3.3 Organisms exchange substance with their environment

Question 1

what are lungs

Answer 1

a pair of lobed structures

Question 2

what is the trachea

Answer 2

Flexible airway that is supported by rings of cartilage
Prevents collapse as air pressure falls
Walls are made of muscle, lined with ciliated epithelium and goblet cells

Question 3

what is bronchi

Answer 3

2 trachea divisions

Also makes mucus to trap dust and have cilia that moves dirt laden mucus to the throat

Question 4

what are bronchioles

Answer 4

Series of branching sub-divisions of bronchi
Walls are muscle lined with epithelial cells
Muscle allows constriction so air flow can be controlled

Question 5

what is the alveoli

Answer 5

About 1 cell thick
Between them, there are collagen
Lined with epithelium
Elastic fibres allow stretching

Question 6

what are the 2 types of ventilation

Answer 6

expiration

inspiration

Question 7

how does expiration work

Answer 7

Expiration:
Breathing out

External intercostal muscles relax. Internal intercostal muscles contract.
Ribs are pulled in and down ( flatten) so the volume of the thorax decreases
Diaphragm relaxes
decrease of thorax volume causes an increase in pressure.
Atmospheric pressure is lower than pulmonary pressure so air is forced out the lungs

Question 8

how does inspiration work

Answer 8

Breathing in
External intercostal muscles contract. Internal intercostal muscles relax.
Ribs are pulled up and out ( raise) and so the volume of the thorax increases
Diaphragm flattens/contracts.
Increase of thorax volume causes a decrease in pressure.
Atmospheric pressure is greater than pulmonary pressure so air is forced into the lungs

Question 9

what is the pulmonary ventilation rate equation

Answer 9

PVR = tidal volume × breathing rate

Question 10

what is pulmonary ventilation rate

Answer 10

volume of air re-entering or leaving the lungs per minute

Question 11

what is tidal volume

Answer 11

volume of air breath in/out the lungs per breath

Question 12

what is breathing rate

Answer 12

number of breaths per minute

Question 13

what is pulmonary ventilation rate

Answer 13

volume of air re-entering or leaving the lungs per minute

Question 14

what is the movement of gas in gas exchange

Answer 14

Oxygen moves around the body down a concentration gradient
Carbon dioxide moves down its own diffusion gradient and pressure gradient but in the opposite direction

Trachea -> Bronchi -> Bronchioles -> Alveoli -> Blood -> body

Question 15

what is the process of starch digestion

Answer 15

Begins in mouth- amylase
( starch → maltose)
Then small intestine duodenum (1st part)- amylase
( starch → maltose )
Then ileum ( last part of small intestine)- maltase
( maltose → α- glucose )
Maltase- membrane-bound disaccharidase

Question 16

what is the entire process of starch digestion

Answer 16

Mouth (I)- chewed food increases the surface area, smaller pieces are easier to swallow 
Mouth (II) – saliva made in salivary gland contains amylase which breaks down starch. Mineral ions help maintain optimum pH of amylase 
Stomach (I)- acidic conditions. Makes salivary amylase acidic which denatures and prevents further hydrolysis of starch 
Small intestine (I)- pancreas releases pancreatic juice containing amylase, protease and lipase into the small intestine. This will break down any remaining starch 
Small intestine (II)- alkaline salts produced by the pancreas and intestine wall will maintain the pH
Small intestine (III)- disaccharides found are maltase, sucrase and lactase. Maltase breaks maltose down into α- glucose.

Question 17

what is protease

Answer 17

Breaks down large insoluble proteins to small soluble amino acids
Produced- stomach, pancreas, small intestine.

Question 18

what is the process of protein digestion

Answer 18

Starts in the stomach and the small intestine ends it.
Endopeptidase- breaks large polypeptides into smaller polypeptides and hydrolases internal peptide bond
Exopeptidases- splits off 1 amino acid at a time working from the end of a polypeptide.
Dipeptidase- hydrolyse small peptides only 2/3 amino acids long. Located on the cell-surface membrane of epithelial cells in small intestine. The products enter cells of the lining of the small intestine.

