Exchange Flashcards
What is the equation for photosynthesis?
6CO2 + 6H2O —-> C6H12O6 + 6O2
What is the equation for respiration?
C6H12O6 + 6O2 —-> 6CO2 + 6H2O
How are leaves adapted?
Large SA
Thin
Selectively permeable
Diffusion gradient
Why is it good that leaves have a large SA?
Greater surface for diffusion
Why is it good that leaves are thin?
Short diffusion pathway
Why is it good that leaves are selectively permeable?
Controls what comes in and out
Why is it good that leaves have a diffusion gradient?
Large diffusion gradient increases the rate of diffusion
How are fish adapted?
Small SA:Vol
Waterproof, gas tight coating
Surrounded by water (salt water has lower water potential)
Specialised internal gas exchange system (gills)
What are the features of gills?
Large SA provided by gill lamellae
Rich blood supply
Countercurrent flow
What is countercurrent flow?
Blood + water flows in opposite directions
Most O2 rich blood + water comes into contact
Most O2 poor blood + water comes into contact
What is good about countercurrent flow?
Maintains favourable concentration gradient across exchange surface
Where are the gills positioned?
Behind their head
How do gills work?
Water enters the mouth + forced over gills then out through the opening
What are gills made of?
Gill filaments staked on top of each other covered in lamellae
What do highly active fish do?
Swim with their mouths open
Why do some fish swim with their mouths open?
Since it maintains high rate of water flow across the gills to provide sufficient O2 for rate for respiration
What is an example of a fish that swims with their moths open?
Sharks
Mackerel
What does the rate of respiration and photosynthesis effect?
Vol of gas
Type of gas
Why can’t insects use their body surface to exchange respiratory gases?
Bodies aren’t permeable
Molecules can’t diffuse in or out
Don’t have a large SA
Why do insects have mechanisms that allow them to conserve water?
Since they are terrestrial
What do terrestrial insects have to balance?
Their need to conserve water with gas exchange
If you were to increase the SA of an insect what would it conflict with?
Water conservation
How do insects reduce water loss?
Rigid exoskeleton
Waterproof
Small SA
Spiracles - open + close to prevent water loss
What is the internal network of tubes called in an insect?
Tracheae
What is the trachea supported by in insects to prevent water loss?
Rings
What does the trachea in insects divide into?
Tracheoles
What do tracheoles in insects allow to happen?
Air to be brought directly to respiring tissues
Why are insects small?
Not enough O2 for them to grow bigger
Trachea system cannot sustain enough O2
Rely on diffusion rather than transport system
Must have a short diffusion pathway
What are the three ways gases move in and out of the tracheal system in insects?
Diffusion gradient
Muscle contractions
Water filled tracheoles
How does the diffusion gradient allow gases to diffuse in and out of insects?
During respiration O2 is used
O2 conc at tracheole ends fall
Creates diffusion gradient
O2 diffuses from atmosphere into tracheoles then cells
CO2 is produced by respiring cells
Diffusion gradient in opposite direction
CO2 diffuses out of the tracheoles + into atmosphere
How does muscle contractions allow gases to diffuse in and out of insects?
Abdominal pumping - contraction of insect muscles
Trachea squeezed and reduced in volume
Some air expelled from trachea
Uses energy
What is abdominal pumping common in?
Large insects
How does water filled tracheoles allow gases to diffuse in and out of insects?
Anaerobic respiration produces lactate
Lactate is water soluble so lowers W.P of muscle cells
Water moves into muscle cells from tracheoles
Volume in tracheole ends decrease
Drawing in air
What happens to the level of oxygen in the trachea when spiracles are closed?
They are low
What causes spiracles to open?
When level of O2 is too low and when level of CO2 is too high
The tracheal system relies on diffusion and a short diffusion pathway, what factor will this limit in all insects?
Size - must be small to ensure a short diffusion pathway
What are the organelles of a palisade cells?
Cell wall Cell membrane Chloroplast Mitochondria Amyloplast SER RER Golgi apparatus Ribosomes Vacuole Nucleus
What do stomatas create?
Short diffusion pathway
What do air spaces all?
An increased SA + allows gases to diffuse around
What do spongy mesophyll layer allow?
Maximum diffusion
What do the stomata, air spaces and spongy mesophyll layer all provide?
Short + fast diffusion pathway
What does the stomata control?
