Exchange

Question 1

How do Microorganisms Obtain Nutrients & Remove Waste?

Answer 1

 by exchange via their surface
 nutrients (e.g. glucose, oxygen) move in by diffusion via their surface
 waste (e.g. carbon dioxide) move out by diffusion via their surface

Question 2

Why are Microorganisms able to perform exchange via their surface?

Answer 2

 have a large surface area to volume ratio
 have a short diffusion distance
 have low demand

Question 3

Why can’t Animals/Plants perform exchange via their surface?

Answer 3

 have a small surface area to volume ratio
 multicellular (large diffusion distance and high demand)
 impermeable surface (prevent pathogens entering and reduce water loss)
 therefore, require specialised Exchange & Transport systems
 exchange system = increases rate of diffusion of nutrients in and wastes out
 transport system = deliver nutrients and remove waste from all cells

Question 4

Why do Fish have Specialised Gas Exchange Systems?

Answer 4

 multicellular organism so has a small surface area to volume ratio, large diffusion distance, high demand & body surface impermeable
 therefore, cannot perform gas exchange (O2 in/CO2 out) via their surface, they require a specialised gas exchange system called Gills

Question 5

Structure of Gills in Fish?

Answer 5

 many gill filaments and gill lamellae = large surface area
 gill lamellae have a thin wall (short diffusion distance) and are permeable
 ventilation brings in pure water (high oxygen, low carbon dioxide) and circulation brings in deoxygenated blood (low oxygen, high carbon dioxide), the water and blood pass over in opposite directions (countercurrent flow), which maintains concentration gradient all the way along the gill lamellae

Question 6

Why do Insects have Specialised Gas Exchange Systems?

Answer 6

 multicellular organism so has a small surface area to volume ratio, large diffusion distance, high demand & body surface made of exoskeleton (impermeable barrier to reduce water loss)
 therefore, cannot perform gas exchange (O2 in/CO2 out) via their surface, they require a specialised gas exchange system called Tracheal System

Question 7

Structure of Tracheal System in Insects?

Answer 7

 starts with openings on body surface called Spiracles
 spiracles contain valves, open = gas exchange, closed = prevent water loss
 spiracles connect to Trachea
 trachea connect to Tracheoles
 tracheoles connect directly to Respiring Cells (delivering oxygen, removing carbon dioxide)

Question 8

How does Gas Exchange occur in Tracheal System of Insects?

Answer 8

 at rest = down a concentration gradient, oxygen moves in & carbon dioxide moves out by simple diffusion
 when active = by ventilation, air inhaled for mass flow of O2 in & air exhaled for mass flow of CO2 out

Question 9

Function of Lungs?

Answer 9

site of gas exchange in mammals (oxygen into blood – used in cells for respiration, carbon dioxide out of the blood – toxic waste product of respiration)

Question 10

What is Lungs made up of?

Answer 10

Trachea, Bronchi, Bronchioles, Alveoli (+ capillaries)

Question 11

Function of trachea, bronchi, bronchioles?

Answer 11

transport of air and filter air, (bronchioles also controls amount of air reaching alveoli)

Question 12

Structure of trachea/bronchi?

Answer 12

 wall made of c-shaped cartilage
 cartilage is strong so trachea/bronchi do not collapse
 cartilage is c-shaped to give flexibility
 lining made of goblet cells and ciliated epithelial cells
 goblet cells make mucus, which traps pathogens/particles
 ciliated epithelial cells have cilia, which pushes mucus up and out of lungs

Question 13

Structure of bronchioles?

Answer 13

 wall made of smooth muscle
 smooth muscle contracts, lumen narrows, bronchiole constricts
 (occurs when surrounded by noxious gases – reduces amount reaching alveoli)
 lining made of goblet cells and ciliated epithelial cells

Question 14

Adaptation of alveoli?

Answer 14

 millions of tiny alveoli that are folded (large surface area)
 thin wall/one cell thick/squamous epithelial cells (short diffusion distance)
 elastic tissue in wall (stretches when breathing in to increase surface area, recoils when breathing out to push the air out)
 ventilation maintains concentration gradient (high oxygen, low carbon dioxide)

Question 15

Adaptation of capillaries?

Answer 15

 millions of tiny capillaries (large surface area)
 thin wall/one cell thick/squamous epithelial cells (short diffusion distance)
 narrow lumen (increases diffusion time, decreases diffusion distance)
 circulation maintains concentration gradient (low oxygen, high carbon dioxide)

Question 16

How O2 moves from the alveoli to the capillaries?

Answer 16

by simple diffusion passing thru the alveolar epithelium and capillary epithelium

Question 17

How CO2 moves from capillaries to the alveoli?

Answer 17

by simple diffusion passing thru the capillary epithelium and alveoli epithelium

Question 18

Inhalation?

Answer 18

1. external intercostal muscles contract
2. internal muscles relax
3. ribcage pulled up and out
4. increased volume in the thorax
5. diaphragm muscles contract and it will move down
6. increased volume in thorax and decreased pressure inside
7. atmospheric pressure is now greater than pulmonary pressure
8. air is forced into lungs

Question 19

Expiration?

