MEMBRANE TRANSPORT, CONNECTIVE AND EPITHELIAL TISSUE Flashcards
Plasma membrane
-water loving heads face water, water hating tails face away from the water
-functions: barrier and maintains internal conditions of the cell, cell communication
-cell communication is important so they can work together towards a common goal
-cell communication happens through receptors and signalling molecules
-provides protection and support
-maintains internal conditions of the cell
-ensures cytosol remains inside the cell
-protect the cell from external environment
-supports cell structure
-communication with other cells
-Fluid mosaic model
Fluid mosaic model
-fluid: not solid or static, phospholipids are constantly moving around
-mosaic: made up of many different molecules, can be embedded or attached
Phospholipids
-form a bilayer
-2 parallel sheets
-due to hydrophilic heads (polar) and hydrophobic tails (nonpolar)
Cholesterol:
-structural integrity and regulates fluidity
-more cholesterol=less fluid
-maintains fluidity and stabilized the membrane
-randomly distributed
Glycolipids
-glyco: means carbohydrate
-lipid: means lipid or fat
-function: stabilize the cell membrane, forms bonds with water
-glycoproteins: carbohydrate and protein, part of the immune system, cell recognition
Proteins
-have many functions: binding sites, cell to cell interactions
-integral proteins and peripheral proteins
Integral
-permanently embedded
-spans the width of the membrane
-channel proteins
-extend through the lipid bilayer
Peripheral
-attached to the membrane
-communication enzymes
-loosely attached to other proteins of the membrane itself through hydrogen bonds
-help with transport
Selective permeability
-allows some substances to cross but not all
-gases and small, fat-soluble molecules can pass easily
-ions must pass through channel proteins
-cell can control flow of substances in and out of the cell
Transport Processes
-movement of substances across the plasma membrane
Passive Transport
-no energy input required
-molecules are moving from high concentration to low concentration
Simple diffusion
-unassisted diffusion across the plasma membrane
-small, nonpolar molecules
Example: O2, CO2, ethanol
-no transport protein is required
-things can diffuse through the plasma membrane but it happens very slowly
-substances moving across the cell membranes without energy input
-uses diffusion
Diffusion of water (=osmosis)
-movement of water through a selectively permeable membrane
-moves from low solute concentration to high solute concentration
-can also be through of as high “water concentration” to low “water concentration”
Facilitated diffusion
-diffusion assisted by a carrier or channel protein
-small charged or polar molecules
-requires a transport protein
-things move through a plasma membrane faster with a transport protein (aquaporins used to move water)
Tonicity
-the ability of a solution to change the volume or pressure of a cell by osmosis
-relative term based on the solute concentration of the solution compared to the concentration within the cell
-the capacity of a solution to modify the volume of a cell
Isotonic
-solution has the same relative solute concentration
Hypertonic
-crenation is the shrivelling of the cell
-solution has higher solute concentration and a lower water concentration
Hypotonic
-hemolysis is when the cell bursts
-solution has lower solute concentration
Active transport
-requires energy
-low to high concentration
-movement of a solute from against its concentration gradient
-from low concentration to high concentration
Primary active trasnport – uses ATP
-uses ATP as energy
-Na+/K+ pump
-found in all cells
-transports 3 Na+ out of the cell and 2 K+ into the cell
-results on a low [Na+] and a high [K+] in the cell
-maintains the proper concentration of potassium ions K+ and sodium ions Na+ inside and outside of the cell
Secondary active transport – no ATP
-using something other than ATP as our energy source
-uses energy source other than ATP
-the energy of one substance moving downs its concentration gradient is used to pump another substance up its concentration gradient
Antiporters:
-two substances move in the opposite direction
Symporters:
-two substances move in the same direction
Tissues
-tight junctions
-gap junctions
-desmosomes
-4 types
1.epithelium
2.connective
3.muscular
4.nervous
Tight junctions
-creates leakproof seal
-seals off the intercellular space
-proteins in the plasma membrane form strands that bind the cells
Gap junctions
-composed of integral plasma membrane proteins called connexons
-functions as pores
-allow small substances (ex. Ions) to move between the cells
