BS120: Lsn 2 & 3 in amino acids & protein chemistry Flashcards
What are the 3 ways proteins can be classified?
based on:
1. function
2. shape of protein molecule
3. composition & solubility
What are the 8 types of protein based on function?
- Storage proteins
- Transport proteins
- Contractile proteins
- Catalytic proteins (enzymes)
- Protective/ defensive proteins
- Structural proteins
- Proteins that act as buffers
- Regulatory proteins
What are storage proteins?
w examples
proteins that store metals and amino acids
examples include:
1. Ferritin [stores iron]
2. Ovalbumin [stores amino acids in egg]
3. Casein [stores amino acids in milk]
What are transport proteins?
involved in binding and carrying metals & substances.
examples include:
1. Serum albumin [calcium, fatty acids, hormones, & many drugs]
2. Transferrin [transports iron, Fe]
3. Ceruloplasmin [transports copper, Cu]
4. Hemoglobin [transports O2 from lungs to tissue and CO2 back to the lungs]
What are catalytic proteins? (enzymes)
involved in catalyzing biochemical reactions.
examples include:
1. DNA polymerase
2. Amylase
3. Pepsin
4. Lipase
What are structural proteins?
involved in providing structural support to cells & tissue.
examples include:
1. Collagen
2. Keratine
What is the most abundant protein in mammals?
Collagen
Where is keratine found?
it is a major component in nails, hair, & outer skin layer
What are contractile proteins?
proteins that aid in Muscle Movement.
examples include:
1. Actin
2. Myosin
What shape is actin and what are other proteins that share that shape?
It is fibrous protein, likefibrin, myosin, & keratine + collagen
What are regulatory proteins?
2 Types of regulatory proteins:
1. Transcription factors
2. Hormones
What are transcription factors?
proteins that are involved in regulating gene expression. (no examples listed)
What are hormones?
regulatory proteins that are involved in regulating metabolic processes.
examples include:
1. insulin
2. glucose
3. growth hormone
What are defensive/protective protein?
proteins that are involved in the immune response.
examples include:
1. Cytokines
2. Immunoglobins/antibodies
3. Clotting factors
Do all proteins act as buffers? Where & how do they act as buffers?
Almost all proteins can act as buffers due to the ionizable groups present within their amino acid composition. This buffering capacity is fundamental in maintaing the acid-base balance of the body.
Where: in blood & tissues
Which are the 2 most important proteins for buffering in the body?
- Hemoglobin
- plasma proteins, ex. albumin
What are the types of protein based on shape?
- Globular proteins
- Fibrous proteins
What are the properties of globular protein?
- Compact & dense
- Roughly spherical shape
- Water soluble
- Digestible
- Physiological/ functional roles
- Tertiary structure folding
What are the properties of fibrous proteins?
- Elongated fibres
- Long polypeptide chains
- Water insoluble
- Limited no. of AAs with highly repetitive sequence
- Strong
- Structural roles
- Secondary structures, with litte tertiary structure
What makes globular protein water soluble & fibrous protein water insoluble?
- In globular protein, the hydrophilic AA residues are on the outside while the hydrophobic AA residues face the inside. this orientation enables globular proteins to be soluble in water.
- In fibrous protein, there is simply a large number of hydrophobic R groups, making them insoluble in water.
What enables enzymes to catalyze specific rxns?
Being globular, the shape of the protein is rendered from the unique folding of it due to interactions between the R groups. These specific shapes are what allow enzymes to catalyse specific reactions.
What does the shape of immunoglobins due to the folding caused by the interaction between the R groups cause?
They allow immunoglobins to respond to specific antigens
What bond can be found in quaternary structures?
Disulfide bonds; they can occur between polypeptide chains
What does the highly repetitive sequence in fibrous proteins cause?
It makes the protein very organized structures that are strong.
- this makes them well-suited for structural roles.
What makes fibrous proteins suited for structural roles?
- insolubility property
- strong & very organized structures
What is another name for fibrous proteins?
AKA scleroproteins
What gives scleroproteins their distinct structural & functional characteristics?
Due to elongated & filamentous forms.
What are the types of protein based on composition & solubility?
- Simple Proteins
- Conjugated Proteins
- Derived Proteins
What are the types of simple proteins?
- Albumins
- Histones
- Protamines
- Globulins
- Glutelins
- Scleroproteins
What are simple proteins?
proteins composed of only AA residues linked by peptide bonds.
What do these proteins yield?
They only yield amino acids upon their hydrolysis
Properties of albumins include:
- soluble in water
- coagulate by heat
- precipitate by high salt concentrations
Examples of albumins:
- Serum albumin
- Ovalbumin (egg whites)
Properties of Histones:
- basic protein
- soluble in water
- insoluble in dilute ammonium hydroxide
- do not coagulate with heat
Where are histones found?
In association with nucleic acids
Properties of protamines:
- basic proteins
- resemble histones but: smaller & soluble in dilute ammonium hydroxide
- also associated with nucleic acids
Properties of globulins:
- insoluble in pure water
- dissolve in dilute salt concentrations
- coagulate by heat
- precipitate using half-saturated salt solutions
What makes globulins special compared to other plasma proteins?
They can be isolated from the other plasma proteins when placed in a half-saturated salt solution, where it precipitates.
What is an example of globulins?
Plasma globulin
Properties of glutelins:
- soluble in dilute acids & alkalies
- mainly found in plants
Properties of scleroproteins:
with examples
- insoluble in water
- ex: collagen & keratin
What are the types of conjugated proteins?
- Nucleoproteins
- Lipoproteins
- Glycoproteins
- Phosphoproteins
- Metalloproteins
- Chromoproteins
- Flavoproteins
What are conjugated proteins?
simple proteins that are combined with non-protein substances (prosthetic group)
What role does the prosthetic group have in conjugated proteins?
The nature of the prosthetic group is the basis for the sub classification of conjugated proteins
What are nucleoproteins?
- they are formed by the combination of histones (simple proteins) and DNA (prosthetic group)
- they are essential components of chromatin
What are Lipoproteins?
- these are lipid-conjugated proteins
- examples include LDL & HDL (low & high density lipids)
What are glycoproteins?
- carbohydrate prosthetic group: less than 4% of the protein is carb.
- majority of the membrane proteins are glycoproteins
- if carb content of protein is greater than 4%: it is called a mucoprotein
