Lecture Exam 2 Flashcards
1
Q
What is the structure of the
golgi complex?
A
collection of flattened, membrane enclosed stacks called cisternae
2
Q
what part of golgi controls protein entry? exit?
A
entry: Cis face
exit: trans face
3
Q
what is the function of the Golgi?
A
modifies, sorts, and dispatches proteins
site of carbohydrate synthesis
4
Q
what types of proteins does the Golgi modify, sort, and dispatch?
A
proteins destined for lysosomes, secretory vesicles or cell surface
5
Q
what are lysosomes?
A
degrade proteins
6
Q
what are secretory vesicles?
A
carry proteins destined for secretion
7
Q
what are proteins destined for the cell surface?
A
proteins sent to the cell membrane
8
Q
how to secretory vesicles get proteins destined for secretion out of the cell?
A
exocytosis with the help of clathrin proteins (sometimes)
9
Q
what is exocytosis?
A
describes the transport of molecules destined for secretion from the cell
10
Q
how does exocytosis work?
A
molecules are carried from the Golgi complex to the cell membrane by vesicles coated with clathrin proteins, vesicle moves to cell membrane (via cell cytoskeleton)and clathrin recognizes binding sites on the cell membrane
vesicles fuse to cell membrane and release the molecule into the extracellular space
vesicle components are incorporated into the membrane (recycled)
11
Q
how are vesicles transported via the cytoskeleton?
A
microtubules and actin filaments (concentrated in the cortex region of cell found adjacent to cell membrane)
motor proteins power movement of vesicles along filaments
12
Q
why must some proteins be modified with a sugar side chain?
A
glycoproteins (proteins with sugar side chain)
side chain important in cell membrane protein’s ability to interact with other cells
side chains can help protect proteins from degradation
side chains can allow signal molecules to recognize and bind to a receptor (i.e. lectins)
13
Q
what carbohydrates does the golgi synthesize?
A
carbohydrates destined for extracellular matrix (animal cells) or cell wall (plant cells)
carbohydrates attached as side chains to proteins and/or lipids
14
Q
describe the structure of the mitochondria
A
double membrane: outer and inner
matrix
outer mitochondrial membrane
15
Q
what does the double membrane of mitochondria look like?
A
outer membrane: forms boundary of the organelle
inner membrane: folded into finger-like projections called cristae
16
Q
what is the mitochondrial matrix?
A
the inner mitochondrial space
17
Q
what is the outer mitochondrial membrane?
A
semi-permeable
contains enzymes involved in the synthesis of mitochondrial lipids
18
Q
What are the 3 types of cellular respiration that occur in the mitochondria?
A
glycolysis
citric acid cycle
electron transport chain
19
Q
describe glycolysis
A
occurs in the cytoplasm
breakdown of glucose –> pyruvate (1 glucose –> 2 pyruvate + 2 ATP)
20
Q
describe the citric acid cycle
A
occurs in the matrix
pyruvate enters cycle, converted into acetyl CoA (2)
net production of 2 ATP, also produces high energy electrons (NADH, FADH2) and CO2
21
Q
describe the electron transport chain
A
proton gradient is used to drive production of ATP by ATP synthase (34) (oxidative phosphorylation)
proton gradient created by high energy electrons being passed from one electron carrier to another
occurs in inner mitochondrial membrane
22
Q
what are mitochondrial myopathies?
A
diseases associated with defects in mitochondria (muscle/nerve tissue due to high rates of ATP consumption)
23
Q
what defects can occur from mitochondrial myopathies?
A
range in severity
infant death, blindness, deafness, muscle weakness, muscle deterioration
24
Q
what type of disorder are most mitochondrial myopathies?
A
genetic disorders: most defects are in genes that encode mitochondrial tRNA (needed for synthesis of mitochondrial proteins) [maternal inheritance pattern]
25
what is the structure of chloroplasts?
surrounded by 2 membranes: outer and inner boundary membrane
boundary membranes surround inner compartment called stroma contains a third membrane system consisting of small flattened sacs
26
what are the small flattened sacs called in chloroplasts?
thylakoids, thylakoids are then arranged in stacks called granum
27
what is the function of chloroplasts?
photosynthesis
28
what are the 2 parts of photosynthesis?
light dependent and light independent reactions
29
describe the light dependent reactions
occur in the thylakoids
involve photosystems I and II (protein pigment complexes)
pigments absorb light-- produces high energy electrons; H2O molecule is split to produce O2
*also produces ATP*
30
describe the light independent reactions
occur in the stroma
energy (ATP + high energy electrons) produced by light dependent reactions is used to drive conversion of CO2 into carbohydrates
31
What is the endosymbiont hypothesis used to explain?
