Exam 1 - Ch. 3 Flashcards
Cell theory
structural and functional unit of life, all organisms are made of 1 or more cells, cells arise from each other
What are the 3 basic parts of a cell?
- plasma membrane
- cytoplasm
- nucleus
plasma membrane
lipid bilayer, separates intra and extracellular fluids
membrane lipids
phospholipids, glycolipids, cholesterol
Phosphate heads
polar and hydrophilic`
fatty acid tails
nonpolar and hyrophobic
glycolipids
lipids with polar sugar groups on outer membrane surface
cholesterol
increases membrane stability
membrane proteins
allow communication with environment, half of plasma membrane, integral proteins and peripheral proteins
integral proteins
firmly inserted into membrane, can have both hydrophobic and hydrophilic regions, function as transport proteins, enzymes or receptors
peripheral proteins
loosely attached to integral proteins, function as enzymes, motor proteins for shape change during cell division and muscle contraction and cell to cell connections
what are the 6 functions of membrane proteins?
- transport
- receptors for signal transduction
- attachment to cytoskeleton and extracellular matrix
- enzymatic activity
- intercellular joining
- cell-cell recognition
transport
a protein that spans the membrane may provide a hydrophilic channel across the membrane that is selective for a particular solute. some hydrolyze ATP as an energy source to actively pump substances across the membrane
Receptors for signal transduction
a membrane protein exposed to the outside of the cell may have a binding site that fits the shape of a specific chemical messenger, such as a hormone.
When bound, the chemical messenger may cause a change in shape in the protein that initiates a chain of chemical reactions in the cell
Attachment to the cytoskeleton and extracellular matrix
elements of the cytoskeleton and extracellular matrix may anchor to membrane proteins, which helps maintain cell shape and fix the location of certain membrane proteins
enzymatic activity
A membrane protein may be an enzyme with its active site exposed to substances in the adjacent solution
A team of several enzymes in a membrane may catalyze sequential steps of a metabolic pathway
Intercellular joining
Membrane proteins of adjacent cells may be hooked together in various kinds of intercellular junctions.
Some membrane proteins of this group provide temporary binding sites that guide cell migration and other cell to cell interactions
Cell to Cell recognition
some glycoproteins serve as identification tags that are specifically recognized by other cells
glycocayx
“sugar covering” at cell surface
cell junctions
Some cells “free”
EX. blood cells, sperm cells, some bound to communities
What are the 3 ways cells are bound?
- tight junctions
- desmosomes
- gap junctions
Tight junctions
purpose is to prevent liquids and small solids from moving between
gap junctions
allows small molecules to pass through
desmosomes
made of keratin, welds cells together and joins cells in a strong plaque
What are 2 ways to cross membrane?
passive and active processes
passive processes
no ATP required
substances move down their concentration gradient
active processes
ATP required
occurs only in living cell membranes
What are types of passive processes?
- simple diffusion
- carrier and channel-mediated facilitated diffusion
- osmosis
simple diffusion
non-polar lipid-soluble (hydrophobic) substances diffuses directly through the phospholipid bilayer
facilitated diffusion
certain lipophobic molecules transported passively by binding to protein carriers and moving through water-filled channels
channel-mediated facilitated diffusion
aqueous channels formed by transmembrane proteins
carrier-mediated facilitated diffusion
transport specific polar molecules too large for channels
osmosis
movement of water across selectively permeable membrane
importance of osmosis
causes cells to swell and shrink, change in cell volume disrupts cell functions especially in neurons
tonicity
ability of solution to alter cells water volume
isotonic
solution with same non-penetrating solution as cytosol
hypertonic
solution with higher non-penetrating solute concentration that cytosol, causes cell shrivel up
hypotonic
solution with lower non-penetrating solute concentration than cytosol, causes cell to swell
active processes of membrane transport
active transport and vesicular transport, both require ATP to move solutes across a living plasma membrane
active transport
moves solutes against concentration gradient, requires the help of carrier proteins
primary active transport
required energy directly from ATP hydrolysis, energy from hydrolysis of ATP causes shape change in transport protein that pump solutes across membrane
secondary active transport
required energy indirectly from ionic gradients created by primary active transport
sodium-potassium pump
located in all plasma membranes, involved in primary and secondary active transport of nutrients and ions, pumps against Na and K gradients to maintain high intracellular K and high extracellular K and high extracellular Na concentration
cotransport
always transports more than one substance at a time