Unit 1 - Cell Physiology Flashcards
how many types of distinct cells are there in the human body?
~200
what are the four broad categories of cells?
1) epithelial cells
2) connective tissue cells
3) nerve cells
4) muscle cells
cells are surrounded by _______ and contain specialized structures called _______.
membranes, organelles
every cell has a nucleus, except:
red blood cells
what is the largest organelle in the cell?
the nucleus
what is the primary function of the nucleus?
storage of DNA in the form of chromatin.
the nucleus is surrounded by a membrane known as the ________, with openings called _________.
nuclear envelope, nuclear pores
nuclear pores facilitate…
- passage of RNA into the cytoplasm
- entrance of proteins that modulate gene expression
what is the nucleolus?
the site of ribosomal RNA synthesis and protein components of ribosomes
what is the smallest cellular organelle?
the ribosome
what is the primary function of the ribosome?
the “protein factory” which translates RNA into protein.
cells that make lots of proteins will have lots of…
ribosomes
do ribosomes have a surrounding membrane?
no
what are the two types of ribosomes?
free ribosomes and membrane-bound ribosomes
which organelle is continuous with the rough ER and the nuclear envelope?
smooth ER
what is the primary function of the smooth ER?
fatty acid synthesis, calcium storage and release, etc.
what is the primary function of the rough ER?
site of protein synthesis
proteins synthesized in the lumen are…
distributed to other organelles or secreted
the orgenelles that is comprised of a series of membranous sacs called cisternae is the…
golgi apparatus
what is the function of the golgi apparatus?
modifies and sorts proteins arriving from the ER, and distributing them to other organelles or to the membrane for secretion.
the small membrane-bound vesicles spread throughout the cytoplasm are…
endosomes
what is the function of the endosomes?
sorting vesicular traffic in the cell
what is the function of the lysosomes?
breakdown:
- damaged/worn out organelles
- engulfed bacteria
- engulfed debris of dead cells
which organelle has an acidic environment and contains digestive enzymes?
lysosomes
what is the function of peroxisomes?
breakdown:
- fatty acids
- detoxification of alcohol
what is the function of the mitochondria? (i swear to god if you say the powerhouse of the cell)
transfers energy in the form of ATP in a process called cellular respiration.
what is the function of the cytoskeleton?
provides structural support, facilitates change in cell shape, an produces cell movement.
what are the three classes of the cytoskeleton?
1) actin filaments
2) intermediate filaments
3) microtubules
which class of the cytoskeleton is made of hollow tubes, and is formed of tubulin subunits?
microtubules
which class of the cytoskeleton is made up of twisted strands of proteins like keratin, desmin, and laminin?
intermediate filaments
which class of the cytoskeleton contains G-actin subunits which form a polymer of two twisting chains, forming F-actin?
actin filaments
what is ribosomopathy?
multiple causes of abnormal ribosomal biogenesis resulting in human disease
true or false: ER stress is not secondary to other diseases.
false. it is secondary to things like cancer, neurodegeneration, and metabolic disease.
what is ER stress?
altered ER funtion results in accumulation of unfolded/misfolded protiens, this may cause apoptosis.
is mitochondrial mytopathy primary or secondary?
haha pranked it can be both
what is a lysosomal storage disorder?
one where toxic material build up in the lysosome.
what are the three key components of the fluid mosaic model?
1) phospholipid bilayer
2) cholesterol
3) proteins
what does it mean for phospholipids to be amphipathic?
they have a hydrophilic head and a hydrophobic tail.
what is the main function of cholesterol in the cell membrane?
to maintain membrane fluidity.
what are the two classes of membrane proteins?
1) integral membrane proteins
2) peripheral membrane proteins
which membrane proteins are amphipathic and are embedded in the membrane/membrane spanning?
integral membrane proteins
which membrane proteins are not amphipathic and lie on the membrane surface?
peripheral membrane proteins
what are the four main functions of the membrane proteins?
1) link adjacent cells together
2) regulate passage of substances into and out of the cell
3) detect chemical messengers arriving at the cell surface
4) anchor cells to extracellular matrix
cell membranes can join together to form…
junctions
what are the three major types of cell junctions?
