MCAT BIO CH. 6 PART 2 Flashcards
How are materials taken into the cells for endocytosis? How do we assure its not mixed with the cell content?
- Invagination of cell membrane
2. Endosome; vesicle formed
What are three types of endocytosis?
- Phagocytosis
- Pinocytosis
- Receptor-mediated endocytosis
What does the literally translation of phagocytosis?
Cell-eating
What is the definition of phagocytosis?
Refers to the nonspecific uptake of large particulate matter into a phagocytic vesicle
What happens to the phagocytic vesicle after it is formed?
Fuses with the lysosome
What is an example of phagocytic human cells?
Macrophages - destroy viruses and bacteria
What does the literally translation of pinocytosis?
Cell-drinking
What is the definition of pinocytosis?
Nonspecific uptake of small molecules and extracellular fluid via invagination
How do primitive eukaryotic cells obtain nutrition?
{pinocytosis
What is receptor-mediated endocytosis?
Receptors bind to a specific molecule outside the cell
How does the cell know when it needs to conduct receptor-mediated endocytosis?
Site marked by pits coated with the molecule clathrin
What is an important example of receptor-mediated endocytosis?
Uptake of cholesterol from the blood
How are cholesterol transported through the blood, based on RME?
By large particles called lipoproteins
What is atherosclerosis?
A buildup of plaque on the walls of the arteries by cholesterol build up sticking to the walls
Does clathrin recognize and bind to lipoproteins?
No, fibrous protein inside the cell that associates with cytoplasmic portion of the cell receptors
Where is clathrin located?
Inside the cell
Which items from the cholesterol receptor-mediated endocytosis, are recycled?
Lipoprotein receptors
What are receptors?
Class of integral membrane proteins that transmit signals from the extracellular space into the cytoplasm
What is a ligand?
molecule that binds to the receptor
What are ligands usually based on cell-surface receptors?
Hormone or neurotransmitter
What is signal transduction?
Ligand binding to the receptor and causing intracellular response
Based on ligand binding to the receptor, how may it involve cancer?
Many cancers involves relaying their signal to the cytoplasm with or without a ligand
What are three types of signal-transducing cell-surface receptors?
- Ligand-gated ion channels
- Catalytic receptors
- G-protein linked receptor
What is ligand-gated ion channels?
Open an ion channel upon binding a particular neurotransmitter
What is example of a ligand-gated sodium channel?
Surface of muscle cel at the neuromuscular junction
What happens when the neurotramsiter ______ binds to the receptor, based on muscle cell?
acetylcholine; open Na+ channel; influx of sodium depolarizes muscle cell and causes contractions
Catalytic receptors have what?
Enzymatic active site on the cytoplasmic side of the membrane
Generally, the catalytic role of the catalytic receptors is that of a protein _____?
Kinase
What is a protein kinase?
An enzyme that covalently attaches P groups to proteins
What is an example of a kinase?
Insulin receptor is an example of a tyrosine kinase
What regulates the activity of kinases?
Modification of proteins with Ps
How does the G-protein linked receptor transmits information?
Transmits within the cell with the aid of a second messenger
What is the most important second messenger based on G-protein linked receptor transmitters?
cycle AMP (cAMP)
What is cycle AMP known as and why?
Universal hunger signal because it is the second messenger of the hormones epinephrine and glucagon
What is the purpose of glucagon?
Energy metabolism (glycogen and fat breakdown)
What is the first step to the G-Protein Mediated Stimulated Transduction Stimulated by Epinephrine?
Epinephrine arrives to cell surface and binds to a specific G-protein linked receptor
What happens when the G-protein linked receptor is activated after epinephrine binds?
The cytoplasmic portion of the receptor activates G-protein
What happens when the G-protein inside the cell is activated from epinephrine?
GDP dissociates and GTP binds in its place
What is it considered when the GTP binds in its place to the protein?
The activated G-proteins
What does the activated G-proteins do when GTP has bounded?
Diffuse through the membrane and activate adenyl cyclase
What happens when adenyl cyclase is activated in the G-Protein Mediated Signal Transduction Stimulated by Epinephrine?
Adenyl cyclase makes cAMP from ATP
What does cAMP do once its created by the activation of adenyl cyclase?
cAMP activates cAMP-dependent protein kinases (cAMP-dPK) in the cytoplasm
What is the function of cAMP-dPK in the G-Protein Mediated Signal Transduction Stimulated by Epinephrine?
Phosphorylates certain enzymes
After phosphorylating certain enzymes, what cascade does that cause based on cAMP-dPK in the G-Protein Mediated Signal Transduction Stimulated by Epinephrine?
Then end result is mobilization of energy
What is an example of an enzyme that is activated based on cAMP-dPK in the G-Protein Signal thing?
Enzymes for glycogen breakdown will be activated and enzymes for glycogen synthesis will be inactivated
What are the two types of g-protein linked receptors?
Stimulatory (G subscript s)
Inhibitory (G subscript i)
For the G-protein linked receptors that have no involvement with cAMP, what do they do instead?
