Cell Biology Exam 1 Flashcards
Cell Membrane Components
Phospholipids, proteins, cholesterol
Phospholipids
membranes are variously composed of these special lipids, they are amphipathic molecules with a hydrophobic and phillic end can assemble as micelle, bi-layer and liposome
hydrophobic effect determines the organization of phospholipids
glycolipids
carbohydrate branches attached to exterior end of lipid replacing the polar head
glycoprotein
carbohydrate attached to the exterior end of a protein in the cell membrane
nearly all membrane proteins are glycoproteins at somelevel
Proteins
functional part of the membrane, the ratio of proteins/lipid ratio depends on complexity of membrane functionality, sequence of amino acids assembled in such a way to be folded or wound up,
there are 2 kinds of membrane proteins: Integral Membrane proteins and Peripheral membrane proteins
Integral membrane proteins
regions of lipid sea, held in position
Peripheral membrane proteins
located on the surfaces of the lipid sea usually on the cytoplasm side
Kinds of membrane proteins
structural - give cell structural integrity, ECM
channels - allow for passive transport of molecule through membrane
transporters - active transport of molecule along natural conc gradient
pumps - active transport of molecule against concentration gradient
transducers - couple a membrane receptor to cytoplasmic enzyme
enzymes - perform cellular work by catalyzing rxn
Cholesterol
added agent involved in cell fluidity, amphipathic steroid, enhances cell membrane stability decreases permeability, helps with packing the phospholipids.
Fluid Mosaic Model
protein and lipid distribution is asymmetrical, in addition of the obvious barrier function a membrane must be able to engage in recognition, transportation and communication.
Membrane recognition
cellular adhesion, cellular interactions with prokaryotic organisms, cellular/tissue identity, cellular immunity
cellular adhesion during growth and development
by cellular density/contact with cell beside it, the part that is recognizable is the stage-specific embryonic antigens (SSEA’s)
cellular adhesion in mature tissues
cell adhesion molecules (CAM’s) are what join the cells together
cadherin
link cells to identical cells
integrin
links cells to the ECM
Cellular binding during diaphysis
The ability of a white blood cell to bond to and exit capillary lining linked to the display of interaction of special surface recognition molecules
cell junctions
adhering or tight junctions by ways of proteins
cellular interactions with prokaryotic cells
certain bacteria have tiny protein threads, fimbriae, to attack the host cell on the glycolipids
cellular binding during diapedesis
ability of WBC to bond to, and exit capillary lining linked to the display and interaction of special surface recognition molecules
cellular/tissue identity
by what carbohydrates are attached can define the type of cells they are “blood typing”
cellular immunity
cells immune systems express certain proteins on plasma membrane call human leukocyte antigens (HLA), these are used to present foreign material to other defender cells
antigen presenting cells
HLA cell that put foreign material on outside of membrane for other defender cells to see and attack
Cell membrane Transportation ways
passive transport, facilitated transport, active transport, vesicular transport
Passive transport
free passage - completely unaided movement governed by diffusion, unfit for nearly all significant biological molecules, movement through phospholipid sea
openings - various types of channels and pours and is selective, any type of unaided passage governed by diffusion, may be close able - added or subtracted from plasma membrane
commons eg: aquaporins, ion channels and gap junctions
Aquaporin
a pore for water, more than 10 different forms found where the proteins fold up in lipid by-layer to combin two hemi-phores
Ion channels
the channels are important for electrically excitable cells such as neurons and muscles, they change membrane potentials
voltage-gated channel - opened by applying voltage
ligand-gated channels - opening by docking a ligand
mechanically-gated channels - opened by physically stressing the cell
chemically-gated channel - opened by the pressence of Ca2+ or phosphorylation of the gate
Gap junction
special case used to direct cell-to-cell transmission, allows for electrical and metabolic coupling of cells, consists of 6 IMP’s termed connexons creating the channel
Facilitated Transport
facilitated diffusion, various types of IMPs that physically carry a solute across the plasma membrane, selective, non-energy dependant - aided by concentration gradient, uses a translocation mechanism to make a conformational change to IMP to create access, they are simple automatic and efficient.