Question 19

why cant glucose diffuse

Answer 19

In the mammalian ileum, the concentration of glucose is to low for glucose to diffuse out into the blood.

Question 20

what is the process of co-transport

Answer 20

Step 1- sodium ions are actively transported out of the epithelial cells into the ileum, into the blood via the sodium-potassium pump. This creates a concentration gradient
Step 2- this causes sodium ion to diffuse from the lumen of the ileum into the epithelial cell, down their concentration gradient. They do this via a sodium-glucose co-transporter proteins. The co-transporter carries glucose into the cell with sodium. As a result, the concentration of glucose inside the cell increases.
Step 3- glucose diffuses out of the cell into the blood, down its concentration gradient through a protein channel through facilitated diffusion

Question 21

what is bile

Answer 21

Made in the liver, stored in gall bladder. Binds to fat droplets and breaks down into smaller fat droplets emulsification- increases surface area for lipase digestion.

Question 22

what is lipase

Answer 22

Breaks down large insoluble lipids, fats and oils into small, soluble fatty acids and glycerol.
Produced- pancreas, small intestine

Question 23

what is a micelle

Answer 23

Made from glycerol, fatty acid, monoglyceride and bile salts to form mixed micelles.
Hydrophobic groups on the inside, hydrophobic groups on the outside.

Question 24

what is the process of blood flow

Answer 24

Superior vena cava brings blood back

Pulmonary artery takes blood to the lungs for oxygenation

Returns to the heart via pulmonary vein

Leaves heart by aorta

Blood goes around the body

The left ventricle has a thicker more muscular wall to allow more powerful pumping to pump blood around the body.

Question 25

what do veins do

Answer 25

Take deoxygenated blood back to the heart under low pressure.
Wider lumen with little elastic/muscle tissue.
Has valves to stop backflow
Blood flow is helped by the contraction of surrounding body muscles.

Question 26

what does arteries do

Answer 26

Carries blood from the heart to the rest of the body
Thick muscular walls
Has elastic tissue to stretch ( maintains high pressure)
Inner lining- endothelium- is folded, allowing the artery to stretch
All carries oxygenated blood apart from the pulmonary artery which
carries deoxygenated blood

Question 27

what do arterioles do

Answer 27

Arteries divide into small vessels called arterioles that form a network throughout the body
Blood is directed to different parts of demand by muscles which contract to restrict blood or relax to allow full blood flow
Arterioles branch into capillaries

Question 28

what do capillaries do

Answer 28

Are found close to cells in exchange tissues ( short diffusion pathway) as substances are exchanged.
Walls are 1 cell thick to have a short diffusion pathway

Question 29

what do valves do

Answer 29

Only open one way. Opening and closing depends on relative pressure of heart chambers
Open- higher pressure behind, forces it to open
Closed- higher pressure in front forces it to close
Blood flow is unidirectional
Atrioventricular valve- links the atria to ventricle
Semilunar valve- links ventricle to pulmonary artery and aorta.

Question 30

what is the cardiac output equation

Answer 30

Cardiac output = stroke volume × heart rate

Question 31

what is cardiac output

Answer 31

Volume of blood pumped by the heart per minute

Question 32

what is stroke volume

Answer 32

volume of blood pumped out the left ventricle during 1 cardiac cycle

Question 33

what is atrial systole in the cardiac cycle

Answer 33

Ventricles are relaxed. Atria contract, decreasing the volume of chambers and increasing pressure. It forces blood into the ventricles. Slight increase in ventricular pressure and chamber volume as ventricles received rejected blood from contracting atria

Question 34

what is ventricle systole in the cardiac cycle

Answer 34

The atria relax. Ventricles contract, increasing their pressure. The pressure in the ventricles ˃ pressure in atria. Forces AV valves shut. Pressure in ventricles ˃ pressure in aorta/ pulmonary artery. Forces SI valves open

Question 35

what is diastole in the cardiac cycle

Answer 35

Ventricles and atria relax. SI valves close. Blood returns to the heart. Atria fills due to high pressure in vena cava/ pulmonary artery. Increases pressure. As ventricles relax, their pressure falls which opens AV valves.

