Exchange and Transport Systems Flashcards
(47 cards)
1
Q
What is needed when organisms exchange substances with the environment?
A
- Cells need to take in oxygen for aerobic respiration and nutrients
- Need to excrete waste products like carbon dioxide and urea
- Most organisms need to stay at roughly the same temperature, so heat needs to be exchanged too
2
Q
Great surface area:volume ratio
A
This is the case for smaller organisms and it affects how quickly substances are exchanged
3
Q
Volume of a cylinder
A
Pi r2
4
Q
Volume of a sphere
A
4/3 Pi r3
5
Q
Diffusion equation
A
S.A x difference in concentration
Length of diffusion path
6
Q
Surface area of a sphere
A
4 Pi r2
7
Q
Features of specialised exchange surfaces
A
- Large surface area relative to volume of the organism which increases the rate of exchange
- Very thin so that the diffusion distance is short and therefore materials cross the exchange surface rapidly
- Selectively permeable to allow selected materials to cross
- Movement of environmental medium e.g. air to maintain diffusion gradient
- Movement of internal medium (transport system) e.g. blood in order to maintain diffusion gradient
- Being thin specialised exchange surface are easily damaged and dehydrated so located inside organism
8
Q
Single-celled organisms
A
- Substances can diffuse directly into or out of the cell across the cell-surface membrane
- Diffusion rate is quick beacuse of the small distances the substances have to travel
- Relatively large surface area, thin surface and short diffusion pathway so no need for specialised gas exchange system
9
Q
Multicellular Organisms
A
- Diffusion across membrane is too slow because…
- Some cells are deep within the body- big distance between them and outside environment
- Larger animals have a low surface area to volume ratio so it’s difficult to exchange enough substances to supply a large volume through a small outer surface
- So multicellular organisms need specialised exchange organs for transport
10
Q
Mass Transport
A
Efficient system to carry substances to and from their individual cells
11
Q
What does metabolic activity do?
A
Creates waste products to be transported away and metabolic activity inside cells creates heat
12
Q
How does body size affect heat exchange?
A
- Easy to lose heat if large surface area:volume
- Hard to lose heat if small surface area:volume
- Smaller organisms need a relatively high metabolic rate, in order to generate enough heat to stay warm
13
Q
How does body shape affect heat exchange?
A
- Compact shape means a small surface area: volume, minimising heat loss
- Less compact shape (bits sticking out) have a larger surface area:volume so increased heat loss from surface
14
Q
Adaptations for heat exchange
A
Whether an animal is compact or not depends on the temperature of its environment- animal’s body shape is adapted to suit its environment
15
Q
Behavioural and Physiological adaptations to aid exchange
A
- Animals with a high surface area:volume ratio tend to lose more water as it evaporates from their surface. This is a problem for animals living in hot regions where water evaporates quickly. Some small desert animals have kidney structure adaptations so they produce less urine to compensate.
- To support their high metabolic rates, small mammals living in cold regions need to eat large amounts of high energy foods such as seeds and nuts.
- Smaller mammals may have thick layers of fur or hibernate when weather gets cold.
- Larger organisms living in hot regions find it hard to keep cool as heat loss is slow. Elephants have large flat ears which increase surface area, allowing more heat loss. Hippos spend much of the day in the water (behavioural adaptation to help lose heat)
16
Q
Gas Exchange Surfaces
A
- Boundary between outside and internal environment of an organism
- Need oxygen and carbon dioxide to diffuse across exchange surfaces as quickly as possible
- Most gas exchange surfaces…
- Have a large surface area
- Thin (often one layer of epithelial cells) so short diffusion pathway
- Organism also maintains steep concentration gradient of gases across exchange surface, which increases rate of diffusion
17
Q
Gas exchange in fish
A
- Lower concentration of oxygen in water than in air
- So fish use the gas exchange surface (gills) to get enough of it
18
Q
Structure of Gills
A
- Water, containing oxygen, enters the fish through its mouth and passes out through the gills
- Each gill is made of lots of thin plates called gill filaments which give a large surface area for exchange of gases
- Gill filaments are covered in lots of tiny structures called lamellae, which increases surface area even more
- Lamellae have lots of blood capillaries and a thin surface layer of cells to speed up diffusion, between water and blood
19
Q
Counter-current system
