Proteins (2.5) Flashcards
Describe the function of enzymatic proteins
Act as catalysts in cellular reactions
State 2 classifications of enzymatic proteins
- catabolic enzymes
2. anabolic enzymes
Provide 2 examples of catabolic enzymes
- lipase
- amylase
Provide 1 example of an anabolic enzyme
- DNA polymerase
Describe the function of hormonal proteins
Coordinate an organism’s activities by triggering a response
Provide 2 examples of hormonal proteins
- insulin
- glucagon
Describe the 2 major functions of immunological proteins
- Protect against disease by recognising foreign bodies and microbes
- Activate immune cells
Describe the function of contractile proteins
Aid muscle contraction
Describe the function of motor proteins
Responsible for the movement of cilia and flagella
Provide 2 examples of immunological proteins
- immunoglobulins (antibodies)
- major histocompatibility complex proteins
Provide 2 examples of contractile and motor proteins
- myosin
- actin
Describe the function of structural proteins
Provide support by forming cellular structures and assist in contractile tissue function
Provide 2 examples of structural proteins
- collagen
- cytoskeleton
Describe the function of transport proteins
Transport of substances through carrier and channel proteins across a semipermeable membrane
Provide 2 examples of transport proteins
- haemoglobin
- sodium-potassium pump
- calcium channel
Describe the function of receptor proteins
Assist the cell in responding to a chemical stimuli
Provide 2 examples of receptor proteins
- neurotransmitter receptors
- hormone receptors
Describe the function of storage proteins
Storage of metal ions and amino acids
Provide 2 examples of storage proteins
- casein (stores amino acids)
- ferritin (stores iron)
Describe proteome
Complete set of proteins expressed by the genome
Describe the genome
Complete set of genes or genetic material of an individual cell or organism.
State what the proteome varies between
- cell type
- developmental stage
- environmental conditions
State the factor that controls the production of proteins within cells
Expression or ‘switching on’ of specific genes in a genome
Describe proteomics
Study of the structure, function, interactions of proteins
State the composition of all proteins
Amino acids
State the 3 structures that compose the structure of amino acids
- Amine group
- Carboxyl group
- Variable R group
State the chemical composition of the amine group of amino acids
NH2
State the chemical composition of the carboxyl group of amino acids
COOH
State how many standard amino acids are involved in the synthesis of proteins within organisms
20 amino acids
Provide 3 examples of the variable characteristics of the amino acid ‘R group’
- Charged/uncharged
- Polar/non-polar
- Hydrophobic/hydrophilic
Define condensation polymerisation
The reaction in which monomers are joined to create a polymer by the removal of water
Explain the process of condensation polymerisation in the synthesis of dipeptides
Hydrogen/oxygen (carboxyl group) + hydrogen (amine group) -> water
Dipeptide is synthesised with a peptide bond holding the two amino acids together
Describe polypeptide chain
Chain of amino acids joined by peptide bonds
Describe what forms the backbone of the polypeptide chain
Repeats of the carboxyl and amine groups
Describe what forms the side chains of the polypeptide chains
R groups
Define proteins
Organic compound consisting of one or more long chains of amino acids, connected by peptide bonds
State what most proteins are required to do…
Bind to other molecules
Describe the impact of a single change to one amino acid within a sequence
Can alter the shape and overall function of a protein
State the 4 different levels of organisation when describing the structure of a protein
- Primary
- Secondary
- Tertiary
- Quaternary
Describe primary structure
Linear sequence of amino acids in the polypeptide chain
Describe the significance of the linear sequence
The linear sequence:
- provides information on how proteins will fold
- compares functional and non-functional proteins (identify what changes to the sequence render protein non-functional)
- provide evolutionary history of the protein
State whether the linear sequence of a protein is unique to every protein. True/false.
True
State the first level of protein organisation
Primary structure
State the second level of protein organisation
Secondary structure
State the third level of protein organisation
Tertiary structure
State the fourth level of protein structure
Quaternary structure
Explain what causes the folding of the polypeptide chain in the secondary level of organisation
Hydrogen bond formation between the amine and carboxyl groups of amino acids
State the 3 major types of secondary structures
- Alpha helix
- Beta-pleated sheets
- Random coil
Describe the process surrounding the formation of the alpha helix structure of secondary proteins
Formation of hydrogen bonds between adjacent amine and carboxyl groups within the polypeptide chain (causes the chain to coil into a helical shape)
Describe the process surrounding the formation of the beta-pleated sheet structure of secondary proteins
Hydrogen bonds form between amine and carboxyl groups in different parts of the adjacent polypeptide chains, causing the chains to fold back on each other
Describe the random coil structure of secondary proteins
Parts of the polypeptide chain appear to have a random structure, however the same pattern of folding occur in all molecules of the same protein.
