CMB Week 1 Flashcards
what is the function of the plasma membrane of cells?
- compartment separation - receptor sites and signal transduction -movement in and out of the cell through channels and carriers on the plasma membrane -cell to cell adhesion
The nucleus is composed of …
nuclear membrane, chromatin, nucleolus
what is the nuclear envelope?
double membrane of nucleus
What is the nucleolus?
site of rRNA transcription and ribosome subunit assembly
What is the purpose of the ribosome?
site of protein synthesis
what is glycosylation?
addition of glycans to proteins, lipids and other organic molecules
what is the function of the smooth ER?
lipid synthesis, glycogenolysis, detoxification, Calcium metabolism
What is the function of the rough endoplasmic reticulum?
contains enzymes for protein folding and glycosylation; membrane specialized for ribosome binding
What is glycogenolysis?
breakdown of glycogen to glucose-6-phosphate and smaller glycogen (n-1)
what is the function of the golgi apparatus?
- Glycosylation and deglycosylation of proteins and lipids - Assembly of proteoglycans - Phosphorylation and sulfation of proteoglycans and proteins - Transport of proteins and lipids from RER to lysosomes, secretory granules or plasma membrane
what is an endosome?
membrane bound compartment in eukaryotic cells, provides an environment for materials to be sorted before it reaches the degradative lysosome
what is the function of lysosomes?
cellular organelles that contain acid hydrolase enzymes that break down waste materials and cellular debris
What is the function of peroxisomes?
contains the enzyme catalase, which metabolizes hydrogen peroxide. Also contains enzymes for beta oxidation of long chain fatty acids
what is the primary function of the mitochondria?
production of ATP and cellular metabolism
What is the function of microtubules?
part of the cytoskeleton, functions - mechanical support, organization of the cytoplasm, transport, motility and chromosome segregation
What are microfilaments (actin filaments)?
thinnest filaments of the cytoskeleton, involved in cytokinesis, movement and changes in cell shape
What is the cytoskeleton?
a meshwork of protein filaments within the cytoplasm that is responsible for cell morphology and movement
What is the composition of microtubules?
Alpha and beta tubulins form a protofilament. 13 protofilaments align side by side in a circle to form a microtubule
what are intermediate filaments?
part of the cytoskeleton, involved in regulating cell shape
what is desmin?
intermediate filament found in muscle cells
What is vimentin?
intermediate filament found in mesenchymal cells
what is neurofilament protein?
intermediate filament found in neuronal cells
What is keratins?
intermediate filament found in epithelial cells
What is epithelium tissue?
lines or covers organ surfaces, regulates the transport of materials, forms glands
What are the four main types of tissue?
epithelium, connective, muscle and nerve
How are subtypes of epithelium tissue classified?
by the number of cell layers and the shape of the cells forming the epithelium
What are the functions of connective tissue?
forms skeletal structures (bone, cartilage, tendon and ligament) provides conduit for blood vessels and nerves provides attachment and support
What is the function of muscle tissue?
specializes in contraction
What are the three types of muscle tissue?
skeletal, cardiac, and smooth
What is the function of skeletal tissue?
attached to the skeleton for voluntary body movement
What is the function of smooth tissue?
responsible for autonomic visceral movement
What is the function of cardiac tissue?
muscle forming the walls of the heart chambers
What is the function of nerve tissue?
specialized for transmission of electrical signals which regulate brain function, muscle and gland activity
What are the two major cell types in nerve tissue?
neurons and glia
What is the function of neurons?
cells that generate and receive electrical signals
What is the function of glia cells?
provides metabolic and structural support to neurons
What is a globin fold motif?
protein motif with 8 alpha helices (A-H) in a specific 3D orientation
What is hemoglobin (Hb)?
a globular, tetrameric protein found primarily in red blood cells and functions to deliver O2 from lungs to peripheral tissues and eliminate CO2 and protons.
What is myoglobin?
globular protein found primarily in muscles that binds oxygen molecules delivered by Hb
What is heme?
an iron-chelated porphyrin prosthetic group found in hemoproteins
What is the principle type of heme found in oxygen binding proteins?
Heme B
What is the composition of heme B?
protoporphyrin IX (4-linked pyrrole groups) and a ferrous ion Fe2+
Which histidine molecule is replaced when O2 binds to the ferrous ion?
the distal Histidine
What is the composition of Hb?
two alpha type subunits and two beta type subunits
What are the alpha type subunits that can be found in Hb?
5’ - zeta - alpha2 - alpha1 - 3’
What are the beta type subunits that can be found in Hb?
5’ - epsilon - gamma G - gamma A - delta - beta - 3’
Which chromosome are the genes for alpha subunits of Hb localized on?
chromosome 16
Which chromosome are the genes for beta subunits of Hb localized on?
chromosome 11
What are the two types of Hb found in embryos?
Hb Gower-1 and Hb Portland
What is the chain composition of Hb Gower-1?
ζ2ε2
What is the chain composition of Hb Portland?
ζ2γ2
What is the chain composition of fetal Hb (HbF)?
α2γ2
What % of adult Hb is composed of HbF?
less than 1%
What is the composition of HbA1 (adult Hb)?
α2β2
What % of adult Hb is composed of HbA1?
98%
What is the composition of HbA2 (adult Hb)?
α2δ2
What % of adult Hb is composed of HbA2?
2%
Approximately how long after birth is HbF replaced with HbA?
12-18 weeks
What is the deoxygenated form of Hb and myoglobin called?
Tense state (T-state)
What is the oxygenated form of Hb and myoglobin called?
Relaxed (R-state)
What is the effect of 2,3-biphosphoglycerate (BPG) on Hb?
Increase quantities of BPG —> Increased affinity of Hb to BPG —> decreased affinity of Hb to O2 —>Hb releases O2 (right shift in curve)
What is the oxygen-binding curve for myoglobin?
Hyperbolic (simple dissociation)
What is the oxygen-binding curve for hemoglobin?
sigmoidal
What is the Bohr effect?
Decrease in pH (periphery -tissues) –> decreases Hb affinity for O2 —> Hb releases O2. Shifts the equilibrium to T-state (right shift in curve)
What is the mutation for sickle cell anemia?
HbS B6 (beta -6): glutamine to valine
what is the mutation for anemia (HbC)?
HbC (beta -6): glutamine to lysine
What is the mutation for mild anemia (HbE)?
HbE (beta 26): glutamine to lysine
What is the mutation for Hb M-Boston (methemoglobin)?
beta58 (histidine to tyrosine)
What is the mutation for Hb M-Saskatoon (methemoglobin)?
beta63 (histidine to tyrosine)
What is carbon monoxide poisoning?
Hb has very high affinity for CO —> CO binds Hb 200x stronger than O2, displacing the oxygen. Carboxyhemoglobin circulates in blood for an extended time without releasing the CO
What is the treatment for CO poisoning?
