Biology Core Principles 1.3 - Cell Membranes and Transport

Developed from the resources provided by Peter Symonds College

There are lots of flashcards, just to ensure that everything is covered for any eventuality in the exams

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What is the purpose of Cholesterol in the Plasma Membrane?
Provides membrane stability and fluidity by fitting between the fatty acid tails
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What is the function of a Glycoprotein?
Cell to cell communication; acts as an antigen for cell recognition
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What is the composition of a Glycolipid?
Carbohydrate + Phospholipid
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What is the main component of a Plasma Membrane?
Phospholipid Bilayer
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What is the name of the model that suggests how a Plasma Membrane looks?
Fluid Mosaic Model: Fluid (because phospholipids and proteins move around each other), Mosaic (because proteins are arranged between the phospholipids)
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Where are the Glycolipids and Glycoproteins found on the Plasma Membrane?
Outside in the tissue fluid
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What is the function of the Extrensic Proteins?
Receptors (only on one side of the bilayer)
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What are the two Intrensic Proteins, and what are their functions?
Carrier Protein, Channel (Aquaporin) Protein; Channel Proteins transport Water/Ions by Facilitated Diffusion; Carrier Proteins transport large charged/polar molecules
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What is the structure of the Carrier Intrensic Protein?
Two columns, acts as a gateway for transporting in and out of the cell, spans the width of the bilayer, gated at the top, charges around the top and the bottom (hydrophillic) and hydrophobic (non-charged) in the middle
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What is the structure of the Channel Intrensic Protein?
Spans the width of the bilayer, two columns, gap down the middle with charges on the inside only
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List features of the Plasma Membrane
Partially Permeable Barriers; made up of Phospholipids in a Bilayer; composed of Proteins and Phospholipid Bilayer; seen as two dark bands under a microscope (7-8nm in width) but shouldn't be visible in a turgid plant cell
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Describe the structure of a Phospholipid
Phosphate head (hydrophillic), Glycerol, 2 x Fatty Acids (hydrophobic)
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What is the function of the Phospholipid BIlayer?
Barrier to charged ions/polar molecules/bulk of water or water soluble molecules; freely permeable to non-charged/non-polar molecules (e.g. Oxygen and CO2) and anything that is lipid based (steroids) or lipid soluble (some vitamins) via diffusion
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What is the structure of an Extracellular Protein?
Tertiary Structure specific to one Molecule, can sit on top/in the head region of the Phospholipid Bilayer (fully charged) or sit partly into the Phospholipid Bilayer (half charged, half not)
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Define Water Potential
The tendency of free water molecules to move into/out of a system/cell
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What is Water Potential measured in?
kPa (Kilopascal(s))
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Define Osmosis
The movement of water from an area of high water potential to an area of low water potential along a water potential gradient through a partially permeable membrane
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What is the Water Potential of Pure Water? (Highest value)
0kPa
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Explain the role of the cell wall in maintaining turgidity
Ψcell = Ψs + Ψp; helps to counteract an outward pressure from the vacuole and cytoplasm (hydrostatic pressure); turgid is when the vacuole and cytoplasm swell; exerts a pressure on to the cell wall, Ψcell = 0; cell wall exerts opposing force
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What molecules move by Osmosis?
Only water (not water molecules attached to a solute)
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What is a Hypertonic Solution?
It has a lower water potential than the cell cytoplasm because it contains higher concentrations of the solute (measured in moles)
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What is an Isotonic Solution?
It has the same water potential as the cell cytoplasm because it contains the same concentration of the solute.
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What is a Hypotonic Solution?
It has a higher water potential than in the cell cytoplasm. It contains a lower concentration of the solute
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What is the effect of a Hypotonic solution on an animal cell?
Lysis: The water potential is higher in the solution than the cell. Therefore, water enters the cell down a water potential gradient by osmosis
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What is the effect of an Isotonic solution on an animal cell?
