Cytoplasm Flashcards
1
Q
Cytoplasm consists of
A
- cytosol ( fluid component)
- organelles
- inclusion
- cytoskeleton
2
Q
Organelles
A
- Ribosomes
- rER and sER
- Golgi apparatus
- Lysosome
- Mitochondria
3
Q
Inclusions (storage)
A
Glycogen
Lipid droplets
Lipofuscin & melanin
4
Q
Components of Cytoskeleton (gives cell its shape)
A
- Microtubules and centrosome
- Microfilaments (actin filaments)
- Intermediate filaments
5
Q
Ribosome job
A
- non-membrane bound
- very large enzyme system
- create place for AA arrangement and to catalyze the peptide bond formation in the process of protein synthesis
- translation (mRNA—> polypeptide chain)
- protein synthesis
6
Q
Ribosomes structure
A
- two subunits (60S and 40S)
Each subunit has strand of rRNA - functional ribosome = 80S
7
Q
Types of ribosomal arrangements
A
- Free or polyribosomes—> released in ER
- Fixed to ER —> rough ER
8
Q
Where does translation occur?
A
Cytoplasm
9
Q
What does translation require?
A
- rRNA
- mRNA
- tRNA
10
Q
What happens during translation if the sequence in DNA is mutated?
A
Protein formed will be defective
11
Q
Translation is using ___ as a template to form ___.
A
mRNA (nucleotide sequence)
Protein chain (amino acid sequence)
12
Q
Where does synthesis of rRNA Occur?
A
Nucleolus
13
Q
What catalyzes the synthesis of rRNA?
A
RNA polymerase I
14
Q
What does rRNA do?
A
Forms ribosomes when bound to other ribosomal proteins
15
Q
What is mRNA?
A
Single stranded molecule with nucleotides
Carries the genetic codes (transcribed from DNA) as codons, determine what AA will be added
16
Q
What is the start codon? what does it do?
A
AUG
Initiates protein synthesis
17
Q
What are the stop codons? What do they do?
A
UAA, UAG, UGA
stop protein synthesis
18
Q
What does tRNA do?
A
Transfer a certain AA molecule to be added in a proper sequence to the growing polypeptide chain, dictated by the sequence of codon on mRNA.
19
Q
Shape of tRNA
A
Clover leaf
20
Q
Where are free ribosomes located?
A
Cytoplasm
21
Q
What can free ribosomes form?
A
Polyribosomes or polysomes ( cluster of ribosomes)
22
Q
What do polyribosomes or polysomes do?
A
Translate a single stand of mRNA
23
Q
Where are proteins destined for?
A
Self use in the nucleus, cytoplasm, mitochondria
24
Q
Where are membrane bound ribosomes located?
A
Surface of ER to become rough ER
25
Product of membrane bound ribosomes are destined for what?
Export out of cell —> cell secretion (enzymes)
26
Two types of ER
rough and smooth
27
Where is the rough ER found?
Adjacent to the nucleus
28
What happens to AA processed by the rough ER?
Will be packaged by golgi and secreted (in calcium dependent manner) for use by other cells.
** these proteins are usually enzymes
29
What happens to the raw material that is endocytosed by a cell?
Processed to become the AAs that will be recycled to participate in the process of protein synthesis again.
30
Protein synthesis process in rER
Start at mRNA 5’ end —> ribosome with signal sequence finds surface receptor to attach to —> signal sequence removed —> protein completed inside and ribosome dissociates —> new polypeptide chain is released in rough ER
31
Structure of sER compared to rER
Smooth= tubular and saccular
Rough= cisternal
32
Functions of smooth ER
- storage of calcium in skeletal and cardiac muscle
- storage of glycogen in liver cells (hepatocytes) “energy storage”
- transport of protein bits from rER to Golgi
- HORMONE SYNTHESIS (in adrenal glands)
33
Cause of Neonatal Jaundice
Normal breakdown of RBCs produce Bilirubin (pigment compound) —> cleared out by liver and excreted in bile
Underdeveloped sER —> Bilirubin is not cleared from blood
34
What is the structure of the Golgi apparatus?
Stack of flattened, slightly curved membrane- bound cisternae
35
Forming face of Golgi
Where vesicles are coming in from sER
“cis face”
36
Maturing face of Golgi
“Trans face”
37
Glycosylation
Addition of Oligosaccharide
- important for proper protein folding and stability to prevent degradation
38
Function of Golgi
Glycosylation —> proteins packed for final destination —> secretory vesicles —> secretory granules —> exocytosis
39
3 leveled of cisternae of Golgi
1. Cis face (forming face)
- closest to rER and nucleus
2. Medial compartment (intermediate face)
3. Trans face
- facing plasma membrane
40
Job of cis face of Golgi
Receive transfer vesicles (from rER)
41
What is the trans face of the Golgi associated with?
Trans Golgi network (TGN)
42
Where does protein sorting occur?