Using 100% oxygen to compete with the CO, reducing carboxyhemoglobin levels rapidly
What is collagen?
most abundant (fibrillar) protein in the human body, with 20 different types
Abnormal collagen synthesis or structure causes dysfunction of…
- cardiovascular organs - bone (fragile) - skin - joints (hyper mobility and arthritis) - eyes (dislocation go lens)
What is the amino acid composition of collagen type I?
33% glycine, 10-13% proline, 10% hydroxyproline (OH-Pro), and 1% hydroxylysine (OH-Lys)
What are the three enzymes that are required for post translational modification (hydroxylation) of Pro and Lys?
Lysyl hydroxylase Prolyl-4-hydroxylase Prolyl-3-hydroxylase
What is Prolyl-4-hydroxylase?
hydroxylates the proline in X-Pro-Gly to 4-OH-Pro
What is Prolyl-3-hydroxylase?
hydroxylates the proline in Hyp-Pro-Gly to 3-OH-Pro
What is a polyproline type II helix?
Secondary structure of collagen - each strand is a loose, left-handed helix, with three residues per turn
What is required in post translational modification of collagen?
Fe2+, oxygen, alpha-ketoglutarate, and ascorbic acid (Vit C)
pinocytosis
the non-specific ingestion of fluid and small molecules via small vesicles
phagocytosis
ingestions of large particles, cell debris, bacteria via pseudopodia
receptor mediated endocytosis
allows entry to specific molecules via receptors in the plasma membrane and clathrin coated pit/vesicles
methemoglobinemia
Mutations cannot bind O2, since the Fe2+ ion is oxidized to Fe3+
thallasemia
general term for an autosomal recessive disorder where one of the globin genes is not expressed properly, leading to anemia
What is the advantage of having glycine in collagen?
-small structure allows the formation of triplex - the 3 collagen chains are able to be packed tightly together
What helps stabilize the triplex of collagen (besides Gly)?
- Hydrogen bonds between the neighboring chains - Disulfide chain interactions
telopeptides
- N and C terminus segments in collagen triple helical region -site of cross linking
What are the steps in the biosynthesis of collagen inside the cell?
- Translation of alpha chains (two alpha-1 and one alpha-2 chains) on the ribosomes of the RER 2. Peptide chains sent to lumen of RER 3. Signal peptidase cleaves the signal peptides from end of preprocollagen –> procollagen 4. Hydroxylation of Pro and Lys 5. Glycosylation on specific hydroxylysines (helps stabilize the triple helix) 6. Intra and inter chain disulfide bond formation 7. Triple helical structure formed inside RER 8. Procollagen goes to the Golgi Apparatus, glycosylation is completed, and procollagen is secreted via exocytosis
preprocollagen
precursor peptide chains of collagen, with signal peptide that directs the chains to the ER
What are the steps in the biosynthesis of collagen outside of the cell?
- Registration peptides are cleaved from both end of the molecule by procollagen peptidase forming tropocollagen 2. multiple tropocollagen molecules self assemble into collagen fibrils, which form into collagen fibers 3. Maturation - intra and inter molecular cross-links of the tropocollagen
catalyzes the hydrolysis of collagen
collagenases - a matrix metalloproteinase (MMPs)
after hydrolysis of the collagen by collagenases, this enzyme finishes the degradation
gelatinases
What are the two major categories of collagen?
fibrillar and network-forming
Name the fibrillar type collagens
types I, II, III, V and XI
Name the network-forming collagen
type IV
Name the fibril-associated collagens
types IX and XII
What is scurvy?
nutritional condition cause by deficiency in vitamin C. very diverse symptoms
What is Ehler-Danlos Syndrome?
group of connective tissue disorders (10 types)
Describe type IV Ehler-Danlos Syndrome
- autosomal dominant mutation resulting in deficiency in type III collagen formation - symptoms: thin skin, easily ruptured arteries and internal viscera
Describe type VI Ehler-Danlos Syndrome
- autosomal recessive deficiency in lysyl hydroxylase - Symptoms: scoliosis, velvety skin, hypermobile joints, tendency towards ocular injuries
Describe type VII Ehler-Danlos Syndrome
- autosomal dominate mutation leads to an inability to remove the N terminal propeptide - Symptoms: hypermobile joint, prone to joint dislocations, soft skin
Describe type IX Ehler-Danlos Syndrome
- X-linked recessive deficiency in lysyl oxidase that results in decreased cross linking - could also be due to copper deficiency - Symptoms: hyper extensible skin, bladder diverticula, skeletal deformities
What is elastin?
- fibrillar protein that provides elasticity to tissue - fibrous and insoluble in H2O
Explain secondary structure in elastin
- lacks a secondary structure, has a coiled structure in which the amino acid residues are highly mobile
What is allysines?
modified lysine residues
enzyme that catalyze lysine to allysine
lysyle amino oxidase also lysyl oxidase
structure of elastin
3 allysines and an unmodified lysine from different regions of the polypeptide chain react to form the heterocyclic structure of desmosine and isodesmosine desmosines covalently cross-link the chains in elastin
what is needed for protein glycosylation?
-an activated sugar (UDP-glucose) - glycosyl transferase enzyme - acceptor protein
In protein glycosylation, how are sugars linked?
covalently through O-links: glycans attach to the hydroxyl oxygen (OH) on serine or threonine N-links: glycans are attached to the nitrogen on asparagine
In N-linked glycosylation, what is the composition of the sugar precursor being added?
14 sugar precursor contains 3 glucose, 9 mannose, and 2 N-acetylglucosamine molecules
dolichol
carrier molecule that is attached to the 14-sugar precursor in N-linked glycosylation, transfers the glycans to the asparagine
What are the two major saccharides from N-linked glycosylation
- high mannose oligos (two N-acetylglucosamines with many mannose residues) - complex oligos: contains any number of of types of saccharides
Inclusion (I)-cell disease
a lysosomal storage disease: defective phosphotransferase - enzyme that transfers phosphates to mannose residues on specific proteins, which serves as a marker for these proteins to be moved to the lysosome. Without the marker, the proteins are not transferred to the lysosome, without these proteins, the lysosome cannot degrade substances, leading to a buildup
gamma carboxyglutamic acid (Gla)
- glutamate side chain modified with addition of a second carboxyl group - found in clotting factors and other protein of the coagulation cascade - requires vitamin K
kinases
enzymes that phosphorylate proteins
phosphatases
enzymes that remove phosphates from proteins
in animal cells, which three amino acids are subject to phosphorylation
serine, threonine, and tyrosine
which amino acid has sulfate modification
tyrosine
proteasome
major mechanism for destruction of cellular proteins
Where is the proteasome located?
cytosol and nucleus
ubiquitin
before being recognized by the proteasome, proteins are tagged by ubiquitin, a small 76 amino acid protein
steps of ubiquitin process
1) ubiquitin-activating enzyme binds ubiquitin to the enzyme via a high energy (ATP) bond 2) this ubiquitin intermediate is transferred to the substrate protein by ubiquitin-conjugating enzymes 3) the ubiquitin is covalently attached to the amino group of an internal lysine of the protein, carried out by ubiquitin-protein ligases 4) ubiquinated proteins are recognized by the proteasome for degradation
disease states associated with the ubiquitin modification system
- defective ubiquitination in cancer result from defective growth promoting proteins - defection ubiquitination is associated with neurodegenerative diseases such as Alzheimer’s, Parkinson’s.
