Biochemistry Proteins Flashcards
(40 cards)
What elements are proteins made from?
Carbon, hydrogen, nitrogen, oxygen, sometimes sulfur, and sometimes phosphorus
These elements are the building blocks of proteins.
What are the various roles of proteins?
- Biochemical - enzymes, hormones, antibodies, buffers
- Structural - membranes, hair, muscle fibers, nails, bones, connective tissue
- Energy - only under conditions of starvation
Proteins perform diverse functions in living organisms.
How are proteins formed?
They are formed when amino acid sub-units combine through the formation of peptide bonds and condensation reactions (removing water). The long chains of amino acids form polypeptides.
This process is essential for building proteins in biological systems.
Describe the structure of an amino acid.
- Amino group - NH2 at one end
- Carboxyl group - COOH at the other end
- Variable group (R group) in the middle
Each amino acid has a distinct R group that influences its properties.
What is the importance of the ‘R’ group?
The ‘R’ groups determine the role and properties of the polypeptide or protein, including its solubility, buffering ability, enzymatic abilities, and role as a hormone or antibody.
The R group can be simple or complex, affecting the overall function of the protein.
What is a dipeptide and how is it formed?
A dipeptide is formed when just two amino acids combine through condensation and the formation of a peptide bond.
This reaction can be reversed by hydrolysis (addition of water).
Fill in the blank: A dipeptide is formed when two amino acids combine through _______.
condensation
This process involves the removal of water.
True or False: Proteins can only serve structural roles in organisms.
False
Proteins have multiple roles including biochemical and energy functions.
Show a hydrolysis and condensation reaction
What is a polypeptide?
A polypeptide is formed when up to 100 amino acids combine through condensation reactions to form a long chain.
Polypeptides are the building blocks of proteins.
What defines a protein?
A protein consists of one or more polypeptide chains that are either folded, branched, or cross-linked.
Proteins perform a variety of functions in biological systems.
What is the primary structure of a protein?
The primary structure is the order or sequence of the amino acids joined together via peptide bonds.
This sequence determines the protein’s characteristics and function.
What is the secondary structure of a protein?
The secondary structure refers to the local folded structures that form within a protein due to hydrogen bonding.
Common types include alpha helices and beta-pleated sheets.
Describe the alpha helix structure.
The alpha helix consists of twists or turns in the chain of amino acids held in place by hydrogen bonds at regular intervals, forming a spiral.
This structure contributes to the overall stability of the protein.
What is the beta-pleated sheet structure?
The beta-pleated sheets consist of anti-parallel chains of amino acids lying adjacent to each other and held in place by hydrogen bonds, resulting in a flat, folded structure.
This arrangement is important for the protein’s overall shape.
What is the tertiary structure of a protein?
The tertiary structure is how the polypeptide chain folds and coils to form a complex, three-dimensional shape, held in place by bonds between the amino acid R-groups.
These bonds include hydrogen bonds, ionic bonds, and disulfide bridges.
What types of bonds are involved in maintaining tertiary structure?
The bonds that maintain tertiary structure include:
* Hydrogen bonds
* Ionic bonds
* Disulfide bridges
* Hydrophobic interactions
Each type of bond contributes differently to the stability of the protein.
True or False: A polypeptide can consist of more than 100 amino acids.
False
A polypeptide is defined as having up to 100 amino acids.
Fill in the blank: The _______ structure of a protein describes the sequence of amino acids.
primary structure
The primary structure is crucial for determining the protein’s properties.
What do we mean by the quaternary structure of a protein?
This level of organisation only exists if there is more than one polypeptide chain
What are the two main types of proteins?
Globular and Fibrous
Describe fibrous proteins
They consist of long, parallel fibres of polypeptide chains, cross-linked to form stable and strong structures, often structural in function
Describe globular proteins
They consist of polypeptide chains folded to give a spherical 3-d shape which is very specific, and leads to biochemical functions
Explain how collagen is a fibrous protein
Each collagen molecule consists of 3 identical helical polypeptides wound around each other and held together by hydrogen bonds to form fibrils
