Cellular Functions Flashcards
Structural proteins
compose the cytoskeleton, aching proteins, and much of the extracellular matrix
most common structural proteins are
collagen, elastin, keratin, actin and tubline
- generally fibrous in nature
Collagen
- makes up most of the extracellular matrix of connective tissue
- important in providing strength and flexibility
Elastin
- important component of the extracellular matrix of connective tissue
- primary role: to stretch and then recoil like a spring, which restores the original shape of the tissue
Keratins
- intermediiate filament proteins found in epithelial cells
- contribute to the mechanical integrity of the cell
- functions as regulartory proteins
- primary protein that makes up hair and nails
Actin
- protein that makes up microfilaments & thin filaments in the myofibrils
- most abundant protein in eukaryotic cells
- have a (+) and a (-) side; this polarity allows motor proteins to travel unidirectional along an actin filament (like a 1 way street)
Tubulin
- protein that makes up microtubules
- microtubules are important in providing structures, chromosome separation in mitosis, and intracellular transport with kinesin and dyneid
- like actin, tubular has polarity; the (-) end of a microtubule is usually located adjacent to the nucleus, whereas the (+) end is usually periphery of a cell
Motor Proteins
- have one or more heads capable of force generation through a conformational change
- have catalytic activity, acting as ATPases to power movement
- responsible for muscle contraction and cellular movement
- Common examples include : myosin, kinesin and dynein
Most common applications of motor proteins
Muscle contraction, vesicle movement within cells, and cell motility
Myosin
- primary motor protein that interacts with actin
- thick filament in a myofibril
- can be involved in cellular transport
- movement at the enact is responsible for the power stroke of sarcomere contraction
Kinesins & Dyeins
- motor proteins associated with microtubules
- have 2 heads, at least one of which remains attached to tubular at all times
- important for vesicle transport in the cell but have opposite polarities
Kinesins main role
- align chromosomes during metaphase and depolarizing microtubules during anaphase of mitosis
- bring vesicles toward the (+) end of the microtubule
Dyeins main role
- involved in sliding movement of cilia and flagella
- bring vesicles toward the (-) end of the microtubule
Binding proteins
bind a specific substrate, either to sequester it in the body or hold its concentration at stead state
Cell adhesion molecules (CAMs)
proteins found on the surface of most cells that aid in the bidding of the cell to the extracellular matrix or other cells
3 major families of adhesion molecules
- cadherins
- integrins
- selectins
cadherins
group of glycoprotein that mediate calcium - dependent cell adhesion
integrins
group of proteins that all have 2 membrane - spanning chains called alpha and beta
Integrins major roles:
- in cellular signaling and can greatly impact cellular function by promoting cell division, apoptosis or other processes
- used for white blood cell migration, stabilization of epithelium on its basement membrane and other processes
selectins
bind to carbohydrate molecules that project from other cell surfaces
where are selectins expressed?
on white blood cells and the endothelial cells that line blood vessels
selectins play an important role in…
host defense
including: inflammation and white blood cell migration
antibodies (aka Immunoglobins)
proteins produced by B cells that function to neutralize targets in the body such as toxins and bacteria, and then recruit other cells to help eliminate the threat
antibodies are made up of
two identical light chains
two identical heavy chains
constant region
involved in the recruitment and binding of other cells of the immune system - such as macrophages
antibodies bind to
antigens
antibodies binding to antigens can cause 3 outcomes:
- Neutralization
- Opsonization
- Aggulinating
Neutralization
Neutralizing the antigen, making the pathogen or toxin is unable to exert its effect on the body
Opsonization
making the pathogen for destruction by other white blood cells immediately
Aggulinating
Clumping together the antigen and the antibody into large insoluable protein complexes that can be phagocytized and digested by macrophages
ion channels
can be used for regulating ion flow into or out of the cell
motor enzymes are not enzymes (TRUE/FALSE)
False.
Motor function is generally considered nonenzymatic, but the ATPase functionality of motor proteins indicates that these molecules do have catalytic activity
3 main types of ion channels
ungated channels
voltage gated channels
ligan gated channels
Antibodies are held together by
disulfide linkages and noncovalent interactions
enzyme linked receptors
participate in cell signaling through extracellular ligand binding and initiation of second messenger cascades
G protein - coupled receptors
have a membrane bound protein associated with a trimeric G protein. They also initiate second messenger systems
Ligand binding engages the _____
G protein
GDP is replaced with
GTP
the alpha subunit dissociates from the beta and gamma subunits
The activated alpha subunit alters the activity of
adenylate cyclase or phosopholipase C
GTP is dephosphorylated to
GDP
the alpha subunit rebind to the beta and gamma subunit
Function of the Gs protein:
stimulates adenylate cyclase, which increases levels of cAMP in the cell
Function of the Gi protein:
inhibits adenylate cycles, which decreases levels of cAMP in the cell
Function of the Gq protein:
activates phospholipase C, which cleaves a phospholipid from a membrane