What is SUMO-ylation?
post-translational modification involved in - transcriptional modification - apoptosis - response to stress - progression through cell cycle
free energy of activation
available energy used to form the reaction intermediate
name the 6 functional classes of enzymes
- oxidoreductases 2. transferases 3. hydrolases 4. lyases 5. isomerases 6. ligases
oxidoreductases
act on many chemical groupings to add or remove hydrogen atoms
transferases
transfer functional groups between donor and acceptor molecules
lyases
Add water, ammonia or carbon dioxide across double bonds, or remove these elements to produce double bonds.
hydrolases
Add water across a bond, hydrolyzing it
isomerases
Carry out many kinds of isomerization (optical or geometric isomers): e.g. L to D isomerizations
ligases
Catalyze reactions in which two chemical groups are joined (or ligated) with the use of energy from ATP.
Klenow fragment
5’—>3’ exonuclease activity is located on a portion of the enzyme (30kDa) that can be separated from the larger portion of the enzyme (70kDa). The 70kDa fragment contains the 5’—>3’ polymerization and the 3’–>5’ exonuclease activity - this is the Klenow fragment
(Prokaryotes) Single-stranded DNA-binding proteins (SSB)
during replication, binds to the DNA to keep the two strands from annealing (keeps it open)
(Eukaryotes) Replication protein A (RPA)
during replication, binds to the DNA to keep the two strands from annealing (keeps it open)
Primosome
complex consisting of primases, ligases, helicases, and other proteins that bind to the Ori and are necessary to synthesize the primer
Replisome complex (OriC)
contains the primosome and other molecules like SSB, pol III and I that are necessary for DNA replication
replicons
In eukaryotic DNA replication, these are the segments between Oris
Modification of the primary transcript (precursor to mature RNA) includes:
- removal of both external and internal nucleotides by ribonucleases 2. base modification 3. addition of nucleotides
tRNA post-transcriptional modification
- 5’ end of tRNA is removed by ribonuclease P (a ribozyme) - 3’ end is removed, the terminal CCA (cytosine-cytosine-adenine) is synthesized - nucleotide bases are modified
mRNA post-transcriptional modification
- addition of a 3’ terminal poly A tail - addition of methylated internal nucleotides and the methylated inverted cap at the 5’ terminus -splicing
initial velocity (Vo)
measured at the very beginning of an enzyme reaction when very little product has been made
steady state
point at which the enzyme-substrate (ES) intermediate remains constant
Assumptions for the Michaelis-Menten rate equations
- [S] >> [E] so only small amount of S bound to E. 2. [ES] does not change, stays at steady state. 3. Initial velocities (Vo) are used so no P is converted to S.
Michaelis-Menten equation
v = Vmax * [S]/K m + [S]
What is Km?
- measure of [S] required for effective catalysis to occur - [S] at 1/2 Vmax - estimate of the equilibrium constant for a given enzyme - small Km: tight binding of S to E - large Km: weak binding
What is Vmax?
- theoretical maximal rate of a reaction - at Vmax, all active sites of the enzyme are saturated with substrate
What is kcat?
- turnover number: max number of substrate molecules converted to product per enzyme per unit of time - kcat = Vmax/E * t
Competitive enzyme inhibition
- inhibitor binds specifically at the catalytic site, competes with substrate for binding - reversible by substrate - Km increased in presence of competitive inhibitor - more substrate is needed for effective catalysis - Vmax - unchanged
Noncompetitive inhibitor
- Binds E or ES complex other than at the catalytic site - substrate can still bind, but with the inhibitor altering the enzyme configuration, the ESI (enzyme-substrate inhibitor) complex becomes inactive - Km - no change, no competition for the substrate binding site - Vmax decreased proportionately to inhibitor concentration (more inhibitors = slower rate)
ACE inhibitors (angiotensin-converting enzyme)
- group of drugs used for treatment of hypertension and congestive heart failure - inhibits ACE to lower blood pressure
Methotrexate
- competitively inhibits dihydrofolate reductase (DHFR) - DHFR synthesizes tetrahydrofolate (folic acid), needed for synthesis of DNA, RNA, thymidylates, and proteins
Aspirin (as an inhibitor)
causes irreversible inactivation of cyclooxygenase (enzyme required for prostaglandin and thromboxane synthesis)
Allosteric inhibition
allosteric inhibitor binds to the allosteric site —> causes the active site to become distorted —> substrate cannot bind
Allosteric activation
there’s a distorted active site on enzyme (S cannot bind) allosteric activator binds to the allosteric site —> active site changes shape to fit substrate
heterotropic effectors
Activating and inhibiting effectors that bind at the allosteric sites
homotropic effectors
Substrate induces distant allosteric effect when it binds to the catalytic site
Feedback inhibition
Product of a metabolic pathway inhibits the activity of an enzyme involved in its synthesis
The vast majority of the cells in the body at any given time are in the …
Go phase (resting phase)
Cell cycle
G1 –> S —> G2 —> Mitosis –> cytokinesis —> Go
G1 phase
cellular contents (excluding chromosomes) are duplicated
S phase
Chromosomes duplicated
G2
Cell ‘double checks’ duplicated chromosomes for error, making any needed repairs
Retinoblastoma protein (pRb)
- tumor suppressor that when hypophosphorylated is ACTIVE: inhibits cell cycle progression - when phosphorylated, pRb is INACTIVE: allowing cell cycle progression
When it is time for a cell to enter S phase, pRb is..
phosphorylated by CDKs (cyclin dependent kinases) and cyclins, which inactivates pRb, allowing cell cycle progression
pRb becomes more and more…
phosphorylated as it goes further in the cell cycle and then becomes hypophosphorylated after mitosis (to inhibit a new cycle)
pRb encoded by…
Rb1 gene
If both alleles of the Rb1 gene are mutated early in life…
the pRb becomes inactivated (allowing cell progression) and results in retinoblastoma - cancer of the eye
cyclins
regulatory molecules controls a cell’s progress through the cell cycle
CDKs are activated when …
bound to a cyclin
The cyclin-CDK pair …
allows phosphorylation to either activate or inactive target proteins for coordinated entry into the next phase of the cell cycle
Cyclins are synthesized…
at specific stages of the cell cycle in response to various molecular signals
neoplasms
abnormal growth of tissue, disturbances in cell cycle control mechanisms are often seen in human neoplasms
Overexpression of cyclin C is associated with what?
