Flashcards
Chapter 6: Exchange
Cards in this deck (91)
- 1What is tissue fluid?Environment surrounding cells of all multicellular organisms
- 2Why is diffusion alone often not sufficient for organisms to survive?Most cells too far from exchange surface
- 3What transport system do larger organisms need and what does this maintain?Mass transport system maintains a diffusion gradient
- 4Higher metabolic rate = _____ exchange neededMore
- 5Materials that need to be exchangedRespiratory gases (O2, CO2)
Nutrients (glucose, amino acids etc)
Excretory products (urea, CO2)
Heat - 6Two ways in which exchange occurs (excluding exchange of heat)Passively - diffusion, osmosis
Actively - active transport - 7As organisms become larger, volume increases at a ______ rate than surface areaFaster
- 8Features developed by organisms for effective exchangeFlattened shape - no cell ever far from surface
Specialised exchange surfaces with large areas to increase SA:volume - 95 features of specialised exchange surfaces1. Large SA relative to volume of organism
2. Very thin - short diffusion pathway
3. Selectively permeable
4. Movement of environmental medium to maintain gradient
5.Transport system for movement of internal medium to maintain gradient - 10Why are specialised exchange surfaces often located inside an organism?They are easily damaged and dehydrated
- 11When an exchange surface is located inside an organism, what must there be a means of?Moving external medium over the surface (e.g. breathing to ventilate lungs in mammals)
- 12SA:volume = ______ ÷ ______Surface area ÷ volume
- 13Single-celled organisms have a ______ SA:volumeLarge
- 14How does gas exchange happen in single-celled organisms?O2 absorbed by diffusion across body surface (cell surface membrane); CO2 from respiration diffuses out [cell wall does not affect this]
- 15What is the tracheae in insects?Internal network of tubes supported by strengthening rings to prevent collapsing. Divided into smaller dead-ended tubes - tracheoles - which extent throughout all body tissues
- 163 ways in which respiratory gases move in and out of the tracheal system in insects1. Along a diffusion gradient
2. Mass transport
3. Ends of tracheoles filled with water - 17How do respiratory gases move in and out of the tracheal system along a diffusion gradient?Respiring cells use up O2 so concentration of O2 at ends of tracheoles falls, creating diffusion gradient which causes gaseous O2 to diffuse from atmosphere into cells. CO2 is removed via a concentration gradient in the opposite direction.
- 18Diffusion in air is ______ than in waterFaster
- 19How do respiratory gases move in and out of the tracheal system by mass transport?Contraction of muscles squeezes trachea, forcing large amounts of air in and out
- 20How do respiratory gases move in and out of the tracheal system due to the ends of the tracheoles being filled with water?In periods of major activity, muscle cells carry out anaerobic respiration - produces lactate which is soluble so lowers water potential of cells. Water moves into cells via osmosis which draws air further into tracheoles. Final diffusion pathway is in a gas
- 21What can gas exchange due to ends of tracheoles being filled with water lead to?More water evaporation
- 22How do gases enter and leave the tracheae?Spiracles
- 23What are spiracles?Tiny pores on body surface which may be open and closed by a valve
- 24Why are the spiracles mostly kept closed?To reduce water loss
- 25Limitations of the tracheal system in insects1. Relies mostly on diffusion of gases which requires short diffusion pathway to be effective
2. Length of diffusion pathway limits size that insects can be - 26Fish are relatively ______ so have a ______ SA:volumeLarge
Small - 27Why is the body surface of a fish not adequate to supply or remove respiratory gases?It has a waterproof and gas-tight outer covering
- 28What specialised exchange surfaces have fish evolved?Gills
- 29Structure/features of the gills- Located behind the head
- Made up of stacked up gill filaments
- Gill lamellae at right angles to filaments - 30What happens to water once taken in by the mouth of the fish?Forced over gills and out through an opening on each side of the body
- 31The flow of water over gill lamellae is in the ______ direction to the direction of blood flowOpposite
- 32What is the term describing the opposite directions of water and blood flows?Countercurrent flow
- 33What happens in countercurrent flow?- Blood already well loaded with O2 meets water with its maximum concentration of O2; diffusion takes place
- Blood with little O2 meets water that has had most but not all O2 removed; diffusion takes place
