Cell Biology Exam 2 Flashcards
(91 cards)
1
Q
General functions of the Golgi Apparatus
A
finish any post-translation modifications
package these proteins into vesicles
ship vesicles to either the plasma membrane or other organelles
-not generally seen in the Light microscope
-in EM’s seen as series of 5-7 flattened membranes sacules
2
Q
4 functional divisions
A
“cis” compartment - vesicles budding side of golgi faces ER, newly synthesized proteins and lipids are modified
“medial” compartment - receives vesicles that have pinched off the edges of the cis sac, further modifications
“trans” compartment - concave side of golgi faces away from ER, vesicles contain stuff released to surroundings
“trans golgi network” - of vesicles having budded from trans, waiting to be shipped
3
Q
Protein golgi is known to be rich in
A
Glycosyltransferase - embedded in the golgi membrane and faces the cisternal side of the sacs, add or modify sugar chains to create glycoproteins, also present are a variety of other receptors and sorting proteins
4
Q
3 Major functions of Golgi apparatus
A
Lysosome formation
Secretory vesicle formation
Plasma Membrane renewal
5
Q
Lysosome formation
A
membrane bound organelles that contain an array of digestive enzymes of class known as hydrolase, these enzymes are sorted by golgi -process is mannose ogliosaccaride on hydrolyses, shuttled to the golgi cis-compartment, in cis compartment the mannose flag is phosphorylated by enzyme glucosamine phosphotransferase, the hydrolyses are gathered by golgi membrane by receptors called mannose-6-phosphate receptors
6
Q
Secretory Vesicle Function
A
these are products separated from hydrolyses
shipped to membrane and released
7
Q
Plasma Membrane Renewal
A
secretory vesicles merge with plasma membrane thereby duming interior contents
adding new phospholipids to the surface
add membrane bound proteins
8
Q
Two forms of Exocytosis from the Golgi
A
constitutive- the default path of such vesicles and their contents, movement to the surface conducted by cytoskeleton
regulated - vesicle binds to the cytoskeleton and is only regulated when the cell is stimulated
9
Q
Lysosomes
A
dissolution body
size and number vary greatly but common in all cells
rich in digestive enzymes called hydrolyses
newly formed lysosomes are called primary lysosomes
when primary lysosomes merge with an endosome they are called secondary
10
Q
3 Major Functions of Lysosomes
A
autophagy
heterophagy
external operations
11
Q
Autophagy
A
self digestion
part of normal turn over of organelles
down regulation of receptors on plasma membrane
12
Q
Heterophagy
A
digestion of foreign materials
phagocytic digestion of other cells/tissues
13
Q
External Operations
A
an uncommon use of lysosomes for extracellular digestion:
- osteoclasts; normal bone recycling
- special neutrophilic attack - vigorous defence seen in chronic inflammatory, autoimmune diseases and seen in some aggressive infections
14
Q
Summary of Lysosomes
A
-have many subtypes of hydraulic enzymes
all are needed to adequately digest any potential substrate
if any enzyme is missing it will not be able to fully digest material leading to disease, storage of residual body
know as lysosome storage diseases
15
Q
Mitochondrion
A
means thread granules, size and number vary greatly
they appear as a cylindrical organelle
possess 2 enclosing membranes
constantly moving
16
Q
Outer Mitochondrial Membrane
A
isolates organelle from the rest of the cytoplasm and is rich in IMP called porin which allows for significant free-passage
17
Q
Inner Mitochondrian membrane
A
is thrown into shelf like folds called cristae that crosses the interior
- number of cristae is directly related to ability to produce ATP
- contains proteins of the electron transport system ATP synthesis and the F1-particle and various transporters related to oxidative phosphorylation
- also a high concentration of phospholipid called cardiolipin which decreases the permeability of the membrane
18
Q
Inner Membrane Space
A
separates the IMM and the OMM
it is an H+ accumulation area and many molecules found in transit in and out
19
Q
Matrix
A
filles the interior of the organelle
contains enzymes of the Krebs cycle
also contin nucleic acid machinery, includes looped DNA ribosomes and tRNAs
20
Q
The organelle does the following functions
A
ADP+p, Carbs and Fat, O2 - IN
ATP, heat, H20 and CO2 - OUT
- oxygen is burned with metabolic food to produce carbon dioxide and water and heat
-the ultimate purpose is to convert ADP to ATP
21
Q
Oxidative Phosphorylation
A
