B1: Cell Structure/Transport Flashcards
Describe method to investigate an onion cell using a microscope.
- Peel off epidermal layer of onion using forceps.
- Put onto microscope slide, adding water to make sure it lies flat.
- Add 2 drops of iodine solution to stain the cells.
- Place cover slip on, making sure no air bubbles are trapped.
- Remove any excess stain and place slide on stage.
- Use low objective lens first and use coarse focus wheel to raise stage closer to the objective lens.
- Look through eyepiece and turn coarse focus wheel to move stage until image is in focus.
- Select higher objective lens and turn fine focus wheel for clearer image.
What is the equation for magnification?
Magnification = Image Size / Actual Size
What are the parts of an animal cell and what is their functions?
Nucleus - controls activities of cell and contains chromosomes and DNA.
Cytoplasm - where chemical reactions take place.
Cell Membrane - controls what enters and leaves the cell.
Mitochondria - site of aerobic repsiration.
Ribosomes - site of protein synthesis.
What parts of a cell are in plant cells but not animal cells and what are their functions?
Cell wall - made of cellulose and strengthens cell and gives it support.
Chloroplasts - site of photosynthesis.
Large permanent vacuole - contains cell sap and keeps cell rigid to support the plant.
How is DNA found in different cells?
In eukaryotic cells (multicellular), genetic material is enclosed in a nucleus.
Prokaryotic (unicellular) cells have a single loop of DNA and contain plasmids.
How are nerve cells specialised?
• They are specialised to carry electrical impulses around the body.
- They have lots of dendrites to make connections to other nerve cells.
- Have long axon to help carry impulse.
- Have lots of mitochondria to make transmitter chemicals for synapse.
How are muscle cells specialised?
• They are specialised to contract/relax for movement.
- Special proteins slide over each other for contraction.
- Have many mitochondria to provide energy.
- Store glycogen to use in respiration.
How are sperm cells specialised?
• They are specialised to fertilise an egg.
- Have a long tail/flagella to allow quicker movement.
- Have large nucleus with genetic information and many mitochondria.
- Acrosome has digestive enzymes to break down cell membrane of the egg.
How are root hair cells specialised?
• Specialised to take in water and mineral ions from the soil.
- Root hairs increase surface area for water to move into.
- Large permanent vacuole speeds up osmosis.
- Many mitochondria to provide energy for active transport.
How are xylem cells specialised?
• Specialised to carry water and mineral ions from roots to shoots.
- Lignin strengthens cell and forms continuous hollow tube that allows water to move through.
- Lignin helps to withstand pressure.
How are phloem cells specialised?
• Specialised to transport sugars from photosynthesis around the plant.
- Sieve plates help allow the movement of substances.
- Many mitochondria to provide energy.
What is diffusion and how is it affected?
Diffusion is the net movement of particles from an area of high concentration to an area of low concentration.
Increased by higher temperatures, greater concentration gradient and a greater surface area to volume ratio.
What is osmosis?
It is the movement of water from an area of high concentration to an area of low concentration across a partially permeable membrane.
What is does it mean if a cell is isotonic, hypertonic and hypotonic?
Isotonic - there is the same amount of water in the external cell as the internal cell.
Hypertonic - more water in internal cell than external so water moves out and crenation happens.
Hypotonic - less water in the cell than external so water moves in and lysis happens.
What happens when plant cells lose or gain water?
When water moves into a plant cell the vacuole swells and the cell is turgot.
If water is lost, the vacuole and cytoplasm shrink as a result of plasmolysis.
Describe the method of investigating osmosis in potato chips.
- Cut potato into similarly sized chips. No potato skin as it is impermeable.
- Measure and record initial mass of each chip using balance.
- Measure 10cm^3 of distilled water using measuring cylinder and pour it into a boiling tube.
- Measure 10cm^3 of different concentrations of sugar solutions and pour into the boiling tubes.
- Put each potato into each boiling tube.
- After a suitable time period, use tweezers to take potatoes out and place on filter paper.
- Use paper towel to remove any excess liquid.
- Measure and record new masses and calculate a % change.
What is active transport?
It is the movement of particles against a concentration gradient, from an area of low to high concentration. It requires ATP energy from respiration.
E.g. root hair cells with mineral ions from soil.
How does low rates of diffusion affect the body?
- Gases and food molecules can no longer reach every cell in the organism by diffusion.
- Metabolic waste cannot be removed quick enough to avoid poisoning.
What are the adaptations in the alveoli for exchanging materials?
- Have a thin membrane for a short diffusion path.
- Have large surface area to increase rate of diffusion.
- Efficient bloody supply and being ventilated maintains a steep concentration gradient for effective gas exchange.
