CELLS Flashcards
What is a cell?
- the cell is the basic structural and function unit of living organisms
- the basis of life- all living things are made of one or more cells
what are three basic components of eukaryotic cells?
- plasma membrane
- cytoplasm
- nucleus
why is it important that the plasma membrane is fluid?
fluid membrane provides for and allows
- cell movement, growth, division
- self-sealing if torn or punctured
describe the basic composition of the lipid bilayer
- phospholipids(75%)
- cholesterol (20%)
- Glycolipids (5%)
amphipathic
lipids have both polar and nonpolar components
- phosphate head (polar)
- fatty acid tails (nonpolar)
what function does cholesterol serve in the lipid bilayer? how does it accomplish this?
cholesterol mediates membrane fluidity
- makes lipid bilayer less fluid at normal body temperature
- increases membrane fluidity at lower body temperature
what are the two types of membrane protein classifications?
- integral proteins
2. peripheral proteins (not part of the bilayer)
describe integral proteins
proteins that extend through or well into the bilayer
they are amphipathic
what are transmembrane proteins? What functions do they serve?
proteins that go all the way through the bilayer
they form ion channels (channel proteins)
and they are also transporters (carrier proteins)
Name the different types of membrane protein functions
- ion channels (pores)
- carriers (selective movement of materials)
- receptors for specific ligands
- enzymatic
- linkers (link membranes of adjacent cells)
- cell identity markers (glycoproteins or glycolipids)
how do carrier proteins function? provide an example
transport specific substances across membrane by changing shape
Amino acids enter body cells via carriers
what is a receptor protein? provide an example
recognizes a specific ligand and alters the cells function in some way
ADH binds to receptors in the kidneys and changes the water permeability of plasma membranes
provide an example of an enzymatic protein
these catalyze a reaction inside or outside the cell.
Lactase enzyme from epithelial cells in the small intestine splits the lactose from dairy products
give an example of a cell identity marker
glycoprotein (self vs nonself)
Major histocompatibility complexes (MHCs)
What is a glycocalyx in eukaryotes?
- sugars that are attached to either proteins (to form gylcoproteins)
- lipids (to form glycolipids)
what is the function of eukaryotic glycocalyx?
- protect cells from enzymatic action
- cell adhesion
- cell recognition (ABO blood groups) (liver phagocytizes aging RBCs because they have fewer sugars in their glycocalyx)
The lipid bilayer is permeable to what type of molecules?
nonpolar uncharged molecules (oxygen, carbon dioxide and steroids)
the lipid bilayer is impermeable to what type of molecules?
ions and large uncharged polar molecules (glucose)
the inner surface of the plasma membrane are usually postively or negatively charged?
negatively
the outter surface of the cell is typically positively or negatively charged?
positively
name the types of passive movement through a bilayer
- simple diffusion
- osmosis
- facilitated fission
what are the types of active transport?
- primary active transport
2. secondary active transport
what are the types of bulk transport?
also known as vesicular transport
- exocytosis
- endocytosis
- transcytosis
what factors influence the diffusion rate and time?
- steepness of gradient
- temp
- surface area of membrane
- diffusion distance
- Mass of the diffusing substance (larger mass slower diffusion)
- size
- density of diffusing substance
8 charge
9 diffusion medium - shape
- permeability of a membrane
- lipid solubility (lipid soluble molecules can move through bilayer)
define isotonic solution
equal concentration of osmotically active solution
define hypotonic solution
lower conc than the cell (water moves into the cell)
define hypertonic solution
higher concentration of cell (cell creneates and water moves out of the cell)
describe molecules that passive diffuse through the lipid bilayer?
- lipid soluble
- small (water, urea)
- assisted by carriers
names the substances that can move in and out of the cell through simple diffusion
- oxygen
- CO2
- Fats
- Alcohol
- fat soluble vitamins (A, D, E, and K)
two polar substances that can diffuse across the membrane?
water and urea
what solutes move by facilitated diffusion?
- fructose
- glucose
- galactose
- some vitamins
allosteric
the protein changes shape due to binding of an effector
describe the concentration of K+ and NA+ inside and outside the cell
K+- is high inside the cell
NA+ is low inside the cell
