PROTEINS Flashcards
1
Q
- are also needed for the maintenance and repair of existing tissues.
- is a naturally-occurring, unbranched polymer in which the monomer units are amino acids
A
Proteins
2
Q
- Elemental composition of proteins
A
Carbon (C), Hydrogen (H), Nitrogen (N), Oxygen (O), most also contain Sulfur (S)
3
Q
o An organic compound that contains both an
amino (-NH2) and carboxyl (-COOH) groups
attached to same carbon atom (α-amino
acid)
A
Amino acid
3
Q
o Vary in size, shape, charge, acidity, functional groups present, hydrogen-
bonding ability, and chemical reactivity.
A
R = amino acid side chain
4
Q
contains one amino group, one carboxyl group and a polar but neutral side chain. Six amino acids belong to this category
A
Polar-neutral:
5
Q
: contains one amino group, two carboxyl groups, the 2nd carboxyl group as part of the side chains. Two amino acids belong to this category
A
Polar acidic:
5
Q
contains two amino groups, one carboxyl group, the 2nd amino group as part of the side chain. Three amino acids
A
Polar basic:
6
Q
- Four different groups are attached to the a-carbon atom in all of the standard amino acids except ________
A
glycine
6
Q
– pH at which the concentration of Zwitterion is maximum – net charge is zero
A
Isoelectric point (pI)
7
Q
the only standard amino acid with a sulfhydryl group ( — SH group).
A
Cysteine:
8
Q
- Under proper conditions, amino acids can bond together to produce an unbranched chain of amino acids.
- The length of the amino acid chain can vary from a few amino acids to many amino acids.
A
Peptides
9
Q
- Covalent bonds between amino acids in a peptide
A
Peptide bonds
9
Q
: bond between two amino acids
A
Dipeptide
10
Q
: bond between ~ 10 - 20 amino acids
A
Oligopeptide
11
Q
: bond between large number of amino acids
A
Polypeptide
12
Q
- Peptides that contain the same amino acids but present in different order are different molecules (constitutional isomers) with different properties
A
Isomeric Peptides
12
Q
o Best-known peptide hormones:
A
oxytocin and vasopressin
13
Q
- Enkephalins are pentapeptide neurotransmitters produced by the brain and bind receptor within the brain
- Help reduce pain
A
Small Peptide Neurotransmitters
13
Q
is an antioxidant and protects cellular contents from oxidizing agents such as peroxides and superoxides
A
Glutathione
14
Q
A is a naturally-occurring, unbranched polymer in
which the monomer units are amino acids.
A
protein
15
Q
A is a peptide in which at least 40 amino acid residues
are present:
A
protein
15
Q
A __________ protein contains one peptide chain
A
Monomeric
15
Q
: A __________ protein contains more than one peptide chain
A
Multimeric
16
Q
A protein in which only amino acid residues are present:
o More than one protein subunit may be present but all subunits contain only amino acids
A
Simple proteins:
17
: A protein that has one or more non-amino acid entities
(prosthetic groups) present in its structure:
o One or more polypeptide chains may be present
Conjugated protein
17
o contain lipid prosthetic groups
Lipoproteins
17
o contain carbohydrate groups,
Glycoproteins
18
o contain a specific metal as prosthetic group
Metalloproteins
19
* A single protein chain adopts a shape that resembles a coiled spring
Alpha-helix (a-helix)
20
* Completely extended amino acid chains
* H-bonding between two different chains – inter and/or intramolecular
* Side chains below or above the axis
Beta-Pleated Sheets
21
: covalent, strong, between two cysteine groups
Disulfide bond
22
Salt Bridge between charged side chains of acidic and basic amino acids
o -OH, -NH2, -COOH, -CONH2
Electrostatic interactions:
23
Between non-polar side chains
* Hydrophobic interactions:
24
* refers to the order in which amino acids are linked
together in a protein
* Every protein has its own unique amino acid
sequence
o Frederick Sanger (1953) sequenced and
determined the primary structure for the first
protein – Insulin
Primary Structure of Proteins
25
* Arrangement of atoms of backbone in space.
* The two most common types : alpha-helix (a-helix) and the beta-pleated sheet (b-
pleated sheet).
* The peptide linkages are essentially planar thus allows only two possible
arrangements for the peptide backbone for the following reasons:
Secondary Structure of Proteins
26
* The overall three-dimensional shape of a protein
* Results from the interactions between amino acid side chains (R groups) that are widely separated from each other.