- Water always has more O2 than blood - 34How does countercurrent flow allow for efficient gas exchange in fish?Diffusion gradient is maintained across the entire width of the gill lamellae (80% of available O2 is absorbed into the blood) so O2 diffuses into blood for whole width
- 35What would happen if the flow of water and blood was parallel in the gills?Diffusion gradient would only be maintained across part of the gill (only 50% of available O2 absorbed); concentrations of O2 would reach equilibrium
- 36What gases are exchanged during photosynthesis?CO2 taken in
O2 produced - 37What can reduce gas exchange with the external air?Using gas produced in one process in another
- 38Name 6 parts that could be labelled on a diagram of the structure of a leafWaxy cuticle
Upper epidermis
Palisade mesophyll
Spongey mesophyll
Lower epidermis
Guard cells/stomata - 393 adaptations of a leaf for rapid diffusion of gases1. Many stomata so no cell is far from a stoma - short diffusion pathway
2. Multiple interconnecting air spaces - gases can come directly into contact with mesophyll cells
3. Large SA of mesophyll cells - 40What are stomata?Minute pores occurring mainly on leaves
- 41Where on a leaf are stomata primarily found and why?Underside/lower epidermis
To reduce water loss - 42What is the role of guard cells?To open/close the stomatal pores by becoming turgid/flaccid; this controls the rate of gaseous exchange
- 43What is another term for the stomatal pore?Stomatal aperture
- 44Guard cells have a ______ outer wall and a ______ inner wallThin outer wall
Thick inner wall - 45What do plants do to balance the conflicting needs of gas exchange and controlling water loss?Stomata are closed at times when water loss would be excessive
- 46For exchange surfaces inside organisms, how saturated with water vapour is the air around them?100% = less water loss
- 47What specifically in insects conflicts with water conservation?Thin and permeable surfaces with large SA - insects can easily dehydrate
- 48What adaptations do insects have to reduce water loss?- Small SA to volume ration to minimise the area over which water can be lost
- Waterproof coverings on body surfaces; rigid exoskeletons of chitin covered with a waterproof cuticle
- Spiracles which can be closed (largely when insect is at rest) - 49What issue does the waterproof covering of insects pose and how is this overcome?Cannot use body surfaces to diffuse respiratory gases
Internal network of tracheae instead - 50Why can't plants have a small SA:volume ratio?Have to photosynthesise which requires large surfaces for capture of light, and gas exchange
- 51What is the term for plants that survive in very dry conditions?Xerophytes - adapted to limit water loss through transpiration and evaporation
- 52What are some of the adaptations of plants to reduce water loss?- Thick cuticles; up to 10% of water loss can occur through the waxy cuticle even though it is a waterproof barrier; the thicker the cuticle the less water lost.
- Rolling up of leaves: protects lower epidermis and traps a region of still air which becomes saturated with water vapour; reduces water potential gradient between leaf and outside.
- Hair on leaves: thick layer, especially on lower epidermis, again traps still, moist air next to the leaf surface.
- Stomata in pits or grooves: traps still, moist air next to leaf.
- Reduced SA:volume ration of leaves: better to be circular in cross-section rather than broad and flat. - 53Give an example of a plant with a thick cuticleHolly
- 54Give an example of a plant that makes use of rolling up leavesMarram grass
- 55Give an example of a plant with hair on its leavesOne type of heather
Lambs ears - 56Give an example of a plant with stomata in pits/groovesPine trees
- 57Why do mammals need to exchange large quantities of O2/CO2?Relatively large organisms so have to support a large volume of living cells.
They maintain a high body temp which is related to them having high metabolic and respiratory rates. - 58Why are the lungs located inside the body?- Air is not dense enough to support and protect such delicate structures
- The body as a whole would otherwise lose lots of water and dry out - 59What are the lungs supported and protected by?Ribcage
- 60How does the ribcage move?Intercostal muscles
- 61What ventilates the lungs?A tidal stream of air
- 62What are the lungs?A pair of lobed structures made up of a series of highly branched tubules which end in tiny air sacs
- 63What structures does air move through in the lungs to get to the exchange surface?Trachea
Bronchi
Bronchioles
Alveoli - 64What is the trachea?A flexible airway supported by rings of cartilage. Tracheal walls are made of muscle lined with ciliated epithelium and goblet cells.