A
- In the gills of a fish, blood flows through the lamellae in one direction and water flows over them in the opposite direction
- Counter-current system means that the water with a relatively high oxygen concentration always flows next to blood with a lower concentration of oxygen
- Means that a steep concentration gradient is maintained over the whole length of the gill between the water and blood (as much oxygen diffuses from water into blood)
- If flow was parallel, concentration of oxygen would be 50/50
20
Q
Gas exchange in dicotyledonous plants
A
- Plants need CO2 for photosynthesis, which produces O2 as a waste gas
- Need O2 for respiration, which produces CO2 as a waste gas
- Main gas exchange surface is surface of mesophyll cells in the leaf (well adapted, large surface area)
- Gases move in and out through special pores in the epidermis (mainly lower epidermis) called stomata
- Stomata open to allow exchange of gases and close if plant is losing too much water
- Guard cells control opening and closing of stomata
21
Q
Gas exchange in insects
A
- Terrestrial insects have microscopic air-filled pipes called tracheae which they use for gas exchange
- Air moves into the tracheae through pores on the surface called spiracles
- Oxygen travels down the concentration gradient towards the cells
- Tracheae branch off into smaller tracheoles which have thin, permeable walls and go to individual cells
- Means that oxygen diffuses directly into respiring cells- insect’s circulatory system doesn’t transport O2
- Carbon dioxide from the cells moves down its own concentration gradient towards the spiracles to be released into the atmosphere
- Insects use rhythmic abdominal movements to move air in and out of the spiracles
22
Q
Limiting water loss in Insects
A
- Close spiracles using muscles if losing too much water
- Waterproof, waxy cuticle all over body and tiny hairs around spiracles, both of which reduce evaporation
- Small surface area:volume ratio
23
Q
Limiting water loss in plants (Stomata)
A
- Stomata are usually kept open during day to allow gaseous exchange
- Water enters the guard cells, making them turgid, which opens stomatal pore
- If plant starts to get dehydrated, guard cells lose water and become flaccid, which closes the pore
- Waterproof covering
24
Q
Limitng water loss in Xerophytes
A
- Plants adapted for life in warm, dry or windy habitats where water loss is a problem
- Stomata sunk in pits to trap water vapour, reducing concentration gradient of water between leaf and air (this reduces evaporation of water from leaf)
- Layer of hairs on the epidermis to trap water vapour round the stomata
- Curled leaves with the stomata inside, protecting them from wind (windy conditions increase rate of diffusion and evaporation)
- Reduced number of stomata, so there are fewer places for water to escape
- Thicker waxy, waterproof cuticles on leaves and stems to reduce evaporation
25
Plants adaptations for rapid diffusion
* Many small pores called stomata, and so no cell is far from stoma so diffusion pathway is short
* Numerous interconnecting air-spaces that occur throughout the mesophyll so that gases can readily come in contact with mesophyll cells
* Large surface area of mesophyll cells for rapid diffusion
26
Structure of gas exchange system
* As you breathe in, air enters the **trachea**
* Trachea splits into 2 **bronchi**- one **bronchus** leading to each lung
* Each bronchus then branches off into **smaller tubes** called **bronchioles**
* Bronchioles end in **small air sacs** called **alveoli** (this is where gases are exchanged)
* **Ribcage**, **intercostal muscles** and **diaphragm** all work together to move air in and out
27
Intercostal muscles
* Found between ribs
* Internal intercostal muscles are on inside of extrenal intercostal muscles
28
Ventilation
* Consists of inspiration and expiration
* Controlled by movements of diaphragm, internal and external intercostal muscles and ribcage
29
Inspiration
* **External intercostal** and **diaphragm muscles contract**
* Causes the ribcage to move **upwards** and **outwards** and the **diaphragm** to **flatten**, **increasing** the **volume** of the **thoracic cavity** (space where lungs are)
* As volume of thoracic cavity increases, **lung pressure decreases** to below atmospheric pressure
* Air will always flow from an area of higher pressure to an area of lower pressure (**down a pressure gradient**) so air flows down trachea and into lungs
* Inspiration is an **active process**- requires energy
30
Expiration
* **External intercostal** and **diaphragm muscles relax**
* Ribcage moves **downwards** and **inwards**, and the **diaphragm curves** again
* Volume of **thoracic cavity** **decreases**, causing air pressure to **increase** to above atmospheric pressure
