Biology

• Cell Theory


  • 1. All living things are made of cells
  • 2. Cells are the smallest and most basic units of life
  • 3. All cells come from pre-existing cell
• Eukaryotes


  • Membrane-bound organelles present
  • DNA organisation: More than one linear strand of DNA packaged in a chromosome in a nucleus
  • Organism nature: Can be unicellular or multicellular
  • Size: Larger (-10-100μm)
  • Method of replication: Mitosis and meiosis
• Prokaryotes


  • Membrane-bound organelles absent (except vesicles)
  • DNA organisation: One circular chromosome and additional plasmids
  • Organism nature: Unicellular
  • Size: Smaller (-0.1-5μm)
  • Method of replication: Binary fission
• Prokaryotes


  A group of single-celled organisms with no nucleus and a circular loop of DNA
• Plasma membrane


  The phospholipid bilayer and embedded proteins which separate the intracellular environment from the extracellular environment. Also known as cell membrane.
• Cytosol


  The aqueous fluid that surrounds the organelles inside a cell
• Ribosomes


  Small RNA-protein structures that are the site of protein synthesis. They either float freely in the cytoplasm or are attached to the RER.
• DNA (deoxyribonucleic acid)

  A double-stranded nucleic acid chain made up of nucleotides. DNA carries the instructions for proteins which are required for cell and organism survival.
• Membrane-bound organelles


  Structure within a cell that is enclosed by a phospholipid bilayer
• Chromosome


  The structure made of protein and nucleic acids that carries genetic information
• Nucleus


  A double membrane-bound organelle that protects and confines the DNA of a cell. Inside the nucleus there's a smaller structure called the nucleolus which is the site of ribosome production.
• Plasmid


  A small, circular loop of DNA that is separate from a chromosome, typically found in bacteria
• Somatic cell


  Any cell that is not a reproductive cell (such as sperm and egg cells). Somatic cells are diploid (2n).
• Mitosis


  The cell division phase which involves the complete separation of sister chromatids and nuclei
• Plant cells have a cell wall in addition to a cell membrane, whereas animal cells have only a cell membrane
• Surface area to volume ratio (SA:V)

  Limits cell size because the bigger the cell gets, the less surface area has for size
• Small cells have large SA:V ratio


  More efficient transport of nutrients in and wastes out of cells, quicker diffusion
• As the cell gets bigger


  The outside is unable to keep up with the needs of the inside
• Components of plasma membrane

  • Lipids (phospholipids and cholesterol)
  • Proteins
  • Carbohydrates
• Forms of passive transport

  • Diffusion
  • Facilitated diffusion
  • Osmosis
  • Active transport
  • Bulk transport
• Diffusion


  The net movement of anything (e.g. atoms, ions, molecules, energy) generally from a region of higher concentration to a region of lower concentration
• Facilitated diffusion


  The passive movement of molecules along the concentration gradient
• Osmosis


  The diffusion of water across a membrane
• Active transport


  The movement of molecules or ions across a cell membrane from a region of lower concentration to a region of higher concentration against the concentration gradient
• Bulk transport


  The movement of macromolecules such as proteins or polysaccharides into or out of the cell
• Photosynthesis


  The process by which light energy is used to convert CO₂ and water into glucose and oxygen
• Photosynthesis


  6CO₂ + 6H₂O→ C₆H₁₂O₆ + 6O₂
• Requirements for photosynthesis


  • Water: absorbed from the soil by the roots
  • Carbon dioxide: obtained from atmosphere
  • Sunlight: from the sun
  • Chlorophyll: pigments are present in plants
• Light-independent reactions


  Also called the calvin cycle
• Light-independent reactions


  NADPH, ATP, CO₂ -> ADP pi, NADP+
• Light-dependent reactions


  NADP+pi, ADP+, H₂O -> O₂, NADP+
• Aerobic cellular respiration


  C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP (30 or 32 energy)
• Stages of cellular respiration

  • Glycolysis
  • Krebs Cycle
  • Electron Transport Chain
• Glycolysis


  Glucose, ADP+ P, NAD+ -> Pyruvate, 2 ATP, NADH
• Krebs Cycle


  Pyruvate (Acetyl CoA), ADP+P, NAD+, FAD+ -> CO₂, 2 ATP, NADH,FADH₂
• Electron Transport Chain


  NADH, FADH, ADP+P, O₂ -> H₂O, 26 or 28 ATP, NAD+, FAD+
• Aerobic respiration


  Happens in the mitochondria, oxygen is present, produces 30 or 32 ATP, glucose + oxygen -> carbon dioxide + water + 30 or 32 ATP
• Anaerobic respiration


  Occurs in the cytoplasm in the absence of oxygen, produces less ATP than aerobic, glucose -> lactate/lactic acid + 2ATP (animal), glucose -> 2 ethanol + 2CO₂ + 2 ATP (yeast)
• Photosynthesis


  Removes CO₂ from the atmosphere, releases O₂ into the atmosphere
• Cellular respiration


  Puts CO₂ back into the atmosphere, uses the O₂ released by photosynthesis to release energy from food