Their G-proteins activate an enzyme called phospholipase C
What does the activation of phospholipase cause, based on the G-protein linked receptors cascade?
Increase in cytoplasmic Ca2+
What is the common theme of all G-protein based signals?
Reliance on G-protein which is a signaling molecule that binds to GTP
What is cAMP considered in the G-Protein mediated Signal Transduction Stimulated by Epinephrine?
Second messenger
What is the internal cytoskeleton composed of in animal cells?
- Microtubules
- Intermediate filaments
- Microfilaments
Based on microtubules, intermediate filaments and microfilaments, what are they all three composed of?
A non-covalently polymerized proteins; massive example of a quaternary protein structure
What is the structural composition of microtubules?
Hollow rod composed of two globular proteins: alpha-tubulin and beta-tubulin
How are the alpha and beta tubulin attached to one another in microtubules?
Polymerized noncovalently
What do the alpha and beta tubulin form together?
Alpha-beta tubulin dimer and many dimers stick to one another noncovalently
Why can only one end of the microtubule elongate and not the other?
Because its anchored to the microtubule organizing center (MTOC)
Where is the MTOC located?
Near the nucleus
What is the first noticeable component within the MTOC?
A pair of centrioles
What is the structural component of centrioles?
A ring of nine microtubules triplets
What happens to the centrioles during cell division?
The centrioles duplicate themeselves, one pair moves to each end of the cell
What happens during mitosis, what is the role of microtubules in achieving mitosis?
Microtubules leave centrioles, attach to replicating chromosomes and pulls them apart
What are asters?
Microtubules leaving the centrioles during mitosis
What are polar fibers?
Microtubules connecting the chromosomes to the aster
What is the name for the assembly of the asters, and polar fibers based on microtubules and centrioles and chromosomes?
Mitotic spindle
What from the chromosome confirms the location of where the microtubules are supposed to connect?
Centromere of each chromosome contains a kinetochore
What are kinetochore fibers?
Tiny microtubules attaching the centromere of each chromome to the spindle
Based on mitosis, microtubules and centrioles, what is essential and what isn’t?
The MTOC is essential, the centrioles are not
What are the two evidences that prove that centrioles are not essential?
- Plants
2. Experimenters
What about plants prove that centrioles are not essential?
Plant cells lack centrioles but still undergo mitosis
What about experimenters prove that centrioles are not essential?
Succeeded in removing the centrioles from animal cells and the cells were still able to undergo mitosis
What do microtubules assist with in the cell, other than attaching to centromeres?
Mediate transport of substances within the cell
What is an example of microtubules assisting with transport of substances within the cell?
Nerve cells, materials are transported from the cell body to the axon terminus on a microtubule railroad
What is the purpose of cilia?
Move fluid past the cell surface
What is an example of cilia being present in the human body?
Cilia on lining cells of the human respiratory tract sweep mucus towards the mouth
Wha tis mucociliary escalator?
Cilia on lining cells of the human respiratory tract sweep mucus towards the mouth
What is flagellum?
Large “tail” which moves the cell by wiggling
The only human cell that has flagellum is…?
Sperm
What is the structure of cilia and flagella?
Cilia are small and flagella are long but they have the same structure with 9 + 2 arrangement of microtubules
How are microtubules bound to one another, the ones forming the 9 ring?
Contractile protein calle dyne
What does dynein cause for the filaments?
Cause movement of the filament past one another
What is the purpose of the basal body?
Anchor Cilium or flagella
What is the structure of the basal body?
A ring of nine triplets of microtubules
What is the structure component of the basal body?
A ring of nine triplets of microtubules
What are microfilaments?
Rods formed in the cytoplasm
How are microfilaments formed?
Polymerization of the globular protein actin
How are microfilaments formed from actin?
Actin monomers form a chain, two chains wrap around each other to form an actin filament
What are microfilaments responsible for?
Gross movements of the entire cell
What type of movements are microfilaments responsible for?
Pinching the diving parent cell into two daughters cell
What is amoeboid movement; what is the protein responsible for it?
Change of cytoplasmic structure; causes cytoplasm plus cell to flow in one direction; microfilament
What is different between microtubules and microfilaments, compared to intermediate filaments?
- Intermediate filaments are heterogeneous, composed of a wide range of polypeptides
- More permanent while micros disassemble and reassemble as needed
What does intermediate filaments seem to be involved in, based on structure?
Involved in providing strong cell structure such as resisting mechanical stress
What is the basement membrane?
A strong molecular sheet made of collagen under the epithelium
What is tight junction?
Epithelial cells prevent movement freely between two areas
What are desmosomes?
Epithelial cells held together but do not form a complete cell
What are gap junctions?
Holes allowing ions to flow back and forth between them
What is another term for tight junctions and why?
Occluding suctions because they form a seal between the membranes of adjacent cells, blocking flow molecules across the entire cell layer
How do tight junctions relate to the plasma membrane?
Block the flow of molecules within the plane of the plasma membrane
What is the apical surface?
The surface of the plasma membrane facing the intestinal lumen
What is the bas-lateral surface?
