Week 4 learning goals Flashcards
Describe Lactose intolerance
caused by missing/ defective lactase enzymes
Management options for lactose intolerance
- avoid dairy products 2. lactase supplements 3. treat dairy products with lactose
Explain the importance of alpha and beta linkages in polysaccharides
Only alpha linkages (starches - amalyases) in polysaccharises can be digested by humans Beta linkages (humans) cannot be digested by humans - enzyme needed is not produced
How does cellulose pass in the human
through the digestive tract as fiber
How does cellulose pass through the digestive tracrt
Many herbivores and microorganisma have symbiotic relationships to produce enzyme in hydrolyaze b linkages
Function of : Enzymes
selective catalysis
Function of : structural proteins
support of cellular structures
Function of : motlility proteins
movement of cells and cell parts
Function of : regulatory proteins
regulation of cellular fxns
Function of : transport proteins
transport of substances across membranes
Function of : hormonal proteins
communication between distant parts of an organism
Function of : receptor proteins
response of cells to chemical stimuli
Function of : defensive proteins
protection against disease
Function of : storage proteins
storage and release of amino acids
Describe in detail the peptide bond formation
Product of condesation - peptides are formed based on structural polarity utlizinf the N and C terminuses
Peptide backbone of a polypeptide
repeating sequence of atoms along polypeptide chain Cα, carbonyl, amino, Cα, carbonyl, amino…
How are the ‘R’ groups oriented along the peptide backbone of a polypeptide?
held together by peptide bond btwn aa’s ‘R’ groups spead out from the back bone
Define Polypeptide
polymer of aa - not neccesarily a functional protein
Define Protein
a functional polypeptide or group of polypeptides
True or False: All proteins are polypeptides but not all polypeptides are considered proteins.
False
N- terminus
End that results in NH3 5’ end
C- terminus
End that results in COO- 3’ end
Primary Structure
Sequence aa’s linked together by peptide bind forming a polypeptide
Secondary structure
local regions of the resulting polypeptide can be then coiled into and helix, one form of secondary structure
Teritary structure
associate w/ each other in a specific manner to form the 3’ structure, which describes the final folding of a polypeptide
What interactions are responsible for stabilizing 3 structure
Covalent bonds H bonds Ionic Bonds Hydrophobic interactions
How do the Interactions occir in a 3 structure
Covalent bonds- occurs btwn SH groups of cysteine Hbonds - polar groups may H bond with one another, or turn outward + H bond w/ the surrounding water moles Ionic bonds - positively + negativeky charged groups may form ionic bonds Hydrophobic interactions - Nonpolar R groups cluster on the inside of the protein, away from aq. enviroment of the cell/ organelles
What interactions are responsible for stabilizing 4 structure
Same as 3 structure However covalent bonds are less likely
What interactions are responsible for stabilizing 2 structures
Hydrogen bonds
Redox rxn
involves a change in oxidation numver
Oxidation indicates
a loss of H
Reduction indicates
a gain of H
Homomeric
all the same subunits in quaternary structure
Hetermeric
different subunits EX: heterotrimer = 3 diff subunits
Multimeric
many subunits can be used to describe a protein w/ more than 1 subunit - subunits may be identical or different
What is a protein domain? Recogonize different structural/ functional regions of a polypeptide as independent domains.
Domains: Portions of the polypeptide chains can fold into compact, semi indepdent units - These are discrete structural function unit within the polypeptide - Domains form their own 3D conformation within the polypeptide - Domains are not sepearate subunit - just parts of polypeptides that are folded differently based on their fxn
Cofactor
non protein components of proteins - can be organic or in organic
Coenzyme
an in organic cofactor EX: some vitamins
Are cofactors necessary for all proteins ?
No
Localization pathways for a polypeptide synthesized from mRNA exported from the nucleus into the cytoplasm
Cytosolic (default) - all ribosomes begin translation in the cytoplasm Endomembrane System 3. Mitochondria/ Chloroplast/ Nucleus/ Peroxisome via Nuclear Locaization Sequence (NLS) - have their own specific tag
Define Signal Peptide
A particular streech of aa’s within a protein. Avg. length 15-30 aa’s - Functions as an address for proteins final destination
Describe the events incvolved in properly targeting a protein to the endomembrane system
Co translation import 1. SRP binds to ER signal sequence and blocks translation 2. SRP binds to SRP receptor ribosome docks on membrane 3. Signal sequence is cleaved by signal peptidase as polypeptide elongates and translocates into ER lumen 4. Completed polypeptide is released into ER lumen, ribosome is released, and translocon pore closes RESULT : BOTH TERMINUS ARE IN LUMEN
SRP
Signal recognition particles
what needs to happen for the N-terminus to be cytoplasmically localized and the C-terminus to be localized in the lumen of the ER?
- Internal start sequence begins in the middle of the polypeptide 2. Protein continues translocation until the C terminus moves through translocon 3. Protein is released laterally into ER membrane
what needs to happen for the C-terminus to be cytoplasmically localized and the N-terminus to be localized in the lumen of the ER?