Diffusion of gases and water vapour
What is the stomata surrounded by?
Guard cells
What do card cells control?
Opening + closing of the stomata
Why is the stomata open in the daytime?
Photosynthesis
Needs lots of CO2
Why is the stomata closed in the dark/night?
No photosynthesis
No need for CO2
What does the transpiration stream do?
Transports water from roots to leaves
How is the transpiration stream created?
As water evaporates from the surface of the leaf
What is the transpiration stream supported by?
Cohesion Tension Theory
What are xerophytes?
Plants living in an area with short water supply
Where are xerophytes’ roots?
Near the surface since that is where the water is
How is the leaf adapted to reduce water loss?
Thick cuticle Rolling up leaves Hairy leaves Sunken stomata Reduced SA:Vol
How does a thick cuticle reduce water loss?
Less water can evaporate off its surface
How does rolling up of leaves reduce water loss?
Traps still, moist air so WP gradient between inside and outside so they’re the same so no water loss
How does hairy leaves and sunken stomatas reduce water loss?
Trap still, moist air so WP gradient is reduced between inside and outside so less water evaporated
How does a reduced SA:Vol reduce water loss?
Smaller SA:Vol = slower rate of diffusion
What is an example of a plant with a thick cuticle?
Holly
What is an example of a plant that rolls up its leaves?
Marram grass
What is an example of a plant with hairy leaves?
Heather
What is an example of a plant with sunken stomatas?
Pine tress
What is an example of a plant with a reduced SA:Vol?
Pine tree leaves
Why is the volume of O2 that needs to be absorbed + the volume of CO2 that needs to be reduced large in mammals?
They’re large organisms with a large volume of cells
Maintain a high body temp as they have a high metabolic + respiratory rate
What is the structure of the lungs?
Lobed structure
Describe the trachea
Flexible airway supported by cartilage rings
What are the muscular walls of the trachea lined with?
Ciliated epithelium and goblet cells
Why is the trachea supported by cartilage rings?
To prevent the trachea from collapsing since the pressure falls when breathing in
Describe the bronchi
Two divisions of the trachea, each leading to one lung
Why do the bronchi produce mucus?
To trap dirt particles
What are the bronchi lined with to trap dirt particles?
Ciliated epithelium + goblet cells
Describe the bronchioles
Series of branching subdivisions of the bronchi
What are the walls of the bronchioles made up of?
Muscle lined with epithelium cells
What does mucus allow the bronchioles to do?
Constrict so they can control air flow in and out of the alveoli
Describe alveoli?
Air sacs at the end of bronchioles
What is between the alveoli?
Collagen and elastic fibres
What is the alveoli lined with?
Epithelium cells
What do the elastic fibres allow alveoli to do?
Stretch as they fill with air and spring back during breathing out in order to expel CO2
What is the alveolar membrane?
Gas-exchange surface
What is breathing?
Ventilation
What is inspiration/inhalation?
When air pressure of the atmosphere is greater than air pressure inside of the lungs, so air is forced into the lungs
What is expiration/exhalation?
When air pressure is of the atmosphere is lower than air pressure inside of the lungs, so air is forced out of the lungs
The pressure changes due to what muscles?
Diaphragm
Internal intercostal muscles
External intercostal muscles
What is the diaphragm?
A sheet of muscle that separates the thorax from the abdomen
Where do the intercostal muscles lie?
Between the ribs
Label a diagram of the lungs
Look up A-level diagram
Describe inspiration
External contract + internal relax Ribs pull upwards + outwards So vol of thorax increases Diaphragm contracts = flattens So vol of thorax increased Atmospheric pressure greater So air forced IN
Describe expiration
External relaxes + internal contract Ribs move downwards + inwards So vol of thorax decreases Diaphragm relaxes = pushed up So vol of thorax decreases Pulmonary pressure greater So air forced OUT
What type of process is inspiration (breathing in)?
Active
What type of process is expiration (breathing out)?
Passive
What is each alveolus surrounded by?
Network of pulmonary capillaries
How thick are the pulmonary capillaries?
Width of one red blood cell
How thick are the alveolus walls?
One layer of cells thick
Why are the diffusion of gases rapid between alveoli and blood?
RBCs slowed as they pass through capillary
Very thin walls = short diffusion pathway
Large SA
Constant breathing movements + constant circulatory blood = steep concentration
What does the blood flow through the pulmonary capillaries maintain?
