Biology notes

• information to cells-

  • cells are the smallest living units of any organism
  • some organisms are composed of a single cell (unicellular) while other organisms are composed of many cells (multicellular)
  • cells come in different shapes according to their wide variety of functions
• Prokaryotic and Eukaryotic cells

  • Prokaryotic organisms are the most abundant form of life. They are the simplest types of cells, yet they perform a crucial role in most ecosystems.
  • prokaryotes lack membrane-bound organelles, e.g. nucleus
  • Eukaryotic organisms have more complex cells and form the most complex organisms on earth.
• Ribosomes produce protein synthesis (element of a prokaryotic cell)
• Plasmid: a genetic structure in a cell that can replicate independently of the chromosomes, typically a small circular DNA strand in the cytoplasm of a bacterium or protozoan. Plasmids are often used in the laboratory manipulation of genes. (element of a prokaryotic cell).
• mitochondria produce energy (ATP), used for cellular respiration (found in the eukaryotic cell).
• humans have 5 organs that are vital for survival - heart, lungs, liver, kidneys and brain
• cell membrane is a selectively permeable barrier that controls the movement of substances in and out of the cell. it separates the interior of the cell from the outside environment.
• The cytoplasm consists of the cytosol and organelles. cytosol is a gel-like substance, made up of more than 80% of water, and contains ions, salts and organic molecules.
• DNA carries hereditary information, directs the cell's activities and is passed from parent to offspring.
• What distinguishes one cell from another?


  Multicellular organisms become different from one another because they synthesise and accommodate different sets of RNA and protein molecules.
• levels of organization -

  Cells -> Tissues ->Organs ->Systems ->Organisms
• Compare + Contrast

  Similarities -

  • DNA
  • Cytoplasm
  • Cell membrane
  • Ribosomes

  Eukaryotic -

  • evolved from Prokaryotes
  • larger and more complex
  • contains organelles (nucleus)
  • single-celled or multicellular
  • multiple linear chromosomes

  Prokaryotic -

  • oldest cell type
  • small and simple
  • lack organelles (nucleus)
  • single-celled
  • single circular chromosome
• Field of view -

  In a microscope, the field of view (FOV) is the diameter of the circle of light that you can see when looking through a microscope. (As the magnification gets bigger, the FOV gets smaller).
• All cells have a nucleus, cytoplasm, cell membrane, mitochondria and ribosomes
• Golgi Bodies: Flattened membrane sacs that store and modify proteins. (They package proteins and have a shipping side and a receiving side).
• Lysosome: an organelle in the cytoplasm of eukaryotic cells containing degradative enzymes enclosed in a membrane. (Garbage truck - digests leftovers).
• Nucleus: the central and most important part of an object, movement, or group, forming the basis for its activity and growth
• Similarities between plant and animal cells - both have a cell membrane, cytoplasm and nucleus

  Differences - plant cell contains a large, singular vacuole that is used for storage and maintaining the shape of the cell. Animal cells have many, smaller vacuoles.
• How do substances move in and out of cells?


  Active Transport

  Passive transport

  • Simple diffusion - no energy required. movement from high concentration to low concentration.
  • Osmosis - movement of water molecules from areas of high solute concentration to low solute concentrations.
• Dilute solution: Has a small amount of solute in a large amount of solvent.
• concentrated solution - Has a large amount of solute in a small amount of solvent.
• Facilitated diffusion - the passive movement of molecules across a membrane down a concentration gradient via a specific channel or carrier protein.
• Active transport - the movement of materials across a membrane agaist their concentration via a specific carrier protein. Requires energy (in the form of ATP) for molecules to move across the membrane. The movement of molecules from an area of high concentration.
• Bulk transport - involves the movement of materials too large to pass through a carrier or channel protein, in membrane-bound vesicles that fuse with the cell membrane.
• compare endocytosis with exocytosis -

  • endocytosis involves cells taking in substances from outside the cell by engulfing them in a vesicle derived from the cell.
  • Exocytosis is where cells shift materials, such as waste products, from inside the cell to the extracellular space.
• contrast active and passive transport:

  Active transport requires energy for the movement of molecules whereas passive transport does not require energy for the movement of molecules.
• Enzymes -catalysts A biological catalyst that speeds up chemical reactions by lowering the activation energy.

  The body needs to either build substances (anabolic) or break down larger substances (catabolic)
• Anabolic: (energy is required) A reaction that builds up molecules from simpler ones
• Catabolic: (energy is released) - Breakdown of complex molecules into simpler molecules
• 3 things that affect enzymes:

  • Temp
  • Ph
  • Substrate concentration
• Enzymes work by having an active site where the reactant(s), or substrate, will fit and react.
• substrates fit into an enzyme active site, so specifically, it is called the lock and key model.

  This lock and key model works in conjunction with the induced fit model, whereby the enzyme will clamp down when the substrate enters the active site.
• Cell requirements:

  • Proteins
  • Carbohydrates
  • fats (lipids)
  • H2O
  • Vitamins
  • fibre
  • minerals
• Once respiration occurs in the cell mitochondria (in eukaryotic cells), the energy is stored in a weak chemical bond in the organic molecule ADP/ATP (Adenosine Deiphosphate, Adenosine Triphosphate)
• How do cells remove waste?


  Diffusion and Osmosis

  The net movement of anything (for example atoms, ions, molecules, energy) generally form a region of higher concentration to a region of lower concentration.
• Osmosis: The spontaneous passage or diffusion of water and other solvents through a semipermeable membrane.
• Cell specialisation: refers to the particular function of that cell.
• Defferentiation: the process that a stem cell goes through to become specialised. i.e. a muscle cell becomes a nerve cell
• Photosynthetic autotrophs: obtain the energy required for carbon fixation from sunlight.
• Chemoautotroph: chemosynthetic autotrophs obtain the energy required for carbon fixation from inorganic chemical reactions.