs produces an elastic recoil, which helps force air out of the lungs

Question 20

Effect of Tar on lungs

Answer 20

Tar is the collection of toxic chemicals in cigarette smoke- many are carcinogenic
-They damage DNA in epithelial cells lining the lung- causes lung cancer- results in cells uncontrollable dividing- Tumour

Question 21

Effects of smoking on the lungs

Answer 21

Causes Emphysema
-Tar from cigarette smoke causes irritaion in the alveolar lining causing:
-Many alveoli to break down- lower SA in lung- les gas diffusion
-Cigarette smoke breaks down the elastic lining in the lining of the alveoli- reduces the ability of the alveoli to recoil during expiration- leaves residual air in the alveoli- prevents fresh inhaled air reaching the gas exchange surface

Question 22

Effect of smoking on Lungs

Answer 22

Causes Bronchitis:
-caused by inflammation of the Bronchiol tubes
-musuc production increases, reducing air flow in and out of the lung
-Tar- paralyses the cilia (removes mucus and microbes)- increased risk of infection