the evolution of chloroplasts and mitochondria
32
what is the endosymbiont hypothesis?
early eukaryotic cells engulfed prokaryotic cells capable of carrying out cellular respiration or photosynthesis thus developing and endosymbiotic relationship
33
what evidence is there to support the endosymbiont hypothesis?
mitochondria and chloroplasts are surrounded by a double membrane
both contain circular DNA (similar to prokaryotes)
both can produce proteins
RNA polymerase and ribosomes found in mitochondria and chloroplasts are similar to prokaryotic types
34
describe the structure of a lysosome
membrane enclosed compartment filled with hydrolytic enzymes (digestive enzymes)
lumen
35
describe the lumen of a lysosome
contains hydrolytic enzymes: nucleases, proteases, lipases etc
all enzymes are acidic hydrolases which require an acidic environment and are only active at an acidic pH
pH of lysosome lumen: 5.0, pH of cytoplasm: 7.2
36
what is the function of a lysosome?
digestion or breakdown of molecules/organelles
37
Describe the structure of the lysosome membrane
contains transport proteins
contains H+ pump that uses energy from ATP hydrolysis to pump H+ ions into the lysosome to maintain acidic pH
38
what do the transport proteins in lysosomes do?
these proteins transport products from macromolecule digestion into the cytoplasm (recycled)
39
how are molecules delivered to the lysosomes?
digestive hydrolytic enzymes are synthesized in the ER and a sugar side chain (mannose 6-P) marks the enzymes for transport to the lysosomes *side chains added in golgi*
40
what are the paths to degradation in the lysosome?
endocytosis
phagocytosis
old/worn out organelles
incorrectly synthesized proteins
41
how does endocytosis occur in the lysosome?
takes up macromolecules from extracellular fluid
molecules are enclosed in a vesicle that fuses with the lysosome
42
how does phagocytosis occur in the lysosome?
objects are engulfed to form a phagosome
phagosome fuses with lysosome
43
how are incorrectly synthesized proteins sent to the lysosomes?
sent via vesicles from golgi
44
how are old/worn out organelles sent to the lysosomes?
enclosed in a membrane (unknown origin) to form a vesicle autophagosome
the autophagosome fuses with lysosome
45
what is autophagy?
describes the digestion of old organelles
46
what are examples of lysosomal storage diseases?
I-cell disease, Tay Sachs disease
47
what are lysosomal storage diseases?
rare inherited disorders characterized by the accumulation of undigested or partially digested macromolecules which ultimately results in cellular dysfunction and clinical abnormalities
48
what clinical abnormalities can be caused by lysosomal storage diseases?
organomegaly (enlarged organs), nervous system dysfunction, ocular pathology
49
what mutations can cause lysosomal storage diseases?
1. enzyme deficiencies of lysosomal hydrolases (hydrolases not functional)
2. defective lysosomal membrane transport protein: transports degraded products out of the lysosome (build up of degraded material in lysosome)
3. defects in intracellular trafficking proteins (proteins that carry vesicles to lysosome) (harmful substances accumulate in the cell)
4. hydrolytic enzymes are secreted into extracellular space rather than being targeted to the lysosome (lysosome is non-functional)
50
what are the treatments for lysosomal storage diseases?
enzyme replacement therapy
hematopoietic stem cell transplantation (transplants cells with functional lysosomes)
gene therapy (introduce genes that encode functional proteins)
51
what is the cellular cytoskeleton?
an intricate network of protein filaments that extend through the cytoplasm with a dynamic structure (constantly changing)
52
how is the cell cytoskeleton different in eukaryotic vs prokaryotic cells?
prokaryotic filaments (MreB, FtsZ) similar to actin and microtubules in eukaryotic cells
53
what is the function of the cellular cytoskeleton?
support of cellular cytoplasm (anchor organelles)
intracellular transport
cell shape
cell motility
54
how does the cellular cytoskeleton play a roll in intracellular transport?
vesicle transport, placement of organelles, segregation of chromosomes into daughter cells during mitosis, cleavage furrow formation during animal cell cytokinesis
55
how does the cellular cytoskeleton play a role in cell motility?
cilia and flagella (microtubules and associated proteins)
actin filaments for muscle contraction
**CILIA AND FLAGELLA HAVE NO ACTIN**
56
describe the organization and structure of the cellular cytoskeleton
each filament is a polymer of subunits
subunits in a filament are held together by non-covalent bonds or hydrophobic interactions
57
what are the 3 components of the cellular cytoskeleton?
microtubules
intermediate filaments
actin filaments
58
What are intermediate filaments?
comprised of elongated fibrous proteins twisted together to form filaments (assembly process not well understood)
have great tensile strength
59
what are examples of intermediate filaments?