Normal: The water potential in the cell and solution is the same. Water will move into/out of the cell down a water potential gradient by osmosis. There is no net gain/loss of water
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What is the effect of a Hypertonic solution on an animal cell?
Crenated: The water potential is higher in the cell that the solution. Therefore, water exits the cell down a water potential gradient by osmosis.
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What is the equation for Water Potential?
Water Potential Ψ (neg/0) = solute potential Ψs (neg/0) + pressure potential Ψp (pos/0)
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What is Hydrostatic pressure?
When water enters a plant cell vacuole by osmosis, exerting an outward pressure on the cytoplasm and cell wall
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What is a Turgid Cell?
Hydrostatic pressure form the cytoplasm + vacuole is opposed by an equal pressure from the cell; Ψcell = 0 (Ψs = Ψp); Healthy Plant
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What is Incipient Plasmolysis?
The point at which the pressure just reaches 0 as the cellular cytoplasm and vacuole are no longer exerting an outward pressure; Ψcell = Ψs (Ψp = 0); 50% of plant cells plasmolysed; Healthy Plant starting to wilt
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What is a Fully Plasmolysed/Flaccid cell?
The cytoplasm and vacuole shrink, meaning the cell membrane moves away from the Cell Wall; Ψcell = Ψs (Ψp = 0); Wilting/Flaccid Plant
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Define Incipient Plasmolysis
When 50% of the cells in a tissue are plasmolysed and 50% are not
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Define Diffusion
Movement of molecules from an area of high concentration to low concentration down a concentration gradient
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Where is Diffusion used in the Cell Membrane, and what energy is used?
Phospholipid Bilayer; Kinetic energy of the molecules; affected by concentration gradient/temperature/surface area/diffusion distance/size of molecule/lipid solubility
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Define Facilitated Diffusion
Movement of molecules from an area of high concentration to low concentration down a concentration gradient via a Channel or Carrier Protein
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Where is Facilitated Diffusion used in the Cell Membrane, and what energy is used?
Channel/Carrier Protein; Kinetic energy of the molecules; affected by the number of specific proteins in the membrane/concentration gradient/temperature
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Define Active Transport
Movement of molecules from an area of low concentration to high concentration against a concentration gradient
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Where is Active Transport used in the Cell Membrane, and what energy is used?
Carrier Protein; ATP from aerobic respiration (lots of mitochondria present, i.e. root hair cells, cells in the kidney); affected by number of specific proteins; can be stopped by the addition of Potassium Cyanide)
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Where is Osmosis used in the Cell Membrane, and what energy is used?
Specific type of hydrophillic Channel Protein called an Aquaporin; Kinetic Energy (aka passive process); affected by the number of specific proteins in the membrane/concentration gradient/temperature
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What limits both Facilitated Diffusion and Active Transport?
Not enough specific Proteins present
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What limits only Active Transport?
A respiratory Inhibitor (Potassium Cyanide) - stops aerobic respiration (no ATP for active transport)
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On a graph, what is the difference in gradient between Diffusion and Facilitated Diffusion/Active Transport
Diffusion has a more shallow gradient but can continue proportionally to the x-axis; Facilitated Diffusion/Active Transport have a steep initial gradient and then levels out as soon as the limiting factors are present
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On a graph, what does the Active Transport line look like when Potassium Cyanide is added?
It decreases the rate of diffusion across the membrane to nought as the concentration difference across the membrane increases
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What is Phagocytosis?
The process by which a cell—often a phagocyte or a protist—engulfs a solid particle to form an internal compartment known as a phagosome.
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What is a structural feature of a cell that can ensure a rapid rate of diffusion?
Infolding of the membrane; Additions to the membrane (where the membrane is pulled off in different directions)
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Other cards in this set

Card 2

Front

What is the function of a Glycoprotein?

Back

Cell to cell communication; acts as an antigen for cell recognition

Card 3

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What is the composition of a Glycolipid?

Back

Preview of the front of card 3

Card 4

Front

What is the main component of a Plasma Membrane?

Back

Preview of the front of card 4

Card 5

Front

What is the name of the model that suggests how a Plasma Membrane looks?

Back

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