Forensic Biology - Membrane

  • Created by: aarafa11
  • Created on: 25-05-20 19:46
Function of a membrane
Separates the cell from its environment; constant internal conditions - Homeostasis; Acts as a semi-permeable membrane
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What is the membrane made of
60% phospholipid, 40% protein
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How is the plasma membrane formed
Phospholipid bilayer - Forms spheres in aqueous environments; Energetically most favourable arrangement
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What does the lipid do in the plasma membrane
constantly move around in their monolayer, but very rarely move between layers
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What does the unsaturated fatty acid do in the plasma membrane
promote flidity by C=C bond in fatty acid tail disrupts packing; Short fatty acids also promote fluidity
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What does the cholesterol do in the plasma membrane
Stiffens the membrane; Cholesterol modulates membrane fluidity by filling spaces between kinks
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Why is fluidity important in a membrane
Ensures even distribution of molecules over membrane (needed for new molecules inserted into membrane & when cells divide); Promotes interactions between proteins, particularly in cell signalling; Allows membranes to fuse with each other
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What molecules can you find in the exoplasmic side of the membrane
oligosaccharie; gycoproteins; cholesterol; phospholipid; integral proteins; hydrophobic ahelix; peripheral protein
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What kind of layer does the cabohydrates form in the exoplasmic side
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What are the functions of the intrinsic membrane proteins
Transport; anchors (link cells extracellular structures; signal receptors; immune system recognition; enzymes
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How is it a semi-permeable membrane
Hydrophobic interior of membrane acts as barrier to ions and polar substances; Molecular movement can allow small quantities of especially smaller molecules through
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What is the difference between passive and active transport
passive requires no external energy whilst active does (using ATP or a protein)
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What affects the rate of diffusion
temperature; volume of container; concentration
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How does a transporter protein move a molecule in or out of a membrane
Substance (substrate) binds to transporter; This alters transporter’s shape (conformational change); Altered shape presents substrate molecule to cytoplasm
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What is a primary active transport
from a hydrolysis of ATP which will induce conformational change to the transporter protein (like a pump); ATP--> ADP + Pi;
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What is a secondary active transport
The transport of 2 substance using electrochemical gradient & trans-membrane transport proteins; no direct use of ATP; High conc of Na+ or H+ outside of cells acts a free energy store- arises from Na/K ATPase;
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Which direction can the 2 substance go in secondary active transport
SYMPORT – both substances transported in same direction; ANTIPORT – one substance goes in one direction, the other substance in the other direction
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What is the threshold for mammals to trigger an action potential
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How oto triiger an action potential
Depolarisation to threshold triggers rapid opening of voltage gated Na+ channels; Allowing a very brief, but rapid influx of Na+ into cell
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What is the resting potential
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What is the order of events from resting potential to action potential
Stimulation caused some Na+ channels to open; as some Na+ enter more channels open thus causing an influx; Neuron is depolarised so it triggers an action potential; all gates open; action potential reached
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How to produce an action potential when the hyperpolarisation is more negative
greater stimulation required to trigger action potential
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How is GABA a inhibitory neurotransmitter
GABAA receptor is a ligand gated ion channel that lets Cl- the into neuron GABA is the ligand, binding to the GABAA receptor opens the Cl- channel
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How does GABA cause hyperpolarisation
GABAA activation - Cl- diffuses into the neuron
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Example of a GABA
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Types of Endocytosis
Phagocytosis and pinocytosis
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Difference between Phagocytosis and pinocytosis
Phagocytosis engulf organism whist pinocytosis engulf large molecules
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How does Endocytosis happen
Vesicles are membrane bound ‘packets’; Membrane the same as plasma membrane; Formed from plasma membrane or can fuse with & become part of plasma membrane
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Card 2


What is the membrane made of


60% phospholipid, 40% protein

Card 3


How is the plasma membrane formed


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Card 4


What does the lipid do in the plasma membrane


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Card 5


What does the unsaturated fatty acid do in the plasma membrane


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