Kaplan Chapter 3 Nonenzymatic Protein Function and Protein Analysis Flashcards
What are Structural protein
They are composed of the cytoskeleton, anchoring proteins,
and much of the extracellular matrix.
The most common structural proteins are collagen, elastin, and tubulin
What is collagen?
Collagen is the most abundant structural protein in the body, providing strength and support to tissues like skin, bones, and tendons. Its synthesis requires vitamin C, and defects in collagen production can lead to conditions like scurvy or osteogenesis imperfecta. Collagen comes in different types (e.g., Type I in bones and skin, Type II in cartilage), each serving specific functions in maintaining tissue integrity.
Key word: Strength and Flexibility
What is elastin?
Elastin is a key structural protein that gives tissues like skin, lungs, and blood vessels their elasticity, allowing them to stretch and return to their original shape. It is primarily found in connective tissues and works alongside collagen to provide both flexibility and strength. Defects in elastin can lead to conditions like emphysema and Marfan syndrome, which affect the elasticity of tissues.
Key word: Restores original shape of Tissue
What is keratin?
Keratin Summary:
Keratin is a tough, fibrous structural protein found in hair, nails, and the outer layer of skin, providing protection and mechanical strength. It is highly resistant to wear and tear, contributing to the body’s barrier against physical and environmental damage. Keratin also forms in epithelial cells in the lining of various organs and tissues.
MCAT Relevance:
Keratin is relevant to the MCAT in questions related to epithelial tissue function, structural proteins, and the body’s protective barriers. It’s also important for understanding the differences between various structural proteins like keratin, collagen, and elastin, as well as disorders related to skin and hair.
Key word: mechanical integrity and regulatory proteins.
What is tubulin?
Tubulin Summary:
Tubulin is a globular protein that forms microtubules, which are essential components of the cytoskeleton. Microtubules provide structural support, aid in intracellular transport, and are crucial for cell division, particularly in the formation of the mitotic spindle.
MCAT Relevance:
Tubulin is important for the MCAT in topics involving cell structure and function, mitosis/meiosis, and intracellular transport mechanisms. Questions may cover the role of tubulin in processes like chromosome separation during cell division, cilia and flagella movement, and the impact of drugs (e.g., taxol) that target tubulin in cancer therapy.
Key word: provide structure, chromosome seperation in mitosis, intracellular transport with kinesin …
- end by nucleus
+ end by the outside
What are motor protiens?
Motor proteins have one or more heads capable of force generation through a conformational change.
They have catalytic activity, acting as ATPases to power movement.
Muscle contraction, vesicle movement within cells, and cell motility are the most common applications of motor proteins.
Common examples include myosin, kinesin, and dynein.
What is ATPase and what does it do?
ATPase Summary:
ATPase is an enzyme that catalyzes the hydrolysis of ATP into ADP and inorganic phosphate, releasing energy for various cellular processes. It plays a key role in active transport, muscle contraction, and maintaining ion gradients across membranes (e.g., the Na⁺/K⁺ pump).
MCAT Relevance:
ATPase is crucial for the MCAT in topics like cellular energy metabolism, active transport, and muscle physiology. Questions may focus on ATPase’s role in maintaining ion gradients, driving processes like nerve impulses, and its function in muscle contraction through the interaction with actin and myosin.
What is a binding protein?
Binds a specific substrate, either to sequester it in the
body or hold its concentration at steady state.
What is cell adhesion Molecules?
CAM bind a specific substrate, either to sequester it in the
body or hold its concentration at steady state.
What is myosin?
Myosin Summary:
Myosin is a motor protein that interacts with actin filaments to facilitate muscle contraction and various cellular movements. It converts chemical energy from ATP hydrolysis into mechanical work, enabling processes like muscle contraction and intracellular transport.