- 65Why is it important for cartilage to support the trachea?To prevent it collapsing when air pressure falls when breathing in
- 66What are the bronchi?Two divisions of the trachea, each leading to one lung. They are similar in structure to the trachea and secrete mucus and have cilia to move mucus to throat. The larger the bronchus, the more cartilage.
- 67What are the bronchioles?Series of branching subdivisions of the bronchi. Walls are made of muscle lined with epithelium. Muscles allow them to control the flow of air in and out of the alveoli.
- 68Why is it important for the bronchioles to control flow of air in the alveoli?To prevent them bursting
- 69What are the alveoli>Minute air sacs at the end of the bronchioles. Collagen and elastic fibres are found between them - elastic fibres allow them to stretch as they fill with air and spring back in order to expel CO2. Lined with epithelium.
- 70What is the gas exchange surface in the lungs called?Alveolar membrane
- 71What is breathing/ventilation?Process of moving air in and out of the lungs in order to maintain a diffusion gradient of gases across the alveolar epithelium
- 72What sets of muscles bring about pressure changes within the lungs?Diaphragm - sheet of muscles separating thorax and abdomen
Intercostal muscles - lie between the ribs
(internal intercostal muscles and external intercostal muscles) - 73What is inspiration?Where air pressure in atmosphere is greater then that inside lungs, air is forced into lungs
- 74What kind of process is inspiration?Active process
- 75Describe the process of inspiration- External IMs contract, internal IMs relax
- Ribs pulled upwards and outwards (increases volume of thorax)
- Diaphragm muscles contract so it flattens (more increase in volume)
- Pressure in lungs thus decreases
- Atmospheric pressure now greater than pulmonary pressure, so air is forced into the lungs - 76What is expiration?Where air pressure in the lungs is greater than that in the atmosphere so air is forced out of the lungs
- 77What kind of process is expiration?Largely passive
- 78Describe the process of expiration- Internal IMs contract, external IMs relax
- Ribs pulled downwards and inwards (decreases volume of thorax)
- Diaphragm muscles relax so it is pushed up by abdominal contents that were previously compressed (more decrease)
- Pressure in lungs is thus increased
- Pulmonary pressure is now greater than atmospheric pressure, so air is forced out of lungs - 79What is pulmonary ventilation?Total volume of air moved into the lungs in 1 minute
- 80What is tidal volume?Volume of air normally taken in per breath when the body is at rest
- 81What is breathing rate?Number of breaths taken in 1 minute
- 82How would you calculate pulmonary ventilation rate?
- 83How big is the diameter of an alveolus?100-300μm
- 84Why are the alveoli located inside an organism?Very thin and delicate so need protection
- 85How many alveoli are there in each human lung?About 300 million (total SA = 70m2)
- 86What are alveoli lined with?Epithelial cells
- 87How thick is the alveolar wall?1 cell thick
- 88What are the alveoli surrounded by?Network of pulmonary capillaries
- 89Width of pulmonary capillariesVery narrow - red blood cells are flattened against the capillary walls to fit
- 90How thick is the capillary wall?1 endothelial cell thick
- 915 reasons why diffusion of gases between the alveoli and the blood are very rapid1. Red blood cells are slowed as they pass through pulmonary capillaries - more time for diffusion
2. Distance between alveolar and red blood cells is reduced due to red blood cells being flattened against capillary walls
3. Very thin capillary and alveolar walls - short diffusion distance
4. Alveoli and pulmonary capillaries have large SA
5. Breathing movements constantly ventilate lungs and action of heart constantly circulates blood - ensures a steep diffusion gradient is maintained
Information
- Description
- Biology A level AQA new specification
- Created by
- Amy Warrell · Apr 2018
- Updated
- May 19, 2018
- Views
- 27
- Rating