Topic 2 - Exchange surfaces + plasma membranes (2.1 to 2.4)

Question 1

What is a gas exchange system

Answer 1

A respiratory system where gas such as oxygen is transported from one membrane to another

Question 2

What makes up the human respiratory system

Answer 2

Gas enters into the body through the mouth and into the trachea. The trachea brings the gas into the lungs, and it splits into two bronchi which enter each side of the lungs. The bronchi the split into bronchioles which then deliver oxygen into the alveoli where gas exchange can occur

Question 3

Why do mammals need a gas exchange system

Answer 3

Mammals require high levels of oxygen, and produce a large amount of co2

the gas exchange system allows mammals to efficiently remove co2 from the blood, and move oxygen into it (via diffusion)

Gas exchange systems are also needed to keep up with our high metabolic rate (reactions such as respiration and protein synthesis)

Question 4

Where are the lungs located (in a human)

Answer 4

They are located in the thorax (in the chest) and are protected by a ribcage

Question 5

What is the structure of the trachea

Answer 5

it has smooth muscle
It is protected by c- ring cartilage
(Small amount smooth muscle )
It has ciliated epithelium
it has a lumen (where the air flows)

Question 6

What is the purpose of the c-ring cartilage in the trachea + bronchi

Answer 6

It provides support and flexibility

this prevents the trachea / bronchi from collapsing, and also permits it to contract

Question 7

What is the purpose of the smooth muscle in the trachea / bronchi

Answer 7

Smooth muscle contracts and relaxes to change the diameter of the lumen.

This lets it adjust airflow - ensuring more efficient respiration

it can also contract to reduce the number of pathogens entering the lungs

Question 8

What is ciliated epithelium

Answer 8

An ‘outside’ layer made of ciliated cells and goblet cells.

the goblet cells are located between ciliated cells

Question 9

What is the purpose of ciliated cells + goblet cells

Answer 9

Goblet cells secrete mucus which traps dirt and pathogen

The cilia then wafts mucus up and out of the airways into the mouth, where it can be swallowed (dissolved by stomach acid) or spat out.

Question 10

What are bronchioles mostly made of

Answer 10

Mostly smooth muscle (to change the lumens size) and ciliated epithelial

some have c-ring cartilage, but most are too small

Question 11

Why does the lumen in the trachea / bronchi / bronchioles need to change size

Answer 11

The lumen can be increased in diameter to allow for more efficient airflow

It can be decreased in diameter to reduce airflow, and reduce the number of dirt / pathogens entering the lungs

Question 12

What are the alveoli

Answer 12

Small air sacks connected to the end of bronchioles.
Gas exchange occurs here

Question 13

How are the alveoli a good adaptation in the lungs

(the lungs adapted to have alveoli)

Answer 13

They have a large surface area to volume ratio (increase rate of diffusion from alveoli to capillaries)

They have a 1 cell thick walls called the squamous epithelial (shorter diffusion distance)
this wall is ‘squamous’ so it is thinner than normal cells

They are surrounded by capillaries (so they can constantly oxygenate blood)

Question 14

How many cells does oxygen / carbon dioxide pass through during gas exchange

Answer 14

2 cells
the squamous epithelial of the alveoli and the 1 cell layer thick (endothelium) capillary wall

Question 15

what does squamous mean

Answer 15

flat.

squamous cells are thinner than regular cells

Question 16

What is Frick’s Law

Answer 16

rate of diffusion ∝ (surface area x concentration difference) / diffusion distance

Question 17

How has the human respiratory system adapted to have a larger surface area

Answer 17

It has a large number of folded alveoli

Question 18

How has the human respiratory system adapted to have a higher concentration difference

Answer 18

Large number of pulmonary capillaries ensure oxygenated blood is always being moved to the alveoli

Breathing constantly ensures oxygen is entering the lungs, and carbon dioxide is leaving

Question 19

How has the human respiratory system adapted to have a low diffusion distance

Answer 19

Both alveoli and capillaries have a 1 cell thick external wall (alveoli has squamous epithelial cells and the capillaries have endothelial cells)
so the diffusion distance is only 2 cells

