The Cell Part 2- The Cytosol And Proteins Flashcards
What is the primary structure of a protein, and how is it determined?
The primary structure of a protein is the sequence of amino acids, which is determined by mRNA codons during protein synthesis.
Describe two types of secondary structures found in proteins and explain the molecular basis for their formation.
Two types of secondary structures in proteins are the α helix and β pleated sheet. They form due to hydrogen bonding between the N–H and C=O groups in the polypeptide backbone. In α helix, hydrogen bonds form within the polypeptide chain spaced four amino acids apart, while β pleated sheets have hydrogen bonds between amino acids in adjacent strands.
What is the tertiary structure of a protein, and what forces contribute to its formation?
Tertiary structure refers to the three-dimensional structure of a polypeptide chain. It is stabilized by various forces, including disulfide bonds, hydrogen bonds, ionic bonds, hydrophobic interactions, and Van der Waals forces.
Name two categories of proteins based on their structural characteristics and provide examples of each.
Two categories of proteins based on their structural characteristics are fibrous proteins and globular proteins. Examples of fibrous proteins include collagen, keratin, and elastin, while examples of globular proteins include catalase, hemoglobin, and insulin.
Explain the process of protein denaturation and provide an example of irreversible denaturation.
Protein denaturation occurs when the secondary, tertiary, or quaternary structure of a protein is disrupted, causing it to lose its specific three-dimensional shape. This can be caused by factors such as extreme temperature or pH changes. An example of irreversible denaturation is the coagulation of egg white (albumin) when it is boiled or fried.
What is recombinant protein, and how is it produced using recombinant DNA technology? Name a commonly used host organism in this process.
Recombinant protein is a manipulated form of protein generated using recombinant DNA technology, where genetic material from one organism is combined with another to produce proteins. This is done using vectors, specialized vehicles for recombinant DNA. Common host organisms for producing recombinant proteins include E. coli for bacterial transformation and eukaryotic cells for transfection. The production of recombinant proteins involves the expression of recombinant DNA within living cells.
List some uses of recombinant proteins and provide examples of recombinant proteins used in each category.
Hormones/Enzymes: Insulin (Humulin), clotting factors (e.g., Factor VIII)
Vaccines/Immunogens: Hepatitis B surface antigen (HBV S Ag)
Therapeutic Antibodies: Anti-HER2 (for cancer treatment), Anti-VEGF (for cancer treatment)
Cytokines/Immunostimulation: Interferon (for immunostimulation)
Assisted Reproduction: FSH (follicle-stimulating hormone)
Blood Clotting: Factors VII, IX, X (for blood clotting)
Metabolism: Exubera (for insulin replacement therapy)
What organelle is responsible for the degradation of organelle proteins, and what is the process by which they are degraded?
Lysosomes are responsible for the degradation of organelle proteins. They use hydrolytic enzymes to break down cellular components, including organelle proteins.
Which cellular structure destroys proteins, and where is it found in the cell?
The proteasome is responsible for destroying proteins, and it is found in both the nucleus and the cytoplasm.
Describe the components of the proteasome
The proteasome consists of a core particle containing catalytic (proteolytic) sites and regulatory caps on each end, each made of a base and a lid.
What is the role of ubiquitin in protein degradation, and how is it attached to the targeted protein?
Ubiquitin serves as a signal for protein destruction. A chain of ubiquitin molecules (polyubiquitin) is attached to the targeted protein. The process involves E1 (Ubiquitin-activating enzyme), E2 (Ubiquitin-conjugating enzyme), and E3 (E3 ligases) enzymes. E1 activates ubiquitin, E2 transfers it to the protein, and E3 ligases catalyze its attachment to a lysine in the substrate protein.
Briefly explain the process of gel electrophoresis, including SDS-PAGE, and its purpose.
Gel electrophoresis is a technique that separates molecules, such as proteins, based on their electrical charge, size, or other characteristics. In SDS-PAGE (sodium dodecyl sulfate polyacrylamide-gel electrophoresis), proteins are treated with SDS and a reducing agent to denature and separate them by size. This technique is used for the separation and identification of proteins, creating a banded pattern.
What is the principle of a Western blot, and how is it used to detect specific proteins?
A Western blot is a technique used to detect specific proteins in a sample. It involves separating proteins through electrophoresis, transferring them to a paper sheet, and then using labeled antibodies to detect the target proteins. The antibodies bind to specific proteins of interest, allowing their detection on the blot. This technique is useful in confirming diagnoses, such as HIV, and studying protein expression in various samples.
What is the main function of the plasma membrane in a cell?
The plasma membrane encloses cell contents, mediates exchange with extracellular fluid (ECF), and plays a role in communication.
According to the fluid mosaic model, what is the structure of the plasma membrane?
The fluid mosaic model describes the plasma membrane as a lipid bilayer within which proteins are inserted. The lipids in the bilayer have hydrophobic tails and hydrophilic heads, organizing their arrangement.
What are integral transmembrane proteins, and what is their role in the plasma membrane?
Integral transmembrane proteins extend entirely through the plasma membrane. They are essential for various functions, including transport, enzymatic activity, and communication. Some proteins attached to the integral proteins are peripheral proteins.
Describe the three types of chemical signal receptors.
The three types of chemical signal receptors are:
Chemically gated channel-linked receptors.
G-protein linked (coupled) receptors.
Catalytic proteins (enzyme-linked or coupled) receptors.
Explain the functioning of G protein-linked receptors, including the role of second messengers and protein kinase enzymes.
G protein-linked receptors are activated when a ligand binds to the receptor. The activated receptor then binds to a G protein, which activates it. The activated G protein, in turn, activates an effector protein (enzyme), causing a change in its shape. The activated effector enzyme catalyzes reactions that produce second messengers, such as cAMP. These second messengers activate other enzymes and ion channels, leading to a cellular response. Protein kinase enzymes, activated by cAMP or other second messengers, transfer phosphate groups from ATP to specific proteins, triggering a series of enzyme activations and cellular responses.
What are tight junctions, and what is their primary function?
Tight junctions are impermeable cell-cell junctions that seal adjacent epithelial cells together. Their primary function is to prevent the passage of most dissolved molecules from one side of the epithelial sheet to the other.
What are the types of cell junctions found in animal tissues?
- desmosomes
- gap junctions
- adherens junctions
Function of desmosomes
These are anchoring cell-cell junctions, usually formed between two epithelial cells. They are characterized by dense plaques of protein into which intermediate filaments in the two adjoining cells insert, mechanically coupling cells into a functional community.
Function of gap junctions
Gap junctions are communicating channel-forming cell-cell junctions present in most animal tissues. They allow ions and small molecules to pass from the cytoplasm of one cell to the cytoplasm of the next, facilitating communication between joint cells.
Function of adherens junctions
Adherens junctions are cell junctions in which the cytoplasmic face of the plasma membrane is attached to actin filaments. Examples include adhesion belts linking adjacent epithelial cells and focal contacts on the lower surface of cultured fibroblasts.
What are the roles of cell adhesion molecules (CAMs) in cellular processes?
Embryonic development.
Immunity.
Wound repair.
Anchoring cells to molecules in the extracellular fluid (ECF) and to each other.
Sensing mechanical tension in the environment.
Transmitting intracellular signals that direct cell migration, proliferation, and specialization.
