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Terms in this set (57)
What two things do plants and animals both require?
Oxygen and carbon dioxide
What happens if there is inadequate oxygen in animals?
No oxygen → no respiration → no energy (ATP) → cells die!
What happens if there is too much carbon dioxide in animals?
Too much carbon dioxide accumulates in blood →
Decreases the pH of the blood →
Affected cellular membranes and enzymes →
Direct diffusion - planarians
Planarians are organisms that allow their cells to exchange gases DIRECTLY with their environment (we can't and so we don't)
What happens in between animals taking in oxygen and expelling carbon dioxide?
• Active movement of air/ water over an exchange surface
• Remember - small uncharged molecules move easily through the phospholipid bilayer of membranes (i.e. oxygen and carbon dioxide)
What does diffusion (gas exchange) depends on?
2. Surface area
3. Concentration gradient
4. Distance of diffusion
True of False - Warm salty water has less oxygen than cool fresh water
True, Warm salty water has less oxygen than cool fresh water
True of False - Air contains less oxygen than water
False, Water contains less oxygen than air
Explain the effects of oxygen being at different heights
- Above 4000m the air is thinner and humans have trouble breathing
- Thus - high altitudes = less oxygen
- This is because oxygen density in the air is much less
- However, it is important to know that the % of oxygen in the air does not change (21% of total gases present)
What are types of gas exchange surfaces?
- Body surface
What are features of effective gas exchange surfaces?
- Large surface area
- A thin barrier for the gases to diffuse across
- A continuous supply of fresh oxygen
- Removal of the gas after transfer
- A continuous fresh supply and the removal immediately after diffusion helps main the concentration gradient
- Water must keep moving over the gills
- Gills MOVE through the water
- Water is MOVED over the gills (this option uses less energy).
Explain counter current flow in animals
- The water and blood flow in opposite directions creating a concentration gradient.
- Oxygen moves passively from the water into the blood.
In very hot weather fish can sometimes be seen 'gasping' for air at the surface. Why?
Because there is less oxygen in the water on hot days because in hot water the oxygen evapotates out causing the fish to breath the oxygen from the air whilst still keeping its gills in the water.
Explain testing for oxygen in animals
- Water animals regularly test the amount of oxygen in their blood.
- Carbon dioxide is easily diffusion into water and this makes oxygen regulation more sensitive than carbon dioxide testing.
What are the advantages for breathing air for oxygen.
Air weighs less than water and is therefore easier to move.
What are the disadvantages for breathing air for oxygen.
- Oxygen needs to dissolve in a liquid before diffusion across membrane can occur
- Evaporation of the liquid contributes to water loss and dehydration.
Explain mouth breathing for amphibians (e.g. frogs).
- Draw air into their mouth →
- Close their mouth and force air into lungs →
- Let air out
Explain skin diffusion for amphibians (e.g. frogs)
Frogs have the ability to exchange gases both in water and on land and can use different areas of their bodies as respiratory surfaces
Explain insects and how they ventilate
- Air passively enters spiracles on the side of their body →
- Tracheal tubes carry air DIRECTLY to the cells
- There is NO need for red blood cells to carry oxygen!
- Do insects have blood as a transportation agent?
Explain the journey of the human lungs
Nasal cavity, Pharynx (just before the epiglottis), Larynx, Trachea, Bronchus, Bronchiole, Alveoli duct, Alveoli sac, Alveoli, Trachea, Tracheal cells secrete mucus and move cilia to trap and expel dust
What are the parts in the human respitory sysem that assist in the trapping and expulsion of dust particals from the airways?
Tracheal cells (mucus + cilia)
Good gas exchange
- Large SA
- Thin barrier between cells and fluid
- Air actively inhaled
- Waste air removed (carbon dioxide)
The diaphragm is a group of muscles that actively move to suck air into the lungs
- Ribs move downwards
- Diaphragm relaxes (at rest) and moves up
- When the muscles relax the air is expelled
- Ribs move outwards
- Diaphragm contracts downwards
Why during exercise air is actively expelled?
Because the carbon dioxide has built up in the body there for it needs to be removed for urgently so there is more room for oxygen to be breathed in.
True or false - When we breathe, we do not exhale ALL the air there is in the alveoli.
- Air is always left in the alveoli to prevent small air sac collapsing
- Think of the balloon example!
- Surfactant is a thin layer of mucus that acts to strengthen the alveoli sacs
- We need surfactant because oxygen needs to dissolve into a solution before it can be transported in our body
What happens to the air in the alveoli?
- All gas exchange surfaces are closely linked to blood vessels
- Most organisms have cells that contain respiratory pigments
- These pigments ink to the oxygen and carry it around the organism
- Respiratory pigments usually contain a metal
Red blood cells contain haemoglobin (Hb):
- In lungs
- Hb + 4O2 → Hb(O2)4
- Hb(O2)4 → Hb + 4O2
At rest, cells usually use only 25% of the oxygen in the red blood cell:
- The rest is stored in the Hb
During exercise the concentration gradient is greater (there is less oxygen available to the muscle cell), thus 75% of the oxygen is removed from the Hb in the red blood cell
- Myoglobin is a respiratory pigment in the muscle - specific unlike haemoglobin
- It is a form of muscle Hb and it stores oxygen in the muscle until all other sources have been used up
What is the advantage of muscle haemoglobin storing oxygen in the muscles? By storing oxygen in the muscles the red blood cells don't need to travel oxygen to them as much as it is already there
Explain removal of carbon dioxide in animals
- 7% is dissolved in plasma
- 23% combined with Hb
- 70% converted into hydrogen carbonate ions (HCO3-) (in red blood cells) and transported in plasma
- Once in the lungs, carbon dioxide is removed and exhaled.