MCAT Relevance:
Myosin is important for the MCAT in muscle physiology, cellular movement, and protein function. Questions might cover its role in muscle contraction (e.g., the sliding filament theory), its interaction with actin, and its function in other cellular processes like cytokinesis and vesicle transport.
Has a thicc neck which is responsible for the power strike of a saccromere contraction.
What is Kinesins and Dyneins?
Kinesins and Dyneins Summary:
Kinesins and dyneins are motor proteins that transport cellular components along microtubules. Kinesins generally move toward the plus end of microtubules (outward from the cell center), while dyneins move toward the minus end (toward the cell center).
MCAT Relevance:
Kinesins and dyneins are important for the MCAT in topics related to intracellular transport, cytoskeleton function, and cell division. Questions may cover their roles in moving organelles, vesicles, and other cargo within cells, as well as their involvement in processes like mitosis and cellular organization.
Importance: has 2 heads, 1 attached to Metaphase, both are important during metaphase for vesicle transoprt/
Dyneiens are involved in the movement of cilia and flagella.
What is Cadherins?
A type of binding protein that are calcium-dependent glycoproteins that hold similar
cells together.
What are Integrins?
A type of binding protein
that have two membrane-spanning chains and permit cells to adhere to proteins in the extracellular matrix. Some also have signaling capabilities.
What are selectins?
A type of binding protein
that carbohydrates on the surfaces of other cells and are most commonly used in the immune system
Selectins are relevant for the MCAT in cellular adhesion, immune response, and inflammation. Questions might address their role in leukocyte trafficking, their function in the inflammatory response, and how selectins interact with other adhesion molecules to mediate cell movement and immune cell recruitmen
What are Antibodies (or immunoglobulins, Ig)
Antibodies (or immunoglobulins, Ig) are used by the immune
system to target a specific antigen, which may be a protein on the
surface of a pathogen (invading organism) or a toxin.
Immunoglobulins contain a constant region and a variable region;
the variable region is responsible for antigen binding.
Two identical heavy chains and two identical light chains form a
single antibody; they are held together by disulfide linkages and
noncovalent interactions.
What is Biosignaling?
Biosignaling is a process in which cells receive and act on signals. Proteins
participate in biosignaling in different capacities, including acting as
extracellular ligands, transporters for facilitated diffusion, receptor proteins,
and second messengers. e proteins involved in biosignaling can have
functions in substrate binding or enzymatic activity
What are Ion Channels used for?
Ion channels can be used for regulating ion flow into or out of a cell.
There are three main types of ion channels: Ungated channels, Voltage-gated channels, Ligand-gated channels
What are Ungated channels?
Ungated channels, also known as leak channels, are ion channels that are always open, allowing ions to flow across the cell membrane freely. They contribute to the resting membrane potential and help maintain ion gradients within the cell.
MCAT Relevance:
Ungated channels are relevant for the MCAT in neurophysiology, cell membrane function, and electrophysiology. Questions may cover their role in maintaining the resting membrane potential, their contribution to the passive movement of ions, and their impact on cellular excitability and signaling.
ALWAYS OPEN
What are Voltage-gated channels?
Voltage-Gated Channels Summary:
Voltage-gated channels are a type of Ion Channel that open or close in response to changes in membrane potential. They are crucial for generating and propagating action potentials in neurons and muscle cells, as they allow ions to flow across the membrane in a controlled manner.
MCAT Relevance:
Voltage-gated channels are important for the MCAT in topics related to neurophysiology, action potentials, and cellular excitability. Questions may focus on their role in the depolarization and repolarization phases of action potentials, their specific ion selectivity (e.g., sodium or potassium channels), and their function in the propagation of electrical signals along nerves and muscles.
are open within a range of membrane potentials.
What are Ligand-gated channels?
Ligand-Gated Channels Summary:
Ligand-gated channels are a type of Ion Channel that open in response to the binding of a specific molecule, such as a hormone or neurotransmitter. This binding causes a conformational change in the channel, allowing ions to flow across the membrane and initiate cellular responses.
