Cell Biology
What is a cell?
The building block that all living things are made from.
Name organelles found in all cells.
Nucleus, cytoplasm, cell membrane, mitochondria, ribosomes.
Name 3 organelles which are not found in animal cells?
Chloroplast, cell wall, large vacuole.
What is the function of the nucleus?
To control the activities of the cell and contain genetic information.
What is the function of the cell membrane?
Controls which substances can go in and out of the cell.
What happens in the cytoplasm?
It is where chemical reactions happen.
What is the function of chloroplasts?
Carry out photosynthesis.
What is the function of the cell wall?
Gives the cell shape and support.
What is the function of the ribosome?
To synthesise proteins.
What are specialised cells?
Cells that are adapted (have particular characteristics) to perform a particular job.
What is the function of a sperm cell?
To fertilise an egg cell.
What are the adaptations of a sperm cell?
Tail for movement, acrosome contains enzymes to break down egg cell membrane, lots of mitochondria to release energy to swim to egg.
What is the function of a nerve cell?
To carry electrical impulses.
What are the adaptations of a nerve cell?
Many dendrites make connections to other nerve cells, and the fat -covered axon speeds up electrical impulses.
What is the function of a muscle cell?
To contract for movement.
What are the adaptations of muscle cells?
Many mitochondria to release energy for muscle contraction.
What is the function of a root hair cell?
To absorb water and mineral ions.
What are the adaptations of the root hair cell?
Large surface area to maximise absorption of minerals and water, lots of mitochondria to release energy for active transport.
What is the function of the xylem?
To transport water and dissolved ions.
What are the adaptations of the xylem?
No top and bottom walls between cells to form continuous hollow tubes through which water is drawn up. Cells are dead, without organelles or cytoplasm, to allow free passage of water. Outer walls are thickened with lignin.
What is the function of the phloem?
To transport dissolved sugars.
What are the adaptations of the phloem?
Made of living cells which are joined end-to-end and contain holes in the end cell walls (sieve plates) forming tubes which allow sugars and amino acids to flow easily through.
What is a tissue?
A group of similar cells which do a job.
What is an organ?
A group of different tissues working together to do a job.
What is a system?
A group of organs which work together to do a job.
How do we calculate total magnification of a microscope?
Eyepiece magnification x objective lens magnification
What is the equation that links magnification, image size and actual size?
Image size = actual size x magnification
Define resolution.
The ability to distinguish between two separate points that are very close together.
Which type of microscope has a higher magnification and resolving power?
Electron microscope.
Why do specimens need to be stained prior to viewing under a microscope?
To see structures more clearly.
Which objective lens should we start viewing with first?
Lowest power objective lens.
Which focus knob should be used at low magnification?
Coarse focus knob.
Which focus knob should be used at high magnification?
Fine focus knob.
What is the key difference between eukaryotes and prokaryotes?
Prokaryotes have no nucleus.
Where is the genetic material found in a prokaryotic cell?
In the cytoplasm.
Give two examples of eukaryotic cells.
Animal cells and plant cells.
Give an example of a prokaryotic cell.
Bacteria.
What is a plasmid?
Small rings of DNA (often containing genes for antibiotic resistance) that are found in some prokaryotes.
What is the function of the flagellum?
Movement.
Define diffusion.
Movement of particles from an area of high concentration to an area of low concentration.
What is cell division used for?
Replacement of old or damaged cells, growth of tissue.
What happens in stage 1 of the cell cycle?
Chromosomes (DNA) and cell organelles replicate.
What happens in stage 2 of the cell cycle?
Mitosis: 1 set of chromosomes move to each end of the cell
What happens in stage 3 of the cell cycle?
Cytoplasm divides to form 2 identical daughter cells.
What is a stem cell?
An undifferentiated cell.
Where are stem cells found in animals?
In embryos and in adult bone marrow.
Where are stem cells found in plants?
Meristem tissue is found at the tips of shoots and roots.
Why are stem cells so important?
They can differentiate into many different specialised cells so can be used to treat diseases.
State three factors that affect diffusion.
Concentration gradient, temperature and surface area.
How does temperature affect the rate of diffusion?
At higher temperature particles have more kinetic energy, so move around more - rate of diffusion increases.
State the relationship between the size of an organism and the SA:V
The bigger the size, the small the SA:V
Describe three adaptations of exchange surfaces.
Large surface area, thin walls, good blood supply.
Define osmosis.
Movement of water from a dilute solution to a concentrated solution.
What will happen to the mass of a piece of potato added to pure water? Explain why.
The potato will gain mass as water moves by osmosis from the dilute solution to the more concentrated solution inside the cells of the potato.
What will happen to the mass of a piece of potato added to a solution of salt/sugar? Explain why.
The potato will lose mass as water moves by osmosis from the more dilute solution inside the cells to the more concentrated solution of salt/sugar.
Define active transport.
Movement of particles from an area of low concentration to an area of high concentration.
Which forms of cell transport are active and which are passive?
Osmosis and diffusion are passive processes whereas active transport requires energy.
Give an example of active transport in plants.
Root hair cells use active transport to transport mineral ions from low concentration in the soil to a high concentration inside the cell.
Give an example of active transport in animals.
Cells in the small intestine use active transport to move glucose from a low concentration in the gut to a high concentration in cells and the bloodstream.
What adaptation do cells that carry out active transport have?
They contain many mitochondria to release energy needed for active transport.