ch 3 cellular level of organization Flashcards
What are the three principal parts of a cell?
- plasma membrane: outer surface of the cell
- separated the cell’s internal environment from the external environment
- selectively permeable: regulates movement in and out of cell -> homeostasis
- communication between cells + cells and cells + environment - cytoplasm: cellular components btw the plasma membrane and the nucleus
- 2 parts: cytosol and organelles
-cytosol: fluid portion of the cytoplasm, contains water + dissolved solutes + suspended materials
-organelles: highly specialized small structures - nucleus: organelle that houses cell’s DNA
- DNA is organized in single molecules called chromosomes which contain genes (hereditary units)
define glycocalyx and its function
sugary coat on the extracellular surface of the plasma membrane, composed of glycolipids and glycoproteins
- pattern differs from cell to cell, helps with recognition (immunity)
-hydrophilic property of carhodrates attracts a film of water creating a slippery surface (helps rbc move thro vessels, and keeps cells in airways and digestive canals from drying out)
- allows cells to adhere to one another for protection again enzymes
what are the main types of lipids in the plasma membrane and describe each one
- phospholipid (contains P):
- amphipathic, head is polar, tail is nonpolar, created a bilayer structure - glycolipids (contains carbohydrate)
- amphipathic, carbohydrate is polar, tail is nonpolar
- only exist on extracellular leaflet, contributes to asymetry - cholesterol (contains -OH hydroxyl group)
- weakly amphipathic, -OH head is polar and forms H bonds with polar portion of phospholipids and glycolipids
- steroid ring and hydrocarbon tail is non polar, dispersed among the fatty acid tails of phospholipids and glycolipids
- occurs in both leaflets
what are the 4 main functions of the plasma membrane
- barrier that separates external and internal environment
- selectively permeable, regulates movement of molecules in and out of cell
- intercellular signalling
- helps identity cell to other cells
what are the two types of proteins
- integral: embedded in the plasma membrane
- covalently attached to fatty acid tails
- amphipathic: polar portions protrude into cytosol and extracellular surface, nonpolar portions extend among the fatty acid region
- transmembrane: spans the entire lipid bilayer, protrudes on both sides
-glycoproteins: protrude into extracellular side - peripheral: not embedded in the membrane
- attached to polar heads of membrane lipids or integral proteins
what are the functions of proteins the the membrane (6)
- ion channels: integral proteins that form pore to allow specific ions to flow thro membrane
- carriers: integral proteins that change shape to selectively move polar/ ions thro membrane
- receptors: integral proteins that serve as cellular recognition sites, recognizes and attaches to ligand (specific type of molecule), which will alter cell’s function
- enzymes: integral and peripheral proteins that catalyze specific chemical rxns
- linkers: integral and peripheral proteins that anchor filaments inside and outside cell to provide stability and shape
- can link proteins in the plasma membrane of neighbouring cells
- may participate in movement of cell - cell-identity marker: glycolipids and glycoproteins forming the glycocalyx, creates unique pattern of proteins that allows cells of the same type of recognized each other during tissue formation
- also recognize and identifies foreign proteins
When stimulating a cell, the hormone insulin first binds to a protein in the plasma membrane. This action best represents which membrane protein function?
the membrane protein is a receptor, and the hormone insulin is the ligand
describe the membranes fluidity
- membrane lipids and some proteins can move freely laterally on the same leaflet
- allows for self healing
- increasing unsaturated lipid content will increase fluidity
-@ hot and normal temps: cholesterol will increase fluidity
-@ cold temps: cholesterol will decrease fluidity - bilateral movement of membrane lipids and proteins requires enzymes
- contributes to asymmetry
describe the membranes selectivity
- highly permeable to nonpolar molecules (o2, co2)
-moderately permeable to small, polar molecules (h20, urea): they move thro gaps in the fatty acid tails due to their small size
-impermeable to ions and charge nonpolar molecules (glucose): require assistance from transmembrane proteins
can macromolecules cross the membrane
yes, but only thro endocytosis and exocytosis due to their large size
can macromolecules cross the membrane
yes, but only thro endocytosis and exocytosis due to their large size
define electrochemical gradient and describe its components
the combined influence of concentration gradient + electrical gradient
concentration gradient: difference in the concentration of a chemical
- O2 and Na+ more abundant in the extracellular fluid
- CO2 and K+ more abundant in the cytol
electrical gradient: difference in the electrical charge
- extracellular: more +
-cytosol: more -
describe diffusion
does not require ATP, uses kinetic energy to move substances down a concentration gradient
simple diffusion: w/o integral protein
facilitated diffusion: required integral membrane (channel or carrier)
what factors influence rate of diffusion
- temperature
- steepness of concentration gradient
- diffusion distance
- mass of solute
- surface area
hydrostatic pressure vs osmotic pressure
hydrostatic pressure: pressure exerted by liquid, produces movement of water
osmotic pressure: pressure exerted by solution with impermeable solute, propertional to the concentration solute that cant cross the membrane
- prevents movement of water
- equals the pressure needed to restore initial condition
