Movement In And Out Of Cells Flashcards
What is diffusion?
Diffusion is the movement of particles from an area of higher concentration to a region of lower concentration down a concentration gradient.
what is meant by a partially permeable membrane?
A membrane which allows small molecules to pass through while blocking large ones.
Describe what happens to a RBC placed in pure water?
when a RBC is placed in pure water, which is a hypotonic solution, the cell has a lower amount of water molecules compared to the water, hence the water enters into the cell causing it to swell and eventually burst due to having no cell wall.
Name one substance that enters a plant root hair cell by active transport?
mineral ions
State two differences between diffusion and active transport.
-Diffusion does not require energy while active transport does.
-In active transport, particles travel against the concentration gradient, while in diffusion, particles travel down along the concentration gradient.
What will happen to a plant placed in a concentrated sugar solution?
When a plant cell is placed in a concentrated sugar solution, which is a hypertonic solution, water from the cell travels out because the cell has a higher water potential compared to the sugar solution; the cell will eventually become dehydrated and shrivel up, becoming plasmolysed.
Why does active transport require energy?
active transport requires energy in the form of ATP because particles travel against the concentration gradient, travelling to a region of their lower concentration from a region of their higher concentration.
Explain the process of osmosis and how it affects plant cells in:
i) pure water
Osmosis is the movement of water molecules from a region of their higher concentration to a region of their lower concentration through a semi-permeable membrane. When a plant cell is surrounded with pure water, which has a higher concentration of water molecules compared to sap vacuole, the water enters the vacuole and the sap vacuole pushes against the cell wall, making the cell turgid due to the water pressure.
A student placed some potato strips in distilled water and others in a salt solution.
i) Describe what will happen to the strips in each case and explain why.
ii) What is the biological term for this process?
i) The potato strips in distilled water will swell up and become turgid because the distilled water will have a higher concentration of water particles compared to the potato, causing water to enter the potato cells. The potato strips placed in the salt solution will become flaccid as the solution will have a lower water potential compared to the cell, causing water from the cell to move out, which will dehydrate the cells.
ii) Osmosis
Compare the processes of diffusion, osmosis, and active transport in terms of:
i) energy requirement
ii) direction of movement
iii) substances moved
Osmosis: no energy required, along concentration gradient, water molecules
Diffusion: no energy required, along concentration gradient, gas and liquid particles. Active Transport: energy in form of ATP, against concentration gradient, gas, solid and liquid particles.
A student places a Visking tubing filled with sugar solution into a beaker of water.
i) Predict what will happen over time and explain why.
ii) Name the process involved.
i) The water will move into the visking tube as it has less water molecules compared to the beaker of water, travelling through the partially permeable tubing.
ii) Osmosis
Explain why large molecules like starch cannot pass through a cell membrane.
-The cell membrane is partially permeable, allowing only certain substances to pass through.
-Small molecules like water, oxygen, and glucose can pass through easily.
-Starch is a large, complex molecule made of many glucose units.
-It is too large to fit through the small pores in the membrane.
-Therefore, starch cannot pass through the cell membrane by diffusion.
How does temperature affect the rate of diffusion?
*The higher the temperature, the faster molecules move
*This is because they have more kinetic energy
*This results in more collisions against the cell membrane and therefore a faster rate of movement across them
What is the main difference between osmosis and diffusion?
Osmosis only takes place in water while diffusion takes place in both liquids and gases.
Name one example of active transport in the human body.
What is meant by the term turgidity in plant cells?
Turgidity is the state of a plant cell when it is full of water and swollen due to osmosis. Water enters the cell and fills the vacuole, pushing the cytoplasm and cell membrane firmly against the cell wall. This pressure is called turgor pressure.
Explain the role of the vacuole in maintaining cell turgidity in plant cells.
The vacuole in a plant cell is filled with cell sap, which contains water, sugars, and salts. When water enters the cell by osmosis, it collects in the vacuole, causing it to swell. As the vacuole enlarges, it pushes the cytoplasm and cell membrane against the cell wall, creating turgor pressure. This pressure keeps the cell turgid (firm), helping the plant stay upright and supported.
Describe the process of active transport and give an example of where it occurs in plants.