keratin filaments: found in hair, nails, epidermis
neurofilaments: found in axon of neuron
60
what is the function of intermediate filaments?
enable cells to withstand mechanical stress when cells are stretched
61
where are intermediate filaments found?
cytoplasm
nucleus
62
how are intermediate filaments laid out in the cytoplasm?
form a network throughout the cytoplasm surrounding the nucleus and extending out to the cell periphery
63
how are intermediate filaments laid out in the nucleus?
mesh of intermediate filaments forms the nuclear lamina, underlies and strengthens the nuclear envelope
64
what are actin filaments?
comprised of actin proteins
each actin subunit has a binding site for ATP or ADP (non-covalent binding)
actin subunits (with bound ATP) then join together to form the filament
65
what are the two forms of actin?
globular actin (g-actin) [unassembled actin]
filamentous actin (f-actin) [assembled actin-- found in filaments]
66
what happens after actin proteins join together to form the filament?
actin hydrolyzes the ATP to ADP and Pi
hydrolysis weakens the actin-actin interactions (dynamic) [filaments can disassemble]
67
what are actin filaments capped?
capped with actin-binding proteins to stabilize the filament
68
what are the two types of actin-binding proteins?
1. capping proteins: bind to the end of actin filaments and stabilize it
2. motor proteins: bind to actin filament and can move along the filament, stabilize
69
what are examples of capping proteins?
tropomodulin, profilin
70
what are examples of motor proteins?
myosin
71
actin filaments have polarity, what does this mean?
have a distinct (+) and (-) end, (+) is more dynamic
72
what are the functions of actin filaments?
skeletal muscle contraction
cleavage furrow formation (cytokinesis in animals)
cell movement
cell adhesion (adhering junctions with cytoskeletal filaments)
73
where are actin filaments located in the cell?
dispersed throughout cell, most highly concentrated in the cortex (layer of cytoplasm just beneath plasma membrane) [for support]
microvilli [for structure in the increased surface area microvilli provide]
74
what are microtubules?
long, hollow cylinders made of tubulin protein
75
what is tubulin?
heterodimer composed of alpha tubulin and beta tubulin
76
how does tubulin form microtubules?
tubulin dimers stack together to form protofilaments which form the wall of the microtubule
77
How do microtubule filaments grow?
both dimers have GDP or GTP binding site
growth occurs when GTP bound tubulin is added to the filament
subsequent to addition, GTP is hydrolyzed to GDP and Pi (makes filament unstable)
78
what part of the microtubule is polarized?
the protofilaments (+) is more dynamic and adds and loses subunits more quickly than (-) end
79
what is the function of microtubules?
support of cellular cytoplasm (anchor organelles)
intracellular transport
cell shape
cell motility
80
describe how microtubules function in intracellular transport
vesicle transport, placement of organelles, segregation of chromosomes into daughter cells during mitosis
81
describe how microtubules function in cell motility
cilia and flagella contain microtubules and associated proteins (dynein)
contain bundles of microtubules in a (9+2) format [picture below]
motor proteins interact with filaments and move along the filament
82
what is dynein?
microtubule motor protein, minus end directed motor protein
as dynein moves along bundles in cilia or flagella, causes filament to bend
83
how was the function of motor proteins discovered?
by loss of function or knockout experiments
84
where are microtubules located in an interphase cell?
centrosome is typically present on one side of the cell nucleus and an array of microtubules radiate outwards from it into the cytoplasm
85
what is a centrosome?
microtubule organizing center
86
where are microtubules located in a dividing cell?
centrosome form the organizing point (poles) of the mitotic spindle
87
What organisms don’t have centrosomes?
Some higher plants and fungi have microtubules formed from different areas around the nuclear membrane
88
What are centrosomes composed of?
Fibrous centrosomes matrix that contains gamma tubules (starts microtubule formation)
89
In animal cells, the centrosome contains:
Centrioles become basal bodies of flagella/cilia in motile cells
Centrioles organize centrosome matrix
90
What is a centromere?
Connects sister chromatids of chromosomes
91
What are kinetochores?
Complex of proteins and RNA molecules attached to the centromere
92
What are the 3 types of microtubules?
Astral microtubules
polar microtubules
Kinetochore microtubules
93
What are astral microtubules?
Anchoring spindle
Face away from the poles towards the membrane
94
What are polar (interpolar) microtubules?
Face center of cell
95
What are kinetochore microtubules?
Face center of cell face the center of the cell and contact chromosomes
96
What is dynamic instability?
Rapid interconversion between a growing and shrinking state
97
What is catastrophe?
Microtubule elongates and then abruptly switches from elongation to shortening
98
What is rescue?
Microtubule switches from shortening to elongation
99
Why do microtubules undergo dynamic instability?
