Movement of substances in and out of cells Flashcards
What is diffusion?
The net movement of particles from an area of high concentration to an area of low concentration down a concentration gradient.
Diffusion is a passive process, so it doesn’t require energy.
How does diffusion occur across a cell membrane?
Diffusion allows substances to pass through a partially permeable cell membrane.
For example, during respiration, oxygen moves into the cell due to a concentration gradient.
What types of particles can move across a semipermeable membrane?
Relatively small particles like oxygen, glucose, and carbon dioxide can move across, but larger particles like starch cannot.
Does diffusion require a membrane?
No, diffusion does not require a membrane to occur.
For example, gases can diffuse in a room.
What factors affect the rate of diffusion?
Factors include temperature, concentration gradient, surface area:volume ratio, and distance particles have to travel.
How does temperature affect diffusion?
Increased temperature means that the substance has more kinetic energy, moving faster and increasing the rate of diffusion.
How does concentration gradient affect diffusion?
The steeper the concentration gradient, the greater the difference between the two concentrations, leading to a faster rate of diffusion.
How does surface area affect diffusion?
A greater surface area provides more space for the substance to move through, increasing the rate of diffusion.
How does distance affect diffusion?
The further the particles have to travel, the longer it will take, decreasing the rate of diffusion.
What is osmosis?
The net movement of water molecules from a region of high water potential to low water potential through a partially permeable membrane.
Is osmosis an active or passive process?
Passive
What type of membrane allows osmosis to occur?
Partially permeable membrane
In osmosis, what direction does water move?
From high concentration of water to low concentration of water.
What characterizes a concentrated solution in terms of water potential?
Low water potential (more solute, less water)
What characterizes a dilute solution in terms of water potential?
High water potential (more water, less solute)
What is an isotonic solution?
A solution where the concentration of solute is the same as in the cell, resulting in no net water movement.
What is a hypertonic solution?
A solution with a higher concentration of solute than the cell, causing water to move out of the cell.
What is a hypotonic solution?
A solution with a lower concentration of solute than the cell, causing water to move into the cell.
What happens to an animal cell in a hypotonic solution?
Water moves into the cell, potentially causing it to burst.
What happens to an animal cell in a hypertonic solution?
It loses water and becomes shrivelled.
What effect does a hypotonic solution have on plant cells?
Water moves into the cell, creating turgor pressure and keeping the plant rigid.
What happens to plant cells in a hypertonic solution?
Water moves out, the vacuole shrinks, and the cell becomes plasmolysed.
Fill in the blank: A _______ solution has a higher concentration of solute than the cell.
hypertonic
Fill in the blank: A _______ solution has a lower concentration of solute than the cell.
hypotonic
True or False: Osmosis requires energy.
False
What is turgor pressure?
The pressure exerted by the fluid in the vacuole against the cell wall in plant cells.
What is active transport?
The movement of particles from an area of lower concentration to an area of higher concentration using energy from respiration.
What type of energy is required for active transport?
Energy from respiration.
In which direction do particles move during active transport?
Against the concentration gradient.
What type of membrane is involved in active transport?
Partially permeable membrane.
What are carrier proteins used for in active transport?
To transport solutes up the concentration gradient.
Provide an example of active transport in plants.
Root hair cells take up water and mineral ions from the ground.
True or False: Active transport can occur in the gut.
True.
What is the main difference between diffusion and active transport?
Diffusion moves down a concentration gradient, while active transport moves against it.
Fill in the blank: Active transport requires _______ to move substances against a concentration gradient.
[energy].
What substances are typically moved during active transport?
Solutes.
In the context of osmosis, what type of particles are primarily involved?
Water.
What type of system was used in Core Practical 4 to investigate diffusion and osmosis?
Both living and non-living systems.
Describe a non-living system used in the investigation of diffusion.
Agar jelly cube with sodium hydroxide and phenolphthalein indicator.
What is observed when the agar jelly cube is placed in hydrochloric acid?
The cube turns pink from green due to the indicator.
What is the independent variable in the acid diffusion experiment?
SA to volume ratio of the cube
SA refers to surface area.
What is the dependent variable in the acid diffusion experiment?
How far the pink colour has gone inside the cube or the time it takes for the entire cube to turn pink
What are the control variables in the acid diffusion experiment?
Volume of hydrochloric acid, time placed in for, ensuring the cube is entirely pink
If measuring time, control the time it takes for the entire cube to diffuse.
What biological material is used in the osmosis experiment?
Potatoes
What is the control concentration in the sucrose solution experiment?
0%
What is the independent variable in the osmosis experiment?
Concentration of sucrose solution
What is the dependent variable in the osmosis experiment?
Mass change of potato
What causes the mass change in potatoes during the osmosis experiment?
Water moving into or out of the potato by osmosis
What indicates that the solution is isotonic in the osmosis experiment?
No weight change
What is the starting condition for the potato in the osmosis experiment?
Starting mass of potato
Fill in the blank: The mass gained by the potato is due to water moving into the potato by _______.
osmosis
True or False: The volume of sucrose solution is a dependent variable in the osmosis experiment.
False
