| How are root hair cells adapted for their function? | They have a large surface area to increase the rate of absorption; Thin walls to decrease the diffusion distance and a good blood supply so that diffusion can happen at a greater rate. |
| What are eukaryotic cells? | Cells with a nucleus, examples are plant and animal cells. |
| What are prokaryotic cells? | Cells without a nucleus, examples are bacteria cells. |
| What is the nucleus? | Contains genetic information and controls the cell. Its found in both animal and plant cells. |
| What is mitochondria? | Reactions for respiration happen here. This produces energy. Its found in both animal and plant cells. |
| What is the cytoplasm? | A jelly-like substance where chemical reactions happen. Its found in both animal and plant cells. |
| What is chloroplast? | This is where photosynthesis happens. It contains chlorophyll which absorbs the light. Its only found in plant cells. |
| What is the cell membrane? | This holds the cell together and controls what enters and exits. Its found in both animal and plant cells. |
| What are ribosomes? | This is where proteins are made. Its found in animal and plant cells. |
| What is a cell wall? | Its rigid and made of cellulose. It supports the cell and is only found in plant cells. |
| What is a vacuole? | This contains cell sap which is a solution of sugar and salts. |
| What are plasmids? | Circular rings of DNA in bacteria cells. |
| What is a nucleoid? | DNA that floats freely in the cytoplasm in bacteria cells. |
| What are bacteria cells? | They are prokaryote cells that don't have a nucleus, mitochondria or chloroplast. They contain a cell membrane, cell wall, plasmids, circular strands of DNA and cytoplasm. |
| What is a microscope? | A piece of equipment that lets us see things that we can't see with the naked eye. |
| What is a light microscope? | A microscope that uses light and lenses to make an image and magnify it. It lets us see individual cells and large sub cellular structures like the cell wall since it has a lower magnification and resolution. |
| What is an electron microscope? | A microscope that uses electrons instead of light to form an image. They have a much higher magnification and resolution so we can see smaller structures like ribosomes and internal structures of organelles. It can also only be used on dead cells. |
| What is the definition of resolution? | What is the definition of resolution? |
| What is the formula for magnification? | Magnification = Image Size ⁄ Actual size |
| A specimen is 50 μm wide. Calculate the width of the image of the specimen under a magnification of ×100. Give your answer in mm. | Image size = Magnification × Actual size
I = 100 × 50
= 5000 μm
= 5 mm
1000 μm = 1 × 10⁻³ mm |
| How are sperm cells specialised? | This is an example of a specialised cell and its job is to get the male DNA to the female DNA.
It has a long tail called a flagellum and a streamlined head to help it move, as well as having a lot of mitochondria to provide energy.
It also carries enzymes in the head to digest the Egg's cell membrane.
They're specialised for reproduction. |
| What is Cell Differentiation? | The process where cells become specialised to perform a certain job. |
| What are stem cells? | Undifferentiated cells. |
| How are nerve cells specialised? | This is an example of a specialised cell and its job is to carry electrical signals from one part of the body to another.
They are long to cover more distance and have branched connection at their ends to connect to other nerve cells, creating a network throughout the body.
They're specialised for rapid signalling. |
| What is an organelle? | A sub-celluar part of the cell. |
| What is resolution? | The ability to distinguish between two points. |
| How do you prepare an onion skin slide? | 1. You use tweezers to get an epidermal tissue.
2. You then drop some water onto the slide, then put the tissue onto the water.
3. Add a drop of iodide to stain the cell so the structures can be observed.
4. Place the cover slip over the specimen. |
| What is used to see MOST human and animal cells? | Methylene blue. |
| What are the different parts of a light microscope? | The different parts include the eyepiece, coarse knob, fine knob, stage, objective lens and the light. |
| How do you prepare a slide for your light microscope? | 1. Clip the slide onto the stage.
2. Select the lowest-powered objective lens.
3. Use the coarse knob to move the stage up to just below the lens.
4. Use the eyepiece and coarse knob until the image is roughly in focus.
5. Adjust the fine knob until your image clears.
6. If you need a greater magnification, use a higher powered objective lens and refocus. |
| How do you draw you microscopic observations? | You would draw them in pencil with clear, unbroken lines. They should be drawn in proportion and labeled. |
| Compare light and electron microscopes (6 marks). | Light microscopes are cheaper than electron microscopes and they use light to see the samples, where electron microscopes use electrons. They also have lower resolution than electron microscopes.
