Topic 3A: Exchange and Transport Systems

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What has a higher surface area : volume ratio - larger or smaller organisms?
Smaller organisms have a larger surface area to volume ratio
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Why is diffusion rate high in single celled organisms?
The substances have small distances to travel
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Give 2 reasons why diffusion through outer membrances is too slow in multicellular organisms
1: there's a big distance between cells deep within the body and the outside environment & 2: they have a low surface area : volume ratio
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What is mass transport?
An efficient system that carries substances to and from the individuals cells
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In mammals what does mass transport usually refer to?
The circulatory system
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What does mass transport involve in plants?
The transport of water and solutes in the xylem and phloem
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How does body size influence the rate of heat loss?
Bigger organisms have a smaller surface area : volume ratio so it is harder for them to lose heat than a smaller organism
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What animal would lose heat quicker: a mouse or a hippo?
A mouse (as it has a larger surface area : volume ratio)
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How does body shape influence the rate of heat loss?
Animals with a compact shape have a lower surface area : volume ratio than animals with a less compact shape (e.g. big ears or tail) which increases heat loss
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Other than body size/shape, give two adaptations a large animal may have to survive in a hot environment
They may spend a lot of time in water or have features that increase surface area (e.g. big ears)
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Other than body size/shape give two adaptions a small animal may have to survive in a cold environment
Thick layers of fur or hibernate when weather gets v cold
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What do gas exchange surfaces have that increase the rate of diffusion?
They have a large surface area & they're thin (to provide a short diffusion pathway)
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Why do single celled organisms not have a specialised gas exchange system?
They have a large surface area : volume ratio, a thin surface and a short diffusion pathway
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How do single celled organisms release and absorb gases by diffusion?
They do it through the cell membrane
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How have fish adapted for gas exchange?
They have gills
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What are gill filaments?
They are the thin plates that gills are made of - they provide a large surface area
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What two structures increase surface area of the gill?
Gill filaments and lamellae
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How does the lamellae speed up diffusion between the water and blood?
The lamellae have lots of blood capillaries (to maintain the concentration gradient) and a thin layer of cells
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How does a good blood supply increase the rate of diffusion?
It mainatins a steep concentration gradient
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How does the counter current system maintain a concentration gradient?
Water and blood flow in opposite ways this means that water with a high conc of oxygen passes over blood with a lower concentration of oxygen - so oxygen diffuses down the conc gradient
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SIMPLY what does the counter current system in a fish do?
It maintains the concentration gradient in the gills
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What is the main gas exchange surface in plants?
The surface of the mesophyll cells
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What do guard cells control?
The opening and closing of the stomata
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What pores do gases move in and out of in a plant?
The stomata
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Why would the stomata close?
To stop the plant from losing too much water
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How is a leaf adapted to its function?
Has a large surface area
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Why do plants need a gas exchange surface?
They need CO2 for photosynthesis (O2 is a waste product) and O2 for respiration (CO2 is a waste product)
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What are trachae?
Microscopic air filed pipes that are used for gas exchange in insects
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What are tracheoles?
They are branched trachae (basically idk im tired)
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How do insects move air in and out of the spiracles?
The use rythmic abdominal movements
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What are spiracles?
Spiracles are pores on the surface of the insects that air moves into
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How do the tracheoles minimise diffusion distance?
They are lined with a single layer of cells so there's a short diffusion distance
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What is a side effect of gas exchange? (v bad)
Water loss
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How do insects control water?
They close their spiracles using muscles, they also have a waxy cuticle and tiny hairs around their spiracles which reduce evaporation
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What happens when a plant becomes dehydrated?
The guard cells lose water and become flaccid (lol) which closes the pore
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What happens to guard cells when water enters the plant?
They become turgid (which opens the stomatal pore)
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What are xerophytes?
Plants that are specially adapted for life in warm, dry or windy habitats
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Give 3 adaptions that xerophytic plants have to reduce water loss
1: thick waxy, waterproof cuticles on leaves and stems, reduced number of stomata, a layer of hairs on the epidermis (to trap water vapour), curled leaves w stomata inside (protecting them from wind)
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How do xerophytic plants reduce the concentration gradient between the leaf and the air?
They have the stomata sunk in pits to trap water vapour
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How does air get into an insects trachae?
Through the spiracles (and down a conc gradient)
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How does air move from the mouth to the blood stream? (as in structures)
Trachea - Bronchus - Bronchioles - Aveoli - Blood stream
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What is ventilation?
Breathing in (inspiration) and breathing out (expiration)
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What happens during inspiration?
Air flows in, thorax volume increases, air pressure decreases, external intercoastal muscles contract, diaphragm contracts (and flattens)
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What happens during expiration?
Air is forced out, thorax volume decreases, air pressure increases, internal intercoastal muscles contract, diaphragm relaxes, causing it to curve upwards
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What one is a passive process? Inspiration or expiration?
Expiration
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How is expiration a passive process?
It doesn't require energy
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What happens during forced expiration?
The external intercostal muscles relax and internal intercoastal muscles contract - pulling the ribcage further down and in
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How is a pressure gradient important during expiration?
Air is forced down the concentration gradient pushing air out of the lungs during expiration as air pressure in the lungs is higher than atmospheric pressure
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What are the cells lining the walls of the aveolus called?
The alveolar epithelium
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What are the walls of the capillary made of?
Capillary endothelium
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What is the role of elastin in the alveolus?
It helps the aveoli recoil to their normal shape after inhaling and exhaling air
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How does oxygen in the air become oxygen in haemaglobin?
Goes down the trachea - bronchi - bronchioles - alveoli - alveolar epithelum - capillary endothelium - blood
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How are alveoli adapted to increase rate of diffusion?
Thin exchange surface (1 cell thick), large surface area (millions of alveoli), steep concentration gradient (good blood supply)
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What are the 4 measures of gas exchange?
Tidal volume, Ventillation rate, forced expiratory volume, forced vital capacity
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What is tidal volume?
It is the volume of air in each breath
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What is the normal tidal volume for a healthy adult?
0.4dm3 - 0.5dm3
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What is ventillation rate?
The number of breaths per minute
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What is the ventillation rate for a healthy person at rest?
About 15 breaths
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What is forced expiratory volume? (FEV1)
It is the maximum volume of air that can be breathed out in one second
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What is forced vital capacity? (FVC)
It is the maximum volume of air that can be breathed out in 1 second
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What is tuberclosis?
It is a lung disease caused by bacteria where immune system cells build walls around the bacteria which forms small hard lumps in the lung
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What does a reduced tidal volume mean?
Less air is being inhaled in each breath, so people have to breathe faster (increasing ventilation rate)
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What is fibrosis?
It is the formation of scar tissue in the lungs which reduces elasticity
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What happens during an asthma attack?
The lining of the bronchioles contract and a large amount of mucus is produced causing constriction of the airways. Forced expiratory volume is reduced
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What are the ethical issues surrounding dissection?
It's morally wrong to kill animals to dissect them as it's unnecessary & animals for dissections weren't raised in a humane way and were killed inhumanely
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Card 2

Front

Why is diffusion rate high in single celled organisms?

Back

The substances have small distances to travel

Card 3

Front

Give 2 reasons why diffusion through outer membrances is too slow in multicellular organisms

Back

Preview of the front of card 3

Card 4

Front

What is mass transport?

Back

Preview of the front of card 4

Card 5

Front

In mammals what does mass transport usually refer to?

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