Compare osmosis and diffusion in terms of the types of substances that are moved across membranes and their energy requirements.
Osmosis is the movement of water molecules along a partially permeable membrane, requiring no energy. Diffusion is the movement of gas and liquid particles freely, requiring no energy.
What factors affect the rate of diffusion, and how do they influence the process?
Factors affecting diffusion include temperature, distance, surface area and concentration gradient. The more the temperature, the higher the rate of diffusion. The less the distance, the higher the rate of diffusion. The more the surface area, the higher the rate of diffusion. The steeper the concentration gradient, the higher the rate of diffusion.
A scientist is investigating the effect of different concentrations of salt solution on plant cells.
i) How would you design an experiment to measure the effect of varying salt concentrations on the mass of plant tissue?
I would take 3 solutions with different salt concentrations in each, and add strips of potato in each. Before adding the strips, would weigh all three potato strips and record their starting weight, after keeping the potatoes in the solutions for a few hours, i would weigh them again and find the difference between the starting weight of each potato and the ending weight and compare them.
A solution of sugar in water is separated from pure water by a semi-permeable membrane.
i) What would happen to the sugar solution over time?
ii) Name the process involved and explain why it happens.
i) The sugar solution would increase in volume.
ii) Osmosis is taking place; since the pure water has more water molecules then the sugar solution, water will travel towards the sugar solution until equilibrium is reached, increasing the volume of the sugar solution and decreasing the volume of the pure water.
List three factors that affect the rate of diffusion.
temperature, surface area, concentration gradient, distance
How does temperature affect the rate of diffusion?
A higher temperature will increase the rate of diffusion. This is because particles have more energy at higher temperatures, which allows them to move more quickly and with more force. This increased movement and force leads to more collisions between particles, which increases the rate of diffusion. For example, hot water will dissolve sugar faster than cold water.
How does the concentration gradient affect the rate of diffusion?
-A concentration gradient is the difference in concentration of a substance between two areas.
-The greater the difference, the steeper the gradient.
-A steeper concentration gradient causes particles to diffuse faster.
-If the concentration gradient is small, diffusion happens more slowly.
-So, the larger the concentration gradient, the faster the rate of diffusion.
What is the relationship between the size of particles and the rate of diffusion?
-Smaller particles diffuse faster than larger particles.
-This is because smaller particles have less mass and can move more easily and quickly.
-Larger particles move more slowly, so their rate of diffusion is slower.
-Therefore, the smaller the particle, the faster the rate of diffusion.
How does the surface area of a membrane influence the rate of diffusion?
-A larger surface area provides more space for particles to pass through.
-This allows more particles to diffuse at the same time.
-Therefore, a greater surface area results in a faster rate of diffusion.
-If the surface area is small, fewer particles can pass through, and diffusion is slower.
-So, the larger the surface area, the faster the rate of diffusion.
Explain how an increase in temperature leads to a faster rate of diffusion.
-An increase in temperature gives more energy to the particles.
-This causes the particles to move faster and collide more often.
-Faster movement means particles spread out more quickly from an area of high concentration to low concentration.
-As a result, the rate of diffusion increases with higher temperature.
-Higher temperature = faster diffusion.
Describe how the concentration gradient influences the movement of substances in and out of cells.
-The concentration gradient is the difference in the concentration of a substance between two areas (inside and outside the cell).
-Substances move from a region of higher concentration to a region of lower concentration.
-The steeper the concentration gradient, the faster the movement of substances across the cell membrane.
-This allows cells to efficiently take in needed substances (like oxygen and glucose) and remove waste products (like carbon dioxide).
-So, the concentration gradient drives diffusion, helping maintain balance in and out of the cell.
A cell is placed in a high concentration of glucose solution. Explain how the surface area to volume ratio of the cell will affect the rate at which glucose enters the cell.
-A larger surface area to volume ratio allows for faster diffusion of glucose into the cell, as more glucose molecules can pass through the cell membrane at once.
-A smaller surface area to volume ratio slows down glucose entry, as fewer molecules can diffuse into the cell at the same time.
Explain why larger molecules (like starch) diffuse more slowly than smaller molecules (like oxygen).
-Larger molecules, like starch, are much bulkier and have more atoms, which makes them less mobile compared to smaller molecules, like oxygen.
