cell biology Flashcards
What are the differences between light and electron microscopes?
Light microscopes: * Relatively cheap * Can be used almost anywhere * Can magnify live specimens * 2D images. Electron microscopes: * Very expensive * Can only be used in a vacuum * Can only magnify not living specimens * Some can produce 3D images.
How do you calculate magnification?
Magnification = size of image / size of real object.
What is resolution?
The ability to distinguish between two separate points (how much detail there is).
How long is the average animal cell?
10-30 nanometres long.
What subcellular structures do animal cells contain?
- Nucleus * Cytoplasm * Cell membrane * Mitochondria * Ribosomes.
What does the nucleus do?
Controls the activities and contains genetic material of the cell.
What does the cytoplasm do?
It is where most of the chemical reactions needed for life take place.
What does the cell membrane do?
Controls what enters and exits the cell.
What do mitochondria do?
The site of aerobic respiration.
What do ribosomes do?
Site of protein synthesis.
What subcellular structures do plant cells have that animal cells don’t?
- Cell wall * Permanent vacuole * Chloroplasts.
What is the purpose of the cell wall?
Contains cellulose which strengthens the cell and gives it support.
What is the purpose of the permanent vacuole?
Filled with cell sap to keep the cell rigid and support the plant.
What is the purpose of chloroplasts?
They contain chlorophyll which absorbs light for photosynthesis to take place.
What plant cells do not have chloroplasts and why?
Root cells and onion cells do not have chloroplasts because they are underground and do not photosynthesise.
What type of cells are animal and plant cells?
Eukaryotic cells.
What type of cells are bacterial cells?
Prokaryotic cells.
How long are the average prokaryotes?
0.2 - 2 nanometres.
What subcellular structures do prokaryotes have?
- Cytoplasm * Cell wall * Cell membrane * One DNA loop * Flagella.
What do plasmids do in a bacterial cell?
They contain DNA which codes for specific features (e.g., antibiotic resistance).
What is the purpose of flagella?
A long strand that lashes about, allowing the cell to move.
What is cell differentiation?
The process by which stem cells become specialised in order to carry out a specific function.
When do animal cells typically differentiate?
At early stages of development.
When can plant cells differentiate?
Throughout life.
What is a nerve cell’s purpose?
To carry electrical impulses around the body.
How are nerve cells specialised to carry out their function?
- Lots of dendrites to connect to other nerve cells * Nerve endings (synapses) contain lots of mitochondria to provide energy needed to make transmitter chemicals.
What is a muscle cell’s function?
To contract and relax to cause movement.
How are striated muscle cells specialised to carry out their function?
- Contain many mitochondria to provide energy needed for contraction and relaxation * Contain special proteins that slide over each other to make the fibres contract.
How is a sperm cell specialised to carry out its function?
- Has a long tail to help it swim to the egg * Contains lots of mitochondria to provide energy for swimming * Has an acrosome which stores digestive enzymes to break down the protective outer layer of the egg * Has a large nucleus which contains genetic information.
What is a root hair cell’s function?
Absorbing water and mineral ions for its plant.
How is a root hair cell specialised to carry out its function?
- Large surface area to maximize the amount of water it can take in * Contains lots of mitochondria to provide energy needed for active transport of mineral ions into the cell.
How is a photosynthetic cell specialised to carry out its function?
- Contains chloroplasts which absorb light needed for photosynthesis * Positioned in the leaves or outer layers of the stem to absorb as much light as possible * Has a permanent vacuole to keep the cell (and the stem) rigid and upright.
What is a xylem cell’s function?
To transport water and dissolved mineral ions from the roots up the plant.
How are xylem cells specialised to carry out their function?
- A chemical (lignin) builds up in dead xylem cell walls to keep cells strong * Cells form long hollow tubes to allow water to easily travel through.
What is a phloem cell’s function?
Transports dissolved sugars made by photosynthesis up and down the plant.
How is a phloem cell specialised to carry out its function?
- Cell walls break down to form sieve plates, allowing movement of dissolved sugars * Companion cells containing lots of mitochondria transfer energy needed to move dissolved sugars.
What is diffusion?
The movement of particles from an area of high concentration to an area of low concentration, along a concentration gradient.
What factors affect the rate of diffusion?
- Temperature * Steepness of concentration gradient.
Where does diffusion take place in living organisms?
- Oxygen moves into red blood cells by diffusion * Carbon dioxide moves out of red blood cells by diffusion * Simple sugars (e.g., glucose) and waste products (e.g., urea) move in and out of cells by diffusion.
What is osmosis?
The movement of water from an area of high concentration to an area of low concentration, along a concentration gradient, through a partially permeable membrane.
What is turgor pressure?
Pressure inside plant cells caused by the vacuole when water can no longer enter a cell, making the cell hard and rigid.
What is active transport?
Movement of particles from an area of low concentration to an area of high concentration, against a concentration gradient.
Where does active transport take place in living organisms?
- When sugars (e.g., glucose) are absorbed from the small intestines to the blood * When root hair cells take up mineral ions from the soil.
What are examples of exchange surfaces and how are they adapted to carry out their functions?
- Fish gills: rich blood supply maintains steep concentration gradient * Alveoli: large surface area and rich blood supply * Plant leaves: flat and thin to provide large surface area.
What are chromosomes?
Thread-like structures that carry genes.
What is a gene?
A small section of DNA that controls a characteristic in the body and makes up chromosomes.
How many chromosomes are contained in the nucleus of a cell?
46 (in 23 pairs).
What is the first stage of the cell cycle?
Replication of DNA to form two copies of each chromosome and synthesis of new sub-cellular structures.
What is the second stage of the cell cycle?
Mitosis: where one set of chromosomes is pulled to each end of the cell and the nucleus divides.
What is the third stage of the cell cycle?
Cytokinesis: the cytoplasm and the cell membranes divide to form two identical daughter cells.
What is a stem cell?
A cell that has not undergone differentiation and is unspecialised.
What cells cannot divide and require adult stem cells?
Red blood cells and skin cells.
Where are adult stem cells found?
In bone marrow.
Where are plant stem cells found?
Meristems (in the stems and roots).
What is cloning?
Producing identical offspring.
What is the difference between embryonic and adult stem cells?
Embryonic stem cells can differentiate into any type of specialised cell; adult stem cells can only differentiate into certain types of cell.
What is therapeutic cloning?
When an embryo is produced with the same genes as the patient, so stem cells from the embryo aren’t rejected.
How do bacteria multiply?
Binary fission.