refers to the oxidation/reduction reactions that utilize oxygen as an acceptor of electrons with the associated phosphorylation of ADP
the broad theory for how mitochondrion pulls electrons off is often terms the chemiosmotic coupling hypothesis
the 3 major components of this process are:
glycolysis
krebs cycle
electron transport system
22
Q
Glycolysis
A
- conversion of glucose to pyruvate in the cytoplasm
- pyruvate enters the matrix and is converted to Acetyl CoA
23
Q
Krebs Cycle
A
acetyl CoA enters a series of reactions
results in production of CO2 and electrons and protons
electrons and protons received by reducing agent mostly NAD
24
Q
Electron Transport System
A
NADH+ oxidation leads to the release of H+ and electrons
H+ pump pulled across the IMM to the inter membrane space
electrons pulled along and thru the IMM by way of many IMPs
the separation of these charges creates a potential energy
cariolipin tends to keep the protons out thus creating a battery
IMM potential is about -160mV and the matrix pH is about 8
25
Proton Motive Force
the real action that happes on/in the IMM as it is fed with raw materials fromt he matrix and this actiond creates a powerful electrochemical gradient
it is maintained by the insulation of the phospholipids called cariolipin
the discharge of this force is done in a controlled fasion
26
ATP Synthetase
special re-entry protein and enzyme of the IMM
| it is otherwise called the F1 particle, it allows for H+ to re-enter the matrix as it converts an ADP to an ATP
27
The transporting proteins of the IMM involved in the energy producing process
there is an antiporter of Pi and OH- and another one for ADP and ATP
O2 and CO2 are able to move thru the membrane with notmuch resistance
28
5 major complexes within the IMM that make up the ETS
Complex 1 often called NADH dehydrogenase
Complex 2 often called fumerate reductase
Complex 3 often called cytochrome b-c
Complex 4 often called cytochrome c oxidase
Complex 5 is ATP synthetase
Iron is nested in these complexes and there are non-protein ubiquinones in the IMM too that are used to shuttle electrons
29
Brown fat cells
they have mitochondrion with leaky IMMs
| these produce little ATP but a lot of heat and is seen in animals that hibernate.
30
Endosimbyotic Theory
they are semi-autonomous organelles that have many of the same propertiese as bacteria: same size, independant loops of DNA, transcription and translantion, can generate ATP, can reproduce, can regulate their pH, are contained in a second membrane
the idea is that two organisms joined in a symbiotic relationship eons ago such that: bacteria prvided ATP and gained protection, the eukaryotic parent cell provided nutrients and protection and gained valuable energy, the symbiotic combination allowed for massive explosion of oxygen-dependant multi-cellular organisms
decendants of ancient organelles because of the suggested common lineage
31
Functions of the Cytoskeleton
```
maintain cellular morphology
respinsible for cellular motility
contraction of a cell
transport vesiucles through the cytoplasm
organize the cytoplasm
external movements
```
32
Basic Component families of Proteins in cytoplasm
microfilaments- solid rod of varying thickness
microtubules - hollow tube-like rods
protein-motors - small associated golbular proteins that work with these microfilaments and microtubules
other associated proteins - of variable size, shape and number
33
Microfilaments
thin, intermediate and thick
| just classified by thickness of the protein
34
Thin - Actin
made of small bead-like sub-unit called G-actine monomers that are assembled into a helical polymer called F-actin
can have a + growing end and a - shrinking end
major component of contractile apparatus in muscle cells representing about 10% of total protein in those cells
other proteins associated with actin are troponin and tropomyosin, critial in muscle contraction
comes in several iso-forms; there are 6 actin genes in the human cell
tropomin is a Ca2+ regulated protein and it influences rope like tropomyosin to make available binding sites of G-actine collectively this is the thin filament in muscle
35
Thick - Myosin
a unique enzyme that can be assembles with other myosin to form interesting myosin structures, their head region has the capacity to walk on actin by hydrolizing ATP-thus they are considered protein motors
a major component of contractile apparatus in muscle cells, but, like actin present in nearly all cells
other proteins often associated with myosin (chaperones)
actin and myosin work together in muscle cells - sliding filament theory.
