Cell Biology

• Types of cells

  • Eukaryotic (plant and animal)
  • Prokaryotic (bacteria)
• Differences between Prokaryotic and Eukaryotic cells

  • Prokaryotic cells are smaller
  • Eukaryotic cells contain a nucleus and have more subcellular structures
• What is the Prokaryotic cell wall made of?

  Made of peptidoglycan
• Genetic information storage in prokaryotic cells

  Found free within the cytoplasm as: A single strand on DNA, Plasmid DNA
• Plasmids


  Single loops of DNA in the cytoplasm of Prokaryotic cells
• Subcellular structures in animal cells

  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Ribosomes
• Extra subcellular structures in plant cells

  • Cell wall
  • Permanent Vacuole
  • Chloroplasts
• Nucleus

  Contains genetic material that controls the activities of the cell
• Cytoplasm

  Gel-like substance where most chemical reactions take place, contains enzymes which control these reactions
• Cell membrane

  Controls what goes in and out of the cell
• Mitochondria

  Where aerobic respiration takes place
• Ribosomes

  Where proteins are made in the cell (protein synthesis)
• Cell wall

  Made of cellulose and strengthens the cell
• Permanent vacuole

  Contains cell sap and a solution of sugar and salts
• Chloroplasts

  Where photosynthesis occurs
• Microscopes used to study cells


  • Light microscope
  • Electron microscope
• Differences between electron and light microscopes

  • Light: uses light and lenses to form an image of a specimen, they let us see individual cells and large subcellular structures
  • Electron: uses electrons to form an image, have a higher magnification, have a higher resolution, let us see smaller things in more detail
• Magnification

  Magnification= image size/real size
• Differentiation

  The process by which a cell changes to become specialised
• Differentiation in animal and plant cells

  • Animal Cells- it may occur as an organism develops and is lost at an early stage
  • Plant Cells- lots of plant cells never lose the ability to differentiate (meristem)
• Examples of specialised cells

  • Sperm Cells- get male DNA to female DNA/ reproduction
  • Nerve Cells- carry electrical signals from one part of the body to another
  • Muscle Cells- to contract to generate energy
  • Root Hair Cells- cells on surface of plant roots that absorb water and mineral ions
  • Phloem and Xylem- transport substances around plants
• Adaptations of sperm cells

  • Long tail and Streamline head to help it swim to the egg
  • Lots of mitochondria to provide energy
  • Carries enzymes in its head
• Adaptations of nerve cells

  • Long to cover more distance
  • Branched connections to connect to other nerve cells to form a network throughout the body
• Adaptations of muscle cells

  • Long to have space to contract
  • Lots of mitochondria to generate energy to contract
• Adaptations of root hair cells

  • Large surface area for absorbing water and mineral ions
• Adaptations of Phloem and Xylem

  • Both have long cells
  • Xylem cells are hollow and Phloem cells have very few subcellular structures so stuff can flow through them
• How many chromosomes are there in a human cell?

  46
• Stages of the cell cycle

  • Growth and replication
  • Mitosis
• Growth and replication stage of the cell cycle

  1. DNA is spread out in long strings

  2. The cell increases the amount of subcellular structures

  3. Then it duplicates its DNA
• Mitosis stage of the cell cycle

  1. The chromosomes line up in the centre of the cell and pulled apart

  2. Then they go to opposite ends of the cell

  3. Membranes form around each sets of chromosomes (the nucleus has divided)

  4. The cytoplasm and cell membrane divide

  5. Two new daughter cells have been produced
• Binary fission

  The way prokaryotic cells reproduce
• Binary fission

  1. The circular DNA and plasmids replicate

  2. The cell gets bigger and the circular DNA moves to opposite ends of the cell

  3. The cytoplasm begins to divide and new cell walls begin to form

  4. The cytoplasm has divided and two daughter cells are produced. Each has one circular DNA but can have different numbers of plasmids
• Stem cells

  Cells that have not been differentiated
• Location of stem cells

  Stem cells can be found in early human embryos and in adult human bone marrow
• Difference between adult stem cells and early human embryos

  Early human embryos can be turned into any type of cell but adult stem cells can only be turned into blood cells
• Uses of stem cells

  They can be differentiated for medicine and research
• How stem cells can help cure diseases

  • Adult stem cells can be transferred from bone marrow of a healthy person and replace faulty blood cells
  • Embryonic stem cells can replace faulty cells in sick people e.g. insulin producing cells for diabetes
• Positives and negatives of therapeutic cloning

  • Pros- made with same genetic material as patient so wouldn't be rejected
  • Cons- risks of being contaminated with a virus in a lab so it the patient could get sicker
• Diffusion

  The spreading out of particles from an area of high concentration to lower concentration
• Factors affecting rate of diffusion

  • Concentration gradient- larger gradient, faster diffusion
  • Temperature- higher temperature, faster diffusion
  • Surface area- larger surface area, faster diffusion