- Signal sequence targets polypeptide to translocon. 2. Stop transfer sequence halts translocation; signal sequence removed. 3. Protein released laterally into ER membrane.
How would multiple membrane-spanning domains be achieved?
Multiple membrane-spanning domains - have alternating start and stop sequences
Conformation
overall, 3D shape of a polypeptide after it’s fully folded.
Native Conformation
conformation that represents the most stable statefor a particular polypeptide
Denaturation
loss of conformation, usually resulting in loss of fxn. caused by changes in cellular enviroment (eg. pH)
Renaturation
Return of denatured polypeptide to its native conformation, usually w/ restoration function
Which of the 4 structures doe conformation alter
tertiary
Factors that could influence protein conformation
Spontaneous self assembly via polarity
Polar R groups will interact with polar soln where as nonpolar will turn inward
Enviroment
How does the enviroment influence the folding of proteins
Native conformation –> Denaturation conditions –> renaturing conditions –> renatured molecule may or may not be the same as previous native conformation
Influences of Enviromental Protein conformation
pH
Temperature
Solvent
Solute concentrations (Especially ions)
Redox status
Mechanical stress
Space
Which structures would be altered in enviromental protein conformation? not altered ?
2 3 4 would be alrered
primary would not because hydrolysis has not occured
Molecular chaperones
protein molecules that assist in the folding of other proteins that cannot fold sponaneously
How does HSP 60 behave
a partially misfolded protein enters one end of the complex
ATP hydrolysis leads to a shape change of the subunit
Creates a hydrophilic enviroment for correct folding of the protein
Correctly folded protein is released
* Different from cytoplasm - Unique enviroment that overrides polarity
How does HSP 70 behave
bound to ATP can associate w/ polypeptides that are still being processed; prevents folding. Chaperone for post- traditionally imported proteins
Post translational import refers to…
proteins that are imported into the organelle after translation
Post translational import is used for what organelles
Mitochondria
Chloroplast
Peroxisome
Nucleus
Describe the events involved in post-translational import of proteins
- HSP 70 binds to polypeptide
- Transit sequence binds to TOM receptor
- HSP70 molecules detach as polypeptide passes through membranes
- Transit sequence cleaved
- Mitochondrial HSP70 molecules bind and release polypeptide as it enters matric
- Polypeptide folds aided by HSP60.
Transit and Signal is used interchangably
Describe the various modifications discussed in class that can occur to a protein during post-translational modification
(6)
Chaperone assisted folding
Acetylation / Deacetylation
Protein phosphorylation
Glycosylation
Lipidation
Proteolytic cleavage
Acetylation/ Deacetylation
histones regulating gene expression
Protein phosphorylation
adds a phosphate group via ATP
Glycosylation
adding small carbohydrates –> glycoproteins
lipidation
adding lipid groups
Proteolytic cleavage
cleaving or breaking down the protein
EX: insulin taking out the C chain
Describe Cystic FIbrosis
A defect in transport functions include:
A genetic disease
Affects secretory cells ex: glands, mucus producing cells
Symptoms include: thick, dehydrated mucus, incessant coughing, lung damage
Lungs become colonized by microorganisms - usually lead to death - pneumonia
No cure; avg life span ~ 35
Structure of cystic fibrosis
spans of 6 transmembrane proteins
Explain why protein structure is so important for protein function
Protein structure is important because if altered the function of the protein changes which typically results in terrible diseases
Sickle Cell Anemia
Sickle Cell anemia → happens due to clumped hemoglobin which typically are free flowing
Sickle cell anemia prevents rbc from flowing freely
This occurs due to an altered primary structure; Glutamine to Valine (Acidic → nonpolar aa)
Describe the basic details of the RBC structure and function.
RBC: Hemoglobin: function to carry O2 around the body via blood flow
Typically free flowing throughout the blood
Define a ‘prion’.
Prion: infectious disease - causing proteins
- result from misfolded PrP proteins
- No change in corresponding PrP disease
Describe prion diseases
Prion diseases cause neurological breakdown which is rare, has no cure and fatal
EX: Mad cow disease or BSE / Creutzfeldt - Jakob disease (humans)
Explanation:
Normal Prion Protein, PrPC
2 structure is rich in alpha helices and Soluble
Disruption results in 2 structure with misfolded pathogenic protein, PrPSC
PrPSC is rich in beta sheets → which drastically changes the 3d structure
PrPSC is highly insoluble and protease resistant
Promotes conversion of PrPC to PrPSC
Aggregates disrupt cellular fxn
Can prion diseases be seen based off primary structure
Primary Structure of PrPC and PrPSC are identical so issues will begin to be shown in secondary structure due to beta sheets occuring instead of alpha
In terms of disease transmission, explain why prion diseases are unlike any other type of disease that is bacterial- or viral-based.
Prions are caused by an infection of proteins
Different Variants of transmission
Familial (increased risk in certain families)
Spontaneous
Health facilities due to sanitary issues
BSE acquired ( eating tainted meat products)