head is the key element in motor movement
regulation of all this is governed by cytosolic Ca2+ concentration therefor tropomyosin in the on and off regulator of this myosin movement
36
Sliding Filament Theory
- ATP used to change the conformation ->changing association with G-actin
- ATP is also used to setup a POWER STROKE->bound to nearby g-actin and ADP is removed
- the only way it can bind is in the presence of Ca2+ to land on troponin attachment site -RIGOR COMPLEX
- hydrolysis of ATP and subsequent release of ADP creates the power stroke
37
Concentration regulation of Ca2+
continually being pumped in to the ECM by most cells and in the muscle cells it is also uniquely pumped in the SER
the ultimate control of contraction is done temporarily by opening Ca2+ channels that will allow cytoplasmic Ca2+ levels to rapidly rise and pump it back
38
Examples of Myosin outside of muscle cells
- contractile ring seen during mitosis (cleavage)
- interior of microvillus have lots of actin, little myosin to hold its shape
- adhering cells to ECM, adhering junctions (cadherin and integrin)
- membrane cytosis
- organelle movement
- secretion, exocytosis require vascular movement
39
Ryanodine receptor
voltage gated ion channel that signals the release of Ca2+ at the Smooth ER after it receives special signal induced by actin potential
40
Intermediate
tend to be tissue and cell specific and all seem to play a structural role
4 major types of Intermediate microfilaments
Keratin
Desmin
Vimentin
Neurofilaments
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Keratin
```
in epithelial cells
provides flexibility and strength
water resistant and tough
sulfer rich
desmosomes
```
42
Desmin
in muscle cells
links actin to myofibrils by forming the Z-line/ discs
links the myofibrils together
43
Vimentin
found in many cells specifically Connective tissue cells
| important for holding some organelles in place
44
Neurofilaments
structural proteins of neurons
| may help maintain the long cytoplasmic prjections
45
Microtubules
-nothing more than a protein rod that appear as tiny tubules
-compesed of tubulin dimers assembled in tiny pipe like structures have just a + end that allows for the addition and deletion of tubulin dimers at that end
-this process of addition requires GTP binding
the 2 microtubules associated proteins that act like motors are: dynein - towards the - end and kinesin - towards the + end
microtubules are formed by a microtuble-organized center
function in a number of cellular processes
46
Microtubule-organizing center
there can be a number of them in a given cell but the one main one is called the centrosome
a centrosome is a collection of two microtubule structures surrounded by a haze of electron-dense material, the structures are each called a centriole whhich has a 9+0 arrangement of microtubule triplets
47
3 Functions of Microtubules
mitotic and meiotic chromosomal movements
intracellular transport of vesicles
ciliary and flagellar movement
48
5 movements that require myosin and dynein
- shuttling of vesicles down axon for synaptic transmission (axoplasmic flow is an important mechanism to deliver new neurotransmitters and other supplies very distant, terminal end of axon)
- secretion (exocytosis)
- movement of chromosomes (spindle apparatus of mitosis and meiosis)
- movement of cillium and flagellum (axoneme)
- cell motility, movement of the entire cell (ambeoid movement)
49
Axoneme
cilia are found in on the surface of cells that move things across them
flagella are singular tails seen only in spermatozoan
they have a 9+2 arrangement of microtuble doublets along their length, and have a regular dynein projection along their length
-held together by a variety of proteins
anchored at their base by a basal body with a 9+0 arrangement of triplets just like the centriole
50
Cell Motility
several mechanisms depending upon speed, slower movers use actin-myosin system and faster movers engage in ambeoid movement
much of this is done using other cytoskeletal components
steps involve chemotaxis, formation of lamellipodium, cytoskeletal anchoring and movement, and plamsa membrane recycling (endocytosis from rear of cell)
the departure of a defender cell from the blood is called diapedesis (most white blood cells do their job extravascularly, movement is signalled by inflammed tissues)
51
Chemotaxi
reception of a chemotactic molecule, signal transduction to interior where cell synthesizes more cytoskeleton in that direction forming a leading lamella
52
Lamellipodium
actin is pulled into this area by membrane myosin, microtubules bring vesicles to add new membrane at the tip
