biology unit 1

• secondary structure proteins - keratin = alpha helixes and fibroin = beta pleated sheets
• advantages of membrane bound organelles - potentially harmful chemicals such as enzymes are isolated and molecules with a particular function like chlorophyll can be concentrated in one area
• 1000 nm = 1 um

  1000 um = 1 mm
• chromatin = coils of DNA bound to protein
• nucleolus = site of formation of rRNA - ribosomes
• mitochondria - 2 membranes separated by a fluid filled (matrix) inter membrane space, inner membrane has folds to increase SA called cristae, contains ribosomes and circular DNA to make their own proteins and self replicate - function is to produce ATP in aerobic respiration and being a cylinder they reduce diffusion distance between outside and centre
• chloroplasts - most in palisade mesophyll, has a double membrane, fluid filled (stroma), contain circular DNA and ribosomes to make their own proteins and self replicate, contain flattened sacs called thylakoids, stack of thylakoids called a granum - contain chlorophyll and increase SA for light absorption
• rough er - has ribosomes on surface and transports proteins made to golgi body
• smooth er - synthesis and transport of lipids
• golgi body - proteins modified (into a glycoprotein for example) and packaged
• lysosomes are pinched off golgi body and contain and isolate potentially harmful digestive enzymes
• centrioles - only in animal cells - organise the microtubules that make the spindle in cell division
• vacuoles contain cell sap that stores glucose, amino acids and minerals and vitamins and pigments and provide support
• cell wall - provides mechanical strength, transport between the gaps and communication between cells via plasmodesmata
• interrelationship of organelles

  1. nucleus contains chromosomes in which the DNA encodes proteins
  2. nuclear pores allow mRNA to leave the nucleus
  3. protein synthesis occurs on the ribosomes - primary structure
  4. polypeptides are packaged and transported by RER to golgi body
  5. golgi body chemically modifies, folds and packages proteins into vesicles
• prokaryotes - no internal membranes, mesosome for respiratio, DNA loose in cytoplasm (some have plasmids which is circular DNA), flagellum
• epithelial tissue - simple = one cell thick, stratifies = layers. cuboidal = salivary gland ducts. columnar = trachea and fallopian tube. squamous = alveoli walls
• muscle tissue - cardiac (doesn’t tire and contracts rhythmically), smooth muscle (skin and walls of digestive and respiratory tracts, involuntary muscles), skeletal (attached to bones, powerful contractions but tire easily, voluntary)
• connective tissue is tissue that connects and supports or separates tissues and organs
• extrinsic proteins are on the surface of the membrane, they provide structural support, form recognition sites and receptor sites for hormone attachment
• intrinsic proteins - carrier = water soluble substance, channel = active transport of ions
• cholesterol in membranes makes them more rigid and stable
• glycoproteins and glycolipids act as hormome receptors for cell to cell recognition
• rate of diffusion -

  1. concentration gradient
  2. thickness of exchange surface
  3. surface area of membrane
  4. molecule size
  5. temperature
  6. nature of diffusing molecules - water or fat soluble
• carrier proteins - water soluble ions pass through - open and close depending on needs of the cell
• channel proteins - large polar molecule for example glucose and amino acids - attaches to binding site and protein changes shape to to release it
• active transport - mineral uptake in root hair cells. molecule or ion combines with specific carrier protein and ATP transfers phosphate group to carrier protein on inside of membrane, carrier protein changed shape and allows molecule or ion across, phosphate ion is released and re combines with ADP to form ATP
• cyanide = respiratory inhibitor
• co-transport - a glucose molecule and 2 sodium ions attach to a carrier protein on the outside of the membrane, carrier protein changed shape and allows them through, both travel to opposite membrane, glucose diffuses into blood by facilitated diffusion and sodium ions by active transport
• water potential is measure in kPa and is the tendency for water molecules to move.
• solute potential - measures how easily water molecules move out of a solution so a higher concentration has a more negative solute potential
• pressure potential in plant cells - pressure put by cell walls as water moves in and cell becomes turgid
• water potential of outside solution is higher - hypotonic - water moves into cell
• water potential of outside solution is lower - hypertonic - water flows out of cell
• water potential of cell = water potential external solution - isotonic
• plasmolysis = cell in a hypertonic solution - vacuole shrinks and cytoplasm moves away from cell wall - cell is flaccid
• incipient plasmolysis - cell loses just enough water for cytoplasm to begin to pull away from cell wall
• osmosis in animal cells - no cell wall so no pressure potential - water potential = solute potential. red blood cells in a hypertonic solution burst and red blood cells in a hypotonic solution shrinks and becomes crenated
• bulk transport = endocytosis and exocytosis. uses ATP because changed shape of cell membrane. endocytosis decreases the overall area and exocytosis increases it
• phagocytosis - lysosome fuses with vesicle and enzymes digest the cells and the products are absorbed into cytoplasm