eg. uniporter, symporter, multiporter
Glucose Tansporter
part of family of similar proteins GLUT 1 thru 5, stimulated by insulin and inhibited by ATP,
Bi-Chloride Antiporter
this anion transporter exchanges a HCO3 for a Cl- in RBCs
Active Transport
a carrier mediated transport system requiring ATP, works against the concentration gradient, selective
two broad types are primary and secondary where sec. does not use ATP directly often called co-transporter
Sodium Potassium pump
the main pump, hydrolysis of ATP is used to run the pump, an antiporter IMP the moves 3 Na out for 2 K in, is electrogenic b/c it moves ionic species, high level of Na is used for secondary co-transports systems
Calcium Pump
a uniporter IMP that moves Ca2+ out per ATP, in all cells, primary active transporter
Hydrogen Potassium Pump
an antiporter IMP that moves H+ out and K in per ATP, primary active transport
Sodium-Glucose Symporter
an IMP that moves 2 Na+ in with 1 Glucose in, glucose levels usually higher in cells so to move in against its gradient sodium is used, since it is then dependant on the sodium pump it is a secondary active transport
Sodium-Hydrogen Antiporter
an IMP that moves H+ out and Na+ in, secondary active transport, relies on sodium gradient by the Na/K pump, common in kidney tubule cells
Sodium-Calcium Antiporter
an IMP that moves Ca2+ out and Na+ in, actually faster than the Calcium pump, econdary active transport, relies on sodium gradient created by Na/K pump
Vesicular Transport
utilizing membrane sphere (vesicles) to shuttle material to and from the cell membrane, technically requires energy, broken down into endocytosis and exocytosis
Exocytosis
vesicles originate at the golgi apparatus and shuttles along the cytoskeleton to the plama membrane so it is moving things out also known as secretion.
Endocytosis
vesicles bud off of plasma membrane towards the interior as form of bulk transport, moving things IN using an endosome, there is 3 types; phagosytosis, pinocytosis and receptor-mediated endocytosis
phagosytosis
involves the engulfment of particulate, gobling of stray material, formation of pseudopodia that envaginate and fuse to form a phagocytic vesicle termed a phagosome
pinocytosis
a fluid phase endocytosis, non-specific internalization common in all cells, involves invagination of membrane to create pinocytotic vesicles
transcytosis
termed used to describe the shuttling of a endocyte across the cell to another surface
receptor-mediated endocytosis
highyl specific internalization, receptor IMP are required, that must bind to a ligand before internalization
multistep process: receptor binding, clathrin pulls membrane down, pulls to create a cage called coated pit, endosome is formed and fuses with CURL vesicle
CURL
Compartment the Uncouples Receptor and Ligand
LDL receptor- LDL endocytosis
receptor that takes in cholesterol to the cell which is synthesized to be used by golgi apparatus and put back into the cell membrane
Cell Membrane Communication 5 categories
endocrine secretion, neuro-endocrine secretion, paracrin secretion, autocrine secretion, synaptice transmission (neuronal secretion)
Endocrine Secretion
the process involves the synthesis and exocytosis of a hormone from a source cell->released hormone enters ECM then into bloodstream where it circulates throughout the body -> then exits blood capillaries and in EC to land on or enter target cells
receptors at target cells determine sensitivity
peptide hormone
water soluble, receptor located on the cell surface, typically transemembrane IMPs
steroid hormone
lipid soluble and can easily cross the plasma membrane, receptors located in either cytoplsm or nucleus inside cell, protein with ligand or DNA binding site, directly turn gene expression on
Autocrine Secretion
synthesis and exocytois of a chemical signal from a cell-> released chemical enters ECM where it stays locally -> then lands on the same cell as a target
Paracrine Secretion
involves the synthesis and exocytosis of a chemical signal loosely called a hormone from a source cell -> released chemical enters ECM where it stays locally -> then lands on nearby target cells
