CH2 | Proteins Flashcards
What are proteins composed of, structurally?
One or more polypeptide chains (subunits) folded into a specific 3-D shape.
How does the genetic coding differ between a polypeptide and a multi-subunit protein?
A single gene codes for a polypeptide chain, whereas multiple genes code for the different subunits of a multi-subunit protein.
What is the typical size (in amino acids) and molecular weight difference between a polypeptide and a protein?
Polypeptides: Usually ≤ 100 amino acids, ≤ 10,000 Da (10 kDa).
Proteins: Usually ≥ 100 amino acids, ≥ 10,000 Da (10 kDa).
What are the three main factors that contribute to the variation among proteins?
Amino acid types (composition), amino acid number, and amino acid sequence.
What is the approximate average molecular weight of a single amino acid residue?
110 Daltons (Da).
How can you estimate the number of amino acid residues in a protein using its molecular weight?
Divide the protein’s molecular weight (in Da) by 110. (Number of amino acid residues ≈ Protein Molecular Weight / 110).
What is the formula to find the number of amino acid residues in a protein?
M.wt (protein) / 110.
What are the four major categories used to classify proteins?
Function, Number of polypeptide chains, Composition, and Structure.
If you classify a protein based on its function, what are some examples of possible functional categories?
Structural, enzyme, hormones, transports, pigments, contractile, storage, toxins.
What are the two main classifications of proteins based on the number of polypeptide chains they possess?
Monomeric (one polypeptide chain) and Multi-subunit (more than one polypeptide chain).
What are the two classifications of proteins based on their chemical composition?
Simple (only amino acids) and Conjugated (amino acids plus other chemical groups).
What are the two major structural classifications of proteins?
Fibrous and Globular.
How are proteins classified?
Based on their functions, the number of polypeptide chains, their composition and their structure.
What is the role of enzymatic proteins, and can you give an example?
Enzymatic proteins selectively accelerate chemical reactions. Example: digestive enzymes.
What is the function of transport proteins? Provide an example.
Transport proteins move substances within an organism. Example: Hemoglobin, membrane channels.
What do receptor proteins do? Give an example.
Receptor proteins respond to chemical stimuli. Example: membrane receptors.
What is the role of storage proteins? Can you name an example?
Storage proteins store amino acids. Examples: Casein, Ovalbumin.
What is the function of contractile and motor proteins? Give an example.
Contractile and motor proteins are involved in movement and muscle contraction. Example: Actin + Myosin.
What do defensive proteins do? Provide an example.
Defensive proteins protect against disease. Example: antibodies.
What is the role of hormonal proteins? Give an example.
Hormonal proteins coordinate cellular activities. Example: Insulin.
What is the function of structural proteins? Provide an example.
Structural proteins provide support. Examples: Keratin, Collagen, elastin.
Name the 8 main functions of protein classification described in this chapter, and give an example for each function.
1) Enzymatic: digestive enzyme,
2) Transport: Hemoglobin,
3) Receptor: Membrane receptor,
4) Storage: Casein,
5) Contractile and motor: Actin,
6) Defensive: Antibodies,
7) Hormonal: Insulin,
8) Structural: Keratin.
What is a monomeric protein?
A protein that consists of a single polypeptide chain.
What are multi-subunit proteins?
Proteins that consist of two or more polypeptide chains (subunits) associated by non-covalent bonds.
What are oligomeric proteins?
Proteins consisting of more than two subunits. (A subcategory of multi-subunit proteins)
What are dimeric, trimeric, and tetrameric proteins?
Dimeric: Proteins with two subunits.
Trimeric: Proteins with three subunits.
Tetrameric: Proteins with four subunits.
Are proteins with more than four subunits common?
No, proteins consisting of more than four subunits are less common.
What are the two categories of protein, when classified according to their number of polypeptide chains?
Monomeric and multi-subunit proteins.
Regarding oligomeric proteins, what types are usually found?
Dimeric, trimeric and tetrameric.
What are simple proteins? Give two examples.
Simple proteins contain only amino acid residues and no other chemical constituents. Examples: ribonuclease A and chymotrypsin.
What are conjugated proteins?
Conjugated proteins contain other chemical groups besides amino acids.
What is a prosthetic group in the context of conjugated proteins?
The non-amino acid part of a conjugated protein, which often plays a vital role in the protein’s function.
How are conjugated proteins further classified?
Based on the chemical nature of their prosthetic groups.
Name three types of conjugated proteins based on their prosthetic groups.
Lipoproteins (contain lipids), glycoproteins (contain sugar groups), and metalloproteins (contain a specific metal).
What are the two main categories to classify proteins, based on their composition?
Simple and conjugated proteins.
Why is the prosthetic group important in conjugated proteins?
It plays an important role in the protein’s biological function.
What are the two major structural classifications of proteins?
Fibrous and globular.
What is the typical function of fibrous proteins? Name two examples.
Fibrous proteins usually have structural roles. Examples: keratin and collagen.
What is a major example of a structural protein?
Collagen.
What are some functions of globular proteins? Give an example.
Globular proteins have diverse functions, including roles as enzymes and regulatory proteins. Example: Hemoglobin.
Which of the two structural classifications has more diverse functions? Give an example of such a protein.
Globular proteins, for example, hemoglobin.
What are the functions associated with the two main categories of protein structure?
Fibrous proteins are mainly structural, while globular proteins are more diverse, and include enzymes and regulatory proteins.
Conjugated Proteins