Overexpression of cyclin C has been found in both neurons and astrocytes in Alzheimer’s
….. often expressed abnormally in lung premalignancy and malignancy, negative marker for prognosis
Cyclin E
Overexpression of cyclin A
accelerates pRb phosphorylation, promoting cell cycle progression
p53
- tumor suppressor protein that has a role at G1/S checkpoint. - p53 can activate DNA repair, can induce growth arrest in the presence of damaged DNA, initiates apoptosis if damaged DNA cannot be repaired
Morphological changes during apoptosis:
- DNA and organelles fragmented and disintegrated - apoptotic body formation that is quickly engulfed by nearby macrophages - no spilling out of content of cell - no inflammation of surrounding area
cell necrosis
traumatic cell death from acute injury with spillage of cell contents into the surrounding area
What are the intracellular signals for apoptosis?
Intracellular signals - can be induced to undergo cell death b/c of lack of nutrients, low oxygen, heat, hypercalcemia
The apoptotic pathway can be controlled by:
direct transduction from pro-apoptotic cytokines: - Tumor necrosis factor (TNF) - primarily produced by macrophages - Fas Ligand- transmembrane protein that binds to its receptor to induce apoptosis
Stem cells have the ability of:
- self-renewal through mitosis (indefinitely) - Differentiating into specialized cell types
Totipotent stem cells
Have the ability to differentiate into all cell types and give rise to an entire organism (e.g. zygote)
Progenitor cells
cannot divide and reproduce themselves indefinitely
Multipotent (progenitor) cells …
can give rise to multiple but limited cell lineages e.g. hematopoietic cells can give rise to all blood cell lines but nor cells of the CNS.
Unipotent (progenitor) cells
can give rise to only one cell or tissue type
Embryonic stem cells are derived from
Derived from the inner cell mass of the blastocyst prior to implantation
Induced pluripotent stem cells
Somatic (body) cells which are reprogrammed to be pluripotent
Erythrocyte (red blood cell) function
- To deliver oxygen to all cells/tissues of the body through blood circulation - Gas exchange through diffusion through the membrane as cells squeeze through capillaries
When RBCs undergo shear stress in constricted vessels, they …
release ATP, leading to vessel wall relaxation and dilation thus promoting blood flow
RBC structure
Plasma membrane of RBC maintains a flexible biconcave disc shape to the cell, which provides greater surface area through gas exchange can occur and increases laminar flow
Rouleaux formation
- occurs when level of serum proteins in elevated - RBCS stack or aggregate - nonspecific indicator of the presence of disease
Mature human RBCs lacks…
a cell nucleus (thus cannot be targeted by viruses) and organelles
RBC Development Pathway
Hemocytoblast (stem cell) —> proerythroblast (committed cell) —> early erythroblast —> late erythroblast —> normoblast —> reticulocyte —> erythrocyte
Hemocytoblast
- stem cell that gives rise to all blood cells - found in the red bone marrow
Normoblasts
Stage at which immature RBC ejects their organelles
Reticulocyte
- no organelles - cell leaves the bone marrow for blood circulation, then most will mature into RBCs - about 1% of red cells in circulation are reticulocytes
Maturation from hemocytoblast to mature RBC takes…
~7 days
How long do RBC’s circulate in the bloodstream?
~120 days
Factors that lead to hypoxia, thereby stimulating RBC production
- hemorrhage - damage to bone marrow - exposure to high altitude - exercise - hemolytic disease (abnormal breakdown of RBCs) - low Hb levels
Where are RBS degraded?
Broken down by macrophages within the liver and spleen,(small amount gets broken down in bone marrow).
What happens to the plasma membrane of RBCs as they age?
- Phosphatidylserine is a phospholipid normally found only in the inner layer of the RBC membrane - As the membrane ages, it displays phosphatidylserine on its surface, allowing for recognition by macrophages
What is the rate of RBC destruction?
~2.5 million/second
What happens when RBCs are hemolyze in the circulation?
- the RBC fragments are engulfed by macrophages and degraded via lysosomal enzymes and: - Iron is released from the heme molecules and stored or released to the blood - Globin is further broken down to AAs - Heme degrades to bilirubin
Hormonal control of RBC concentration
- Erythropoietin is produced and released in response to low blood O2. - Erythropoietin increases RBC production and protects the cell line from apoptosis
Heinz bodies
small round inclusions found within RBCs that result from: - damaged Hb - an inherited mutation - chronic liver disease The damaged cells will be eliminated by macrophages, often leading to Heinz body anemia
Mendel’s 3 Functional Principles
- Traits are passed on by genes 2. Genes have more than one form called alleles 3. There are at least 2 alleles for each trait
Mendel’s 2 laws of inheritance
- Law of Segregation 2. Law of Independent Assortment
Law of Segregation
Every individual possesses a pair of alleles for any particular trait and each parent passes only one randomly selected copy of its alleles to offspring
Law of Independent Assortment
Separate genes code for separate traits, and are passed independently of one another (not entirely correct in modern genetics)
genotype
genetic makeup of a person
phenotype
physical appearance
Autosomal dominant disorders
Manifest in the heterozygous state (one allele is mutated)
Incomplete penetrance
individual inherits mutant gene, but appears normal
variable expressivity
A trait is seen in all patients carrying a mutant gene, but is expressed differently in the phenotype
Autosomal Recessive disorders
- both alleles at a gene locus is mutated - unaffected parents are called carriers and each of their offspring has 25% of having the autosomal recessive trait - tend to be more severe and appears in childhood
X-linked disorders
- occur from mutations on the X chromosome - affected male does not transmit the disease to his son but all of his daughters are carriers
X-inactivation
One of the X chromosomes is randomly inactivated in the cells of women
How many genes on mitochondrial DNA?
- 37 genes, all of which are essential for normal mitochondrial function - 13 of these genes provide instructions for making enzymes involved in oxidative phosphorylation
Mitochondrial DNA is usually inherited…
from the maternal lineage
Mutations in mtDNA mostly affect which system/organs?
The central nervous system; organs that are dependent on oxidation phosphorylation
Heteroplasmy
Presence of more than one mtDNA variant (normal and mutated) within a cell, tissue or individual.
