Aqa 1 - cell biology

• Which organelles do plant and animal cells both have?

  Cell membrane, cytoplasm, genetic material in a nucleus, mitochondria, ribosomes
• How do bacteria cells compare to plant and animal cells in terms of size?

  They are much smaller
• What do bacterial cells contain?

  Cytoplasm, cell membrane, cell wall. They do NOT have a nucleus - their DNA is a single loop, there may be one or more small rings of DNA called plasmids.
• What is the function of the nucleus?

  Controls the cells activities and contains the DNA.
• What is the function of the cytoplasm?

  Where chemical reactions take place
• What is the function of the cell membrane?


  To control what enters and leaves the cell
• What is the function of mitochondria?

  Where aerobic respiration takes place, provides the cell with energy
• What is the function of ribosomes?

  Where proteins are synthesised (made)
• What is the function of the chloroplast?

  Where photosynthesis takes place
• What is the function of the permanent vacuole?

  Filled with cell sap to help keep the cell turgid
• What organelles are in plant cells but not animal cells?

  Chloroplast, cell wall, vacuole
• What is the cell wall made of in plants and algal cells?

  Cellulose
• Why are plant and algal cell walls made of cellulose?


  To strengthen the cell
• What is the function of a sperm cell and how are they specialised to do this?

  Their function is to fertilise an egg cell. They have:

  -Tail to swim towards the egg

  -Many mitochondria in the midpiece to provide energy for swimming

  -Acrosome at the front, enzymes to break down egg cell membrane

  -Nucleus containing DNA to fuse with egg cell
• What is the function of a nerve cell and how are they specialised to do this?

  Their function is to transmit electrical signals through the body. They have:

  -Dendrites to receive signals

  -Axon to transmit the signal

  -Axon is covered with a fatty sheath to speed up nerve impulses
• What is the function of a muscle cell and how are they specialised to do this?

  Their function is to contract to allow movement.

  They have:

  -Layers of filaments that cause contraction

  -Many mitochondria to provide energy via respiration for contraction
• What is the function of a root hair cell and how are they specialised to do this?

  Their function is to absorb water and mineral ions from the soil. They have:

  -Root hairs to increase surface area, allowing more water and ions to be absorbed

  -Thinner walls so water can move through easily

  -Mitochondria for active transport of ionsSee an expert-written answer!We have an expert-written solution to this problem!
• What is the function of a xylem cell and how are they specialised to do this?

  Their function is to transport water and dissolved ions in a plant. They have:

  -No top and bottom walls between cells, creating a continuous hollow tube

  -Cells are dead, with no organelles or cytoplasm, so water can move freely

  -Cell walls are strengthened with lignin for support
• What is the function of a phloem cell and how are they specialised to do this?

  Their function is to transport dissolved sugars and amino acids around the plant. They have:

  -Cells are joined end to end, with holes in the end cell walls, which allow sugars and amino acids to flow easily through

  -Few subcellular structures to allow materials to flow easily
• When do most types of animal cells differentiate?

  At an early stage
• When do most types of plant cells differentiate?

  They retain the ability to differentiate throughout life
• In mature animals, what is cell division used for?

  Repair and replacement of cells
• What is cell differentiation?

  When a cell acquires different sub-cellular structures to enable it to carry out a certain function.
• What has electron microscope allowed us to see?

  Sub-cellular structures
• How is an electron microscope different to a light microscope?

  Electron microscopes have higher magnification and resolution.
• What is the magnification equation?


  Magnification = image size / real size
• [Triple only] What is binary fission and how quickly does it happen?

  Bacteria multiplying by simple cell division. Can happen as often as once every 20 minutes if cells have enough nutrients and a suitable temperature.
• [Triple only] Where can bacteria be grown?

  Nutrient broth solution, or on agar gel plates.
• [Triple only] What are uncontaminated microorganism cultures used for?

  Investigating the action of disinfectants and antibiotics.
• [Triple only] Why should petri dishes and culture media be sterilised before use?

  To prevent contamination
• [Triple only] Why should loops used to transfer microorganisms to the media be sterilised by passing them through a flame?

  Any microorganisms on the loop are killed to prevent contamination
• [Triple only] Why should the lid of the Petri dish be secured with adhesive tape and stored upside down?

  Prevents drops of condensation from dropping onto the agar
• [Triple only] Why should cultures generally be incubated at 25°C?

  To prevent growth of harmful bacteria
• [Triple only] What is the formula to calculate cross sectional areas of colonies?


  πr²
• What is the cell cycle?


  The stages where cells divide. One of these stages is mitosis.
• What happens in the cell cycle (generally)?

  Genetic material is doubled and then divided to form two identical cells
• What else needs to happen to the cell before it can divide?

  Subcellular structures need to increase in number, eg ribosomes and mitochondria.
• What happens during mitosis?


  One set of chromosomes is pulled to each end of the cell and the nucleus divides. The cytoplasm and cell membrane divide to form two identical cells.
• Why is mitosis important?

  For the growth and development of multicellular organisms.
• What is a stem cell?

  An undifferentiated cell of an organism that can give rise to many more cells of the same type