* Air is forced **down** the **pressure gradient** and out of the lungs
* **Passive process**-no energy required
31
Forced Expiration
* **External intercostal muscles** **relax** and **internal intercostal muscles contract**, pulling the ribcage further **down** and **in**
* Movement of 2 sets of **intercostal muscles** is said to be **antagonistic** (opposing)
* Requires energy
32
Alveoli
* Microscopic air sacs where gas exchange occurs (millions found in the lungs)
* Alveoli surrounded by a network of capillaries
33
Respiratory gases in tracheal system
* Along a **diffusion gradient**- cells **respire**, oxygen is used up so **concentraion** towards ends of tracheoles **falls**
* This creates a **diffusion gradient** that causes gaseous oxygen to diffuse from the atmosphere along the **trachea** and **tracheoles** to the cells
* **CO2** is produced during respiration which creates diffusion gradient in **opposite direction**
* Causes gaseous CO2 to diffuse along the tracheoles and trachea from cells to atmosphere (diffusion more **rapid** in **air** than in water)
* **Mass transport**= contaction of muscles in insects can squeeze the trachea enabling **mass movements** in and out
* This further **speeds up** exchange of respiratory gases
* During major activity, **muscle cells** around tracheoles **respire** (carry out some **anaerobic respiration**)
* This produces **lactate** which is **soluble** and lowers water potential of muscle cells
* Water therefore moves into **cells** from tracheoles by **osmosis**
* Water in ends of tracheoles **decreases** in **volume** and in doing so **draws air** further into them
* Means final diffusion pathway is in a **gas** rather than a liquid , so diffusion is more **rapid**
* **Increases rate** at which air moves and **evaporation**
34
Alveoli Structure
* Wall of each **alveolus** is made from a **single layer** of thin, flat cells called **alveolar epithelium**
* Walls of capillaries are made from **capillary** **endothelium**
* Walls of alveoli contain a **protein** called **elastin**
* Elastin is **elastic**- helps alveoli to return (**recoil**) to their normal shape after inhaling and exhaling air
* **Reduced distance**, **thin walls**, **steep concentration gradient**, **large surface area**
35
Movement of oxygen and carbon dioxide through the gas exchange system
* **Air** (containing oxygen) moves down the **trachea**, **bronchi** and **bronchioles** into the **alveoli**
* This movement happens **down** a **pressure gradient**
* **Oxygen** then moves into the blood where it can be transported round the body (happens **down** a **diffusion gradient**)
* **Carbon dioxide** moves down its own diffusion and pressure gradients, but in the **opposite direction** to oxygen so that it can be **breathed out**
36
Gas exchange in the Alveoli
* Oxygen **diffuses out** of the alveoli, across the **alveolar epithelium** and the **capillary endothelium**, and into a compound called **haemoglobin** in the blood
* Carbon dioxide **diffuses into** the alveoli from the blood
37
Factors affecting the rate of diffusion
* **Thin exchange surface**- alveolar epithelium is only **one cell thick** so **short diffusion pathway** (speeds up diffusion)
* **Large surface area**- there a millions of alveoli which speeds up rate of gas exchange
* **Steep concentration gradient** of oxygen and carbon dioxide between the alveoli and the capillaries, which increases the rate of diffusion
* **Constantly maintained** by **flow** of **blood** and **ventilation**
38
Tidal Volume
Volume of air in each breath
39
Ventilation Rate
Number of breaths per minute
40
Forced Expiratory Volume (FEV1)
Maximum volume of air that can be breathed out in one second
41
Forced Vital Capacity (FVC)
Maximum volume of air it is possible to breathe forcefully out of the lungs after a really deep breath in
42
Effect of lung diseases on gas exchange
* **TB**, **fibrosis**, **asthma** and **emphysema** all reduce the rate of gas exchange in the alveoli
* Less oxygen is able to **diffuse** into the bloodstream, the body cells recieve less oxygen and the rate of **aerobic respiration** is **reduced**
* Means **less energy** is **released** and sufferers often feel **tired** and **weak**
43
What are restrictive diseases and how to interpret on graph?
* Diseases which make it difficult to fully breathe in (fibrosis)
* On graph, **FVC** would be severely reduced because it's hard to get air into lungs
* **FEV1** is likely to high compared to FVC beacuse someone with a restrictive disease is able to breathe out fairly normally
44
Risk factors
* Something that increases chance of getting a disease, doesn't mean you will definitely get it though
* Also other factors need to be taken into consideration when drawing conclusions
45
Correlations of Lung Diseases
46
Risk Factors of Lung Disease
47
