cell biology B1 -

• Eukaryotic cells

  Plant and animal cells with a cell membrane, cytoplasm and genetic material enclosed in a nucleus
• Prokaryotic cells

  Bacterial cells that are much smaller, have cytoplasm and a cell membrane surrounded by a cell wall, and genetic material not enclosed in a nucleus but as a single DNA loop and possibly plasmids
• Main sub-cellular structures

  • Nucleus
  • Cell membranes
  • Mitochondria
  • Chloroplasts in plant cells
  • Plasmids in bacterial cells
• Parts of animal cells

  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Ribosomes
• Additional parts of plant cells

  • Chloroplasts
  • Permanent vacuole filled with cell sap
  • Cell wall made of cellulose
• Cell specialisation

  Cells may be specialised to carry out a particular function, e.g. sperm cells, nerve cells, muscle cells in animals, root hair cells, xylem and phloem cells in plants
• Cell differentiation


  As an organism develops, cells differentiate to form different types of cells. Most types of animal cells differentiate at an early stage, while many types of plant cells retain the ability to differentiate throughout life.
• Electron microscope

  Has much higher magnification and resolving power than a light microscope, enabling study of cells in much finer detail
• Magnification

  Calculated as size of image / size of real object
• Chromosomes

  Made of DNA molecules, found in pairs in body cells, carry a large number of genes
• Cell cycle


  1. Genetic material is doubled, then divided into two identical cells

  2. Cell needs to grow and increase sub-cellular structures before division

  3. DNA replicates to form two copies of each chromosome

  4. In mitosis, one set of chromosomes is pulled to each end of the cell and the nucleus divides

  5. Cytoplasm and cell membranes divide to form two identical cells
• Stem cells

  Undifferentiated cells capable of giving rise to many more cells of the same type, and from which certain other cells can arise from differentiation
• Types of stem cells

  • Embryonic stem cells
  • Adult stem cells (e.g. from bone marrow)
  • Meristem cells in plants
• Therapeutic cloning

  Producing an embryo with the same genes as the patient, so stem cells from the embryo are not rejected by the patient's body and may be used for medical treatment
• Diffusion

  The spreading out of particles of a substance in solution or gas, resulting in a net movement from an area of higher concentration to an area of lower concentration
• Factors affecting rate of diffusion

  • Concentration gradient
  • Temperature
  • Surface area of membrane
• Osmosis

  The diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
• Active transport

  Moves substances from a more dilute solution to a more concentrated solution (against a concentration gradient), requiring energy from respiration
• Processes of transport into and out of cells

  • Diffusion
  • Osmosis
  • Active transport
• The nucleus is the largest organelle, containing DNA
• The nucleus is the largest organelle, containing DNA
• Mitochondria are responsible for energy production through respiration
• Ribosomes synthesize proteins using mRNA as a template
• DNA contains genetic information that controls all activities within the cell
• Ribosomes are small structures found floating freely in the cytoplasm or attached to the endoplasmic reticulum
• Ribosomes are small structures that make proteins
• Ribosomes synthesize proteins using instructions provided by mRNA molecules
• Lysosomes contain digestive enzymes that break down waste material inside the cell
• Rough endoplasmic reticulum is where ribosomes attach to synthesise proteins
• Lysosomes contain digestive enzymes that break down waste products within the cell
• Vacuoles store water, nutrients, or waste products within plant cells
• Vacuoles store water, nutrients, or waste products within plant cells
• Smooth endoplasmic reticulum is involved with lipid metabolism
• Vacuoles store water, nutrients, or waste products within plant cells
• Smooth endoplasmic reticulum is involved with lipid metabolism
• Smooth endoplasmic reticulum is involved with lipid metabolism
• Chloroplasts are found only in plants and algae, where they carry out photosynthesis.
• Chloroplasts are found only in plants and algae, where they carry out photosynthesis.
• Vacuoles store water, nutrients, or waste products within plant cells
• Chloroplasts are found only in plant cells and are involved in photosynthesis.