-Smaller molecules can move more easily through the spaces between particles, allowing them to diffuse faster
Discuss how membrane thickness affects the rate of diffusion and provide an example of this in living organisms.
-Thinner membranes lead to faster diffusion because molecules travel a shorter distance.
-Thicker membranes lead to slower diffusion due to the greater distance molecules must travel.
-An example is the alveolar membrane in the lungs, which is thin to allow fast and efficient gas exchange.
A student is conducting an experiment to investigate how temperature affects the rate of diffusion.
i) Outline the procedure the student should follow, and describe what the expected results would be.
The student will prepare several containers with the same type of diffusion medium (e.g., agar jelly or water).
The student will set up a water bath to heat or cool the containers to different temperatures (e.g., cold, room temperature, and warm).
The student will place the diffusion medium in each container and allow it to equilibrate to the desired temperature.
A small amount of a diffusing substance (e.g., potassium permanganate or food colouring) will be placed in the centre of each container.
The student will observe and measure how far the substance diffuses from the centre at regular intervals (e.g., every 2 minutes).
The student will control variables such as the amount of diffusing substance, the size of the container, and the duration of the experiment.
At higher temperatures (e.g., 40-50°C), the substance will diffuse faster. This happens because molecules move more rapidly when heated, increasing the rate of diffusion.
At room temperature (e.g., 20-25°C), the diffusion rate will be moderate.
At lower temperatures (e.g., 5°C), the substance will diffuse more slowly due to slower molecular movement at lower temperatures.
A scientist observes that the diffusion of oxygen into a cell occurs more quickly when the cell is exposed to more oxygen outside.
i) Explain why this happens and how the concentration gradient affects diffusion.
The rate of diffusion of oxygen into a cell is faster when the concentration of oxygen outside the cell is higher because of the concentration gradient.The diffusion of oxygen into a cell occurs more quickly when there is a greater difference in oxygen concentration (a steeper concentration gradient) between the outside and inside of the cell.
A larger concentration gradient allows oxygen molecules to move more rapidly into the cell, speeding up the process of diffusion.
Two beakers are filled with water, one containing sugar and the other containing salt.
i) How would the rate of diffusion compare in each beaker, and which factors (other than concentration) might influence this rate?
The rate of diffusion will likely be faster in the salt solution compared to the sugar solution due to the smaller size of salt molecules.
Factors influencing diffusion include temperature, molecular size, solvent properties, surface area, and concentration gradient.
A student places a crystal of potassium permanganate in a beaker of water.
(a) Describe what they would observe over time.
(b) Explain why this is an example of diffusion.
(c) How could the student speed up the rate of diffusion?
a) The student would observe the purple colour of the potassium permanganate crystal slowly spreading out from the crystal into the water. Over time, the entire beaker of water would gradually turn a uniform light purple colour.
(b) This is an example of diffusion because the potassium permanganate particles are moving from an area of high concentration (the crystal) to an area of low concentration (the surrounding water), without the need for energy. The particles spread out evenly until they are equally distributed throughout the water.
(c) The student could:
Increase the temperature of the water (heat speeds up particle movement).
Stir the solution to help distribute the particles more quickly.
Crush the crystal to increase its surface area, allowing more particles to diffuse at once.
An experiment is set up with two beakers: one contains cold water and the other warm water. A drop of food dye is added to each.
(a) Predict what will happen in each beaker.
(b) What factor is being tested?
(c) Explain how temperature affects the rate of diffusion.
a) In the beaker with warm water, the food dye will spread out (diffuse) more quickly, and the colour will become evenly distributed faster.
In the beaker with cold water, the food dye will diffuse more slowly, and it will take longer for the colour to spread throughout the water.
(b) The factor being tested is temperature.
(c) Higher temperatures give particles more kinetic energy, causing them to move faster. This increases the rate of diffusion, allowing the dye to spread out more quickly in warm water. In contrast, lower temperatures result in slower-moving particles, which reduces the diffusion rate.
A student cuts equal-sized pieces of potato and places them into different concentrations of sugar solution.
(a) Describe how the student could measure osmosis using these potato pieces.
(b) What results would you expect in pure water, a dilute sugar solution, and a concentrated sugar solution?