receptors on target cells determine sensitivity
eg. Endothelial cells lining blood vessels can secrete stimulants to the underlying smooth muscle cells to induce vasoconstriction
During fetal development target tissues secrete nuerotrophic factor which serves as a chemo-attractent molecule. Nerve Growth Factor
Synaptic Transmission (Neuronal Secretion)
transmitting end of neurone; small intercellular space or ECM; and a receiving cell
receptors postsynaptic side determine sensitivity, selectivity due to physical construction of synapse
4 Basic Categories of chemical signalling (reception)
steroid hormone receptor mechanism, ligand-gated receptor mechanism, G-protein receptor mechanism, enzymatic receptor mechanism
Steroid Hormone Receptor Mechanism
b/c steroids are lipid soluble they pass thru membrane, receptor is inside cell and has a steroid DNA and Gene-regulatory domain
Ligand-gates Receptor Mechanism
involves a external receptor site as an IMP where ligand binds to the receptor to open the channel
Nicotininc Acetylcholine Receptor
receptor has ligand attach and IMP undergoes a conformational change to allow for Na and K to pass, stimulates an action potential by secondarily activating voltage gated K channels nearby creating an Excitatory post synaptic potential, the Ach is broken down by acetylcholinesterase
receptor
an IMP that receives a primary messenger and indigoes a conformational change which convey message further
transducer
a PMP that relays/converts signal from receptor to amplifier
amplifier
IMP that boost signal by activation many secondary messengers
secondary messengers
cytosolic signalers formed by phosphorylated precursor that activate internal agent
internal effector
cytosolic protein that activate other proteins by phosphorylating them
cAMP
cyclic adenosine monophosphate system
protein phosphorylation
when a protein is phosphorylated and it changes its conformation and is thereby activated
protein kinase
enzyme that phosphorylate other proteins
protein phosphotase
enzyme that de-phosphorylate other proteins
The Mechanism of G-Protein-Linkes Receptor
External signal (first messenger) Receptor Transducer Amplifier Phosphorylated precursor Second Messenger Internal Effector Cellular Response
3 major types of transducer G-proteins
Gs - stimulatory, and activates adenylate cyclase
Gi - inhibitory, and inhibits adenylate cyclase
Gp - stimulatory, and activates phospholipase C
What are the G-Proteins subunits?
alpha subunit - the most variable and functionally important
beta and gamma - are similar, these bind the molecule together and hold it in the cell membrane
Amplifiers relavent to this course
these PMPs produce many copies of the second messenger
adenylate cyclase - converts ATP into cAMP
phospholipase C - converts PIP2 into IP3 and DG,
Second Messengers relevant to this course
cAMP - stimulates A-kinase
IP3, DG, and Ca2+- variously stimulates C-kinase and calcium/calmodulin kinase
Internal effectors relevant to this course
A-kinase - activated by cAMP
C-kinase- activated by DG
Ca2+/calmodulin kinase - activated by Ca2-
The Activation of the cAMP Signal Transduction
with the activation of adenylate cyclase by activated G-protein, cAMP made.
cAMP diffuse in cytosol and binds to A-kinase, this releases a catalytic component (c) from the regulatory cap (r)
A-kinase phosphorylates cellular proteins, thus activating them, conformational change allows this to happen
In-Activation of the cAMP Signal Transduction
system shuts down by a number of mechanisms that relate to the continual recycling of molecules, done by phosphatase enzymes available in the cell
- GTP -> GDP then causing G-protein to become quiet
- protein-P _> protein then returning them to resting conformation
- cAMP ->AMP thus eliminating the second messenger
The Activation of the IP3, DG, Ca2+ Signal Transduction
- with the activation of PL-C by activated G-protein IP3 and DG are made by cannibalizing the membrane phospholipid called PIP2.
