What is the difference between a eukaryotic cell and a prokaryotic cell?
A eukaryotic cell is a cell that has genetic material enclosed in a nucleus.
A prokaryotic cell is a cell where the genetic material is not enclosed in a nucleus.
What is the role of the cytoplasm?
The cytoplasm is where many chemical reactions of the cell take place.
What is the role of the cell membrane?
The cell membrane allows substances in and out of the cell.
What is the role of the mitochondria?
The mitochondria is the site of respiration.
What is the role of ribosomes?
Ribosomes are the site of protein synthesis.
What is the role of the cell wall?
The cell wall provides structure and support to a plant cell.
What is the role of the chloroplasts?
The chloroplasts are the site of photosynthesis in plant cells.
Name 3 organelles found in a plant cell but not in an animal cell.
3 organelles that are only found in plant cells are:
- Cell wall
- Permanent Vacuole
What is a specialised cell?
A specialised cell is a cell that is adapted to its function.
Describe and explain 3 ways in which a sperm cell is specialised.
A sperm cell is specialised because it has:
- a tail so that it can swim towards the egg for fertilisation.
- Many mitochondria so that it can produce energy for movement.
- An acrosome containing digestive enzymes to penetrate the egg
Describe and explain how a nerve cell is specialised.
Nerve cells are specialised to carry electrical impulses around the body. They have several adaptations including;
- Dendrites to make connections to other nerve cells.
- Long axons that carry the impulse from one place to another
- A myelin sheath for insulation
- Synapses contain many mitochondria to produce the energy needed to make neurotransmitter
Describe and explain how a muscle cell is specialised.
Muscle cells are adapted to contract and relax. Striated muscle cells have three main adaptations;
- They contain special proteins that slide over each other making the fibres contract.
- They contain many mitochondria to produce the energy needed to contract and relax.
- They can store glycogen which is used to produce energy.
Describe and explain the adaptations of root hair cells.
Root hair cells have 3 main adaptations:
- They have a projection which increases the surface area available for water to move in to the cell.
- They have a large permanent vacuole which speeds up the movement of water in to the cell
- They have many mitochondria to produce the energy needed to move ions and minerals in to the cell.
Compare the maginification and resolution of a light microscope and an electron microscope.
An electron microscope has a much higher magnification and resolving power than a light microscope. This means that it can be used to study cells in a much finer detail.
Describe how bacteria multiply.
Bacteria multiply by binary fission as often as every 20 minutes.
Describe how to prepare an uncontaminated culture using aseptic technique.
- Petri dishes and culture media must be sterilised before use.
- Pass an inoculating loop through a flame to sterilise it.
- Dip the loop in the culture and wipe over the culture media.
- Secure the lid of the petri dish with tape.
- Store the dish upside down. Incubate at 25 degrees celsius.
Describe the stages in the cell cycle.
- Before the cell can divide it grows and increases the number of sub-cellular structures.
- The DNA replicates to form 2 copies of each chromosome.
- One set of chromosomes is pulled to each end of the cell and the nucleus divides.
- The cytoplasm and cell membranes divide to form two identical cells.
Explain why cell division by mitosis is important in multicellular organisms.
Cell division is important so that organisms can grow and repair damaged cells.
What is a stem cell?
A stem cell is an undifferentiated cell that can differentiate in to a specialised cell.
Where are stem cells found in plants?
Stem cells are found in the meristem tissue of plants.
Where are stem cells found in humans?
Stem cells can be found:
- in adult tissue such as bone marrow (adult stem cells)
- human embryos (embryonic stem cells)
Explain why embryonic stem cells are more useful than adult stem cells in medical treatment.
Stem cells from an embryo are not rejected by the patient's body.
Explain why people may object to the use of stem cells from embryos as a medical treatment.
The use of stem cells has potential risks such as transfer of viral infection, and some people have ethical or religious objections.
Explain how stem cells from meristems in plants can be useful.
Stem cells from meristems can be used to produce clones of plants quickly and economically.
Rare specied can be cloned to protect from extinction.
Crop plants with special features such as disease resistance can be cloned to produce large number sof identical plants for farmers.
Diffusion is the spreading out of particles of any substance in solution, or particles of a gas from a high concentration to a low concentration.
Describe three factors that affect the rate of diffusion.
Factors which affect the rate of diffusion are:
- the concentration gradient (difference in concentration)
- the temperature
- the surface area of the membrane
Describe the surface area : volume ratio of a single celled organism and explain how this is important in the transport of molecules in to the cell.
Single celled organsims have a large surface area : volme ratio. This allows sufficient transport of molecules into and out of the cell to meet the needs of the organism.
Describe 4 ways in which the effectiveness of an exchange surface in an organism can be increased.
The effectiveness of an exchange surface can be increased by:
- having a large surface area
- a membrane that is thin, to provide a short diffusion pathway
- having an efficienct blood supply to maintain a steep concentration gradient
- being ventilated (in animals)
Describe how water moves by osmosis.
Osmosis is the movement of water across a partially permeable membrane from a dilute solution (high water concentration) to a concentrated solution (low water concentration)
What is active transport?
Active transport moves substances against a concentration gradeint (from a low concentration to a high concentration). Active transport requires energy from respiration.