unit 1 summary

• prokaryotic cells 


  a group of single-celled organisms with no nucleus and a circular loop of DNA.
• eukaryotic cells 


  a group of single and multi-celled organisms with a nucleus and linear strands of DNA.
• nucleus 


  • doubble membrane
  • Its role is to protect and confine the genetic information (DNA) of the cell. Inside the nucleus is a smaller structure known as the nucleolus which is the site of ribosome production.
• ribosomes


  made of ribosomal RNA (rRNA) and proteins that fold into a large and small subunit. Cells have many ribosomes, which either float freely in the cytoplasm or are attached to the rough endoplasmic reticulum.
• Rough endoplasmic reticulum


  membranous chain of connected and flattened sacs which are coated with ribosomes. This allows to synthesise and modify proteins.
• Smooth endoplasmic reticulum


  membranous chain of connected and flattened sacs which are not coated with ribosomes. responsible for the production of lipids in a cell.
• gogli apparatus 


  Stacked flattened sacs that are the sites of protein sorting, packaging, and modification for use in the cell or export.
• lysosome 


  membrane-bound vesicle that contains digestive enzymes. It is responsible for breaking down cell waste and toxins, acting like a garbage disposal.
• mitochondrion 


  a highly folded inner membrane surrounded by a second outer membrane. Mitochondria are the site of aerobic cellular respiration, a chemical reaction that produces the ATP required to power cellular processes. They also contain their own DNA and ribosomes.
• chloroplast 


  A double membrane-bound organelle that contains flattened, fluid-filled sacs that are the site of photosynthesis.
• vacuole 


  A membrane-bound sac that is used for water and solute storage. Vacuoles can also play a role in maintaining plant cell structure.
• plasma membrane 


  selectively permeable barrier between the intracellular and the extracellular environment. phospholipid bilayer with embedded proteins
• cell wall


  A sturdy border outside the plasma membrane that provides strength and structure to plant, bacterial, and fungal cells.
• vesicle 


  A small, membrane-bound sac that transports substances into or out of a cell, or stores substances within a cell.
• Cytoskeleton


  A large network of protein filaments that start at the nucleus and reach out to the plasma membrane. The cytoskeleton is critical for maintaining shape and transporting vesicles around the cell.
• comparing plant & animal cells

  plant cells have a cell wall made of cellulose, chloroplast, large vacuole. animals cells do not
• phospholipid bilayer 


  a double layer of amphiphilic molecules (hydrophilic head, hydrophobic tails) that forms the primary component of cell membranes.
• cell theory 


  1 all living things are made up of cells

  2 cells are the smallest and most basic units of life

  3 all cells come from pre-existing cells.
• fluid mosaic model

  • plasma membrane is fluid because phospholipids continually move laterally (side to side)
  • ‘mosaic’ component of the model comes from the proteins and carbohydrates embedded in the membrane
• passive processes


  osmosis: diffusion of water from an area of low concentration to an area of high concentration. (up concentration gradient)

  diffusion: Nonpolar and small molecules can freely diffuse across the plasma membrane. molecules move from an area of high concentration to an area of low concentration (or ‘down their concentration gradient’)

  facilitated diffusion: Molecules that are too large or too charged to freely cross the plasma membrane- use a protein channel, to move down their concentration gradient into or out of the cell.
• hypertonic, isotonic & hypotonic

  • hypertonic solutions have higher solute concentrations, so water moves into a hypertonic solution from areas with lower solute concentrations.
  • isotonic solutions have equal solute concentrations, so there is no net movement of water.
  • hypotonic solutions have low solute concentrations, so water moves from a hypotonic solution into adjacent areas with a higher solute concentration.
• active transport


  protein meditated: uses membrane proteins to move molecules across a membrane against their concentration gradient.

  bulk transport: uses vesicles to move large molecules or groups of molecules into or out of the cell. comes in two forms: exocytosis and endocytosis.
• ATP


  moves molecules against their concentration gradient, produced in the mitochondria.
• prokaryotic cell cycle 


  binary fission: Prokaryotes, such as bacteria, reproduce rapidly via binary fission, which produces two genetically identical copies of a cell. (cytokinesis)
• eukaryotic cell cycle 


  The eukaryotic cell cycle is composed of three stages including interphase, mitosis, and cytokinesis.

  • interphase — cellular growth and duplication of chromosomes
  • mitosis — separation of sister chromatids and the formation of two new nuclei
  • cytokinesis — division of the cytoplasm and formation of two daughter cells.
• mitosis 


  PMAT- prophase, metaphase, anaphase, telophase
• apoptosis


  natural and controlled death of cells within our body.

  • 1 Activation of caspases
  • 2 Digestion of cell contents
  • 3 Cell shrinks
  • 4 Membrane blebbing and breakage

  After apoptosis, phagocytes engulf and digest the free-floating apoptotic bodies by phagocytosis.