From Molecules to Organisms: Membrane Structure … · Membrane Structure and Function ... •Movement of substances across cell membranes can ... -Active transport requires energy
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Structure & Function (LS1A) Membrane Structure and Function
•All cells have similar structures and those structures have similar functions.
•Cell membranes:-separate living cells from their non-living environment,-are made of a phospholipid bilayer, -and are selectively permeable.
Non polar tails
Polar head
Phospholipid
Hydrophobic environment
Hydrophilic environment
Hydrophilic environment
Plasma Membrane
The hydrophobic interior prevents charged substances (ions, polar molecules) from passing through the membrane, therefore membranes are selectively permeable.
•Cell membrane structure is described as a fluid mosaic.-Fluid- lateral movement of molecules-Mosaic- diverse protein molecules embedded in a framework of phospholipids
Fibers of the extracellular matrix
Glycoprotein
Carbohydrate (of glycoprotein)
Microfilaments of the cytoskeleton
Phospholipid
CholesterolProteins
CYTOPLASM
Glycolipid
OUTSIDE CELL
Cholesterol which is wedged into the bilayer, it helps stabilize the phospholipids at body temperature but also helps keep the membrane fluid at lower temperature. Carbohydrate bound to proteins (glycoprotein) and to lipids (glycolipid) serve as identification tags. Membrane proteins attach the membrane to the cytoskeleton and external fibers, provide identification tags, form junction between adjacent cells, function as enzymes, cell receptors and facilitate signal transduction, as well as facilitate the movement of materials across the cell membrane.
•Movement of substances across cell membranes can occur through both passive transport and active transport.
-Passive transport substances diffuse through membranes without cellular work, no ATP (diffusion, osmosis, facilitated diffusion).
EQUILIBRIUMMolecule of dye High Concentration Membrane
EQUILIBRIUMMembraneHigh Concentration
1. Diffusion is the tendency for particles to spread out spontaneously to regions where they are less concentrated. A substance diffuses down a concentration gradient, from areas of high concentration to areas of lower concentration.No energy (ATP) required.
2. Osmosis is the diffusion of water across a selectively permeable membrane. Hypertonic- solution have a high solute concentrationHypotonic- solution have a low solute concentrationIsotonic- solution have equal concentrationsNo energy (ATP) required.
ATP
Hypotonic
Solute molecule
HYPOTONIC SOLUTION
Hypertonic
HYPERTONIC SOLUTION
NET FLOW OF WATER
Solute molecule with cluster of water molecules
Selectively permeable membrane
Selectively permeable membrane
Water molecule
Isotonic
•Movement of substances across cell membranes can occur through both passive transport and active transport.
-Passive transport substances diffuse through membranes without cellular work, no ATP (diffusion, osmosis, facilitated diffusion).
•Movement of substances across cell membranes can occur through both passive transport and active transport.
-Passive transport substances diffuse through membranes without cellular work, no ATP (diffusion, osmosis, facilitated diffusion).
3. Facilitated diffusion is the movement of a molecule across a biological membrane by a specific transport protein.The transport protein provides a pore for the passage of a particular solute (sugars, amino acids, atomic ions and water).No energy (ATP) required.
1. Active Transport requires that a cell expend energy to move molecules a crossed a membrane.Transport proteins actively pump specific solute across a membrane against the solute’s concentration gradient.Energy (ATP) required.
ATP
Transportprotein
FLUID OUTSIDE CELL
First solute
Phosphorylated transport protein
2 ATP transfers phosphate to protein
3 Protein releases solute outside cell
4 Second solute binds to protein
Second solute
5 Phosphate detaches from protein
6 Protein releases second solute into cell
First solute, inside cell, binds to protein
1
•Movement of substances across cell membranes can occur through both passive transport and active transport.
-Active transport requires energy from the cell, ATP required (active transport, exocytosis, endocytosis).
•Movement of substances across cell membranes can occur through both passive transport and active transport.
-Active transport requires energy from the cell, ATP required (active transport, exocytosis, endocytosis).
2. Exocytosis is the process by which large molecules (such as proteins) are exported outside the cell.A membrane-enclosed vesicle filled with macromolecules (green) moves to the plasma membrane and fuses with the plasma membrane, spilling the contents of the vesicle outside the cell. Energy (ATP) required.
•Movement of substances across cell membranes can occur through both passive transport and active transport.
-Active transport requires energy from the cell, ATP required (active transport, exocytosis, endocytosis).
1. Endocytosis is the process by which large molecules are imported into the cell.A cell takes in macromolecules or other particles by forming vesicles or vacuoles from it plasma membrane.Energy (ATP) required.
•Osmoregulation is the active regulation of the level of water in an organism.
•Water balance problems are somewhat different for plant cells and animal cells.
ISOTONIC SOLUTION
HYPOTONIC SOLUTION
HYPERTONIC SOLUTION
(1) Normal
(4) Flaccid
(2) Lysing
(5) Turgid
(3) Shriveled
(6) Shriveled
ANIMALCELL
PLANTCELL
Plasma membrane
Animal cells prefer isotonic environments, where the net flow of water into the cell is equal to the flow of water out of the cell. Plant cells prefer a hypotonic environment, which creates a net flow of water into the cell. The plant’s cell wall prevents the cell membrane from bursting, creating turgid pressure.
Osmotic water gain through gills and other parts of body surface
Uptake ofsalt ions by gills
Excretion of large amounts of water in dilute urine from kidneys
Gain of water and salt ions from food and by drinkingseawater
Osmotic water loss through gills and other parts of body surface
Excretion of saltions from gills
Excretion of salt ions and small amounts of water in scanty urine from kidneys
Freshwater fishes gain water by osmosis and tent to lose solutes. It takes the work of three organ systems (digestive, respiratory, excretory) to achieve the proper water and solute balance.
Saltwater fishes internal fluids are lower in total solutes than seawater, therefore it loses water by osmosis through its body surfaces. It takes the work of three organ systems (digestive, respiratory, excretory) to achieve the proper water and solute balance.
Paramecium are Protozoans (single celled animals that live in fresh water and have contractile vacuoles. Why would this type of organisms need contractile vacuoles to survive?
Terrestrial animals obtain most of their water from food and drink. They lose water by urination, defecting, and evaporation as they breathe and perspire. Why is it not healthy to drink salt water?
•Osmoregulation in organisms
hypotonic
hypertonic
Contractile vacuoles pump water out to prevent the cell from bursting.
Saltwater is hypertonic to human blood and fluids. So, if you drank saltwater you would actually lose more water than you gained, effectively dehydrate your body.