Electron microscopes can only see dead cells, but they can see the structure of sub-cellular structures (organelles) unlike light microscopes. Electron microscopes have a higher magnification. |
| How are muscle cells specialised? | the function of muscle cells is to contract quickly. The cells are long so they have space to contract and contain lots of mitochondria to generate energy.
It's specialised for contraction. |
| How are root hair cells specialised? | Root hair cells are found on the surface of plant roots that grow into long hairs. This gives the plant a large surface area for absorbing water and mineral ions from the soil.
It's specialised for absorbing water and minerals. |
| How is the phloem and xylem cells specialised? | The phloem and xylem cells from phloem and xylem tubes transport food and water around the plant.
To form the tubes, the cells are long and joined end to end.
Xylem cells are hollow in the centre and phloem cells have few sub-cellular structures so stuff can easily flow through.
They're specialised for transporting substances. |
| What are embryonic stem cells? | They are stem cells that are undifferentiated. They can turn into any type of cell. They're found in early human embryos. |
| What are adult stem cells? | They are stem cells that are found in the bone marrow and also undifferentiated. They can turn into many, but not all cells. Only certain ones like blood cells. |
| What is therapeutic cloning? | This is when the nucleus of a differentiated cell is taken from a patient and inserted into an empty egg cell from a donor. This is done so the stem cells contain the same genes as the patients and isn't rejected.
The cell gets stimulated to divide and develop into an embryo, making it available for therapeutic use, since it can grow into any human transplant, this would make it a transplant. |
| How can embryonic stem cells cure disease? | They can replace faulty cells in sick people.
For example, you can make insulin-producing cells for people with diabetes.
You can make nerve cells for people paralysed with spinal injuries too. |
| What are advantages of therapeutic cloning? | - It can cure medical conditions.
- It produces replacement cells of any type.
-The cells can be used for research.
- It reduces the waiting time for transplants. |
| What are disadvantages of therapeutic cloning? | - Potential life can be destroyed.
- There's a poor success rate.
- It may transfer viruses.
- Not all the risks are identified.
- There are a low number of egg donors. |
| What are meristems? | Plant stem cells found in apical meristems, this is the root, shoot and stem. |
| Why are some people against stem cell research? | - Its potential human life so it shouldn't be used for experiments.
- Scientists should focus on finding more stem cells so people don't need to rely on embryos.
- Its banned in some countries but in the UK it has strict guidelines.
- Curing patients is more important than the rights of embryos.
- The embryos are unwanted ones from fertility clinics which would have been destroyed if they weren't used for research. |
| What are chromosomes? | Coiled up lengths of DNA molecules. They contain a lot of genes. |
| What is the cell cycle? | The process where body cells in multicellular organisms divide to produce more cells. |
| What is G1 in the cell cycle? | This is the stage of Growth.
This is where the cellular contents, excluding chromosomes, are duplicated. |
| What is S in the cell cycle? | This is the DNA replication stage.
Here the 46 chromosomes are duplicated by the cell. |
| What is G2 in the cell cycle? | This is the preparation for mitosis stage, here repairs are made. |
| What is mitosis in the cell cycle? | This is where the cell divides into two. It's the separation of the nucleus, cytoplasm and divides into two identical daughter cells. |
| What are the stages of mitosis? | Prophase - The DNA condenses and chromosomes become visible and the nuclear membrane breaks down.
Metaphase - Chromosomes line up at the centre of the cell.
Anaphase - Cell fibres pull them apart. The two arms of chromosomes go to each side of the cell.
Telophase - A membrane forms around each of the sets of chromosomes. These becomes the nuclei of the new two cells - the nucleus has divided.
Cytokinesis - The cytoplasm and membrane divide creating two diploid daughter cells that are identical. This is cell division. |
| What are gametes? | Sex cells. |
| What is diffusion? | The movement of fluid particles from a high concentration to a low concentration, passively. |
| What does the rate of diffusion depend on? | It depends on temperature, the concentration, surface area and distance. |
| Why is diffusion important for plants and animals? | Diffusion is important in animals for gas exchange for basic breathing in the alveoli, and it allows food and water to be absorbed in the bowels.
