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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