- IP3 enters cytosol, DG moves thru membrane, IP3 stimulate the release of ER stored Ca2+, DG binds to near C-kinase
- Ca2+ binds to the Ca2+/calmodulin kinase, this phosphorylates the proteins, fairly fast acting but temporary
- C-kinase phosphorylates cytosolic proteins, this is somewhat slow
In-Activation of the IP3, DG, Ca2+ Signal Transduction
this system is shut down by a number of mechanisms that relate to the continual recycling of molecules, done by various phosphotase enzymes
GTP->GDP, thus causing it to become quiet
IP3->IP2 thus eliminating this second messenger
Ca2+ re-pumped back into ECM and into ER
Protein-P->Protein thus returning them to resting conformation
Enzyme Receptor Mechanism
this process involves an external receptor that spans the membrane and can directly phophorylate cytosolic proteins
-external, ligand binding domain
-membrane-spanning domain
-internal, catalytic domain
most of these are tyrosine kinases because they add phosphates to tyrosine residues on proteins of the cell interior by using ATP
Nucleoplasm
the contents of the nucleus
Cytoplasm
the bulk of the cell including the cell organelles and fluid
Cytosol
fluid inside cell mostly water, amino acids, proteins, fatty acids, lipids, nucleotides, simple sugars and complex carbohydrates
Sytoskeleton
an array of proteins that can criss cross the interior
Organelles
ER, Golgi Apparatus, lysosomes, mitochondria
Functions of the Endoplasmic Reticulum (Smooth and Rough)
Protein synthesis Hydroxylation (Smooth but some Rough) Glycosylation (Rough but some smooth) Glycogenolysis (Smooth) Sterol Metabolism (Smooth) Lipid Synthesis (Both) Calcium Storage (Smooth)
Hydroxylation
addition od hydfroxyl group to lipid-soluble toxins, converting them to water-soluble molecules that can be easily disposed of
can be done to complete the synthesis of certain molecules
Glycosylation
addition of sugar residue (to specific amino acids) in peptide chains, usually done on rough endoplasmic reticulum bound ribosomes
Glycogenolysis
breakdown of glycogen to glucose
Sterol Metabolism
steroid hormone synthesis in endocrine glands
cholesterol synthesis and availability for membrane stability
Lipid Synthesis
new phospholipids added to cytoplasmic side of ER bilayer
the special enzyme used to flip the new lipid to the cisternal side to prevent mono-lipid layer formation is the flippase
Calcium Storage
common muscle cells as a way to sequester Ca2+ during the resting state
alpha helices
amino acid chain that has commonly spiraled into large sections
globular
when the alpha helices fold up further this is what they form
5 kinds of proteins based on their structure
tripartite (transmembrane) single pass, hydrophilic region extends from both sides, single hydrophobic region spanning the membrane, hydrophobic regions as an alphas helix
multipass (transmember) IMP -multiple helices spanning over lipid by-layer, may contain polar or charged amino acids that contribute to formation of an aqueous pore
non-spanning IMP - embedded in one side
PMP ionically bonded to another IMP or PMP
PMP ionically bonded to an phospholipid
Extra-Cellular Matrix
structural proteins in between cell that connect them and hold them together
Stage-specific embryonic antigens
family of glycolipids expressed in embryogenesis
linked to specific stages of development
affect the further growth of the embryo
cell adhesion molecules
family of glycoproteins involved in maintaining tissue integrity
diffusion
the net movement of molecules from an area of high concentration to an area of low concentration
osmosis
thee diffusion of water across a semi-permeable membrane
transport maximum
the maximum rate of penetration allowed through a cell
Donnan Effect
imbalance in distribution of mobile ions and causing water to achieve its own equilibrium by moving
Donnan Swelling
it the cell is unable to move molecules out it this is what happens
Polarized cells
since the cell is then constantly moving Na+ out of the cell and the Proteins -ve and Cl- inside create differences in charges from the inside to the outside.
Electrical potential across cell
the net potential across the plasma membrane is about 60-mV
Action Potential
There is a voltage at which enough gates open to briefly overwhelm the pumps, and cause very serious membrane action to occur
this is a self-propagating wave of depolarization due to sequential ionic gating
Digoxin
poison found in Digitalis Foxglove plant. The toxin binds top the sodium pump in cardiac muscle cells and inhibits it. Therefore a higher level of Ca is in the heart causing strong heart beat, can be used for congestive heart failure
Residual Bodies
any indigestible materials persist as permanent phagosomes