DNA sequencing
Process of determining the precise order of nucleotides within a DNA molecule
Epigenetics
The study of changes in gene expression or cellular phenotype caused by mechanisms other than changes in the underlying DNA
Hardy-Weinberg equilibrium equation
p (squared) + 2pq + q (squared) = 1; p (Squared) = frequency of homozygosity for allele p q (Squared) = frequency of homozygosity for allele q 2pq = frequency of heterozygosity
Imprinting
Important functional differences exist b/w the paternal allele and the maternal allele - these differences result from an epigenetic process called imprinting
Imprinting occurs in the …
ovum or the sperm, before fertilization
Maternal imprinting refers to …
transcriptional silencing of the maternal allele (Paternal imprint - silence of paternal allele)
Prader-Willi syndrome is characterized by
mental retardation, short stature, hypotonia, profound hyperphagia, obesity, small hands and feet, and hypogonadism
Angelman syndrome is characterized by
mental retardation, ataxic gait, seizures, and inappropriate laughter
In Prader-Willi syndrome, which chromosome is affected?
an interstitial deletion in paternal chromosome 15
Heme containing proteins
- O2 binding proteins - Hb and Myoglobin 2. microsomal and mitochondrial cytochromes 3. enzymes
In Angelman syndrome, which chromosome is affected?
an interstitial deletion in maternal chromosome 15
Enzyme used in the initial enzymatic step in heme biosynthesis
ALA-synthase (E1)
Enzymes used in the last enzymatic steps in heme biosynthesis
E7 - protoporphyrin III oxidase E8 - ferrochelatase
ALA-synthase (E1)
catalyzes the synthesis of d-Amino-levulinic acid (1st precursor in heme synthesis)
The ring system of heme is derived from ….
8 residues each of Succinyl CoA and glycine
In heme biosynthesis, the Suc-CoA is produced by the …
Krebs cycle
In heme biosynthesis, the glycine comes from the …
cytosol
In heme biosynthesis, the Fe2+ ion is transported from the …
cytosol
Protoporphyrin-III oxidase (E7) ….
Converts protoporphyrinogen to protoporphyrin
Ferrochelatase (E8) …
Inserts the iron (Fe2+) ion into the ring
The initial step (E1) and last steps (E7 and E8) of the biosynthesis of heme occur in the
mitochondria
The intermediate steps in heme take place in the ….
cytosol
Heme A is found in
cytochrome A
Heme C is found in
cytochrome C
ALA synthase is synthesized in the …. and acts in the …..
cytosol, mitochondria
ALA-synthase uses ….. as a coenzyme for ….
pyridoxal-phospate (Vit B6); decarboxylation
Two isoforms of ALA synthase
- ALAS-E or ALAS2 or erythroid - expressed in RBC precursor cells 2. ALAS-N or ALAS 1 - nonspecific isoform
Heme acts as a ….inhibitor, repressing …..
feedback; transcription of the gene for d-Aminolevulinate synthase
Inherited ALAS-E deficiency is responsible for ….
sideroblastic anemia
Porphyria results in.. .
the excretion and accumulation in tissues of heme biosynthetic intermediates
Nitrogen oxide is bound to …. of Hb, and is ….
bound to the R form of Hb and is released in the periphery when Hb releases O2
Heme oxygenase is found in …
Reticuloendothelial cells
Neurologic porphyria
- example of Acute intermittent porphyria - due to porphobilinogen deaminase deficiency (E3) - Permanent nerve damage and death may result if not treated promptly
In the first step of heme degradation, heme is converted to …. by ….
biliverdin; heme oxygenase
What are the extracellular signals for apoptosis?
Extracellular signals - hormones, toxins, cytokines, growth factor withdrawal
Pluripotent stem cells
Can differentiate into any of the fetal or adult cell type, but cannot give rise to an embryo
S nitrosothiols (function)
When Hb is deoxygenated, RBCs release S nitrosothiols, which dilates vessels thus directing more blood to areas of oxygen depletion
Erythropoietin (function)
A hormone that acts on hemocytoblasts to become proerythroblast, thereby becoming committed to the RBC line
What role does testosterone play on RBC production?
Increases production and effectiveness of erythropoietin
What organ produces erythropoietin?
kidneys
Assumptions of the Hardy-Weinberg Law
For a single autosomal locus in a large population, genotype frequencies can be calculated from allele frequencies after one generation if: 1) mating takes place at random 2) allele frequencies are the same in men and women 3) mutation, selection, and migration are negligible
Hematocrit
Volume percentage of RBCs in blood (normal in adults 40-45%)
Mean Corpuscular Volume (MCV)
- average volume of one RBC - Total blood volume * Hematocrit/# of RBCs
Mean Corpuscular Hemoglobin (MCH)
In a blood sample, the average mass of Hb per red blood cell
Allosteric activators …. the apparent Km
decrease
Allosteric inhibitors … the apparent Km
increase
In heme degradation, biliverdin is reduced by …. to …. This reaction requires …
In heme degradation, biliverdin is reduced by biliverdin reductase to bilirubin IX. This reaction requires NADPH.
Where is bilirubin catabolized?
Liver
Bilirubin is ….. in aqueous solutions at physiological pH, needs a …. in blood
poorly soluble; transporter
What is the molecule that transports bilirubin in the blood?
albumin
Secretion of bilirubin diglucuronide
Secreted into bile —> intestine —> feces
Some bilirubin diglucuronide can be …. from the intestine and transported to the …. for excretion
reabsorbed; kidney
Unconjugated bilirubin is bound …. to albumin
noncovalently
Hyperbilirubinemia
abnormalities may occur in any one or more of the biosynthesis steps, leading to hyperbilirubinemia, in which there is either an elevation in unconjugated bilirubin or both unconjugated and conjugated bilirubin
Three genetic disorders associated with the overproduction of unconjugated bilirubin (unconjugated Hyperbilirubinemia)
- Gilbert’s syndrome (neonatal jaundice) - Crigler-Najjar syndrome type I - Crigler-Najjar syndrome type II
- Gilbert’s syndrome (neonatal jaundice) - Crigler-Najjar syndrome type I - Crigler-Najjar syndrome type II
Three genetic disorders associated with the overproduction of unconjugated bilirubin (unconjugated Hyperbilirubinemia)
These disorders are caused by a mutation in what gene? Gilbert’s syndrome (neonatal jaundice); Crigler-Najjar syndrome type I and type II
glucuronyl transferase gene
Crigler-Najjar syndrome type I is associated with …
severe jaundice and neurological impairment due to kernicterus (bilirubin encephalopathy)
Crigler-Najjar syndrome type II is less …. and is associated with
severe; lower serum bilirubin concentration and affected patients survive into adulthood without neurological impairment
In neonatal or physiological jaundice, the glucuronyl transferase enzyme is …
temporarily decreased in newborns
Neonatal or physiological jaundice resolves itself as …; and the infant is treated with …
the liver matures after a few days following birth; exposure to UV light
Anemia is a condition in which the body does not have enough …
healthy RBCs
Two main reasons for anemia
- underproduction of mature RBCs 2. Loss of RBCs
Idiopathic aplastic anemia is a condition in which …
the bone marrow fails to properly make blood cells. May result from injury to the blood stem cells
Aase syndrome
anemia caused by poor development of the bone marrow
Fanconi’s anemia
due to an abnormal gene that damages cells, which keeps them from repairing damaged DNA
Megaloblastic anemia
anemia with larger then normal RBCs due to deficiency in folic acid or vit B12
Pernicious anemia
decrease in RBCs that occurs when the body cannot properly absorb B12 from the gastrointestinal tract
Hypochromic anemia
underproduction of Hb, less Hb is deposited in the cells
Iron deficiency anemia
- most common form of anemia - causes of Fe deficiency: blood loss, poor absorption of Fe by the body, and too little Fe in the diet
Hemolytic anemia
Due to premature destruction of RBCs
Intrinsic (genetic) reasons for hemolytic anemia
- abnormalities in the proteins that build normal RBCs - hemoglobinopathies
Extrinsic reasons for hemolytic anemia
- abnormal immune system responses - blood clots in small blood vessels - certain infections - side effects from medications
Congenital spherocytic anemia
disorder of the surface layer (membrane) of RBCs - leads to RBCs that are shaped like spheres and premature breakdown of RBCs
…. can modify bases and cause the introduction of base changes to subsequent DNA replication. These inducers of mutations are called ….