1) desmosomes
2) tight junctions
3) gap junctions
what are desmosomes?
stong links that give high structural integrity.
what are tight junctions?
forms tight barriers so things can’t get through the cells.
what are gap junctions?
pores between cells, allowing passage of ions and small molecules.
what are the four mechanisms that molecules use to cross membranes?
1) diffusion
2) protein-mediated transport
3) vesicular transport
4) epithelial transport
true or false: nonpolar molecules diffuse across cell membranes relatively quickly
true
true of false: polar molecules diffuse across membranes relatively quickly
false
what is diffusion?
movement of molecules from high concentration to low concentration
the direction of diffusion is a product of the balance between one-way movement between compartments, this is referred to as:
net flux
what is the equation for Fick’s First Law of Diffusion?
J = PA(Co-Ci)
why is protein mediated transport necessary?
it is used for molecules that are not membrane permeable
what are the two main types of protein mediated transport?
- facilitated diffusion
- active transport
what is facilitated diffusion?
protein-mediated movement of ions, amino acids, and other small molecules that cannot move through the membrane by simple diffusion
what are the two broad categories for protein-mediators used in facilitated diffusion?
- ion channels
- transporters
true or false: ion channels and membrane transports are not selective towards specific molescules, so any molecule can move down and transporter
false
what are the two forces that contribute to ion flux across membranes?
- ion concentration (chemical)
- electrical gradient between the outside and inside of a cell (membrane potential)
what are ion channels?
transmembrane proteins that form pores
how are larger molecules protected from passing through the cell membrane?
very small diameter
ion channels are selectively permeable to specific ions, this selectivity is determined by:
1) channel diameter
2) charge of the polypeptides
3) number of water molecules associated with ion
diffusion of ions through ion channels by a process called:
channel gating
what are the three types of ion channel gates?
1) ligand gating
2) voltage gating
3) mechanically gating
the binding of specific molecules to a channel that causes conformational change is called:
ligand gating
a change in membrane potential which causes conformational change is called:
voltage gating
a physical change in the membrane to allow ions to pass through the membrane is called:
mechanical gating
what are the three basic steps of protein mediated transport?
1) solute binding to specific site on protein
2) conformation change in transporter
3) dissociation of solute from binding site
magnitude of flux through transporters dependent of four factors. what are those four factors?
1) solute concentration
2) affinity of transporter for solute
3) number of transporters in the membrane
4) rate at which the transporter goes through conformational change
in facilitated diffusion, solutes move ______ their concentration gradient. in active transport, solutes move _______ their concentration gradient.
down, up
what is secondary active transport?
the use of an electrochemical gradient across a membrane to help solutes move down their concentration gradient
what is primary active transport?
the direct use of ATP to help solutes move down their concentration gradient
in the sodium-potassium ion pump, Na+ is moved ____ the cell while K+ is moved ____ the cell
out of, into
how many Na+ and K+ are moved in/out of the cell for every ATP the sodium-potassium pump uses?
three Na+ and two K+ ions
true or false: vesicular transport requires molecules to pass through the membrane
false
what is vesicular transport?
transport which is achieved by enclosure of materials into vesicles that pinch off from the membrane
the process where membrane envaginations enclose small volume of extracellular fluid, which are taken into the cell is:
endocytosis
the process where intracellular membrane-bound vesicles fuse with the plasma membrane and release their contents into the extracellular fluid is:
exocytosis
what are the three common types of endocytosis?
1) pinocytosis
2) phagocytosis
3) receptor-mediated cytosis
- nonspecific
- includes water and whatever solutes are present
- vesicle fuses with lysosome
theses are all properties of:
pinocytosis
- specific
- unique to specifalized immune cells (phagocytes)
- involves uptake of bacteria or cell debris from damaged tissue
- internalized vesicle fuses with lysosome
these are all properties of:
phagocytosis
what is receptor mediated endocytosis?
clustering of receptors to allow select concentrations of solutes into the vesicles, can involve the formation of clathrin coated pits
- restricted to small molecules
- generates relatively small vesicles called caveolae
- contents delivered to the cytosol
these are all properties of:
potocytosis
what are the two functions of exocytosis?
