b3- movements of molecules in and out of cells Flashcards
How does diffusion work in cell membranes?
Diffusion allows substances to pass into or out of cells across the cell membrane- but they must be dissolved and there must be a concentration gradient present.
What is diffusion?
The process by which particles of a substance spread out from each other, moving from a region of high concentration to a region of low concentration down a concentration gradient. The particles must be free to move for this to happen.
What is active transport?
It is the process which is used to move dissolved molecules from low concentration to high concentration against a concentration gradient. Unlike diffusion, this process requires energy from respiration.
How does active transport work?
It is carried out by a series of protein carriers within the cell membrane. These have a binding site, allowing a specific dissolved substance to bind to the side of the membrane where it is at a lower concentration. Energy from respiration then changes the shape of the protein so that it releases the substance onto the other side of the membrane.
What is the advantage of active transport?
It allow cells to absorb dissolved substances from very dilute solutions, which is otherwise an impossible process.
Examples of where active transport is used:
Root hair cells- absorbing mineral ions from the soil
Small intestine villi cells- used alongside diffusion to maximise the absorption of glucose and other substances.
What is osmosis?
It is the movement of water molecule from a dilute solution (with a high proportion of water molecules) to a more concentrated solution (with a low proportion of water molecules) across a partially permeable membrane.
What is a partially permeable membrane?
It allows small soluble molecules like water to pass through it freely, but prevents larger molecules from doing so. In a cell, the cell membrane acts as a partially permeable membrane.
What happens during osmosis?
Water molecules move across the membrane at random in both directions, but more water moves from a high concentration to a low concentration.the overall net effect is that water levels in the higher concentrated side drop, whilst rise on the other side. Eventually the concentrations of water on either side become equal, so effectively there is no overall movement of water.
What happens if a cell has a more dilute solution inside it than outside it?
The overall movement of water is out if the cell, which in animal cells would cause the cell to shrivel up, whilst in plant cells this would cause the membrane and cytoplasm to shrink away from the cell wall, making the plant cell flaccid (limp)
What happens if a cell has a more concentrated solution inside it than outside it?
Then the overall movement of water is into the cell. In plan cells, this makes it swell as the cytoplasm and membrane push against the cell wall, which resists further expansion so supports be cell which becomes turgid. Animal cells don’t have a cell wall so the cell will burst, which is why it is important that the concentration of water outside cells is constant.
What does diffusion need to work efficiantly?
A small distance over which substances have to diffuse, and an organism which has a large surface area compared to its volume.
Common features of exchange surfaces include:
Having a large surface area- achieved through a folded surface
A thin exchange surface for a short diffusion distance
A good blood supply due to an extensive capillary network in exchange organs- distributes exchange materials and maintains a concentration gradient
Good ventilation through breathing- maintains concentration gradient
How are villi adapted for the maximum absorption of digested food molecules:
- the folded villi greatly increase surface area of intestine
- the villi are made of a single layer of thin cells- short diffusion distance
- there is an extensive blood capillary network beneath the villi to distribute absorbed food molecules
What happens during extended periods of exercise?
A lot of glucose is used up during respiration
The body generates heat as they respire more
They sweat more to cool down
What is the negative effects of sweating?
You lose water and mineral ions, with loss of water occurring at a much faster rate potentially leading to dehydration at it disturbs the balance of ions and water.
Why is it important to maintain the correct balance of mineral ions?
It is essential for cells to function efficiently and effectively. If the balance changes it could lead to too much water moving in or out of the cells which damage them.
What is the effect of drinking sports drinks?
.sports drinks contain water, sugar and mineral ions at levels which are most effective at maintaining performance - rehydrating the athlete as well as replacing the glucose and maintaining the correct ion/water balance for cells to function effectively. This helps the athlete to continue exercising for longer
How do you evaluate sports drinks?
Sports drinks manufacturers often make claims about the performance benefits of using their branded sports drinks, but it is important that these claims are evaluated based on valid data from controlled trials of a large sample of athletes. Depending on the ratio of substances, sports drinks will have different effects.
What are the lungs adapted for?
ventilation – the movement of air into and out of the lungs
gas exchange – the ‘swapping’ of gases between the alveolar air and the blood
What is the anatomy of the lungs?
The lungs are located within the upper part of your body called the thorax. They are surrounded by the ribcage (which protects them) and in between the ribs are intercostal muscles which play a role in ventilating the lungs.
Beneath the lungs is a muscular sheet called the diaphragm. This separates the lungs from the abdomen of the body and also plays a role in ventilating the lungs
What happens when air enters the body?
Within the lungs is a network of tubes through which air is able to pass. Air is firstly warmed, moistened and filtered as it travels through the mouth and nasal passages. It then passes through the trachea and down one of the two bronchi and into one of the lungs.
After travelling into the many bronchioles, it finally passes into some of the millions of tiny sacs called alveoli, which have the specialised surfaces for gas exchange.
What happens when you inhale?
The intercostal muscles contract, expanding the ribcage outwards and upwards.
The diaphragm contracts, pulling downwards to increase the volume of the chest.
Pressure inside the chest is lowered and air is sucked into the lungs.
What happens when you exhale?
