Topic 1-Cell Biology Flashcards
What does a nucleus do?
- Contains the genetic DNA of the organism
- Enclosed in a nuclear membrane
- Controls and regulates the activities of the cell
What is cytoplasm?
- Liquid substance in which chemical reactions occur
- Contains enzymes (biological catalysts, i.e. proteins that speed up the rate of reaction)
- Organelles are found in it
What is the cell membrane?
-Controls what enters and leaves the cell
What do ribosomes do?
- Where protein synthesis occurs
- Found on a structure called the rough endoplasmic reticulum
What do chloroplasts do?
- Where photosynthesis takes place, providing food for the plant
- Contains chlorophyll pigment (which makes it green) which harvests the light needed for photosynthesis
What is a permanent vacuole?
- Contains cell sap
- Found within the cytoplasm
- Improves cell’s rigidity
What is a cell wall?
- Made from cellulose
- Provides strength to the cell
What are plasmids?
Small rings of DNA
What happens when cells differentiate?
-They gain sub-cellular structures in order for it to be suited to its role
How are sperm cells specialised to carry the male’s DNA to the egg cell for successful reproduction?
- Streamlined head and long tail to aid swimming
- Many mitochondria (where respiration happens) which supply the energy to allow the cell to move
- The acrosome (top of the head) has digestive enzymes which break down the outer layers of membrane of the egg cell
How are nerve cells specialised to transmit electrical signals quickly from one place in the body to another?
- The axon is long, enabling the impulses to be carried along long distances
- Having lots of extensions from the cell body (dendrites) means branched connections can form with other nerve cells
- Nerve endings have many mitochondria which supply the energy to make special transmitter chemicals called neurotransmitters.
- These allow the impulse to be passed from one cell to another
How are muscle cells specialised to contract quickly to move bones or to simply squeeze, therefore causing movement?
- Special proteins (myosin and actin) slide over each other, causing the muscle to contract
- Lots of mitochondria to provide energy from respiration for contraction
- They can store a chemical called glycogen that is used in respiration by mitochondria
How are root hair cells specialised to take up water by osmosis and mineral ions by active transport from the soil as they are found in the tips of roots?
- Large surface area due to root hairs-more water can move in
- Large permanent vacuole affects the speed of movement of water from the soil to the cell
- Mitochondria to provide energy from respiration for the active transport of mineral ions into the root hair cell
How are xylem cells specialised to transport water and mineral ions up the plant from the roots to the shoots?
- Upon formation, a chemical called lignin is deposited which causes the cells to die. They become hollow and are joined end-to-end to form a continuous tube so water and mineral ions can move through
- Lignin is deposited in spirals which helps the cells withstand the pressure from the movement of water
How are phloem cells specialised to carry the products of photosynthesis (food) to all parts of the plants?
- Cells walls of each cell form structures called sieve plates when they break down, allowing the movement of substances from cell to cell
- Despite losing many sub-cellular structures, the energy these cells need to be alive is supplied by the mitochondria of the companion cells
How do you figure out the size of an object?
Size of image/magnification = size of object
What is a nutrient broth solution?
It involves making a suspension of bacteria to be grown and mixing with sterile nutrient broth (the culture medium).
In a nutrient broth, why must you stoppper the flask with cotton wool?
To prevent air from contaminating it
When working with a nutrient broth, why is it important to shake the flask regularly?
To provide oxygen for the growing bacteria
How do you grow microorganisms on an agar gel plate?
The agar acts as the culture medium, and the bacteria grown on it form colonies on the surface
- Hot sterilised agar jelly is poured into sterilised petri dish (cool and set)
- Inoculating loops are dipped in solution of microorganism and spread over agar evenly
- Lid is taped on and incubated so microorganisms can grow
Why must petri dishes and culture media be sterilised before use, which is often done by an autoclave (an oven) or UV light?
They are likely to be contaminated with other microorganisms. These could be harmless but will compete with the desired bacteria for nutrients and space, or they could be harmful (eg. a mutation), potentially creating a new pathogen
Why must inoculating loops be sterilised by passing them through a flame?
This kills unwanted microorganisms
Why should the lid of the Petri dish be sealed, but not completely, with tape
Sealing stops airborne organisms from contaminating the culture, but it should not be sealed all the way around as this would result in harmful anaerobic bacteria growing (due to no oxygen)
Why should the Petri dish be stored upside down?
This is to prevent condensation from the lid landing on the agar surface and disrupting growth
Why should the culture be incubated at 25 degrees?
If it were to be incubated at a higher temperature, nearer 37 degrees (body temp), it would be more likely that bacteria that could be harmful to humans would be able to grow as this is their optimum temperature. At lower temperatures, colonies of such bacteria would not be able to grow
How do you test the effectiveness of antibiotics against the growth of a certain bacteria?
Soak the paper disks in different types/concentrations of antibiotics and place on an agar plate evenly spread with bacteria. One disc should be a control, soaked in sterile water. There should be no death of bacteria with this disk (showing the change in inhibition zone size is purely due to the antibiotics)
How many pairs of chromosomes does each cell of the body have?
23 pairs, 46 chromosomes in total
What are the 3 stages of the cell cycle?
Interphase
Mitosis
Cytokinesis
What happens during Interphase?
In this stage the cell grows, organelles grow and increase in number, the synthesis of proteins occurs, DNA is replicated and energy stores are increased
What happens during Mitosis?
The chromosomes line up at the equator of the cell and cell fibres pull each chromosome of the ‘X’’ to either side of the cell
What happens during Cytokinesis?
Two identical daughter cells form when the cytoplasm and cell membranes divide
Why is mitosis important in multicellular organisms?
Important in their growth and development and when replacing damaged cells
What are embryonic stem cells?
- Form when an egg and sperm cell fuse to form a zygote
- They can differentiate into any type of cell in the body
- Scientists can clone these cells (though culturing them) and direct them to almost any cell in the body
How could embryonic stem cells be used?
- To replace insulin-producing cells in those suffering from diabetes
- New neural cells for diseases such as Alzheimer’s
- Nerve cells for those paralysed with spinal cord injuries
What are adult stem cells?
If found in bone marrow, they can form many types of cells including blood cells