2.2 parts of cells Flashcards
what is cytoplasm and whats it mad eof
material between PM and nucelus
- contains cytosol laregly water with diss protines, salts, sugars and toher solutes
inclusions: chemical substances like lipid droplets, glycogen granules and pigment
- houses the organelles
which organelles have membranes, whcih dont
membranous: mitochondria, peroxisomes, lysosomes, ER golgi
nonmembranous: cytoskeleton, centroles, ribosoems
describes mitochondria
- doubdle mmebrna structure
- rpodves most of cells ATP via aerobic resp
- contains their own dna (mDNA) and RNA
- mDNA encodes for 37 genes
*cristea are little strutures between the mitochondrial mmebranes
ribosomes
granules contianing protein and rRNA
- stie of protein synthesis:
Free ribsoomes synthesize soluble cytoplasmic proteins
membrane bound ribosomes: synthesize protiens to be icnorperated into membranes and free vesicle grnaule protien
ER and RER
ER: interconencted tubes and parallel membranes enclosing cisternae (fluid filled cavity)
*contoniuos w/ nuclear memrbane
RER:
- studded with ribosomes, manufactures all secreted protins
- responsible for synthesis of integral memrbane proteins and phospholipids of cell membranes
Smooth
- tubules arranged in a looping network
- catalyzes following reactions in various organs of body
- Liver: lipid and colesterol metabolism, glycogen breakdown and along w/ kidneys detoxification of drugs
- Testes: synthesis of steroid based hormones
- Intestinal cells: absorption, synthesis and transport of fats
- Skeletal/cardiac muscle: storage and release of Ca2+
Golgi
- stacked and flattened membranous sacs
- function: modifcation, conc and packaging of proteins
steps
- transport vessels from ER fuse with the cis face of golgi
- proteins pass trhough golgi to trans face
- secretory vesicles leave transface of golgi stack and move to designated parts of cell
lysosomes
large, abundant in phagocytes
- spherical membranous bags containing digestive enzymes
- digest ingested bacteria viruses and toxins
- degrade non functional organelles
- breakdown glycogen and release thyroid hormone
- breakdown non useful tissue
- breakdown bone to release Ca2+
Secretory lysosomes are found in WBC, immune cells and melanocytes
peroxisomes
membranous sacs contianing oxidases and catalases
- detoxify harmful or toxic substances
- neturalize dangerous free radicals
*free radicals have highly reactive chemicals with unapired electrons
what does cytoskeleton consist of
cytoskeleton = dynamic, elaborate series of rods running throuhg cytosol
consists of microfilaments, intermediate filaments and microtubules
*Important in shaping PM -> moving vesicles and maintiang structural stability and strength
Ex are: microfilaments made of actin subunits,
Intermediate filaments: fibrous subunit, microtubule (tuulin subunit)
describe microfilaments
- fleixble and dynamic strands of Helical actin
- shapes, braces and strengthens the cytoplasmic side of the PM
- attach to cell adhesion molecules (CAMs) function in endo adn exocytosis
*Microvilaments need to be dynamic to vesibles can get up to the PM, filaments get remodelled, always asociated with the palsma membrabe, involved in cellular extensions
describe intermediate filaments
- rope like structure
NOT dynamic *unlike microfilaments)
- rigid, long, striaght fibers that provide mechanical strength and resistance to sheer stress
- associated wtih desmosomes (plaques)
what are mcirotubules
- dynamic, hollow tubes made of spherical protein tubulin
*can be remodeled and shaped depending on cell needs
- determine the overall shape the cell, dsitruption of organelles and intracellualr transport
what are motor molecules
- microfilaments and microtubules function in motility by interacting with motor molecules
- are powered by ATP and hav eprotein extensions that appear to look like microscopic legs
- these legs allow them to “walk” along microtubules/microfilaments
ex: mysen in mucle cells,
*all motor proteins powered by ATP, protein structure makes them look like they are walking along the cell
what organelles work with mototr molecules? how does centrosome and microctubules work together?