Alveoli wall cells are ‘squamous’ which means they are thinner than normal cells

Question 20

What is a phospholipid

Answer 20

A lipid molecule combined with a phosphate group

it has a fatty tail and a phosphate head

Question 21

Where are phospholipids found

Answer 21

In plasma cell membranes

Question 22

How does the phosphate head in phospholipids attach to the lipid

Answer 22

The phosphate head binds to the glycerol in the lipid

Question 23

What are the two fatty acids in phospholipids

Answer 23

A saturated fatty acid (single carbon bond)

an unsaturated fatty acid (carbon double bond)

the unsaturated acid is bent slightly

Question 24

What are the main properties of a phospholipid

Answer 24

Hydrophilic phosphate head (attracts water)

Hydrophobic fatty tail (repels water)

Question 25

What are plasma membranes

Answer 25

The plasma membrane (aka cell membranes) is a selective barrier that surrounds all cells

Question 26

what is the purpose of the plasma membrane

Answer 26

It is selectively permeable (controls what enters and exits a cell)

It separates the substance inside and outside the cell

it allows cell signaling (contains receptors)

Question 27

What is the phospholipid bilayer

Answer 27

A thin polar 2 layer cell membrane which makes up plasma membranes - made from phospholipids

It separates extracellular and intracellular fluids

Question 28

How are phospholipids arranged in the phospholipid bilayer

Answer 28

The hydrophilic phosphate heads point outwards

the hydrophobic fatty tails point inwards towards each other

Question 29

What does amphipathic mean / amphipathic molecule

Answer 29

‘dual nature’

A molecule with an arrangement of a positive / negative charge and an uncharged area

Question 30

Why do phospholipid bilayers form

Answer 30

When the phospholipids are in water (specifically plasma in humans) The hydrophilic head will point outwards to the water, and the neutral hydrophobic tails will face each other

Question 31

What is the charge of the phosphate head in phospholipids

Answer 31

negative

Question 32

What is the charge of the fatty tail in phospholipids

Answer 32

neutral

Question 33

How is the plasma membrane adapted to deal with changing temperatures

Answer 33

When compressed by a low temperature the unsaturated fatty tails ‘elbow’ the adjacent phospholipids saturated fatty acid.

This creates more room between phospholipids, helping to maintain fluidity preventing the cells from freezing / rupturing

Question 34

When is having more saturated fatty acids in phospholipids bad for cold environments

Answer 34

When compressed saturated fatty acids press in to each other making a fairly dense rigid membrane

This reduces fluidity, which could cause the cell to rupture

Question 35

Are there more or less saturated fatty acids at high temperatures

Answer 35

More saturated fatty acids

Question 36

What is the fluid mosaic model

Answer 36

A model that shows the structure of a plasma membrane

Question 37

What can be found in plasma membranes

Answer 37

Phospholipids
Proteins (several types)
Cholesterol

Question 38

What is the purpose of Cholesterol in plasmas membranes

Answer 38

Maintains fluidity by preventing fatty acid chains sticking together

Reduces membrane permeability to small water soluble molecules (e.g prevents ions leaking in /out)

Question 39

What is the purpose glycolipids + glycoproteins do in plasmas membranes

Answer 39

Cell recognition / signaling
Facilitating immune response

They provide energy to the cell

Question 40

What is the purpose of carrier proteins in plasma membrane

Answer 40

Protein carriers / carrier proteins

Proteins with specific binding sites that allow for selective transport in and out of plasma membranes

Question 41

What is the purpose of protein channels in plasma membrane

Answer 41

Channels that allow multiple specific molecules to flow freely through them into a cell

Question 42

What are integral (intrinsic) proteins

Answer 42

Proteins that span the whole layer of the plasma membrane, such as protein channels

Question 43

What are peripheral (extrinsic) proteins

Answer 43

Proteins that do not span across the whole layer of the plasma membrane

They function of as receptors and are often connected to glycolipids / glycoproteins