Tertiary Structure of Proteins
27
* Quaternary structure of protein refers to the organization among the various peptide chains in a multimeric protein:
Quaternary of Proteins
28
protein molecules with elongated shape:
o Generally insoluble in water
o Single type of secondary structure
o Tend to have simple, regular, linear structures
o Tend to aggregate together to form macromolecular structures, e.g., hair, nails,
etc
* Fibrous proteins:
29
protein molecules with peptide chains folded into spherical or
globular shapes:
o Generally water soluble – hydrophobic amino acid residues in the protein core
o Function as enzymes and intracellular signaling molecules
* Globular proteins:
30
associated with cell membranes
o Insoluble in water – hydrophobic amino acid residues on the surface
o Help in transport of molecules across the membran
* Membrane proteins
31
Fibrous proteins
Globular Proteins
* Alpha-Keratin & Collagen
* Myoglobulin & Hemoglobin
32
o Provide protective coating for organs
o Major protein constituent of hair, feather, nails, horns and turtle shells
o Mainly made of hydrophobic amino acid residues
o Hardness of keratin depends upon -S-S- bonds
o more –S-S– bonds make nail and bones hard
Alpha-Keratin
33
o Most abundant proteins in humans (30% of total body protein)
o Major structural material in tendons, ligaments, blood vessels, and skin
o Organic component of bones and teeth
o Predominant structure - triple helix
o Rich in proline (up to 20%) – important to maintain structure
Collagen
34
o An oxygen storage molecule in muscles.
o Monomer - single peptide chain with one heme unit
o Binds one O2 molecule
o Has a higher affinity for oxygen than hemoglobin.
o Oxygen stored in myoglobin molecules serves as a reserve oxygen source for working muscles
Myoglobulin
35
o An oxygen carrier molecule in blood
o Transports oxygen from lungs to tissues
o Tetramer (four peptide chains) - each subunit has a heme group
o Can transport up to 4 oxygen molecules at time
o Iron atom in heme interacts with oxygen
Hemoglobin
36
Enzymes are best known for their catalytic role.
o Almost every chemical reaction in the body is driven by an enzyme
Catalytic proteins:
37
immunoglobulins or antibodies are central to functioning of the body’s immune system.
* Defense proteins:
38
: Bind small biomolecules, e.g., oxygen and other ligands, and transport them to other locations in the body and release them on demand.
* Transport proteins
39
transmit signals to coordinate biochemical processes
between different cells, tissues, and organs.
o Insulin and glucagon - regulate carbohydrate metabolism
o Human growth hormone – regulate body growth
* Messenger proteins:
40
Necessary for all forms of movement.
o Muscles contain filament-like contractile proteins (actin and myosin).
* Contractile proteins:
41
Confer stiffness and rigidity
o Collagen is a component of cartilage a
o Keratin gives mechanical strength as well as protective covering to hair,
fingernails, feathers, hooves, etc.
* Structural proteins:
42
Span a cell membrane and help control the movement
of small molecules and ions.
o Have channels – help molecules can enter and exist the cell.
o Transport is very selective - allow passage of one type of molecule or ion.
* Transmembrane proteins:
43
Bind (and store) small molecules.
o Ferritin - an iron-storage protein - saves iron for use in the biosynthesis of new
hemoglobin molecules.
o Myoglobin - an oxygen-storage protein present in muscle
* Storage proteins:
44
- an iron-storage protein - saves iron for use in the biosynthesis of new
hemoglobin molecules.
Ferritin
45
- an oxygen-storage protein present in muscle
Myoglobin
46
Often found “embedded” in the exterior surface of cell
membranes - act as sites for receptor molecules
o Often the molecules that bind to enzymes (catalytic proteins), thereby turning
them “on” and “off,” and thus controlling enzymatic action.
Regulatory proteins:
47
Particularly important in the early stages of life - from embryo to infant.
o Casein (milk) and oval albumin (egg white) are nutrient proteins
o Milk also provide immunological protection for mammalian young.
Nutrient proteins:
48
- reverse of peptide bond formation:
o Results in the generation of an amine and a carboxylic acid functional groups.
o Digestion of ingested protein is enzyme-catalyzed hydrolysis
o Free amino acids produced are absorbed into the bloodstream and transported
to the liver for the synthesis of new proteins.
Hydrolysis of proteins
48
– Makes it easy for enzymes in our body to hydrolyze/digest protein
Denatures proteins
49
o Glycoproteins produced as a protective response to the invasion of microorganisms or foreign molecules - antibodies against antigens.
Immunoglobulins
50
o Transport triacylglycerols synthesized in
the liver to adipose tissue.
Very-low-density lipoproteins (VLDL):
50
a conjugated protein that contains lipids in addition to amino acids
* Major function - help suspend lipids and transport them through the bloodstream
Lipoprotein:
50
o Transport dietary triacylglycerols from intestine to liver and to adipose tissue.
Chylomicrons:
51
o Transport cholesterol synthesized in the liver to
cells throughout the body.
Low-density lipoproteins (LDL):
52
o Collect excess cholesterol from body tissues
and transport it back to the liver for degradation to bile acids.
High-density lipoproteins (HDL):
66