MCAT Relevance:
Ligand-gated channels are relevant for the MCAT in topics related to cell signaling, synaptic transmission, and neurophysiology. Questions may address their role in neurotransmission, the mechanisms of signal transduction, and how ligand binding influences channel activity to affect cellular functions.
What are Enzyme-Linked Receptors
Enzyme-Linked Receptors Summary:
Enzyme-linked receptors are membrane proteins with three main domains: a membrane-spanning domain, a ligand-binding domain, and a catalytic domain. When a ligand binds to the receptor, it induces a conformational change that activates the catalytic domain, leading to a cascade of biochemical events inside the cell. Examples include receptor tyrosine kinases (RTKs), which dimerize and autophosphorylate upon ligand binding, initiating further signaling.
MCAT Relevance:
Enzyme-linked receptors are key in cell signaling and signal transduction pathways. Questions may focus on their structure, activation mechanism, and the role of RTKs and other enzyme-linked receptors in cellular processes. Understanding these mechanisms is crucial for topics related to cellular responses and intracellular signaling cascades.
What are G Protein-Coupled Receptors (GPCRs)
G Protein-Coupled Receptors (GPCRs) Summary:
GPCRs are integral membrane proteins with seven α-helical segments that facilitate signal transduction. They operate through a trimeric G protein complex consisting of α, β, and γ subunits. Ligand binding to a GPCR activates the associated G protein by exchanging GDP for GTP on the α subunit, which then dissociates from the β and γ subunits. The activated α subunit influences downstream effectors like adenylate cyclase or phospholipase C, leading to changes in second messenger levels. The α subunit eventually hydrolyzes GTP to GDP, re-associating with the β and γ subunits, and returning to its inactive state.
MCAT Relevance:
GPCRs are crucial for understanding cell signaling pathways, receptor mechanisms, and pharmacology. Questions might focus on the GPCR structure, the process of G protein activation, the role of different G protein types (Gs, Gi, Gq), and the impact on second messenger systems such as cAMP or IP3/DAG. Understanding these concepts is essential for comprehending how cells respond to various stimuli and how drugs can influence these pathways.
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 α subunit dissociates from the β and
γ subunits. The activated α subunit alters the activity of adenylate cyclase or
phospholipase C. GTP is dephosphorylated to GDP; the α subunit rebinds to the β and γ subunits.
What is Electrophoresis?
Electrophoresis uses a gel matrix to observe the migration of proteins
in response to an electric field.
What is Native PAGE?
Native PAGE maintains the protein’s shape, but results are difficult
to compare because the mass-to-charge ratio differs for each
protein
What is SDS-PAGE?
SDS-PAGE denatures the proteins and masks the native charge so
that comparison of size is more accurate, but the functional protein
cannot be recaptured from the gel.
What is Isoelectric focusing?
Isoelectric focusing separates proteins by their isoelectric point (pI); the protein migrates toward an electrode until it reaches a
region of the gel where pH = pI of the protein.
What is X-ray
crystallography used for?
Protein structure is primarily determined through X-ray crystallography aer the protein is isolated, although NMR can also
be used.
How is Amino acid composition determined?
Amino acid composition can be determined by simple hydrolysis, but
amino acid sequencing requires sequential degradation, such as the
Edman degradation. [The Edman degradation selectively and sequentially
removes the N-terminal amino acid of the protein, which can be analyzed
via mass spectroscopy.]
How are Activity levels for enzymatic samples determined?
Activity levels for enzymatic samples are determined by following the process of a known reaction, often accompanied by a color change.
How is Protein concentration determined?
Protein concentration is also determined colorimetrically, either byUV spectroscopy or through a color change reaction.
BCA assay, Lowry reagent assay, and Bradford protein assay each
test for protein and have different advantages and disadvantages.
The Bradford protein assay, which uses a color change from browngreen to blue, is most common
