Cell structure

• Problems with chemotherapy

  - Resistance

  - Multidrug resistance

  - Toxicity

  - Treatment-induced tumors

  - Damage fast replicating cells like hair producing cells
• Treatment of cancer

  - Preventing DNA from replicating

  - Inhibiting the metaphase stage of mitosis by interfering with spindle fibre formation.
• Nuclear division


  When the nucleus divides either into two (mitosis) or four (meiosis)
• Interphase

  Occupies most of the cell cycle, and is sometimes know as the resting phase because no division takes place.
• Replication of viruses


  Attach to their host cell with attachment proteins on their surface. They inject viral nucleic acid into the host cell. Genetic information on the viral nucleic acid then provides the instructions for the host cells metabolic processes.
• Cell division in prokaryotic cells

  Binary fission

  Circular DNA molecular replicates and both copies attach to the cell membrane. Plasmids replicate. Cell membrane begins to grow between the two DNA molecules and begins to pinch inward dividing the cytoplasm. A new cell forms between the two molecules of DNA, two identical daughter cells each with a single copy of circular DNA and plasmids.
• Telophase


  The chromosomes reach the poles and become longer and thinner, finally disappearing altogether, leaving only widely spread chromatin. The spindle fibres disintegrate and the nuclear envelope and nucleolus re form.
• Anaphase


  Spindle fibres pull the sister chromatids apart at the centromere. Individual chromatids now referred to as chromosomes are at each pole.
• Metaphase

  Chromatids are joined by the centromere and are lined up along the equator of the cell. Spindle fibres obvious.
• Prophase (mitosis)


  Chromosomes first become visible. Centrioles move to the poles of the cell. Spindle fibres develop from the centrioles. Nuclear envelope disintegrates and nucleolus disappears.
• Mitosis


  part of eukaryotic cell division during which the cell nucleus divides
• Structure of bacterial cells

  Bacterial cells are eukaryotic and lack membrane-bound, specialized organelles. Their interior consists of only the cytoplasm, ribosomes, and genetic material.
• Prokaryotic cells


  do not have a nucleus or other membrane-bound organelles
• Eukaryotic cells


  Contain a nucleus and other organelles that are bound by membranes.
• Circulatory system

  Pumps and circulates blood. Made up of organs including heart, arteries and veins.
• Respiratory system


  Used for breathing and gas exchange. Made up of organs including trachea, bronchi and lungs
• Digestive system


  Digests and processes food. Made up of organs that include salivary glands, oesophagus, stomach, duodenum, ileum, pancreas and liver.
• Organ systems


  A group of two or more organs working together for a specific job; e.g. the digestive system
• Organs


  A structure consisting of several tissues adapted as a group to perform specific functions.
• epithelial tissue


  Sheets of tightly packed cells that line organs and body cavities
• Tissues


  Groups of cells with a common structure and function.
• Cell specialisation


  When cells take on special features to enable them to carry out a specific task
• Vacuoles function

  - Support herbaceous plants and herbaceous parts of woody plants, by making cells turgid

  - Sugars and amino acids may act as a temporary food store

  - Pigments may colour petals to attract pollinating insects
• Vacuoles

  Cell organelle that stores materials such as water, salts, proteins, and carbohydrates
• Cell Wall functions

  - Provide mechanical strength in order to prevent the cell busting under pressure created by the osmotic entry of water

  - To give mechanical strength to the plant as a whole

  - To allow water to pass along it and so contribute to the movement of water through the plant
• Cell wall features

  - Consists of a number of polysaccharides such as cellulose

  - Thin layer called the middle lamella which marks the boundary between adjacent cell walls and cements adjacent cells together.
• Ribosomes 70s


  Found in prokaryotic cells, mitochondria and chloroplasts, is slightly smaller than 80s
• Ribosomes 80s


  Found in eukaryotic cells around 25nm in diameter
• Ribosomes

  site of protein synthesis
• Function of Lysosomes

  - Hydrolyse material ingested by the phagocytic cells (white blood cells and bacteria)

  - Release enzymes to the outside of the cell (exocytosis) in order to destroy material around the cell

  - Digest worn out organelles so that the useful chemicals they are made of can be re-used

  - Completely break down cells after they have dies (autolysis)
• Lysosomes

  Formed when the vesicles produced by the Golgi apparatus contain enzymes proteases and lipases. They also contain lysozymes, enzymes that hydrolyse the cell walls of certain bacteria.
• Functions of Golgi Apparatus

  - add carbohydrates to proteins to form glycoproteins

  - produce secretory enzymes, such as those secreted by the pancreas

  - secrete carbohydrates, such as those used in making cell walls in plants

  - transport, modify and store lipids

  - form lysosomes
• Golgi Apparatus


  A system of membranes that modifies and packages proteins for export by the cell
• Functions of S.E.R

  - Synthesise, store and transport lipids

  - Synthesis, store and transport carbohydrates
• Smooth Endoplasmic Reticulum (SER)


  Lacks ribosomes on its surface and is often more tubular in appearance.
• Functions of R.E.R

  - Provide a large surface area for the synthesis of proteins and glycoproteins.

  - Provide a pathway for the transport of materials, especially proteins, throughout the cell.
• Rough Endoplasmic Reticulum (RER)

  Has ribosomes present on the outer surface of the membranes.
• Endoplasmic Reticulum (ER)


  Elaborate three dimensional system of sheet like membranes spreading through the cytoplasm Continuous with the outer nuclear membrane. The membranes enclose a network of tubules and flattened sacs called cisternae.
• How are chloroplasts adapted to their function?

  Thegranal membranes

  - Provide alarge surface area for attachment of chlorophyll, electron carriers and enzymes that carry out the first stage of photosynthesis

  - These chemicals are attached to the membrane in order

  
  

  Fluid of stroma

  - Possesses all theenzymes needed to make sugarsin the second stage of photosynthesis

  
  

  Contain both DNA and ribosomes

  - So they canquickly and easily manufacture some of the proteins needed for photosynthesis
• Stroma


  Fluid filled matrix where the second stage of photosynthesis (synthesis of sugars) takes place. Within the stroma are a number of other structures such as starch grains.