Concentration gradient
Why is good that RBCs are faltened against pulmonary capillary walls?
Short distance between RBCs and alveolar air
Describe the path which O2 goes from an alveolus to the blood
Enters through the alveolar epithelium then enters the blood through the endothelial cell of the capillary
Describe the structure of the ileum
Walls folded Villi Thin walls, lined with epithelium cells Rich network of capillaries Large SA
Why does the ileum have a large SA?
For an increased rate of absorption
How do villi increase efficiency of absorption?
Large SA for diffusion
Thin walls = short diffusion pathway
Well supplied with blood vessels
Epithelium cells posses microvilli = further increased SA
Why do villi have muscles?
To help them to move so they can mix the contents of the ileum and maintain a conc gradient
How are amino acids absorbed?
Co-transport
Describe the structure of bile salts
One end lipophilic (fat soluble) + hydrophobic
Other end lipophobic + hydrophilic
Because of their structure, how do bile salts arrange themselves?
Lipophilic ends in fat droplets, leaving lipophobic end sticking out
How are monosaccharides absorbed?
Glucose = active transport with NA+ via co-transporter protein
How are amino acids absorbed?
Co-transport
How are monoglycerides and fatty acids absorbed?
Micelles help move them towards epithelium as constantly break up and reform to release them
Fatty acids + monoglycerides lipid-soluble so diffuse easily across epithelium
Describe the oesophagus
Carries food from the mouth to stomach
Describe the stomach
Muscular sac with an inner layer that produced enzymes
What is the role of the stomach?
To store and digest food
Describe the ileum
Long muscular tube where food is further digested by enzymes produced by its walls + glands
Describe the large intestine
Absorbs water from the secretions of many digestive glands
Describe the rectum
Final section of the intestines, where the faeces is stored before being removed by the anus
What is the process of the faeces being removed?
Egestion
Describe the salivary gland
Secretes amylase via a duct, situated in the mouth
Describe the pancreas
Large gland situated below the stomach
What does the pancreas secrete?
Pancreatic juice
What does pancreatic juice contain?
Protease, lipase and amylase
What two stages does digestion take place in?
Physical breakdown
Chemical breakdown
Describe physical breakdown
Large food is broken down into smaller pieces by means of structures
Describe chemical breakdown
Large insoluble molecules hydrolysed by enzymes into smaller soluble molecules
What is needed to hydrolyse a larger molecule?
More than one enzyme
What do all digestive enzymes functions by?
Hydrolysis
What is hydrolysis?
Splitting up larger molecules by adding H2O to the bonds that hold them together
What are carbohydrates hydrolysed by?
Carbohydrase/amylase
What are lipids hydrolysed by?
Lipase
What are proteins hydrolysed by?
Protease
What are the hydrolysis products of carbohydrates?
Monosaccharides
What are the hydrolysis products of lipids?
Fatty acids + glycerol
What are the hydrolysis products of proteins?
Amino acids
How are carbohydrates digested?
Amylase produced by salivary gland Hydrolyses alternative glycosidic bond of starch Maltose formed Hydrolysed by disaccharidase maltase Form monosaccharide alpha glucose
How are lipids digested?
Lipase produced in pancreas
Hydrolyses ester bond in triglyceride
Forms fatty acids + monoglycerides
Lipids split into micelles by bile salts
How are micelles formed?
Large lipid molecule emulsified by bile salts
Forms small lipid molecules
Lipase digestion
Form micelles
Where are the bile salts produced?
Liver
What is a monoglyceride?
Glycerol molecule with one fatty acid attached
What are proteins digested by?
Peptidases (proteases)
What do endopeptidase do?
Hydrolyses peptide bonds within protein molecules
What do exopeptidase do?
Hydrolyses peptide bonds at the ends of protein molecules
By removing single amino acids from proteins
What do dipeptidase do?
Hydrolyses peptide bond between 2 amino acids of a dipeptide
Where is a dipeptidase located?
Cell-surface membrane of epithelial cells in the small intestine (ileum)
What two examples of endopeptidases that are synthesised in the pancreas and secreted into the small intestine?
Trypsin
Chymotrypsin
What is an example of an endopeptidase that is released into the stomach by cells in its lining?
Pepsin
What conditions does pepsin only work in?
Acidic