(c) How can the student ensure this is a fair test?
a)The student can:
Cut equal-sized potato pieces (same length and thickness).
Measure and record the initial mass of each piece using a balance.
Place each piece into different concentrations of sugar solution (e.g., pure water, dilute, and concentrated).
Leave them for a fixed amount of time (e.g., 30 minutes to 1 hour).
Remove, blot dry, and measure the final mass of each potato piece.
Calculate the change in mass to determine whether water entered or left the cells by osmosis.
(b) Pure water (hypotonic):
The potato gains mass as water enters the cells by osmosis. Cells become turgid.
Dilute sugar solution:
The change in mass may be small or negligible, depending on how close the solution concentration is to that of the potato cells.
Concentrated sugar solution:
The potato loses mass as water moves out of the cells. Cells become flaccid or plasmolysed.
(c)
Use the same volume of solution for each beaker.
Keep all beakers at the same temperature.
Leave all potato pieces in solution for the same amount of time.
An investigation is carried out to compare the uptake of mineral ions by plant roots in the presence and absence of oxygen.
(a) What is the role of oxygen in this process?
(b) Which transport process is being investigated?
(c) What would the results show if active transport is involved?
(a) Oxygen is needed for aerobic respiration in plant root cells. This respiration provides the energy (ATP) required for the active transport of mineral ions from the soil into the roots.
(b) The transport process being investigated is active transport.
(c) If active transport is involved:
In the presence of oxygen, there would be a greater uptake of mineral ions because energy from respiration is available.
In the absence of oxygen, the uptake of mineral ions would be reduced or stop completely, because no energy (ATP) is produced for active transport.
You are given three egg shells with the inner membrane intact, and you place them in different solutions.
(a) How does this model osmosis?
(b) What observations would show that osmosis has occurred?
a) This setup models osmosis because the egg membrane acts like a partially permeable membrane, similar to a cell membrane. It allows water molecules to pass through, but not larger solute particles. When the egg is placed in different solutions (e.g., pure water, dilute solution, concentrated solution), water moves in or out of the egg depending on the concentration gradient—just like osmosis in real cells.
(b) In pure water:
The egg would swell and gain mass as water moves into the egg by osmosis.
In a concentrated sugar or salt solution:
The egg would shrink and lose mass as water moves out of the egg by osmosis.
In an isotonic solution:
There would be little or no change in the size or mass of the egg, as water moves in and out at the same rate.
A student wraps a piece of dialysis tubing filled with starch and glucose and places it in a beaker of iodine and water. After 30 minutes, the beaker turns blue-black, but the inside of the tubing tests positive for glucose.
(a) Which substances moved in and out of the tubing?
(b) What does this tell you about the permeability of the membrane?
a) Iodine moved into the dialysis tubing and reacted with the starch inside, turning it blue-black.
Glucose moved out of the dialysis tubing into the beaker (you can test this by checking the beaker solution with Benedict’s test).
Starch did not move out of the tubing because it is a large molecule.
(b) This shows that the dialysis tubing is selectively (partially) permeable:
It allows small molecules like iodine and glucose to pass through.
It blocks large molecules like starch from passing through.
how does diffusion help organisms?
- obtain many requirements
- get rid of many of their waste products
- carry out gas exchange for respiration
where does the energy for diffusion and osmosis come from?
Energy for diffusion and osmosis comes from kinetic energy of random movement of molecules and ions.
What is osmosis?
Osmosis is the net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane.
how does water move into and out of cells by osmosis?
why is it important that the cells in an animal’s body are surrounded by a liquid with the same conc. as the liquid in the cell?
Animal cells must be in an isotonic environment (same concentration as inside the cell).
This prevents too much water from entering the cell, which could cause it to swell and burst.
It also prevents too much water from leaving the cell, which could cause it to shrink and dehydrate.
An isotonic solution ensures no net movement of water by osmosis.
This helps the cells maintain their shape and function properly.
It is essential for the health and stability of animal cells
when does a plant wilt?
A plant wilts when it loses more water than it can take in. This can happen if:
The plant is not absorbing enough water from the soil.
Water loss through transpiration (evaporation from leaves) is too high.