Explain marine mammals
- Marine mammals have
- More myoglobin and haemoglobin
- Larger blood volumes
- Good blood pH buffer to tolerate bicarbonate ions in the body.
Explain the gas exchange in plants during the day
During the day: the rate of photosynthesis (making food) is usually greater than the rate of respiration (burning food).
- Thus, more carbon dioxide is used than can be produced by cellular respiration
- Consequently, plants take up more carbon dioxide from the environment to maintain an adequate rate of photosynthesis
- Some of the oxygen produced during photosynthesis is used in cellular respiration
- The remainder oxygen diffuses out of the leaf
Explain the gas exchange in plants at night
At night: when photosynthesis not occurring, plants take in oxygen and release carbon dioxide
- It is important to note that carbon dioxide is both a nutrient and waste product of green plants
- RESPIRATION OCCURS ALL THE TIME
Explain the gas exchange of simple plants e.g. Mosses
- Leaves are small and extremely thin (only 1- cell thick)
- Each cell is in direct contact with the surrounding environment
- Oxygen and carbon dioxide can easily diffuse directly between the air and the contents of each cell
Explain gas exchange in complex plants e.g. vascular plants
- Exchange of oxygen and carbon dioxide occurs in the leaves, stems and roots
- Exchange occurs via diffusion through stomata (singular = stoma)
- Rate of movement of gases between air spaces AND the external environment is regulated by the stomata
- When stomata are closed, the exchange of oxygen, carbon dioxide AND water vapour between the plant and its environment virtually stops
- Only small quantities of gases are able to pass directly through the epidermis and the overlying cuticle (the outer waxy layer)
Are plant cells loosely packed?
Yes, plant cells are loosely packed, allowing diffusion of gases through intercellular spaces, which are filled with air
Which concentration gradient do gases move along?
Gases move along concentration gradients which is always high to low
Animal gas exchange
Gases move along concentration gradients - always high to low
Plant gas exchange
- Oxygen in → Carbon dioxide out (respiration)
- Carbon dioxide in → Oxygen out (photosynthesis)
Stomata are tiny pores in the epidermis, bordered by two highly specialised epidermal cells called guard cells
Where is stomata located?
- Stomata can be located on any part of a plant except the roots, but in most species they are most abundant on the surface of leaves. Because they have bigger surface area fro sunlight exposure.
Describe the appearance of stomata
- The number and size of stomata on a leaf vary according to the plant species and the environmental conditions under which it has grown
- In a typical plant, most stomata are on the underside of the leaves, away from the drying effect of the sun's rays (thermal energy).
are stomata in floating aquatic plants, such as water lilies confined to the upper epidermis?
Yes, stomata in floating aquatic plants, such as water lilies, are confined to the upper epidermal because there is more gas in the air and its not scared of dehydration because it can absorb water from where it lives.
Where are stomata in eucalyptus?
In plants such as eucalyptus, which are adapted to dry conditions, stomata are often in sunken pits in the surface of the leaves - this reduces the direct flow of air across them and so reduces water loss.
Evaporation of H2O from a plant is called
What is the
Process: Roots → Stems →Leaves→Out of leaves
What are the guard cells in the stomata filled with?
Guard cells in the stomata are filled with water so carbon dioxide can get in and photosynthesis occurs. If water was evaporated the guard cells would close and photosynthesis would not occur.
What are the structural features of guard cells?
- Joined at their ends in pairs
- Cell walls are thicker on the side adjacent to the stoma
- Bands of inelastic fibres run around each cell wall
Explain guard cells and water
- When water passes into the guard cells, their internal fluid pressure, or turgor, increases
- This causes them to expand in the only direction possible: lengthways
- The guard cells buckle and open the stoma
Explain the process of guard cells in water
Guard cells filled with water → turgid → open
Guard cells NOT filled with water → flaccid → closed
What conditions favour the opening of stomata
Abundant of water, light and low internal carbon dioxide concentrations
Explain evaporation of water (loss of water)
- Plants (terrestrial) must keep water lost to a minimum
- Moist surfaces plants use for gas exchange are the major site of water loss
- The stomata must act to balance the plant's need to obtain carbon dioxide for photosynthesis against the dangers of drying out
Explain plants during day and night
During day light:
- Plant photosynthesise, large volumes of carbon dioxide and oxygen are exchanged with the environment through open stomata
- Stomata closed if it is very hot and dry (but this will drastically reduce the rate of photosynthesis)
- Stomata are usually closed
- In the epidermis of green stems, there are stomata through which gas exchange takes place
- In woody stems (and mature roots), the epidermis is replaced by a layer of cork cells that are water proof and air proof
- However, air passes freely through groups of loosely packed cells to the cells beneath
- these cells are called lenticels
- Roots exchange gases with the air in spaces in the soil
- Oxygen readily diffuses into the film of moisture surrounding root hairs, and then into the roots themselves
- When soil is waterlogged due to excessive rain or poor drainage, the spaces in the soil are filled with water instead of air
Explain aquatic plants
- In aquatic plants, roots are often continuously submerged
- Oxygen diffuses from aerial parts of the plant into the submerged organs
- Some aquatic plants show adaptations that help in gas exchange (this will be discussed later in the year)
- Pondweed's and water hyacinths float on water because the leaf stalks are swollen with large, air-filled intercellular spaces
- Mangroves have specialised roots called penumatophores (containing large intercellular spaces) that assist in gas exchange
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