The intercostal muscles relax, the ribcage drops inwards and downwards.
The diaphragm relaxes, moving back upwards, decreasing the volume of the chest.
Pressure inside the chest increases and air is forced out.
How do negative pressure ventilators work? e
the patient is placed in an airtight machine from the neck down, and a vacuum is created around the thorax. This creates a negative pressure, which leads to the expansion of the thorax and a decrease in pressure. As a result, air is drawn into the lungs. As the vacuum is released, the elasticity of the lungs, diaphragm and chest wall cause exhalation.
How do positive pressure ventilators work?
air is forced into the lungs through a tube which is inserted into the trachea. As the ventilator pumps air in, the lungs inflate. When the ventilator stops, the elasticity of the lungs, diaphragm and chest wall cause exhalation.
What are the advantages of negative pressure ventilators?
Effective at treating many polio patients over the years
What are the disadvantages of negative pressure ventilators?
Patient is confined to the machine
The vacuum on full-body machines can affect the abdomen, leading to the pooling of blood in lower parts of the body
What are the advantages of positive pressure ventilators?
Useful during operations, where surgeons need access to the body
Effective at ventilating the lungs
What are the disadvantages of positive pressure ventilators?
Long-term ventilation requires the tube to be surgically inserted into the trachea through the neck
What is a haemoglobin?
The red protein found in red blood cells that transports oxygen around the body.
What is a oxyhaemoglobin?
A chemical formed when haemoglobin bonds with oxygen.
How does carbon dioxide diffuse out of the blood?
Blood arriving in the alveoli has a higher carbon dioxide concentration which is produced during respiration by the body’s cells. However, the air in the alveoli has a much lower concentration of carbon dioxide, meaning there is a concentration gradient which allows carbon dioxide to diffuse out of the blood and into the alveolar air.
How does oxygen diffuse into the blood?
blood arriving in the alveoli has a lower oxygen concentration (as it has been used for respiration by the body’s cells), while the air in the alveoli has a higher oxygen concentration. Therefore, oxygen moves into the blood by diffusion and combines with the haemoglobin in red blood cells to form oxyhaemoglobin.
What is the differences in percentages of inhaled and exhaled air?
Oxygen 21 % of inhaled air 16% of exhaled air Carbon dioxide 0.04 % of inhaled air 4 % of exhaled air Nitrogen 79 % of inhaled air 79% of exhaled air
What are the adaptions of the alveoli?
They are folded, providing a much greater surface area for gas exchange to occur.
The walls of the alveoli are only one cell thick. This shortens the diffusion distance across which gases have to move.
Each alveolus is surrounded by blood capillaries which ensure a good blood supply. This is important as the blood is constantly taking oxygen away and bringing in more carbon dioxide - which helps to maintain the maximum concentration gradient between the blood and the air in the alveoli.
Each alveolus is ventilated, removing waste carbon dioxide and replenishing oxygen levels in the alveolar air. This also helps to maintain the maximum concentration gradient between the blood and the air in the alveoli.
What is the role of the roots?
The role of the roots is to absorb water from the soil by osmosis and dissolve mineral ions from the soil by active transport.
What happens to the water and mineral ions in the plant?
The mineral ions are transported around the plant where they serve a variety of functions, whilst the water is transported to be used as a reactant in photosynthesis, as well as to cool the leaves by evaporation and support the leaves and shoots by keeping cells rigid.
What are the adaptions of the root hair cell?
the tube-like protrusion provides a greater surface area across which water and mineral ions can be exchanged
the tube-like protrusion can penetrate between soil particles, reducing the distance across which water and mineral ions must move
the root hair cell contains lots of mitochondria, which release energy from glucose during respiration in order to provide the energy needed for active transport
What is the job of the leaves?
One of the main functions of leaves is as a major site of photosynthesis – to produce glucose from water and carbon dioxide with the input of energy from sunlight.
What is the adaption of the leaves?
Flattened shape- Larger surface area to absorb light and carbon dioxide
Thin -Short diffusion distance for carbon dioxide to diffuse into leaf cells, and oxygen to diffuse out of leaf cells
Stomata -Can open to allow diffusion of carbon dioxide into the leaf from the atmosphere, and the diffusion of oxygen and water vapour out of the leaf
What is the internal structure of a leaf (Label from top to bottom, on diagram if available)
Waxy cuticle, Upper Epidermis, Palisade mesophyll, air spaces, spongy mesophyll, lower epidermis, waxy cuticle. Stomata is the gap at the bottom, with the guard cells with the chloroplasts either side of it.
What are the adaption of the internal structure of a leaf?
Internal air spaces in spongy mesophyll layer- Increases surface area of leaf to absorb more carbon dioxide
Guard cells around stomata - Allows the size of stomata to be adjusted (eg they close the stomata to prevent wilting)
How do the guard cells work?
the guard cells open and close the stomata depending upon the amount of potassium ions present in the fluid in the cell. The more potassium ions that are present, the more the cells become turgid (swollen) and the bigger the opening.
What are the guard cells and stomata used to control?
The size of the opening is used by the plant to control the rate of transpiration and therefore limit the levels of moisture in the leaf which prevents it from wilting.