Question 36

how are plants adapted for efficient gas exchange

Answer 36

Leaves have many small holes called stomata which allow gases to enter and exit the leaves.
The large number of these means no cell is far from the stomata, reducing the diffusion distance.
Leaves also possess air spaces to allow gases to move around the leaf and easily come into contact with photosynthesising mesophyll cells.

Question 37

how are single-celled organisms adapted for efficient gas exchange

Answer 37

Single celled organisms are small so they have a large surface area to volume ratio.
Oxygen is absorbed by diffusion across their body surfacewhich is covered only by a cell- surface membrane.
In the same way, carbon dioxide from respiration diffuses out across their body surface.
Cell walls are completely permeable
Gas exchange occurs by diffusion across their membranes.
Has a short diffusion pathway. No need for a specialised gas exchange system.

Question 38

what are fish’s characteristics that means they have to have a specialised exchange surface

Answer 38

Have a waterproof, and therefore gas-tight outer covering. relatively large, so they also have a small surface area to volume ratio, therefore not adequate to supply and remove their respiratory. Specialized exchange surface- gills

Question 39

what are gills structure

Answer 39

within the body of the fish, behind the head. Made up of gill filament (thin plates) which give it a large surface area. The gill filaments are stacked up in a pile. At right angles to the filaments are gill lamellae which increase the surface area of the gills. Filamentare covered in theses tiny structures. Water is taken in through the mouth and forced out the gills and out through an opening in each side of the body.

Question 40

what is the counter-current system and how does it allow an efficient gas exchange system

Answer 40

blood and the water flow over the gill lamellae in opposite directions. Means water with a relatively high concentration of oxygen always flows next to blood This arrangement means that:
Blood with little oxygen in it meets water which has most, so diffusion of oxygen from the water to blood takes place.
Means a steep concentration is maintained between water and the blood- so as much oxygen as possible diffuses from water into the blood

Question 41

why do insects need direct transport of gas

Answer 41

Insects do not possess a transport system therefore oxygen needs to be transported directly to tissues undergoing respiration.

Question 42

how do insects get a direct transfer of gas

Answer 42

This is achieved with the help of spiracles, small openings of tubes, either bigger trachea or smaller tracheoles, which run into the body of an insect and supply it with the required gases.
Gases move in and out through diffusion, mass transport as a result of muscle contraction and as a result of volume changes in the tracheoles. Network of tubes- trachea and tracheoles.
Spiracles- can be opened and closed and compromise between gas exchange and water loss.

Question 43

how do gases move in and out of the tracheal system along the diffusion gradient

Answer 43

• When cells are respiring, oxygen is used up in so it’s concentration towards the end of thetracheolesfalls.
• creates a diffusion gradient that causes oxygen to diffuse from the atmosphere to tracheae and tracheoles to the cells.
• Carbon dioxide is produced by cells during respiration- creates a diffusion gradient in the opposite direction, causing carbon dioxide to diffuse along the tracheoles and trachea into the atmosphere.
• diffusion in air is more rapid than in water, so respiratory gases are exchanged quickly by this method.

Question 44

how do gases move in and out of insects using mass transport

Answer 44

The contraction of muscles in insects can squeeze the trachea enabling mass movements of air in and out.
this further speeds up the exchange

Question 45

how do gases move in and out of insects using water at the end of tracheoles

Answer 45

• ends of the tracheoles are filled with water.
  During periods of major activity, the muscle cells around the tracheoles respire carry out some anaerobic respiration, produces lactate, which is soluble and lowers the water potential of the muscle cells, so water moves into cells from the tracheoles by osmosis. The water in the ends of tracheoles decreases in volume and so draws air further into them. This means the final diffusion pathway is a gas rather than a liquid phase and therefore diffusion is more rapid.