Chemical and irradiation-inducted reactions; mutagens
Phenotypically silent mutations
If a mutation occurs in the noncoding regions of the DNA sequence. Will not alter proteins
Silent mutation
mutations that occur within coding sequence, but does not cause a change in the protein
Phenotypically expressed mutations
- If the mutation occurs in coding regions and causes a change in protein, its presence will be known. - Alters the structure and function of the protein - phenotypically expressed mutation may or may not result in pathology
Conservative change (amino acid)
- when an amino acid is changed to another AA of similar size and chemical nature - generally does not change the structure of the protein
Non-conservative change (amino acid)
- when an AA is changed to another AA of different size and/or chemical nature - usually results in the change of the structure of the protein
Invariant Amino Acids
- AAs that are necessary for the function of the protein - if change occurs in the functionally active site of the molecule, even conservative changes can result in the loss of function
Missense mutations
Point mutations where a base change causes coding for a different AA
Nonsense mutations
Result when a codon that codes for an AA is mutated to form a termination codon
Read-through mutation
Mutation of termination codon to an AA codon, resulting in a larger than normal protein
Frameshift mutation
Caused by the insertion or deletion of a single nucleotide within the coding region
Transition mutation
when one purine-pyrimidine pair is substituted for another purine-pyrimidine pair
Transversion mutation
a purine-pyrimidine pair is substituted for a pyrimidine-purine pair
Triplet expansion mutation
- generally a series of G and C that are repeated hundreds or thousands of times
While both the alpha and beta genes may have mutations, the most frequently seen hemoglobinopathies result from mutations in the ….
beta gene
Mutations of Hb globin genes can cause …
- unstable Hb structure 2. increased or decreased O2 affinity 3. increase in the rate of oxidation of the heme Fe2+ ion to the ferric Fe3+ state 4. an imbalance in the synthesis of globin chains 5. changes in the properties of the globin chain
Beta-thalassemia
synthesis of the beta globin gene is decreased or absent
How is HbF affected by beta-thalassemias?
HbF is synthesized normally since the alpha chain (and gamma subunit) synthesis is normal
In beta-thalassemia, the alpha chains form …., and these …. resulting in cell death, thus RBC cannot …
In β-thalassemia, the alpha chains form tetramers, and these precipitate resulting in cell death, thus RBC cannot mature
Hb Bart’s
- gamma tetramer - found in individuals with α-thalassemia and β-thalassemia
Beta Thalassemia minor
- Individuals make some adult hemoglobin - only one of the beta globin alleles is mutated (heterozygous) - microcytic anemia
Genotype for beta thalassemia minor
β/β-
Beta thalassemia major (Cooley’s disease)
- homozygous - both alleles of beta chain are mutated - severe anemia (hypochromic anemia) - need blood transfusions - short life span (15-25 yrs)
Genotype for beta thalassemia major
β-/β-
α-thalassemia
Synthesis of the α-globin chain is defective
How many copies of the α-globin gene on each chromosome 16?
Two copies (4 alleles)
When one of the four α-globin genes is defective, the individual is a …., with …
When one of the four α-globin genes is defective, the individual is a silent carrier, with no symptoms
Genotype for α-thalassemia (silent carrier)
α1/α1 α2/α2-
When two of the four α-globin genes are defective, the individual has …., with …
When two of the four α-globin genes are defective, the individual has α-thalassemia trait, with mild anemia
Genotype for α-thalassemia trait
α1-/α1- α2/α2 OR α1/α1- α2/α2-
When three of the four α-globin genes are defective, the individual has …., with …
When three of the four α-globin genes are defective, the individual has hemoglobin H disease, with mild to severe hemolytic anemia
Genotype for Hemoglobin H disease
α1-/α1- α2-/α2
If all four of the α-globin genes are defective, … results
hydrops fetalis (fetal death)
Hb Bart’s has an extremely … for oxygen, resulting in almost …. to the tissues
Hb Bart’s has an extremely high affinity for oxygen, resulting in almost no oxygen delivery to the tissues
In Hemoglobin H disease, … tetramers …
beta tetramers precipitate
Aneuploidy
the presence of an abnormal number of chromosomes in a cell
Trisomy
the presence of three sets of a chromosome
Down’s Syndrome
- trisomy 21 - genetic disorder caused by the presence of all or part of a third copy of chromosome 21. - Associated with physical growth delays, characteristic facial features, and mild to moderate intellectual disability
Edward’s syndrome
- trisomy 18 - has a very low rate of survival - heart abnormalities, kidney malformations, and other internal organ disorders
Monosomy
- cells are missing a chromosome
Trisomy 13
- abnormalities in nervous system, musculoskeletal, and urogenital
Trisomy 22
- frequent cause of spontaneous abortion during the first trimester of pregnancy - Progression to the second trimester and livebirth are rare
Klinefelter Syndrome
- presence of more then two X chromosomes in males (XXY, XXXY) - primary feature is sterility – more severe if three or more X chromosomes are present
Turner Syndrome
- condition in which females are partly or completely missing an X chromosome (XO)
Mosaic or Mosaicism
denotes the presence of two or more populations of cells with different genotypes in one individual who has developed from a single fertilized egg
Microdeletion
tiny deletion that cannot be seen in a chromosome test (karyotype)
Barr body
inactive X chromosome
In females with extra copies of the X chromosome, how many of the X chromosomes is active?
Only one X chromosome is active - all extra copies are inactivated
Interstitial duplication
duplications within a chromosome
Interstitial duplication results in … than extra chromosome duplication
less impairment
When duplicated chromosomes are maternal, it is …
more likely to result in pathologies.
Chromosome Translocations
a chromosome abnormality caused by rearrangement of parts between nonhomologous chromosomes
Balanced Translocation
even exchange of material with no extra or missing genetic information
Unbalanced Translocation
the exchange of chromosome material is unequal resulting in extra or missing genes
Karyotype
the number and appearance of chromosomes in the nucleus of a eukaryotic cell
What type of abnormalities can be seen with karyotype?