The plant is in a hypertonic solution, causing water to leave the cells by osmosis.
Wilting occurs because the plant cells lose turgor pressure, making the plant soft, droopy, and lacking rigidity.
what is active transport?
Active transport is the movement of molecules or ions into or out of a cell through a cell membrane from a region of their lower concentration to a region of their higher concentration against a concentration gradient, using energy released during respiration.
What is osmosis?
Osmosis is the net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane.
Why is turgidity important?
-It keeps the plant firm and upright.
-It supports soft tissues like leaves and young stems.
-It helps maintain the shape of the plant cell.
what is a hypotonic solution? give examples. 2m
A hypotonic solution has a lower concentration of solutes than the inside of the cell. Eg. distilled/purifies/soft water
what is a hypertonic solution? give examples. 2m
A hypertonic solution has a higher concentration of solutes than the inside of the cell. Eg. hard/mineral water
what does the term flaccid mean? 1m
Flaccid refers to a state where a plant cell has lost turgor pressure, causing it to become soft and limp. This occurs when a plant cell is placed in a hypertonic solution (one with higher solute concentration than inside the cell), causing water to move out of the cell by osmosis. As a result, the vacuole shrinks and the cell becomes flaccid, losing its firmness.
What does the term plasmolyse mean?
Plasmolysis is the process where the plasma membrane of a plant cell pulls away from the cell wall due to water loss in a hypertonic solution. As water leaves the cell, the vacuole shrinks, and the cytoplasm pulls away from the cell wall, causing the cell to become plasmolysed.
why don’t plant cells burst when placed in a hypotonic solution?
The presence of the cell wall in plant cells prevents them from bursting when placed in a hypotonic solution. The cell wall resists excessive expansion by providing structural support, allowing the cell to become turgid without breaking.
How does gas exchange take place in the lungs?
The alveoli are tiny air sacs in the lungs with a rich blood supply and thin walls, oxygen in the inhaled air is at a higher concentration in the alveoli and diffuses into the blood capillaries, where oxygen concentration is low. At the same time, carbon dioxide in the blood is at a higher concentration and diffuses into the alveoli to be exhaled.
How do body cells exchange gases?
Oxygen diffuses from the red blood cells into body cells for aerobic respiration. CO2, produced during respiration, diffuses from the body cells into the blood to be transported to the lungs.
how does diffusion in the small intestine happen?
After digestion, glucose and amino acids are in a high concentration inside the small intestine and diffuse into the blood capillaries in the villi.
how is waste removed from the kidneys?
Some waste molecules like urea diffuses from the blood plasma into the kidney tubules for excretion.
How are the lungs adapted for diffusion? 5m
They have a large surface area which increases space for O2 and CO2 to diffuse. They also have very thin walls for a short diffusion distance, making gas exchange faster.
They also have a moist surface, which aid diffusion as gases dissolve in moisture.
They also have a rich blood supply, which helps in maintaining a steep concentration gradient.
They also have constant ventilation through breathing, which keep oxygen high in alveoli and CO2 low to help maintain gradient.
How is the small intestine adapted for diffusion? 3m
They have villi and microvilli which greatly increases the surface area for diffusion and active transport.
They have thin walls which means that nutrients only have to travel a short distance to diffuse.
They have a rich capillary network which quickly carries away absorbed nutrients which keeps the concentration gradient steep.
how does gas exchange for photosynthesis take place?
CO2 diffuses from the air into the leaf of the stomata, it moves into the air spaces inside the leaf and then into the palisade mesophyll cell where photosynthesis.
How is oxygen released in the environment?
During photosynthesis, O2 is produced in the chloroplasts of leaf cells, so O2 concentration becomes higher inside the leaf than outside, so it diffuses out through the stomata.
how does respiration take place in plant cells?`
All cells, including root, stem and leaf cells respire, O2 needed for respiration diffuses into the cells and CO2, a byproduct, diffuses out.
how are water vapours diffused?
Water vapour produced during transpiration diffuses out from the cell surfaces into the air surfaces in the leaf, and then out through the stomata.
how does diffusion within the cell take place?
Molecules like O2, CO2 and glucose diffuse between organelles within the cell. Eg. O2 diffusing into the mitochondria for respiration.
