GCSE - Topic 2 - Cell Transport - Year 9 Flashcards
What is diffusion?
Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration.
What states does diffusion occur in?
Diffusion happens in both solutions and gases - that’s because the particles in these substances are free to move about randomly.
How does the size of the concentration gradient affect the rate of diffusion?
The bigger the concentration gradient (the difference in concentration), the faster the diffusion rate.
How does the temperature affect the rate of diffusion?
A higher temperature will give a faster diffusion rate because the particles have more energy, so move around faster.
What does a cell membrane do?
They hold the cell together, as well as letting stuff in and out of the cell. Dissolved substances can move in and out of cells by diffusion.
Which molecules can diffuse through a cell membrane?
Only very small molecules can diffuse through, though things like oxygen, glucose, amino acids and water are able to.
Give an example of a big molecule that can’t fit through the membrane.
- Starch
- Proteins
How does the surface area of the membrane affect the rate of diffusion?
The larger the surface area of the membrane, the faster the diffusion rate, because more particles can pass through at once.
What is osmosis?
The net diffusion of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.
What is a partially permeable membrane?
A partially permeable membrane is just one with very small holes in it. So small, in fact, only tiny molecules (like water) can pass through them, and bigger molecules (e.g. sucrose) can’t.
How do the water molecules move during osmosis?
The water molecules pass both ways through the membrane during osmosis. This happens because water molecules move about randomly all the time.
What does having more water molecules on one side than on the other mean?
Because there are more water molecules on one side than on the other, there’s a steady net flow of water into the region with fewer water molecules, i.e into the stronger sugar solution.
Is osmosis a passive movement?
Osmosis is a passive movement of water molecules from an area of higher water concentration to an area of lower water concentration.
Is the concentration of minerals higher in a root hair cell or the soil around them?
The conentration of minerals is usually higher in the root hair cells than in the soil around them.
Do minerals move in or out of the root hairs?
Minerals should move out of the root hairs if they followed the rules of diffusion.
What does active transport do?
It allows the plant to absorb minerals from a very dilute solution, against a concentration gradient. This is essential for its growth. Active transport needs ENERGY from respiration to make it work.
What are factors that increase the rate of diffusion?
- More particles
- Bigger surface area to diffuse across
- Shorter distance to diffuse
- Temperature
- Mechanical movement (stirring or wind)
Which diffuses faster, a liquid or a gas? Why?
Gas. Because they can move more easily as the particles are more spread out.
A pant cell put in a dilute solution becomes ____.
Turgid.
Plasmolysed is when the cytoplasm _____.
Shrinks.
Osmosis will lead to the swelling of a raisin, but it will not burst because…
It is a plant.
What type of transport protein is involved in active transport?
Carrier protein.
What is active transport?
The movement of molecules from a low concentration to a high concentration area. The process requires energy and goes against the concentration gradient.
Cells involved in active transport usually have a lot of ________ to provide the energy they need.
Mitochondria.
What’s an example of diffusion?
In the lung of a mammal, oxygen moves from the alveoli to the blood.
What’s an example of osmosis?
In the kidney of a mammal, water moves from the nephron to the blood.
How do carrier proteins allow for facilitated diffusion?
They bind specifically to the molecule they assist.
Is diffusion a passive process?
Yes.
What’s a passive process?
A passive process means that no energy is needed.
During diffusion, do molecules move down or against the concentration gradient?
Down. They move from an area of high concentration to an area of low concentration.
What does a partially permeable membrane do?
Allow small molecules to pass through by diffusion, for example, water, oxygen and carbon dioxide.
Are flaccid (plasmolysed) cells or Turgid cells larger?
Turgid cells, they’re filled with water.
What’s a turgid cell?
When water enters a plant cell by osmosis and pushes on the cell wall causing the cell to swell.
What’s a flaccid cell?
When water leaves a plant cell by osmosis, the cell contents shrink and the cell membrane pulls away from the cell.
Which subcellular structures are in an animal cell?
Nucleus Cytoplasm Cell membrane Mitochondria Ribosomes
Which subcellular structures are in a plant cell?
Rigid cell wall (made of cellulose) Permanent vacuole Chloroplasts Nucleus Cytoplasm Cell membrane Mitochondria Ribosomes
Which subcellular structures are in a bacteria cell?
(May contain) One or more small rings of DNA called plasmids Single circular strand of DNA Cell wall Cell membrane Cytoplasm
What does the nucleus do?
Contains genetic material that controls the activities of the cell.
What does the cytoplasm do?
Gel-like substance where most of the chemical reactions happen. It contains enzymes that control these reactions.
What does the cell membrane do?
Holds the cell together and controls what goes in and out.
What do the mitochondria do?
These are where most of the reactions for aerobic respiration take place. Respiration transfers the energy that the cell needs to work.
What do the ribosomes do?
These are where proteins are made, via protein synthesis.
What does the rigid cell wall do?
It supports the cell and strengthens it. It’s also made of cellulose.
What do the chloroplasts do?
These are where protein synthesis occurs, which makes food for the plant. They contain a green substance called chlorophyll, which absorbs the light needed for photosynthesis.
What are the specialisations of a sperm cell?
It has a long tail and a streamlined head to help it swim to the egg. There are a lot of mitochondria in the cell to provide the energy needed. It also carries enzymes in its head to digest through the egg cell membrane.
What’s the function of a nerve cell?
To carry electrical signals from one part of the body to another.
What are the specialisations of a nerve cell?
These cells are long (to cover more distance) and have branched connections at their ends to connect to other nerve cells and form a network throughout the body.
What’s the function of muscle cells?
To contract quickly.
What are the specialisations of a muscle cell?
They are long (so that they have space to contract) and contain lots of mitochondria to generate the energy needed for contraction.
What’s the function of a root hair cell?
To absorb water and minerals.
What are the specialisations of a root hair cell?
Root hair cells are cells on the surface of the plant roots, which grow into long “hairs” that stick out into the soil. This gives the plant a big surface area for absorbing water and mineral ions.
What’s the function of phloem and xylem cells?
They form phloem and xylem tubes, which transport substances such as food and water around plants.
What are the specialisations of phloem and xylem cells?
To form tubes, the cells are long and joined end to end. Xylem cells are hollow in the centre and phloem cells have very few subcellular structures, so that stuff can flow through them.
Is active transport a passive process?
No, it’s an active process. This means it requires energy.
What’s a hypotonic solution?
A solution that has more water molecules (higher concentration of water) than inside the cell.
What’s an isotonic solution?
A solution that has the same concentration as inside the cell.
What’s a hypertonic solution?
A solution that is more concentrated than inside the cell.
What’s an active process?
Something that requires energy.
Is diffusion a specific process?
No.
Is osmosis a specific process?
Yes.
Is active transport a specific process?
Yes.
