Exchange Flashcards
What does passively mean
No metabolic energy is required
What does actively mean
Metabolic energy is required
Where does exchange take place?
At the surface of an organism
Describe a small organisms SA:V ratio
Large
Describe a large animals SA:B ratio
Small
What features have evolved to allow all cells to exchange?
A flattened shape
- so no shape is ever far from the surface
Specialised exchange surfaces
- large surface areas to increase the SA:V ratio
How to calculate the SA:V ratio
Calculate SA
Calculate V
Simplify the ratio
Features of specialised exchange surfaces
Large surface area relative to organism volume
- increases exchange rate
Thin to great short diffusion pathway
- increases exchange rate
Selectively permeable
- allows specific materials to cross
Transport system
- Maintained diffusion gradient
Describe the relationship between diffusion, surface area, concentration, and length of the diffusion pathway
Diffusion (proportional) surface area x difference in concentration / length of diffusion path
Why does an organism with specialised exchange surfaces need to have a means of moving the medium over its surface?
Specialised exchange surfaces are easily damaged and dehydrated
So they are located inside the organism for protection
Name two general things that need to be exchanged between organisms and their environments
Respiratory gases (CO2, O2)
Nutrients
Excretory products
Heat
Name three factors affecting the rate of diffusion
Surface area
Thickness of cell membrane
Permeability of cell membrane to the substance attempting diffusion
Concentration gradient across the membrane
Temperature
How does gas exchange occur in single celled organisms?
Oxygen is absorbed by diffusion
Across the body surface
Carbon dioxide diffuses out
Across the body surface
Due to a small SA:V ratio
Describe the route taken by oxygen in insect gas exchange
Air enters the spiracles Into the trachea Down to the diffusion gradient To the tracheoles Oxygen diffuses Across the cell surface membrane to muscle cells
Describe the route taken by carbon dioxide in insect gas exchange
Carbon dioxide diffuses across the cell surface membrane Into the tracheoles Moves down the diffusion gradient To the trachea And out of the spiracle
Why are insects small
Their tracheal system relies on diffusion
So every cell must be close to the system
To create a short diffusion pathway
What are the three ways respiratory gases move in an insect
Along a diffusion gradient
Mass transport
Tracheole ends are filled with water
Describe how a diffusion gradient is created in a tracheal system
Resourcing cells use up oxygen
Dropping O2 concentration
Creating a concentration gradient from the atmosphere to the cells
Repairing cells produce CO2
Increasing CO2 concentration
Creating a concentration gradient from the cells to the stomp sphere
How does mass transport of gasses occur in insects?
Muscles contract in the insect
Squeezing the trachea
Moving mass amounts of air in and out
Speeding up exchange
How does the ends of an insects tracheoles being filled with water assist in gas exchange?
Muscle cells anaerobically respire
Producing SOLUABLE lactate
Lactate lowers the water potential of muscle cells
Water moves into the muscle cells by osmosis
Decreasing the volume of the tracheoles
Drawing air further into the system
What is a consequence of insects having water in the ends of their tracheoles?
Increased water evaporation
what state are the spiracles typically in? Why?
Closed - to prevent water loss
Explain why there’s a conflict in insects between gas exchange and water conservation
Gas exchange requires a thin permeable surface with a large area
Conserving water requires thick water proof surfaces with a small area
Therefor both cannot occur together
What is the specialised gas exchange surface of a fish?
gills
- Gill filaments
- Gill lamellae
What is the purpose of gill filaments and Gill lamellae
To increase the surface area of the gills
What is countercurrent flow?
The flow of water and blood in opposing directions (in fish) across Gill lamellae
What are the advantages of countercurrent flow?
Maintains a diffusion gradient along the entire gill lamellae
More oxygen diffuses from the water into the blood
Why is water flow in fish one way but exchange in the lungs is two way?
Less energy is required
As the flow doesn’t need to reversed
As water is dense and difficult to move
What is the difference between gas exchange in animals and plants?
Photosynthesis occurs in plants but not animals
How does gas exchange during photosynthesis differ from when the plant is not photosynthesising?
Some CO2 produced by respiration is used in photosynthesis
Some O2 used in respiration is a product of photosynthesis
But most gas exchange occurs by diffusion into and out of the leaf
What are the similarities between gas exchange in an insect and a plant?
No living cell is far from the external air
Diffusion occurs in gas phase
Both have pores for gas exchange
Pores close to avoid excessive water loss
What adaptations does the leaf have for gas exchange?
Stomata
- short diffusion pathway
Air spaces
- increases gas contact with Mesopotamia cells
Mesophyll cells have large SA
- rapid diffusion
What differences are there between gas exchange in a plant and an insect?
Insects can create mass air flow but plants cannot
Insects have a smaller SA:V ratio than plants
Insects have tracheae for gases to diffuse along but plants do not
Insects do not interchange gases between respiration and photosynthesis but plants do
What is the function of closing the stomata?
Help control water loss by evaporation/transpiration
How do insects limit water loss?
Have a small SA:V ratio
Waterproof coverings
Close spiracles
How does a small SA:V ratio limit water loss?
Minimises h e area over which water is lost
How do waterproof coverings limit water loss?
Water cannot leave via osmosis as easily
How does closing the spiracles limit water loss?
