1.3-Cell membranes and transport Flashcards
Define Fluid?
Because phospholipid molecule within a layer can move relative to each other.
Define musaic?
Because proteins within phospholipid layer are of different sizes, shapes and form different patterns.
Define cell membrane?
Fluid mosaic model?
1.Extrinsic protein
2.Intrinsic protein (Channel / carrier proteins)
3.Cholestrol
4.Glycoprotein
5.Phospholipid Bilayer
Extrinsic Protein?
Those with sugars attached glycoproteins form glycocalyx layer of membrane which has role in cell-to-cell recognition or hormone receptor sites.
Intrinsic protein: Channel protein
-Channel protein pores lined with polar hyophilic groups that allow charged ions through eg Na+.
Carrier protein:
Allow large polar molecules through, eg water soluble sugars and amino acids.
Cholesterol:
Found in between phospholipid making it rigid and stable, less fluidity, membrane less permeable.
Permeability increase by:
Lipid soluble substances:
(Vit A) and small molecules (O and co2) and move directly through phospholipid bilayer.
Water soluble substances:
(Glucose, ions, polar molecules) cant pass through hydrophobic fatty acids tails and so must use intrinsic proteins to pass through.
Active transport?
Movement of molecules against concentration gradient from low conc to high conc. Process require energy in form of ATP from respiratory.
Graph (AT):
Trend seen
-Mineral s ion taken by active transport.
-Active transport need energy ATP.
-ATP made in respiration, so no respiration, no ATP, no uptake.
Diffusion?
Movement of molecules from region of low concentration to high region down a conc gradient. Passive process requires no ATP, occurs through Phospholipid bilayer.
Diffusion increase by:
-Thinner membrane
-Small molecules
-LSA
-Inc temp
-Higher conc gradient
Facilitated diffusion?
Movement of molecules from a region of high conc to a region of low conc down a conc gradient. Passive process directly through phospholipid bilayer (Carrier protein or channel) used
Difference with substances enter cell through protein channels.
Co-transport?
Type of facilitated diffusion.
Eg. molecule of glucose and 2 Na ions attaching to carrier protein on outer side of membrane. This changes shape of protein enough to flip them to inside membrane. Then can diffuse separately through cell.
Osmosis?
Passive movement of water molecules across semi-permeable membrane, from a region of high water potential to a region of low water potential, until equilibrium is reached.
Water potential?
used in formulae; Ψ = ΨS + ΨP.
Scale 0=Pure
-300= some dissolved solutes
-800= more solute are in solution more - water potential.
In plant cell, Turgid?
In hypotonic cells take up water by osmosis.
Pressure potential inc as cytoplasm pushes on cell wall.
Incipient plasmolysis?
Cell has lost enough water from cell membrane to start being drawn away from cell wall.
This lower the pressure potential to 0.
Plasmolysed?
Cell in hypertonic (more conc) solutions become flaccid(floppy).
In animal cell?
it is important animal
cells are in an isotonic solution (same
concentration of dissolved solutes inside and
outside cell) as they lack a cell wall. Cells can
burst in hypotonic and shrink in hypertonic
solutions due to osmosis.
Tonicity?
– refers to concentration of solute
Hypertonic?
-means high conc of solute and .’. low WP.
