2.1 Cell Structure

• Structure of an animal cell

  Animal cell:

  
• Structure of plant cells

  Plant cell:

  
• What organelles do plant cells have that animal cells do not

  1 A cellulose cell wall

  2 A vacuole

  3 Chloroplasts
• Describe the cell-surface membrane

  All cells are surrounded by a cell surface membrane which are formed from a phospholipid bilayer made of proteins
• Function of the cell-surface membrane

  Controls the exchange of materials between the internal cell environment and the external environment. It also has receptor molecules on it which allows it to respond to chemicals like hormones
• Describe the structure of the nucleus

  An organelle present in all eukaryotic cells which is surrounded by a nuclear envelope which has many pores

  
• Why are nuclear pores important

  They are channels which allow mRNA and ribosomes to travel out of the nucleus as well as allowing enzymes to travel in.
• Function of the nucleus

  Controls the cell’s activities by controlling the transcription of DNA and contains the genetic material of the cell
• Structure of mitochondria

  Cristae - inner membrane folds

  Matrix - formed by the cristae, contains enzymes needed for aerobic respiration

  
• Function of mitochondria

  The site of aerobic respiration which produces ATP - a common energy source in the cell
• Where can ribosomes be found

  1 Freely in the cytoplasm

  2 As part of the rough endoplasmic reticulum
• Structure of ribosomes

  1 Made up of proteins and RNA

  2 not surrounded by a membrane
• Function of ribosomes

  Site of translation (protein synthesis)
• Structure of the Rough Endoplasmic reticulum (RER)

  Surface covered in ribosomes, formed from continuous folds of membranes continuous with the nuclear envelope
• Function of the RER

  Processes proteins made by the ribosomes
• Structure of the Smooth Endoplasmic Reticulum (SER)

  Does not have ribosomes on the surface
• Function of the SER

  Involved in the production, processing and storage of lipids, carbohydrates and steroids
• Structure of the Golgi apparatus

  Flattened sacs of membrane

  
• Function of the Golgi apparatus

  Modifies proteins and lipids before packaging them into golgi vesicles
• Structure of a Golgi vesicle

  A small fluid-filled sac in the cytoplasm, surrounded by a membrane and produced by the Golgi apparatus.
• Function of a Golgi vesicle

  Transport the proteins and lipids to their required destination

  
• Structure of a lysosome

  Specialist forms of vesicles surrounded by a membrane
• Function of lysosomes

  Contain hydrolytic enzymes called lysozymes which can break down biological molecules.
• Function of the centrosome

  Organises the spindle fibres during cell division

  
• Structure of the large permanent vacuole

  A membrane-bound organelle which contains cell sap.

  
• Function of the vacuole

  Helps to maintain pressure inside the cell and keep it rigid
• Structure of chloroplasts

  Surrounded by a double membrane

  
• Function of chloroplasts

  Site of photosynthesis

  • Light-dependent phase, thylakoids
  • Light-independent stage takes place in the stroma
• Structure of the cell wall

  A rigid structure that surrounds the cell membrane made up of cellulose
• Function of the cell wall

  Provides structural support
• Define specialised cell

  A cell that has differentiated and has special features that allow it to carry out a particular function
• Describe how neurones have been specalised

  1 The myelin sheath covering the axon, speeds up nerve impulses

  2 Axons are long, enables fast communication over long distances
• Describe how muscle cells have been specialised

  1 Layers of protein filaments, can slide over each other causing muscle contraction

  2 High density of mitochondria, provide energy for muscle contraction
• Describe how sperm cells have been specialised

  1 Haploid nucleus, when the sperm cell fuses with an egg cell the embryo will contain a diploid amount of chromosomes

  2 Acrosome, contains digestive enzymes that break down the outer layer of an egg cell so they can fuss

  3 Flagellum, rotates which allows the sperm cell to move towards the egg
• Describe how root hair cells have been specialised

  1 Root hairs, increase surface area so the rate of water uptake by mitosis is greater

  2 Mitochondria, produces energy for the active transport of mineral ions
• Describe how xylem cells have been specialised

  1 No top and bottom walls, forms a continuous hollow tube which water is drawn upwards in

  2 Dead cells, allow free movement of water

  3 Thick outer walls (lignin), strengthen tubes which helps support the plant
• Describe how phloem cells have been specialised

  1 Made of living cells

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

  3 Few subcellular structures, aid the flow of materials
• Define a tissue

  A group of cells that work together to perform a particular function
• Define organs

  Tissues that work together
• Define organ systems

  Different organs work together to form organ systems