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• What does it mean if a cell is described as ‘prokaryotic’?

  Prokaryotic cells do not contain a nucleus.
• Name 3 features of plant cells that are not present in bacterial cells.

  Nucleus

  Mitochondria

  Chloroplasts
• What is the function of the mitochondria? [1 mark]


  Where respiration takes place, providing the cells with energy.
• What structures are A. and B. ?

  A.Vacuole

  B.Mitochondria

  
• Red blood cells are specialised animal cells. Compare the structure of a red blood cell with the structure of a plant cell (6)

  Differences:

  • RBC no nucleus, PC nucleus
  • Chlorophyll may be in PC, no chlorophyll in RBC
  • RBC is biconcave, different shapes of PC
  • RBC contain haemoglobin, PC do not. Similarities
  • Both have cytoplasm and cell membrane
• When placed into a beaker of water a red blood cell bursts, a plant cell does not burst.

  Explain why the red blood cell bursts but the plant cell does not burst (2)

  Water enters the cell wall by osmosis, RBC has no cell wall.

  Plant cell has a cell wall, which prevents it from bursting.
• Which diagram shows oxygen moving by diffusion?

  1

  
• What is the function of the nucleus? (1)


  Contains genetic material which controls the activity of a cell.
• Name one type of cell that does not contain a nucleus. (1)

  Three possible answers- Bacteria, red blood cell, xylem.
• Eukaryotes - Plant and animal cells that have a cell membrane, cytoplasm, and genetic material enclosed in a nucleus.
• Prokaryotes - Bacterial cells that contain cytoplasm, cell membrane surrounded by cell wall.
• Cell membrane


  Controls passage of substances into and out of the cell.
• Cytoplasm


  Where chemical reactions take place.
• Mitochondria


  Where aerobic respiration takes place.
• Ribosomes


  Where protein synthesis occurs.
• Chloroplasts (plant cells only)


  Absorb light to make food by photosynthesis.
• Permanent vacuole (plant cell only)


  Filled with cell sap.
• Cell wall (plant and bacteria)


  Made of cellulose, strengthens the cell.
• sperm cells - specialised for reproduction, long tail and head to help swim to the egg. A lot of mitochondria to provide energy.
• Nerve cells - specialised for rapid signalling, long to cover more distance, branched connections to connect to other nerve cells. Forms a network throughout the body.
• Muscle cells - specialised for contraction, contract quickly, long for lots of space to contract, a lot of mitochondria for energy.
• Root hair cells - specialised for absorbing water and minerals, grow into hairs to increase surface area of plant, more water/mineral uptake.
• Phloem and xylem cells - specialised for transporting substances, tubes for transporting food and water around plants. Xylem are hollow, phloem have very few subcellular structures so stuff can flow through them.
• As an organism develops, cells differentiate to form different types of cells.
• • Many types of plant cells retain the ability to differentiate throughout life.
• • Most types of animal cell differentiate at an early stage.
• In mature animals, cell division is mainly restricted to REPAIR and REPLACEMENT. As a cell differentiates it acquires different sub-cellular structures to help it carry out a certain function. It has become a specialised cell.
• Examples of differentiated cells in mature animals are skin or blood cells.
• An electron microscope has much higher magnification and resolving power than a light microscope.
• $Magnification =$$size of image/ size of real object$

  
• Electron microscopes can show us tinier things like ribosomes and plasmids.
• Light microscopes use light and lenses to magnify.
• Light microscopes let us see individual cells and large subcellular structures such as nuclei.
• A specimen is 50μm wide. Calculate the width of the image of the specimen under a magnification of x100. Give your answer in mm.

  image size = magnification x real size

  image size = 100$*$50

  =5000μm

  =5mm
• The nucleus of a cell contains chromosomes made of DNA
•  Each chromosome carries a large number of genes.
• In body cells the chromosomes are normally found in pairs.
• Cell cycle - During the cell cycle the genetic material is doubled and then divided into two identical cells.
• Cell division by mitosis is important in the growth and development of multicellular organisms.
• • Growth and DNA replication:

  1. Cell grows and increases the amount of subcellular structures, such as mitochondria and ribosomes.
  2. It then duplicates its DNA.

  • Mitosis:

  1. Chromosomes are pulled apart by cell fibres.
  2. Membranes form around each set of chromosomes.
  3. Cytoplasm and cell membrane divide.
  4. Cell has now produced two new daughter cells.