It allows water to be lost through transpiration in the leaves. It also allows gas exchange in plants through photosynthesis. |
| What is osmosis? | The passive movement of water molecules through a partially permeable membrane from a higher concentration to a lower concentration. |
| What happens to a plant cell when water enters it? | It becomes turgid (swelled up) due to pressure increase and the vacuole is enlarged. It's also hypotonic, it works best here. |
| What happens to a plant cell when water leaves and enters it? | It becomes flaccid (limp and floppy) due to pressure decrease. It's also isotonic and normal. |
| What happens to a plant cell when too much water leaves it? | It becomes plasmolysed (sub cellular cells shrink) and the sub cellular structures are shrunk. It's also hypertonic. |
| What happens to an animal cell when too much water enters it? | Its cell membrane bursts, this is known as lysis. It's also hypotonic. |
| What happens to an animal cell leaves and enters it? | It's in a normal state when this happens. It's also isotonic. |
| What happens to an animal cell when too much water leaves it? | It becomes shrivelled. It's also hypertonic. |
| What is active transport? | The movement of bigger molecules or ions from a low to high concentration. It requires energy since it goes against the concentration gradient. |
| What do you need for active transport to work? | Energy and carrier channel proteins so big molecules can go into a cell since it can't get through the membrane and it needs to go against the concentration gradient. |
| Where does the body use active transport? | Sometimes there is a lower concentration of nutrients in the gut than the blood, so active transport is used here for glucose and amino acids.
In the small intestine, the body moves glucose into the blood.
In the kidneys, the body reabsorbs glucose into the blood. |
| What is mechanical digestion? | When food is broken down by when you pulverise and chew. It's a physical process. |
| What is peristalsis? | The contraction and expanding that your oesophagus uses to move your food down. |
| How do root hair cells use active transport? | Minerals move into root hair cells via active transport, since its taken from a very dilute solution and is against the concentration gradient. |
| How and why are gasses and dissolved substances diffused into or out of the cell across a cell membrane in single celled organisms? | It's diffused directly into or out of a cell across a cell membrane because they have a large surface area compared to their volume. |
| How and why are gasses diffused into or out of the cell across a cell membrane in multi celled organisms? | Because they have a smaller surface area than their volume, they need some sort of exchange surfaces to have efficient diffusion.. |
| What do exchange surfaces have to do? | They have to allow enough of the necessary substances to pass through. |
| How do exchange surfaces do their job properly? | They have a thin membrane to decrease diffusion time and distance.
They have a large surface area to increase the rate of diffusion.
They have a rich blood supply.
They are well ventilated. |
| How are the lungs adapted for gas exchange? | It contains millions of thin alveoli for diffusion. |
| How does alveoli do its job? | They are specialised to maximise the diffusion of oxygen and carbon dioxide by;
Having a large surface area (75m² in humans).
Having a moist lining for dissolving gases.
Having thin walls.
Having a rich blood supply. |
| How are the villi adapted to work? | They are inside the small intestine and exchanges substances by;
Having a large surface area.
Having single layer of surface cells.
Having a rich blood supply for the absorption of substances. |
| How do leaves allow gas exchange? | The stomata allows carbon to diffuse in through the underside of the leaf.
Oxygen is produced - through photosynthesis - and water vapour (mostly) diffuse out of the stomata.
The flattened shape maximises the area and the cells walls have air spaces also increasing surface area. |
| How is the stomata closed | Guard cells close the stomata if the plant is losing water faster than it an be replaced, preventing it from wilting. |
| How are gills adapted for gas exchange? | By having large filaments, this increases the surface area for gas exchange.
The filaments are covered by lamellae which increases the surface area more. |
| How does lamellae help gas exchange? | It increases gas exchange by;
Having lots of capillaries for diffusion.
Having a thing surface layer to minimise the distance.
Having a large concentration gradient between water and blood.
The concentration of oxygen in the water being higher than the bloods', meaning as much as possible will diffuse into the blood. |