Monosomy, trisomy, big deletions, duplications and rearrangements
Genomic array study
- multiple probes are used - detects small deletions or duplications anywhere in chromosomes
Subtelomeric FISH
Used to detect small deletions and translocations involving the tips of chromosomes
Florescence in-situ hybridization (FISH) can detect …
microdeletions and microduplications
Pathogenic CNVs are mostly
- bigger - more deletions than duplications - contain genes expressed in CNS
Copy Number Variant (CNV)
- structural variations, alterations of the DNA - present in most individuals - due to genetic recombination - most CNVs are stable and heritable
Florescence in-situ hybridization (FISH)
Use of florescent probes to detect and localize the presence or absence of specific DNA sequences on chromosomes
Benign CNVs are mostly
- smaller - present in healthy relative - more duplications than deletions
Exome Sequencing
a technique for sequencing all the protein-coding genes in a genome
Co-dominant Inheritance
- two different versions of the allele can be expressed - each version makes a slightly different protein - Both alleles influence the genetic trait or determine the characteristics of the genetic condition
Rett’s Syndrome
- X-linked lethal because males die before birth - neurodevelopmental disease - Only females get disease
Heme oxygenase catalyzes the cleavage of the …., opening the ring.
Heme oxygenase catalyzes the cleavage of the α-methene bridge on the porphyrin ring, opening the ring.
Heme oxygenase requires … to cleave the porphyrin ring.
Heme oxygenase requires O2 and NADPH to cleave the porphyrin ring.
The α-methene carbon from the porphyrin ring is converted to …, which is released via the ….
carbon monoxide (only endogenous source of CO), which is released via the respiratory tract.
The iron ion from the breakdown of heme is released in …., bound by…
ferric form, ferritin
UDP glucuronyl transferase transfers …; forming …
UDP glucuronyl transferase transfers UDP glucuronate onto bilirubin IX; forming diglucuronide
In normal bile the …. is the major form of excreted bilirubin, with only small amounts of the …
In normal bile the diglucuronide is the major form of excreted bilirubin, with only small amounts of the monoglucuronide.
Conjugated bilirubin
Bilirubin with its glucuronate donor: diglucuronide and monoglucuronide
Conjugated bilirubin is relatively …., so very little should circulate in the blood.
Conjugated bilirubin is relatively water-soluble, so very little should circulate in the blood.
Elevated conjugated bilirubin in circulation leads to high …
Elevated conjugated bilirubin in circulation leads to high urinary concentrations with the characteristic deep yellow-brown color
The deposition of conjugated and unconjugated bilirubin in skin and the sclera …
The deposition of conjugated and unconjugated bilirubin in skin and the sclera gives the yellow to yellow-green color seen in patients with jaundice.
Unconjugated bilirubin has a high affinity for …., which leads to the impairment of cell membrane function, especially in the …
Unconjugated bilirubin has a high affinity for membrane lipids, which leads to the impairment of cell membrane function, especially in the nervous system.
Hepatocellular disease occurs when bilirubin ….
Hepatocellular disease occurs when bilirubin binds covalently to serum albumin.
What is the rate limiting enzyme in heme biosynthesis?
δ-Aminolevulinic Acid Synthase (ALA)
What is the most abundant type of collagen in the body?
type I (90%)
The collagen protein is a … helix, usually composed of … and a third chain with …
The collagen protein is a triple helix, usually composed of two identical chains (α1) and a third chain with slightly different chemical composition (α2).
The most common pattern (motif) in the amino acid sequence of collagen are …, where X is an …
The most common pattern (motif) in the amino acid sequence of collagen are Gly-Pro-X and Gly-X-Hyp, where X is an amino acid other than Gly, Pro, or Hyp
Collagen is synthesized by what type of cell?
Fibroblast
Secondary structure: alpha helix
- right-hand coil or spiral (helix) conformation where each backbone N-H (amide) group is hydrogen bonded to the backbone carboxyl group of an amino acid 4 residues away - the side chains of the amino acid are pointed outward
Oxygen trap
the storage of blood in the presence of anticoagulant acid citrate dextrose will result in lower levels of BPG, and when this stored blood is transfused, this leads to poor release of O2
Genotype for HbS
α2βS2
Genotype for HbC
α2βC2
partial pressure of O2 (pO2) in lungs
100mm Hg
pO2 in tissues
26 mm Hg
Acidic Bohr effect; location
When Hb is deoxygenated, some ionic and hydrogen bonds are formed, and protons are taken up. Occurs in tissues
Alkanine Bohr effect; location
When Hb is oxygenated, some ionic and hydrogen bonds are broken, and protons are released. Occurs in lungs
The amino groups of lysine are enzymatically converted to aldehyde groups to form … This is done by the enzyme …
In collagen, the amino groups of lysine are enzymatically converted to aldehyde groups to form allysine. This is done by the enzyme lysyl oxidase.
The aldehyde groups on allysine reacts with … or with another … to form covalent bonds, called ….
The aldehyde groups on allysine reacts with Lys amino groups or with another aldehyde group of another allysine to form covalent bonds, called cross-links.
The enzyme lysyl oxidase is dependent on …
copper
chain composition of type I collagen
two α1 chains and one α 2 chain
Defect in intracellular copper transport results in
Menke’s kinky hair syndrome
Defect in intracellular copper distribution results in
cutis laxa (inelastic skin)
Elastase
enzyme that cleaves and degrade elastin
Elastase is inhibited by
alpha-1-antitrypsin
If elastase inhibitor is decreased in concentration, this causes elastase to …
If elastase inhibitor is decreased in concentration, this causes elastase to degrade elastin in the lungs.
Two main extracellular fibrillar proteins
collagen and elastin
Three categories of intracellular fibrillary proteins
microfilament, microtubules, and intermediate filament
Structure of myosin contains heads that … and a …
Structure of myosin contains heads that bind actin and a coiled-coil tail.
Microtubules are constructed as …, to enable cells to …
Microtubules are constructed as hollow tubes, to enable cells to change shape in response to external and internal signals.
Two drugs that interfere with microtubule formation
colchicine and taxol
Colchicine, … microtubules, resulting in the inhibition of the …
Colchicine, disassembles microtubules, resulting in the inhibition of the action of the white blood cells that mediate inflammation by the precipitation of uric acid in the joints.
Taxol is used as an … drug because it blocks … by binding to the ….
Taxol is used as an anticancer drug because it blocks cell division by binding to the beta-tubulin subunits in the microtubules.
Microtubules are formed from the polymerization of
a dimer of alpha and beta tubulin (globular proteins)
At one end of a protofilament, the alpha subunit is exposed and this is the …
At one end of a protofilament, the alpha subunit is exposed and this is the minus end.
At one end of a protofilament, the beta subunit is exposed and this is the …
At one end of a protofilament, the beta subunit is exposed and this is the plus end.