- replaces cell surface membrane lost during endocytosis
- allows secretion of membrane impermeable molecules into extracellular fluid
epithelial cells line the cavities and surfaces of:
vesicles and organs
in an epitheleal cell, the surface that faces the hollow organ/tube is called the:
apical membrane
in and epithelial cell, the surface that faces the lumen is called the:
transcellular pathway
the limited movement of diffusion of water and small ions across epithelial cells is called the:
paracellular pathway
utilizes the processes of diffusion and protein-mediated transport and involves the flow against concentration gradient in an epithelial cell
transcellular pathway
physiological homeostasis depends on:
communication between cells
how do cells communicate with each other?
receptors
how do cells process signals?
- lipid-soluble messengers
- water-soluble messengers
once a cell has recieved a signal, it must be “processed”, this is called:
signal transduction
how do cells recieve signals from other cells?
receptor proteins
- most common
- bind to plasma transmembrane receptors
these are characteristics of what type of signal?
water-soluble signal
- can diffuse through membrane
- bind to intracellular receptors
- generally transduce signal via change in gen expression
these are characteristics of what type of signal?
lipid-soluble signal
cell signaling depends on ligand-receptor interactions, including:
1) specificity
2) affinity
3) saturation
4) competition
what is ligand-receptor specificity?
the ability of a receptor to only bind a limited number of ligands
what is ligand-receptor affinity?
the strength of a ligand binding to a receptor
what is ligand-receptor saturation?
the extent to which receptors are bound by a ligand
what is ligand-receptor competition?
presence of other ligands which “compete” for receptor binding sites
- a lowering of the number of target cell receptors
- can occur in response to sustained high levels of signal (negative feedback)
- reduces cell response to frequent/intense stimulation
- common mechanism is internalization
these are all characteristics of:
down-regulation
- an increase in the number of target cell receptors
- can occur in response to sustained low levels of signal (positive feedback)
- increases cell response to low-level stimulation
- can occur through increased insertion of receptor-containing vesicles into the cell membrane
these are all characteristics of:
up-regulation
the process of ______ translates a signal into a cellular response.
signal transduction
cellular responses to signals can include changes in:
1) membrane properties
2) cellular metabolism
3) secretory activity
4) rate of proliferation/differentiation
5) contractility
in the transduction of lipid-soluble signals, the response is primarily mediated by ___________, leading to a change in gene expression
nuclear receptors
1) circulating signal diffuses from circulation across membrane into cell
2) signal enters nucleus and binds receptors
3) ligand-receptor complex functions as a transcription factor, changing expression (mRNA) level of target gene
4) change in mRNA abundance effects in change in protein level, leading to cellular response
these are the steps of:
transduction of lipid-soluble signals
what are the two phases of signal transduction?
1) binding of signal to receptor (first messenger)
2) signals generated by receptor activation (second messenger)
many second messenger systems rely on _________ to effect change
phosphorylating proteins
enzymes that phosphorylate proteins are called:
protein kinases
what are the four common mechanisms of water-soluble ligand signaling?
1) receptors that function as ion channels
2) receptors that function as enzymes
3) receptors that interact with cytoplasmic kinases
4) receptors that interact with G-proteins
receptors that interact with cytoplasmic kinases are called:
janus kinases
G-proteins “couple” receptor with effector proteins to generate:
second messengers
which G-protein inhibits production of cyclicAMP?
Gi
which G-protein activates the production of cyclicAMP?
Gs
which which G-proteins activates phospholipase C>?
Gq
PKA has multiple targets, meaning:
it can elicit multiple responses in the same cell
cAMP is a potent second messenger, thus its levels are:
tightly regulated
How do signals cause the cytosolic calcium concentration to increase?
- activation of plasma membrane calcium channel
- opening of calcium channel on the ER membrane
- active transport of calcium out of the cell blocked by a second messenger
how does increased calcium concentration elicit a cellular response?
typically via binding proteins and activating them
cessation of intracellular signaling is required to:
prevent overstimulation of the cell
what are the three main steps to cessation of signal transduction pathways?
- decreased concentration of signal
- change in receptor conformation
- receptor mediated endocytosis