How are plant cells adapted for diffusion? 4m
Plant cells have many stomata, allowing efficient entry of CO2 and exit of O2 and water vapour.
There are airspaces inside leaves which allow easy diffusion if gases between cells.
Leaves are thin for a short diffusion path for gases.
Guard cells control the stomatal opening to balance gas exchange and water loss.
How is water absorbed into kidney cells?
In the kidneys, water is reabsorbed from the urine into the blood by osmosis. The concentration of water in the blood is higher than in the urine, so water moves from the urine (where it is more concentrated) into the blood (where it is less concentrated) across the kidney cells.
how does water enter red blood cells?
When red blood cells are placed in a hypotonic solution (low solute concentration), water moves into the cell by osmosis, causing the cell to swell. If placed in a hypertonic solution (high solute concentration), water will leave the cell, causing it to shrink.
how does water enter the roots from the soil?
Plant roots absorb water from the soil through osmosis. The soil has a higher water concentration compared to the root cells, so water moves from the soil into the root cells through the cell membranes.
how is turgidity in plants maintained?
In a hypotonic solution (e.g., pure water), water moves into the plant cell by osmosis, causing the vacuole to fill and the cell to become turgid (firm). This helps maintain structural integrity in plants.
how is glucose absorbed from the digestive tract into the intestine?
In the small intestine, glucose is absorbed from the digestive tract into the blood using active transport. Even when the concentration of glucose in the intestinal cells is lower than in the blood, glucose is actively transported into the blood against the concentration gradient, using energy from ATP.
how do mineral ions enter the roots through the soil?
Plant roots actively absorb mineral ions (like nitrate, potassium, and phosphate) from the soil. Despite the lower concentration of these ions in the soil, roots use energy (ATP) to actively transport these ions into the root cells against the concentration gradient.
how are sugars transported around a plant?
Phloem cells in plants actively transport sugars (mainly sucrose) from the leaves (where they are produced in photosynthesis) to other parts of the plant. This process requires energy to move sugars against the concentration gradient.
how are root hair cells adapted for osmosis?
Long, thin extensions called root hairs increase the surface area for water absorption through osmosis from the soil.
The cells in the root hair are specialised to have a high concentration of solutes (like minerals), creating a concentration gradient that encourages water to move from the soil (high concentration of water) into the root cells (lower concentration of water).
how is the vacuole and cell wall adapted for osmosis?
Vacuoles inside plant cells store water and help maintain turgidity (pressure against the cell wall). This prevents wilting and helps the plant stand upright.
The cell wall provides structural support and helps the plant resist excessive water intake, allowing the plant to stay firm without bursting.
how are leaf cells adapted for osmosis?
In leaves, cells have a high concentration of sugars and minerals, so water moves into these cells from surrounding tissues via osmosis, ensuring photosynthesis and other processes are efficient.
how are kidneys adapted for osmosis?
In the kidneys, nephrons have specialized structures (such as the loop of Henle) that create a concentration gradient, allowing for the efficient reabsorption of water through osmosis. This ensures that water is conserved in the body, especially when dehydrated.
how are red blood cells adapted for osmosis?
Cell membranes of red blood cells are selectively permeable, allowing water to enter or exit by osmosis, which helps maintain their shape and function. This is especially important in regulating cell volume in varying external environments.
how are root hair cells adapted for active transport?
Mitochondria in root hair cells provide energy (via ATP) for the active transport of mineral ions such as nitrate, potassium, and phosphate into the plant, even when their concentration is lower in the soil compared to the plant.
how are phloem adapted for active transport?
Sieve tube elements in the phloem actively transport sugars (produced in leaves) to areas where they are needed (like roots and fruits) through active transport.
Companion cells in the phloem use energy to help load sugars into the sieve tubes, creating a high concentration of sugar that moves through the plant.
how is the small intestine adapted for active transport?
The epithelial cells lining the small intestine actively transport glucose (and other nutrients) from the lumen of the gut into the blood vessels, even when glucose concentration in the cell is higher than in the lumen. This is essential for providing the body with energy from digested food.
how are RBCs adapted for active transport?
Red blood cells use active transport to load oxygen from the lungs into the blood plasma and to release oxygen in tissues that need it.