Target finding: microtubules probe their environment looking for targets
Elongate to search for target, if not found Microtubule will shorten and assemble again
Contact with target: stabilizes the microtubule
100
Are all microtubules dynamic?
NO
for example, Axon microtubules used to transport vesicles carrying neurotransmitters are not dynamic
101
What are microtubules associated proteins (MAPs)?
Proteins that can bind to microtubules
Have a variety of functions including microtubule stability and motor function, can also cause disassembly of microtubules (katanin)
102
What is kinesin?
(+) end directed motor protein
103
Skeletal muscle fibers are made of:
Actin filaments
104
What is myosin II?
Action binding protein that binds to the actin filaments
105
What protein is a superfamily?
Myosin is in a superfamily of proteins that contain many different forms of myosin
106
What kind of protein is myosin II?
A (+) end directed motor protein, also interacts with microtubules
107
How does myosin II produce movement?
ATP hydrolysis
108
What is the structure of myosin II?
Head domain (motor domain) and tail domain
Uses ATP hydrolysis (removal of phosphate) to move along the actin filament
109
Describe ATP hydrolysis
Releases energy to power movement of motor protein
Change conformation of head domain and allows it to bind and release from the filament
110
Individual molecules of myosin can what?
Link together to form myosin chains (bundles of thick filaments)
111
What is a sarcomere?
Functional unit of skeletal muscle
112
What is the structure of a sarcomere?
Each sarcomere contains bundles of thick and thin filaments
Thick consisting mainly of myosin
Thin consisting mostly of actin (and troponin, tropomyosin)
113
How does muscle contraction work?
Actin filaments slide over the myosin filaments
The myosin II has ATP bound to the head region, and the hydrolysis of ATP causes the myosin head to bind to actin
114
Further describe muscle contraction
Myosin moved along the actin towards the (+) end of the filament: sliding of myosin over actin
ATP rebinds to myosin: causes myosin to release from actin
115
What does calcium do for muscle contraction?
Regulates the interaction between actin and myosin
116
What happens when there is an absence of calcium?
Tropomyosin/troponin complex: inhibitory protein complex that binds to actin and prevents association with myosin
117
What happens when there is calcium present?
Tropomyosin/troponin is released from actin filament allowing myosin to bind (uncovers myosin binding site)
118
What is the sarcoplasmic reticulum?
Refers to the endoplasmic reticulum in skeletal muscle cells
119
What activates a rise in intracellular calcium?
Cell signaling (ex. Neurotransmitters)
120
What is the cell signaling pathway?
Neurotransmitter binding activated an enzyme: phospholipase C
Phospholipase C breaks down a phospholipid into 2 molecules (one being IP3: inositol triphosphate)
IP3 binds to calcium ion channels on membrane of smooth ER causing channels to open
121
What is the structure of the nucleus?
Surrounded by a double membrane (nuclear envelope)
Membrane contains pores that allow for transport of molecules into/out of the nucleus
122
What types of molecules are transported into/out of the nucleus?
Into: enzymes involved in DNA replication/transcription
Histone proteins
Out: mRNA, ribosomes
123
What is the function of the nucleolus?
Produces ribosomes needed for protein synthesis/translation
124
What is the function of the nucleus?
Contains genetic material (DNA)
Organization (chromatin, chromosomes)
Site of DNA and RNA synthesis
125
What is chromatin?
DNA and bound histones, tightly packed DNA
126
Why is chromatin bound tightly?
Positive histones and negative DNA
127
when is chromatin seen in the cell cycle?
Interphase (G1, G2, S)
128
What are chromosomes?
Condensation (unpacking) of chromatin
129
Where are chromosomes in the cell cycle?
M phase
130
What is the general structure of the endoplasmic reticulum?
Organized into branching tubules and flattened sacs that extend through the cytoplasm, tubules interconnect so the membrane forms a continuous sheet
Membrane enclosed a single internal space called the lumen
131
What is the difference between the rough and smooth er?
Rough: attached ribosomes on the membrane
Smooth: no ribosomes
132
What is the function of the rough ER?
Protein synthesis and protein folding
133
What proteins are associated with the rough ER?
Transmembrane proteins, water soluble proteins
134
What are transmembrane proteins?
Proteins that span the width of the membrane (plasma membrane or organelle membrane)
Examples: integrins, channel proteins, etc
135
What are water soluble proteins?
Protein that is fully translocated across the ER membrane and released into the ER lumen (resident ER proteins) OR proteins destined for secretion or lumen of an organelle (hormones)
136
What are the functions of the smooth ER?
Lipid synthesis: phospholipids, fatty acids, steroids
Carbohydrate metabolism
Detoxification of the cell
Calcium storage
137
What type of cells have a large ER?
Liver cells (due to detoxification properties)