53
Pseudopod
the large leading foot of the ambeoid movement by the plasma mebrane
54
Nucleus
spherical and bounded by 2 unit membranes called the nuclear envelope which separates the cytoplasm from the nucleoplasm
composed of 4% DNA and 1% RNA
storage sire for DNA
has a dark granular appearance
55
Inner Nuclear Membrane
called the nuclear lamina
| provides support for the nuclear envelope as well as binding sites for chromatin and nuclear RNA
56
Outer Nuclear Membrane
is continuous with endoplasmic reticulum and can be studded with cytoplasmic facing ribomsomes
proteins are usually made and are destined for the nuclear envelope or the perinuclear space
57
Perinuclear Space
is b/w the INM and the ONM and is often continuous with some RER cisternae
INM and ONM connected by many perforations each called a nuclear pore complex
58
Nuclear Pore Complex
has a central channel a mere 10 nm in width
number of pores extremely variable but it covers 10%-30% of the envelope surface area, number of pores is directly related to the transcriptional activity of the cell
59
Interior of Nucleus
it is very organized
nuclear lamina maintains a kind of structural intergrity of nucleus
nuclear matrix is a web/matrix of protein that provide nuclear space
main critical material in nucleus is called chromatin
60
Chromatin
consists of protein assopciated with DNA, this protein is involved in regulation, copying or packaging
chromatin appears granular and is seen in two general sub forms: euchromatin and heterochromatin
special kind of chromatin called the nucleolus
chromatin can be super condensed into chromosomes
61
Euchromatin
dispersed and transciptionally active
often located throughout the nucleus
mRNA being made and sent to the cytoplasm
62
Heterochromtin
higly condensed and trancriptionally inactive
generally located at the periphery or around the nucleolus
amount is directly related to unique activity of the cell
comes in two functional sub-types: constitutive heterochromatin (always condensed), facultative heterochromatin (can be dispersed as needed)
63
Nucleolus
a prominent dense and roughly spherical mass of chromatin
there may be one or two of them in a nucleus
composed of RNA and protein and some DNA and is a site of ribosomal production
64
Chromosome
a chromosome is a manageale package of DNA for cell division
46 such threads seen during nuclear division only
actually 2 complete sets of 23
65
Mitosis
somatic cell division where the contents of the nucleus must be accurately duplicated and separated
involves karyokinesis and cytokinesis
an understanding of cell division presumes an understadning of the key stages in the larger life cycle of a cell termed the cell cycle
66
Karyokinesis
division of the nucleus
| done with remarkable precision
67
Cytokinesis
division of the cytoplasm
| is somewhat haphazard
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Essential reasons for cell division
- normal growth and development
- tissue maintenance
- wound repair
- immine response
69
Cell Cycle
starts with the moment a cell is born and ends at the moment it divides into two new daughter cells
since DNA matters most it is represented from a nuclear frame of reference
length of the cell cycle is highly variable
-controlled by proteins called cyclin-dependant kinases and are further controlled bu small family of cyclins
-further stimulated by mitogens
70
Interphase 3 major phases
G1
S
G2
71
G1
first growth phase and highly variable in duration
this is the stage with the cell lives most of its life
G0 can be used to describe a cell that has divided and never intends to divide again
72
S
a DNA synthesis phase and duplication phase
duplicated DNA remains attached to original strand
the cell may carry on its usual function but without any real access to DNA and RNA
73
G2
second growth phase where cell prepares for mitosis
| cell may carry on its usual functions and it grows
74
M
designated for the stage of mitosis
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"N" number
is the measure of the numer of complere sets of essential hereditary information
normal somatic cells are 2N in interphase b/c there is one set from the mnother and one from the father\
4N is a relatively breif state in preparation for cell division and ots the product of the S phase back in interphase
N is the genetic content of a gametis cell
76
4 Major Phases of Mitosis
Prophase
Metaphase
Anaphase
Telophase
77
Prophase
a first phase of chromasomal formation
the slowest phase
chromatin condenses by coiling to form chromosomes with 2 chromatids