The cell facing the tissues beneath the plasma membrane
How do the apical surface and bas lateral surface relate to the tight junctions?
Aplical surface has different membrane proteins than the plasma membrane on the other side of the baslateral surface
Why are desmosomes called point desmosomes?
They are concise points, not bands all the way around the cell
How is the desmosomes anchored to the plasma membrane?
By plaque formed by the protein keratin
Where do the intermediate filaments attach based on the desmosomes?
To the inside of the desmosomes
The fluid mosaic model describes the plasma membrane as fluid, how does that relate to desmosomes? Can they move freely?
No because they are anchored by the intermediate filaments
What do gap junctions allow that desmosomes don’t?
Allows cytoplasms to mix by pore-like connections between adjacent cells
Gap junctions disallow the mixing of….?
Polypeptides and organelles
In what part of the body are gap junctions pertinent?
In smooth muscle and cardiac muscle, they allow the membrane depolarization of an action potential to pass directly from one cell to another
What are all the phases of the cell cycle?
- G1, S, G2, mitosis and cytokinesis
What does the S phase of the cell cycle entail?
The cell actively replicates it genome
What does the M phase of the cell cycle entail?
Mitosis and cytokinesis
What is mitosis?
Partitioning of the cellular components (genes and organelles) in two halves
What is the interphase based on cell cycle?
G1, S and G2
Where does the cell mostly spends its time?
Interphase
How do cells that are less capable of reproducing themselves, reproduce?
By reproduction of less specialized pre-cursor cells called stem cells
What happens during the interphase?
Genome is spread out and DNA is accessible for the enzymes to replicate
What happens at the end of the S phase?
The nucleus contains two contains two complete copies of the genome
What are the four stages of mitosis?
- Prophase
- Metaphase
- Anaphase
- Telophase
What is the first sign of prophase?
Genome becomes condensed and tightly packed chromosomes instead of diffuse chromatin
What are homologous pairs?
Identical-appearing sister chromatin pairs (23 pairs of pairs)
What are important factors that occur during prophase?
- Nucleolus disappear
- Spindle and kinetochore fibers appear
- Centriole pairs move to opposites
What is pro metaphase?
Nuclear envelope converts itself into many tiny vesicles
What are important factors that occur during metaphase?
- Chromosomes line up
What is the term used when describing the chromosomes lining in the middle of the cell?
Metaphase plate
Why can the chromosomes line up at the center of the cell?
Because the kinetochore of each sister chromatid is attached to spindle fibers that attach to MTOC at opposite ends
What are important factors that occur during anaphase?
- Spindle fibers shorten
- Centromeres pulled apart
- Cell elongates
- Cleavage furrow
What is the cleavage furrow during anaphase accomplished by?
Ring of microfilaments encircling the cell and contracting
What are important factors that occur during telophase?
- Nuclear membrane forms
- Chromsomes decondense
- Nucleolus becomes visible
What is the ploid number for the daughter nucleus after mitosis ?
2n chromsomes
What is a karyotype?
Display of an organism’s genome
When is the picture taken for karyotypes?
Metaphase
What is oncogenes?
Mutated genes that induce cancer
When was the first oncogene found?
Isolated from a retrovirus found in chickens
What are teratomas?
Oncogenes cause tissues to dedifferentiate and tumors with formed tissues from multiple germ layers
What are protooncogenes?
Normal versions of genes that allow for regular growth patterns but can be converted into oncogenes under the right circumstances
How can the conversion of protooncogenes create oncogenes?
Conversion may be due to mutation or because of exposure to a mutagen
What do tumor suppressor genes do?
Produce proteins that are the inherent defense system to prevent the conversion of cells into cancel cells
What are the two primary means of cancer prevention?
- Detect damage to the genome and halt cell growth and division
- Trigger programmed cell death if the damage is too severe
What is an example of a product of a tumor suppressor gene?
p53
How does the process of apoptosis start?
Cell shrinks and cytoskeleton disassembles, nuclear envelope breaks down and genome broken into pieces
What enzymes are responsible for apoptosis?
Family of proteases called caspases
Why are caspases called that way?
Have a cysteine in their active site and they cleave their target proteins at aspartic acid sites
How are the caspases initially produced?
In their inactive form, procaspases
How many caspases are there in humans and how are they grouped?
12 and they’re grouped by two categories, initiators or effectors
What are initiator caspases?
Response to extra or intra cellular cell death signals by clustering together and activate each other
What does the clustering of initiator caspases lead to?
Cascade to activate effector capsases
What are effector caspases?
Effector caspases cleave a variety of cellular proteins to trigger apoptosis
What is oxidative stress?
Level of production of reactive oxygen species outstrips the cell’s ability to detoxify them
Why can oxidative stress cause cancer?
The damage it can cause sets up conditions in the cel to allow oncogenes to become active and cell growth to be impacted
Why is creating oxidative stress sometimes beneficial for the body?
Used in immune system; activated phagocytes produce it to kill pathogens
What does the ability to restore damaged tissues depend on?
Depends on how stem cells are maintained in the body of an organism
What is senescence?
The process of biological aging which occurs at both the cellular and organismal level