Answer 19

1. internal intercostal muscles contract
2. external muscles relax
3. rib cage moves down and in
4. volume in the thorax decreases
5. diaphragm muscles relax and it is pushed up
6. decreased volume in thorax increased pressure inside
7. pulmonary pressure is now greater than atmospheric pressure
8. air is forced out of the lungs

Question 20

Formula for Pulmonary Ventilation?

Answer 20

 PV = tidal volume x ventilation rate
 tidal volume = volume of air breathed in/out in one breath
 ventilation rate = number of breaths per minute
 Pulmonary Ventilation = volume of air breathed in/out per minute

Question 21

Function of Intestines?

Answer 21

site of exchange of digested nutrients in mammals

Question 22

What is Digestion?

Answer 22

 Breakdown of Large Insoluble Molecules into Small Soluble Molecules (so they can move into the blood and then into the body cells)
 Starch/Glycogen (Carbohydrates) into Glucose by Amylase (Salivary in mouth, Pancreatic in small intestine) and Maltase/Lactase/Sucrase (on lining of small intestine)
 Proteins into Amino Acids by Endopeptidase/Exopeptidase/Dipeptidase (Endopeptidase in stomach, Exopeptidase in small intestine, Dipeptidase on lining of small intestine)
 Lipids into Monoglyceride and 2 Fatty Acids by Lipase (in small intestine)

Question 23

What do Intestine Absorb?

Answer 23

 Small Intestine absorbs small soluble nutrients (glucose, amino acids, monoglyceride and fatty acid, vitamins and minerals)
 Large Intestine absorbs water

Question 24

Why do Humans/Mammals require a Specialised Transport System?

Answer 24

 multicellular organisms therefore have large diffusion distances and high demand
 need a transport system to deliver nutrients and remove waste from all cells
 transport system in humans/mammals called Circulatory System
 Circulatory System made of heart, blood vessels, blood
(heart pumps blood, blood vessels carry blood, blood carries nutrients/waste)

Question 25

Why is the transport system in mammals called a double circulatory system?

Answer 25

the heart pumps twice, the blood goes through the heart twice – generates enough pressure to supply all body cells

Question 26

Why is the transport system in mammals called a closed circulatory system?

Answer 26

blood is transported in blood vessels – helps to maintain pressure and redirect blood flow

Question 27

Lipid digestion?

Answer 27

- hydrolysed by lipases produced in the pancreas - hydrolyse ester bonds to form fatty acids and monoglycerides - lipids are first broken down into micelles by bile salts produced by the liver - this process in called emulsification - it creates a larger surface area for the enzyme to be able to work more rapidly

Question 28

Bile salts?

Answer 28

- one end is soluble fat (lipophilic) but not in water - other side is insoluble in fat (lipophobic) but soluble in water (hydrophilic) - fat is prevented from sticking back together

Question 29

Protein digestion?

Answer 29

-peptidases hydrolyse peptide bonds in protein - endopeptidases - hydrolyse in the central region forming smaller polypeptide. Increases SA for exopeptidases - exopeptidases - hydrolyse at terminal amino acids of the peptide molecules formed by endopeptidases - dipeptidases - hydrolyse the bonds between the two amino acids of a dipeptide. Membrane bound- part of the cell surface membranes of the epithelial cells lining the ileum.

Question 30

Absorption of triglycerides?

Answer 30

1. lipid mixed with bile salts 2. this forms micelles 3. monoglycerides and fatty acids are released 4. monoglyceride and fatty acids are absorbed through the membrane of the ileum 5. monoglycerides and fatty acids are converted back to triglycerides in the endoplasmic reticulum 6. triglycerides are packaged back into chylomicrons 7. chylomicrons released by exocytosis 8. chylomicrons go into lymphatic vessels and then into the bloodstream

Question 31

Chylomicrons?

Answer 31

- a small fat globule composed of protein and lipids - they transport fat from the intestine to the liver and to dispose tissue - the chylomicrons are synthesised in the lining of the intestine

Question 32

how are dicotyledonous plants adapted for gas exchange?

Answer 32

- guard cells open and close to allow o2 in and co2 out - stomata allows gasses in - air spaces- create a diffusion pathway

Question 33

how is water loss limited in insects?

Answer 33

- small SA : vol ratio- minimises the area over which water is lost - rigid exoskeleton- waterproof cuticle - made of chitin - spiracles- open and close to reduce water loss

Question 34

how do gasses move in and out of the tracheal system?

Answer 34

- diffusion gradient - muscle contractions - water filled tracheoles

Question 35

how does a diffusion gradient allow gasses to move in and out of the tracheal system?

Answer 35

- oxygen is used during respiration - concentration of oxygen at tracheae end falls which creates a diffusion gradient - oxygen diffuses from atmosphere - co2 is produced by respiring cells - diffusion gradient in opposite direction - co2 diffuses into the atmosphere

Question 36

how does muscle contractions allow gasses to move in and out of the tracheal system?

Answer 36

- abdominal pumping - tracheae squeezed, which reduces their volume - some air is expelled from tracheae - uses energy

Question 37

how does water filled tracheoles allow gasses to move in and out of the tracheal system?

Answer 37

- anaerobic respiration produces lactate - lactate is water soluble - water potential of the muscles becomes more negative - water moves into muscle cells from tracheoles - volume in the tracheoles decreases, drawing air in from the atmosphere