-the presence of the second chromatic is the consequnece of the S phase and chromatids appears after significant condensing of the chromosomes
-chromatids held together at centromeres by 2 proteins called kinetochores
-at same time the nucleolus disappears and the nuclear envelope disintegrates at the end of prophase
- when the spindle aparatus has formed and nuclear envelope has broke it is refered to as prometaphase
78
Spindle Apparatus
as the cytoskeleton beark down but centrosomes reproduce and migrate to opposite pole on either side of the nucleus this is what is grown
there are 3 types of microtubules involved:
-astral microtubules; star like as they spray out from the centromere to organize and anchor spindle
-kinetochore microtubules; from centrosome to kinetochore protein that pull chromatids apart
-polar microtubules; from centrosomes to nearly other centrosome that seem to push poles apart
AS THE SPINDLE APARATUS FORM THE NUCLEAR ENVELOPE BREAKS
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Metaphase
a middle phase of chromosomal alignment
chromosomes line up on an equatorial plate
spindle aparatus connets to kinetochores
80
Anaphase
a back phase of separation of chromatids
a radid separation of sister chromatids as the centromeres split
former chromatids are pulled to the respective centrosome poles of the spindle apparatus forming a v-shape when pulled
force generation is unknown but believe to be due to
81
Telophase
the end phase of reconstrustion
newly arrived chromosomes at poles de-condensed
a reversal of prophase: chromosomes dissapear into regular chromatin, nuclear envelop returns, nucleolus reforms, mitotic spindle disassembles
cytokinesis occurs: contractile ring pulls plasma membrane in and pinches off, mostly a myosin-actin action
82
Summary of Mitosis
all mammalian cells have the capacity to divide
tissue growth through cell division is very tightly regulated in multicellular organisms
-cancer cell develop (transformation) when they escape the normal regulation of the cell cycle, they grow in the absence of a stimulation or instruction to do so
-cancer cells also seem to lack contact inhibition
-cancer cell populations appear different, malignant cells typically have large nuclei, a high mitotic index
-cancer cells have different surface proteins and cytoskeletal organization
-loss of division constraints results in many deleterious effect
83
cell division constraint losses
- rapid cell division and tumour formation
- both physical and physiological damage ensues
- migratory tendencies (metastasis) as they often do not require specific anchoring to the ECM and escape to new locations where they proliferate
- tissue and organ dysfunction as cancer cells corrupt surrounding tissues and out-compete for metabolites
84
static cell populations
G0
terminally differential cell that don't divide
examples include skeletal muscle, cardiac muscle and nervous muscle
85
expanding cell population
G0->G1
terminally differentiated but retain capacity to divide if needed
examples include liver, kidney, some endocrine glands and generally distributed stem cells
86
renewing cell population
G1->S->G2->M->etc.
continually replacing their cells
examples include epidermis, GI tract lining, some exocrine glands, blood cells and spermatozoa
87
Mitotic Index
the percent of cells showing mitotic figures
in a slide or photo area of a piece of tissue it is the number of cells that are in mitotic states
-humans have a renewing cell population below 5%
-malignant cancer cell population can have a mitotic index of about 0.1 to 0.2 (10%-20%)
88
Cyclins
these are the proteins that control the cell cycle making sure everything is in order before it goes to the next step
-also known as cyclin dependant kinases
89
Tumor-suppressor genes
these genes develop the proteins that stop the cells from dividing, the brake pedal
90
Oncogenes
this is the protein that instructs the cell to divide, it is the as pedal
2 examples of an oncogene that are expressed when they are not suppose to be:
ras - codes for mutant G-protein that binds GTP but can't cleave to GDP leading to cellular proliferation
erb - codes for a damaged epidermal growth factor (EGF) such that it does not require the growth factor to function, so it is on all the time
-some cancerous cells are known to show chromosomal translocations where two different chromosomes exchange sections
91
Ways to alter gene expression in future therapeutic hopes
- turn cell cycle regulatory gene "on" or "off"
- block mRNA transcripts from offending genes
- block the metastatic process
- teach the immune system to recognize key surface -molecules
- stimulate immune system to work hard
