Topic 2

Cards (130)

  • Describe the process of transcription:
    > DNA helicase breaks the hydrogen bonds and unzips the two strands of DNA
    > Complimentary RNA nucleotides move into place and form hydrogen bonds with the exposed bases
    > RNA polymerase moves along the strands and formulates phosphodiester bonds
    > The mRNA moves through the nuclear pores
  • Fick's Law equation
    Rate of diffusion SA ×ΔConcentrationDiffusion dis\frac{SA\ \times\Delta Concentration}{Diffusion\ dis}
  • what is a glycolipid
    lipids with polysaccharide chain attached
  • what is carrier protein
    > move large molecules into or out of cell
    > involve in diffusion (facilitate diffusion)
  • facilitated diffusion
    large molecules or charged particles diffuse through the bilayer by carrier/ channel protein
  • how is transcription involved in enzyme synthesis
    > DNA unzips and H-bond between complementary strands broken
    > template strand is used for mRNA synthesis
    > RNA polymerase is used to join RNA nucleotides
  • how do carrier proteins work
    > large molecule binds to a specific site in carrier protein
    > protein changes shape and releases the molecule on the opposite side of the membrane
  • glycoprotein
    proteins with a polysaccharide chain attached
  • describe the process of endocytosis
    > cell surrounds a substance with a section of its cell membrane
    > cell membrane pinches off to form a visicle
    > vesicle contains ingested substance
    > process uses ATP for energy
  • describe the process of exocytosis
    > release substance produced the cell
    > vesicles contains the substances fuse with the cell membrane and release it outside the cell
    > process uses ATP for energy
  • why doesn't the membrane allow water soluble substance though it ?
    because the centre of the membrane is hydrophobic due to the tails
  • why is the membrane partially permeable
    > small molecules can move through the gaps between phospholipids
    > large molecules and ions can only pass through channel and carrier protein
  • how does active transport works?
    > molecule attaches to carrier protein
    > ATP is hydrolysed in the cell releasing energy
    > energy is used to make the carrier protein to change shape
    > this moves molecules across the membrane, releasing it on the other side
  • why do results differ in beetroot investigation
    > beetroot cells may have been damaged when cutting
    > beetroot pieces not rinsed before being placed in ethanol
    > colorimeter not calibrated properly
  • what is the structure of the cell membrane
    > phospholipid molecules from a continuous layer
    > contain proteins, cholesterol, glycoprotein and glycolipids
  • role of cholesterol in cell membrane
    > fits between phospholipid forming bond with them
    > increases the rigidity of the membrane, making it less fluid
  • describe the effect of ethanol on the permeability of beetroot membrane cell
    > ethanol causes membrane to be disrupted as phospholipids dissolving in ethanol
    > membrane protein are denatured by low pH in ethanol
    > betalin can escape from the cell when membrane is disrupted
  • why are substances taken into the cell by endocytosis
    they are too large to be taken in by carrier protein
  • channel protein
    > form pores in the membrane, allowing charged particles to diffuse through
    > different channel protein, different particles
    > all have a specific shape and can be opened or closed
  • how are mammalian lungs adapted for efficient gas exchange
    > large SA:V due to many alveoli and capillaries
    > short diffusion distance due to alveoli/ capillaries are one cell thick
    > good blood supply due to many capillaries and this ensures a steep concentration gradient
  • why is the bilayer fluid
    phospholipids are constantly moving
  • why the Darson Danielle model does not support the fluid mosaic model
    > molecules cannot diffuse through 2 protein layer
    > no carrier/ channel protein for facilitated diffusion
  • Evidence for fluid mosaic model
    Frye-Edidin experiment
    > fusing of human and mouse cell together
    > later observed the mixing of both cell
    > demonstrating the membrane is fluid
  • what is a codon
    three adjacent bases
  • in Meselson and Stahl experiment, what are the two samples of bacteria grown in
    one in N14 (light nitrogen)
    Another one in N15 (heavy nitrogen)
  • in the Meselson an Stahl experiment, what happens when a sample of DNA is taken from each batch and spun in a centrifuge
    heavy DNA settled lower than the light DNA because it‘s heavier
  • what would happen in DNA replication was conservative
    the original DNA strands would stay together and the new DNA molecule would contain 2 new strands
  • what is tRNA
    > found in cytoplasm
    > has an amino binding site at one end and an anticodon on the other end
    > carries amino acid used to make proteins to the ribosomes
  • what is semi conservative replication
    half new, half original DNA strand
  • how are amino acids joined together to form the 3D structure of a protein
    > peptide bond form between amine group and carboxyl group of another AA
    > Primary structure - sequence of AA in a protein
    > Primary structure folds and held together by bonds
    > bonds include: disulphide bond, ionic bond and H-bond between R groups
  • Step two of DNA replication
    > each original single strand is a template for a new strand
    > complementary base pairing - free floating DNA nucleotides pair up with their complementary bases
  • How can a gene mutation result in a protein not being synthesised
    > mutation changes base sequence
    > a premature stop codon/ frame shift is changed
    > Transcription/ translation does not occur
  • what is the template in mRNA synthesis
    the base sequence that directs the synthesis of the complementary mRNA stand
  • in Meselson and Stahl experiment, what happens as the bacteria reproduce
    > they take up nitrogen from the broth to help make nucleotide for new DNA
    > nitrogen gradually became part of the bacteria’s DNA
  • describe step three of DNA replication
    > condensation reaction join the nucleotides of the new strand together
    > catalysed by DNA polymerase
    > hydrogen bonds form between the bases on the original and new strand
  • define genetic code
    the sequence of base triplets in DNA or mRNA which codes for specific amino acid
  • why does transcription occur?
    > DNA is too large to move out of the nucleus
    > so a section is copied onto mRNA
  • describe step one of DNA replication
    > DNA helicase breaks H-bond between complementary bases
    > Helix unwinds forming 2 single strands
  • what is mRNA
    > made in nucleus during transcription
    > carry DNA genetic code into cytoplasm
    > single strand
    > shorter than DNA
  • what is the template in mRNA synthesis
    > RNA nucleotides attach to mRNA strand
    > base sequence that directs the synthesis of the complementary mRNA strand