Water cannot exit via the spiracles down the water potential gradient via osmosis
Define xerophyte
A plant adapted to living in areas where water is in short supply
Eg. Dry, windy, hot conditions
Name three adaptations does a plant have to prevent water loss
A thick cuticle
Leaves that roll up
Hairy leaves
Stomata in pits or grooves
Reduced SA:V ratio
How does a thick cuticle limit water loss
Reduces water loss by evaporation by increasing the diffusion pathway length
How does rolling up leaves limit water loss?
Stomata become trapped inside a pocket of air
This region becomes saturated with water vapour increasing its water potential
There is no water potential gradient therefore no water loss
How does hairy leaves limit water loss?
Traps still moist air next to the leaf surface
Reducing the water potential gradient
So less water is lost by evaporation
How does having stomata in pits or grooves prevent water loss?
Traps still moist air next to the leaf surface
Reducing the water potential gradient
So less water is lost by evaporation
How does having a reduced SA:V ratio limit water loss?
Slower rate of diffusion
Must be balanced with need for photosynthesis
Why must the volume of oxygen absorbed and carbon dioxide removed large in mammals?
Large organisms with a large number of cells
High body temperature due to high metabolic rate
Describe the route taken by inhaled air from the atmosphere to the blood stream
Nasal cavity / mouth Trachea Bronchi Bronchioles Alveoli Capillaries
Describe the lungs features
Lobed structures
Consisting of branches tubules
Called bronchioles
Ending in tiny air sacs called alveoli
Describe the features of the trachea
Flexible airway
Supported by cartilage
To prevent the trachea collapsing due to pressure drop
Ciliates epithelium and goblet cells
Prevent infection
Describe the features of the bronchi
Two leading to each lung
Flexible airway
Supported by cartilage
To prevent the trachea collapsing due to pressure drop
Mucus and cilia to remove dirt and prevent infection
Describe the features of the bronchioles
Many branches from bronchi
Muscle tissue allows constriction
To control flow of air in and out of alveoli
Describe the features of alveoli
Large supply
For increased SA for faster rate of diffusion
Elastic fibres allow alveoli to stretch to fill with air
Define ventilation
The movement of air into and out of the lungs
Describe inspiration
External intercostal muscles and diaphragm muscle contract
Internal intercostal muscles relax
Ribs move up and out
Increasing thorax volume
This reduces the pressure in the lungs
Creating a pressure gradient
So air is forced into the lungs
Describe expiration
External intercostal muscles and diaphragm muscle relax
Internal intercostal muscles contract
Ribs move down and in
Decreasing thorax volume
This increases the pressure in the lungs
Creating a pressure gradient
So air is forced out of the lungs
In ventilation which process is active and which is passive?
Inspiration is active
Expiration is largely passive
Define tidal volume
The volume of air skin in a breath (at rest)
Typically 0.5dm3
Define ventilation rate
The number of breaths per minute
Typically 12-20
Define pulmonary ventilation rate
The amount of air taken into the lungs in a minute
How to calculate luminary ventilation rate?
PVR=TVxVR
Name 3 adaptations of the alveoli that increase diffusion rate
Large surface area
Thin cells
One cell layer thick
Close to capillaries
High O2 concentration
What factors increase the risk of lung disease
Smoking
Air pollution
Genetic make up
Infection
Occupation
List the major parts of the digestive system
Oesophagus Stomach Ileum/Small intestine Large intestine Rectum Salivary Glands Pancreas Liver
What is digestion?
The physical and chemical breakdown of food
Outline physical digestion
Mastication/Chewing of food into smaller pieces
Providing a larger surface area for chemical digestion
Churning of the stomach also breaks up food
Outline chemical digestion
Enzymes hydrolyse large insoluble molecules into smaller soluble ones
Outline carbohydrate digestion
Amylase (produced in mouth and pancreas) hydrolyses starch into maltose
Maltase (lining of ileum) hydrolyses maltose into alpha glucose
Sucrase hydrolyses sucrose into glucose and fructose
Lactase hydrolyses lactose into glucose and galactose
Outline lipid digestion
Lipids are hydrolused into micelles
by bile salts (liver) in emulsification
to increase the surface area of lipids
Outline protein digestion
Endopeptidases hydrolyse bonds in the central region to form a series of peptide molecules
Exopeptidases hydrolyse terminal amino acids to form dipeptides and amino acids
Dipeptidases hydrolyse dipeptides into amino acids
Outline the features of villi in the ileum
Increase surface area for diffusion
Thin walled to reduce diffusion pathway length
Muscle to move to maintain diffusion gradients
Rich blood supply to carry away absorbed olecules and maintain a diffusion gradient
Microvilli to increase surface area for diffusion
Outline the absorption of amino acids and monosaccharides
Diffusion and co-transport
From the ileum
Into the bloodstream
Briefly outline the absorption of triglycerides
- lipid droplets are hydrolysed into micelles
- Micelles carry monoglycerides and fatty acids to ileum
- Monoglycerides and fatty acids diffuse into the cell
- The smooth ER reforms triglycerides
- Golgi associates triglycerides with cholesterol and lipoproteins to form chylomicrons
- Chylomicrons exits cell by exocytosis into the lacteals