*purple lines are licrotubules, have pos charges at the end, interior of centrosome is more engative
- kenesin moves from centroosme to outer side
- dyein goes from pos to negative
orgenelles: mitochondira, secretory vesciles, lysosomes
what are Centrioles
- small barrel shaped organelles located near the nucleus
*always found in pairs, has a pinwheel of 3 triplets, 9 triplets interacts to form centroiles
- Pinwheel array of nine triplets of microtubules
- organize mitotic spindle during mitosis (organization point for microtubules)
- form the bases of cilia and flagella
*cloud of yellow around is single tubulin monomers that form centrosome matrix , from there can form microtubules
what are the celular extensions/ how do they work
- cillia and flagella
- contain microtubules which run along the length of the structure and motor molecules
- have a basal body (centriole) with 9 triplets associated, (has 9 doublets which join with another microtubule forming triplet)
- outer microtubule doublets and two central micotubules are helf together by radial spokes
- as you move up cillum, there are dyein arms (motor proteins) in the membrane extensions attached to the doublets
*motor proteins are only fond on one side of microtubule duplets to let cillia or flagella bend and move
describe the movement of Cilia
A microtubule of dyna mol interacts with legs of B, creates bending of microtubule, contraction and relaxation allows for power and revovery stroke
- movement is like a back in ofrth beating
- cilia are important move movement of mucus across cell surfaces (ex in lungs)
*flagella move in a properller like motion, used for properling the whole cell while cilia move substances across cell surfaces
what are microvilli
fingerlike projections of the PM that increase SA for abs
*cellular extensions associated with actin are called microvilli - the actin can contract and move things around
Parts of Nucelus
Nucelous
Has a numclear membrane that curved in and also forms inner spaces in membane called Nuclear pore complex
Allows for communiaction of mRNA formed/ proteins to come in
Stands alsong the membrane called nuclear lamina
describe the Nuclear Envelope
- encloses jellylike nucleoplasm that contains essential solutes
- outer membrane is continuous with teh RER
- Pore complex regulates transport of large molecules into and out of nucleus
What is Chromatin
threadlike strands of DNA (30%) , histone proteins (60%) and RNA (10%)
- arranged in nucleosomes
- condense into barlike bodies called chromosomes when cells start to divide
1. DNA double helix
2. DNA winds around histones to form nucleosomes, now chromatin
3. forms a tight helical fiber
4. looped domain strucutre
5. forms chromatid then the metaphase chromosome
cell cycle is borken into two main phases, what are they?
Interphase:
- growth (G1)L metabolic activity and vigorous growth
- G0: cells that permanently cease dividing
- syntheis (S): DNA replications
- growth (G2): preparation for division
*key point in interphase is duplication of the centrosome
Mitotic phase: mitosis and cytokinesis
Describe DNA replication (preparation of it)
- during S phase
- Helicase untwists so separate the two strands so polymerases can some in and start replicating
- Site of DNA separation = replication bubble
- Y shaped region at end if replication fork
- Topoisomerase DNA gyrase
- Interacts on other side and knicks the DNA to relieve stress
- Leading and lagging strand
- Lagging has chunks of DNA (okazaki frag)
- DNA Pol 3: active on leading and lagging strand
- Creates an exact comp of Dna (pictures in light blue)
- Requires a primer to work
- Primase primes the DNA so DNA Pol can come and replicated
what enzymes are invovled in DNA replication, how do they work to replicate it?
- proteins at site of DNA replication is called replisome
*include; primase, helicase, gyrase, ligase, DNA Pol I and III
- Helicase and gyrase separates and reduces stress
- Primase puts primer goes 5’ to 3’
- Stand is extended by DNA pol3
- On leading get cont DNA formation
- DNA pol 1 comes along and removes RNA primer and will replace with DNA
- DNA ligase will fix any knicks
describe prophase
Early Prophase:
- chromosomes become visible - each w/ two chromatids joined at centromere
- Centrosomes separate and migrate towards opposite poles
- mitotic spindles and asters form
Late Prophase
- nuclear envelope gradments
- asters separate and goes to diff poles
- kinetochore microtubules attach to kinetochore of centromeres and draw them towards the equator of the cell
- Polar microtubules assist in forcing poles apart
*centrosome and aster are like same thing
describe metaphase
- organization of chromosomes along metaphase plate
- have enzyme separase that cleaves sister chromatids at the centromere
*separase cleaves sister chromatids at centromere
Describe Anaphase
Separation of sister chromatids becoming daughter chromosomes
describe Telophase and Cytokinesis
Nuclear envoleope starts to reform
Nucleolus reforms
chromosome losen up
Get a cleavage furrow, contractile elements pull membrane in to get final cleavage (cytokinsis, breaks cells into their own cells)
What internal regulators control cell division
- surface-to-volume ratio of cells (as cells get bigger it promotes cell division)
- protein mediators: for example cyclins and cyclin-dependent kinases
- Checkpoint 1 (g1): critical in determining progression (if not progress then it goes to G0)
- Checkpoint (G2): requires critical threshold amount of M-phase promoting factor (MPF) to move to next stage
What are external regulators of Cell division
- Chemical signals: such as growth factors and hormones
- Contact inhibition: Cell-to-cell contact can prevent cell division
*cells that dont follow rules can lead to cancer, contact inhibtion is removed when cell is damaged
what are the 3 types of RNA and thier roles?