The minus end of the microtubule is called the
microtubule organizing center (MOC)
The plus end of the microtubule is the …, where …
The plus end of the microtubule is the fast-growing end, where tubular monomers are added.
The plus ends of the microtubules are oriented toward …
The plus ends of the microtubules are oriented toward the cell periphery (outside).
Microtubules support the movement of …
Microtubules support the movement of organelles and vesicles in the cell.
Kinesin is a
Kinesin is a motor protein that uses ATP to move along the microtubule.
Kinesin has two … that bind to the … and a … that binds the …
Kinesin has two heads that bind to the microtubule and a tail that binds the vesicles being transported.
Kinesin transports materials to the … of microtubules, i.e. from the … microtubule to the …
Kinesin transports materials to the plus end of microtubules, i.e. from the center of the microtubule to the periphery.
The movement of kinesin from the minus end of the microtubule to the plus end is called
anterograde vesicular traffic
Dynein is a
motor protein that uses ATP to move along the microtubule.
Dyneins move vesicles to the … of the microtubule, i.e. from the …
Dyneins move vesicles to the minus end of the microtubule, i.e. from the periphery to the interior of the cell.
The movement of dynein from the plus end of the microtubule to the minus end is called
retrograde vesicular traffic
List the different domains in enzymes:
- prodomain - catalytic domain - substrate-binding site -transmembrane domain
Pro domain of the enzyme
keeps the enzyme inactive
catalytic site of enzymes
contains the catalytic residues that catalyze the the reaction by acting on the substrate
endogenous inhibitors
enzyme inhibitors that are present in the body, and act as naturally occurring inhibitors
4 factors that regulate enzyme activity
1) substrate availability 2) enzyme availability 3) enzyme activation 4) enzyme inhibitors
In enzyme regulation, substrate availability is related to
- amount of substrate available - location of the substrate - conformation of the substrate
active site of the enzyme
the catalytic site and the substrate-binding site
Two types of cyclooxygenase (COX) enzymes
COX 1: constitutively expressed, including in the GI mucosa COX 2: induced by inflammation
COX inhibitors inhibit …. synthesis. COX inhibitors therefore reduce ….
COX inhibitors inhibit prostaglandin and thromboxane synthesis. COX inhibitors therefore reduce inflammation.
The valine amino acid on COX 2 allows for …, making COX 2 more …
The valine amino acid on COX 2 allows for preferential binding, making COX 2 more selective.
Because COX 2 inhibitors are more selective, they have fewer …. than …
Because COX 2 inhibitors are more selective, they have fewer GI side effects than general COX inhibitors.
Amyloid precursor protein (APP) is a transmembrane protein that is …
Amyloid precursor protein (APP) is a transmembrane protein that is critical to neuron growth, survival, and post-injury repair.
Normally, APP is cleaved by
α-secretase
In Alzheimer’s disease, APP is cleaved by …, generating two fragments, …
In Alzheimer’s disease, APP is cleaved by β-secretase (BACE1), generating two fragments, APPsβ and C99.
In Alzheimer’s disease, the C99 fragment from beta cleavage, is further cleaved by …, generating …
In Alzheimer’s disease, the C99 fragment from beta cleavage, is further cleaved by γ-secretase, generating amyloid-beta protein (Aβ).
In Alzheimer’s disease, amyloid plagues results from
accumulation and deposition of Aβ protein
trypsin is secreted by the … as a zymogen, called ….
trypsin is secreted by the pancreas as a zymogen, called trypsinogen
Trypsinogen is activated in the … by the highly specific enzyme called …
Trypsinogen is activated in the bowel by the highly specific enzyme called enterokinase.
Acute pancreatitis, as a consequence of …, there is excess of active .. in relation to its …
Acute pancreatitis, as a consequence of inflammation/ irritation in the pancreas, there is excess of active trypsin in relation to its inhibitor
What are the 4 major classes of proteases?
- serine proteases 2. aspartyl proteases 3. metalloproteases 4. cysteine proteases
Proteases catalyze the …
Proteases catalyze the hydrolysis of peptide bonds
Metalloproteases Use a metal … to coordinate and activate the …
Metalloproteases Use a metal (zinc) to coordinate and activate the attacking water molecule
The extracellular matrix (ECM) plays key roles in ….
The extracellular matrix (ECM) plays key roles in supporting cells within tissues and maintaining cellular functions, including cell proliferation and differentiation, apoptosis.
Matrix metalloproteinases
group of enzymes that are capable of degrading all kinds of extracellular matrix proteins
Three families of Zn-dependent metalloproteases
- Matrix metalloproteinases (MMPs) 2. ADAMs (A Disintegrin and Metalloproteinase) 3. ADAMTSs (ADAMs with a thrombospondin motif)
Proteases are involved in a wide variety of biological processes such as
- digestion of food - intracellular protein degradation - orchestrating complex biological processes - remodeling of extracellular matrix proteins
ADAMTS-2 cleaves
the propeptides of type I and II collagen prior to fibril assembly.
Ehlers Danlos Syndrome type VIIC is caused by a mutation in …, this leads to…, causing …
Ehlers Danlos Syndrome type VIIC is caused by a mutation in ADAMTS-2, this leads to disorganized collagen fibers, causing skin and other connective tissue problems.
When developing a catalytic site inhibitor as a drug, it is best to develop a … inhibitor, i.e. the drug will inhibit …. and not …. This reduces the potential …
When developing a catalytic site inhibitor as a drug, it is best to develop a selective inhibitor, i.e. the drug will inhibit only the targeted enzyme and not interfere with similar enzymes. This reduces the potential side effects.
Protoporphyria: enzyme involved and characteristics
Ferrochelatase (E8) levels are down, resulting in the excretion of protoporphyrin IX in the feces. Both liver and erythropoietic tissues are affected
General transcription factors
minimal requirement for recognition of the promoter, recruitment of RNA polymerase II and initiation of transcription
Specific Transcription factors
- bind sequences within and outside of the core promoter - required to regulate gene expression
The transcription initiation complex is
involved in regulation of transcription; includes RNA polymerases and general transcription factors
α2-macroglobulin is an example of an endogenous inhibitor. α2-macroglobulin: function
α2-macroglobulin is an example of an endogenous inhibitor. α2-macroglobulin: function - protease inhibitor with a bait region containing cleavage sites for many enzymes. When enzyme cleaves the region, the conformation of α2-macroglobulin tetramer changes and traps the enzyme (inactivates it).
Congenital Disorders of Glycosylation (CDG)
inborn errors of metabolism in which glycosylation of a variety of tissues of proteins and/or lipids is deficient or defective
Post-translational modification of insulin includes
- synthesis of proinsulin in ER (includes folding, oxidation, and signal peptide cleavage) - Transported to Golgi, proinsulin is processed by a series of proteases to form mature insulin
… residues in histones can activate transcription.
Acetylation of lysine
… residues in histones can inactivate transcription
Methylation of lysine