(E.g. all insulin molecules will have the same random coil structure)
Describe the formation of a functional protein in the tertiary level of organisation
Further folding of polypeptides, forming more stable globular or fibrous 3D shapes
State what tertiary protein structure is usually a combination of…
Alpha helices and beta-pleated sheets
State the unique types of bonds associated with tertiary protein structure
- disulfide bridge formation
- hydrogen bonds
- hydrophobic packing
- van der Waal interactions
State whether the tertiary structure is the final structure for some proteins. True/false.
True
Outline the factor encouraging the spontaneous folding of smaller tertiary-structured polypeptides
Chemical environment
Outline the factor required by large, complex proteins in assisting them to fold correctly and refold if they denature
Specialised proteins (chaperonins)
Define denature
Irreversible change in tertiary protein structure that results in the loss of function.
Describe the formation of a functional protein in the quaternary level of organisation
Two or more polypeptide chains join together (polypeptides may be identical or different)
State what a protein with a prosthetic group is known as
Conjugated protein
Describe prosthetic groups
Inorganic compound that is involved in protein structure or function
Describe conjugated protein
Protein that contains a non-protein group
Provide 1 example of a conjugated protein
Haemoglobin
Describe chaperonins
Protein molecules that assist in the proper folding of other proteins
State what chaperonins provide polypeptides with
Area to fold in without the influence from the cytoplasmic environment, such as changes in pH
State the 2 types of protein classification
- Fibrous proteins
2. Globular proteins
Describe fibrous proteins
Elongated and insoluble (structural roles)
Provide 2 examples of fibrous proteins
- collagen (connective tissue)
- keratin (hair and nails)
Describe globular proteins
Compactly folded and coiled (spherically shaped) and generally soluble
Outline the structure of globular proteins (e.g. core and outer region)
Hydrophobic core
Hydrophilic outer region
Provide 2 examples of globular proteins
- enzymes
- hormones
Provide a major factor supporting the loss of function of a protein
Denaturation
State 3 factors of the environment that affect protein structure and function
- temperature
- pH
- concentration of ions/molecules that act as cofactors
Describe the structural changes of a protein due to denaturation
- hydrogen bonds
- disulfide bridges
- hydrophobic interactions
- van der Waals forces
… broken - altering protein shape
State what a protein which is partially denatured may be able to do…
Fold again (renature)
Describe the effect of temperature on protein function
- high temp -> denaturation due to bond breakage
- low temp -> bonds are not flexible enough to accommodate conformational changes
Describe the effect of pH on protein function
Protein tertiary structure is affected when the pH leaves optimal range
Describe the effect of cofactors on protein function
Some proteins require non-protein chemical compounds for their biological function.
Provide 1 example of a cofactor and its’ effect on protein function
Magnesium - cofactor
Essential for chlorophyll function
Lack of magnesium results in yellowing of leaves
Describe anabolic reaction
Biochemical reaction in which larger molecules are made from smaller molecules, which requires an input of energy to build new bonds.
Describe catabolic reaction
Biochemical reaction in which there is a breakdown of macromolecules into smaller molecules, releases energy.
State the 2 major classes of beta pleated sheets
- antiparallel beta sheets
2. parallel beta sheets
Describe parallel beta sheets
Two peptide strands running in the same direction held together by hydrogen bonds
Describe the antiparallel beta sheet
Two peptide strands run in opposite direction held together by hydrogen bonds
Describe the alpha carbon
Carbon atom next to the carboxyl group
Describe cleaving as a protein modification
Cleaving of polypeptide chains to give smaller chains, that may fold or join to produce functional proteins
Describe glycosylation as a protein modification
Addition of a carbohydrate tag to assist in cell recognition
Describe phosphorylation as a protein modification
Addition of phosphate groups to contribute to proteins 3D shape or assist in signalling
Describe lipid attachment as a protein modification
Lipids attached to them which anchor the protein to the plasma membrane
Describe degradation
Polypeptide chains tagged for degredation when they are no longer useful - amino acids are reused in the formation of other proteins
Describe level of folding of globular proteins
Tertiary or quaternary folding
Describe level of folding of fibrous proteins
Little or no tertiary folding
Where is DNA located in cells?
Nucleus
State what the functional diversity of proteins is explained by
Amino acids being assembled into a variety of polypeptide chains
Describe polymerise
Production of a large molecule from many repeating smaller units by CPR
Describe the process by which an amino acid chain is synthesised
Peptide bond forms by CPR between the COOH end of one amino acid and the amino end of another amino acid
State what can different proteins to be produced when expressing the same gene
Removal of different arrangements of introns
