Biology Summary Part 2 on Revision Cards

Revision summary part 2- from revision notes part 1

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  • Created by: sophie
  • Created on: 09-12-12 19:00

Prokaryotes

PROKARYOTIC

  • No true nucleus
  • Naked DNA
  • DNA in a nucleoid or plasmid
  • Average diameter- 0.5-5 um
  • Circular DNA
  • 70s ribosome(smaller than eukaryote)
  • cell wall= Petidoglycan
  • no membrane bound organelles
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Eukarotes

Eukaryotes

  • has a true nucleus
  • DNA wrapped around protiens
  • DNA in a nucleus
  • Average diameter of cell- 10um
  • Linear chromosomes
  • has membrane bound organelles
  • 80s ribosome(larger than prokaryotes)
  • In plants cell wall present made of cellulose
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Roles of membranes at surface

  • Seperates the cell from external environment
  • controls what enters and exits the cell
  • for example, only small or lipid molecules can pass directly through the bilayer
  • Larger molecules can be transported through carrier or channel protiens, this is called facilitated diffusion
  • Cell surface membrane can also contain glycoprotiens that can act as receptors
  • Is a partially permeable barrier
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Roles of membranes within cells (from markscheme)

  • surrounds organelles
  • prevents disruption of reactions
  • Reactions take place on membranes
  • enzymes attached to membranes isolates DNA
  • the nuclear pore allows RNA to leave the nucleus
  • intracellular transport
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Effects of changing temperature on membranes

  • Increasing the temperature would make a membrane more fluid and more permeable
  • More Kinetic energy- increased movement of phospholipids- membrane= LEAKY
  • E.g- Beetroot- cell membrane damaged- release red pigment
  • Structure of protien components of the membrane denatures


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Cell Signalling (from mark scheme)

Communication between cells to trigger a reaction

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Cholesterol (REMEMBER SPELLING OR LOSE MARKS)

Cholesterol- provides mechanical Stability, this steroid molecule fits between fatty acid tails and helps make barrier complete

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Glycoprotiens

  • Act as antigens for cell recognition 
  • Act as a receptor- binding site for chemicals
  • can hold cell together
  • receptors for cell signalling
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Cholesterol (REMEMBER SPELLING OR LOSE MARKS)

Cholesterol- provides mechanical Stability, this steroid molecule fits between fatty acid tails and helps make barrier complete

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Hormone Receptors

A hormone molecule binds to a receptor on a target cell surface membrane because the two have complementary shapes. Binding of the hormone and receptor causes the target cell to respond in a certain way.

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Hormones and a target cell

Hormones are chemical messengers, produced in specific tissues and then released into the the organism. Any cell with a receptor for the hormone molecules is called a target cell.

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Hijacking receptors

Viruses enter cells by binding with receptors on the cell's plasma membrane that normally bind to the host's signalling molecules.

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Beta-blockers

Drugs are complementary to the shape of the receptor molecule, this is a beta blocker

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