TGN - trans Golgi network
43
What are proteins sorted into in the TGN?
1. Secretory vesicles— destined to extracellular (hormones, neurotransmitters, collagen)
2. Plasma membrane — protein as integral part of PM
3. Lysosomes — enzymes stored in lysosome
44
What’s bigger? Rough ER or Golgi cisternea?
Rough ER
45
What are the degrative enzymes that lysosomes possess?
Proteases
Lipases
Nucleases
Phosphatase
Phospholipases
Sulfatases
B- glucuronidase
46
Two main processes involving lysosomes
Heterophagy and autophagy
47
Autophagy
Cell uses lysosomes to dispose of excess or no functioning organelles or membranes
48
What is autophagy important for?
Recycling amino acids
Especially for long half life proteins, membrane proteins, and extracellular proteins
49
Heterophagy
Done by macrophages and neutrophils
50
Similarities between secretory vesicles and lysosomes
1. Originate from trans face of Golgi
2. Membrane bound
3. Globular in shape
51
Differences between secretory vesicles and lysosomes
1. SV contain proteins meant to be secreted out of cell (exocytosis) -- lysosomes contain proteins needed by cell to carry out autophagy and Heterophagy within cell
2. SV migrate towards cell membrane for exocytosis — lysosomes float around the cytoplasm until used
3. SV final destination is extracellular — lysosome final destination within cytoplasm
52
What do mitochondria do?
Make ATP
53
Why are mitochondria highly folded?
Higher surface area
54
What are the folds of mitochondria called?
Cristae
55
What are the functions of mitochondria?
- Carries enzymes for aerobic respiration
- production of ATP
56
What are the structural components of mitochondria?
1. Outer membrane
2. Intermembranous space
3. Inner membrane: forming cristae
4. Inner cavity: filled with mitochondrial matrix
57
Glycolysis
Converts glucose anaerobically to pyruvate
58
Where does glycolysis occur?
Cytoplasm
59
What happens to the puruvate produced in glycolysis?
Imported into mitochondria and oxidized to CO2 and H2O.
60
What is the Krebs / TCA cycle? (Basic)
Chain of enzymatic rxns used by most organisms to produce energy by aerobic respiration.
61
Examples of inclusions
Glycogen
Lipid droplets
Lipofuscin and melanin
62
Dark granules in TEM image
Lipid droplets
63
Where are Lipofuscin found?
No dividing cells (cardiac muscle cells, neurons)
64
Functions of cytoskeleton
1. Structure
2. Movement
65
Components of cytoskeleton
1. Microfilaments
2. Intermediate filaments
3. Microtubules
66
Microtubules
- thickest
- made of alpha Tubulin and beta tubulin subunits
- hollow, tube like
67
TEM image of Microtubules and actin Microfilaments
Green from nucleus—> Microtubules
Red around —> actin
68
Where do Microtubules develop from?
MTOC - Microtubules organizing center
69
What does tubulin in MTOC act as?
Nucleating sites for further polymerization
70
What are two motor proteins?
Dynein and kinesin
71
What does the motor proteins walk on?
Microtubules
72
What allows for movement of organelles on the surface of Microtubules?
Motor proteins ( dynein and kinesin) —> walk on MT —> drag organelles along MT
73
What are the core structures of cilia made of?
Microtubules
74
What is the arrangement of cilia?
9+2
75
What surface of the cell are cilia found on?
Apical (top)
76
What’s longer, cilia or microvilli?
Cilia
77
What are Microfilaments made of?
Proteins called actin (circle/globular shaped)
78
How many strands does each actin filament have?
2
79
What are the bead like subunits that assemble a strand of actin called?
G-actin = actin monomer
80
Once g-actin are polymerized into a strand what are they called?
F-actin (look like fiber)
81
When two strands of F-actin wind around eachother what are they then called?
Microfilament
82
Summary of microfilament structure
G-actin monomer polymerized to forms
—> F-actin strand —> strands wind around eachother to form —> microfilament
83
Where are microfilaments found?
Core of microvilli
(“Fuzz” in cross section of
Microvilli)
84
What does actin play an important role in?
Cell movement
85
How does actin contribute to cell movement?
Anchoring to plasma membrane via intrinsic membrane proteins
Hold microvilli up straight —> gives structure/strength
86
Why are microfilaments important in cytokinesis?
Formation of contractile ring
87
What is the function of intermediate filaments?
Structural: Linking intracellular structures and to plasma membranes
88
What is the Diameter of Microtubules?
About 25 nm
89
What is the diameter of an actin monomer?
6 nm
90
What is the diameter of intermediate filaments?
8-10 nm
91
What are intermediate filaments made of?
Filaments of protein
92
Examples of intermediate filaments
- cytokeratin (epidermis) — epithelial origin
- vimentin (muscles) — mesodermal origin
- desmin — muscle cell origin
- neuro-filament proteins — nerve cell origin
- lamin — formation of nuclear membrane, located at inner side of nuclear membrane