- mRNA: carries genetic info from DNA in nucleus to ribosomes in Cytoplasm
*has 5’ cap, poly-A-tail,
- tRNA: bound to amino acids base pair with the codons of mRNA at the ribosome to begin process of protein synthesis
*top end has the aa to elongate the polypeptide that corresponds with anticodon sequence on the tRNA
- rRNA: structural component of ribosomes
*has a large and small subunit
*nucleolus is associated with generation of rRNA< because so much transcription to make RNA nuceolus is darker region
what are the transcription factors?
- promotes loosening of histones from DNA in area to be transcribed by binding to the promoter region
- mediates the binding of RNA polymerase II to the promoter
- RNA polymerase uses RNA triphosphates as substrates on the template stand
- piece of DNA not used as template is the coding trand because the mRNA to be build will have th esame coded sequence
- TATA box is the point of initiation of transcription
what are the 3 steps of transcription
- Initiation: Binding of RNA Pol II
- Elongation: RNA Pol II elongates
- Termination
how is DNA losened for transcription
Part of initiation
- HAT can come in and acetylates the histones, this losens the binding of the histones to DNA
- Can also have chromatin remodeling complex that can come in to losen DNA
*two ways to initiate gene transcription
describe initiation
- enhancer and promoter region are not lcose together, but when soemthing bidns to enhancer region DNA can bend and twist to get the enhancer region close to start site
RNA pol binds to DNA< separates and makes a copy of the template trans
Signma factor helps to enhance the specificity of the interaction
Improves function of RNA pol
Makes copy of tempplate strand?
Double check that
transcription elongation
RNA polymerase with sigma factor goes along ang elongates the RNA transcript
- Uracil is incoorperated instead of Thymine
- transcrription occurs in mitochondira
- mRNA is processed by: 5’ cap, poladenylation and splicing
Now have this RNA refered to pre mRNA< must modifty so that you can make proteins
Exons and introns (spacers need to be removed)
Splicing event with splicosomes
Poly A trail and guanine cap
Mol then transported out of nucleus and into sytosol
Describe translation
- initiation
- Leader sequence on mRNA (AUG) attaches to the small riosomal unit, methionine charged initiator tRNA binds to the small subunit
- Small ribosomal subint interacts with AUG at the P site
- Start codon then recognized by anticodon and will bind to P site
- Use GTP as energy source, phosphorlyation to prep for protein translation
- Large subunit comes in (have fmet trna, large and small -> forms initiation complex)
- Elongation
- at A site get a new tRNA binding a specific codon on the mRNA mol
- robosome moves down mRNA mol, metis removed from previous tRNA a the E site, and then A site is reopened
- note can have multiple ribsomes interacting on the rna mol
- Termination
* When encounters stop codom
what is the role of the RER in protein synthesis
- mRNA ribosome complex is directed to the rough ER by SRP.
- SRP binds to receptor site
- SRP is released and the growing polypeptide snkaes through the ER membrane pore into the cisterna
- the signal sequence is clipped off by an enzyme. as protin syn cont, sugar groups can be added to the protein
- in this ex, compelted protein is released form risocome and folds into 3d confomation aided my chaperone mol
- protein is enclosed within a protein (coatomer) coated transport veiscle.
- vesicle can make its way to golgi for further protein processing
