Cell Organelles

Front 1

Prokaryote

Back 1

Prior to a nucleus

Front 2

Eukaryote

Back 2

True nucleus

Front 3

Karyon

Back 3

Greek referring to nucleus

Front 4

Heterochromatin

Back 4

Highly condensed and transcriptionally inactive DNA.

Front 5

Euchromatin

Back 5

Much less condensed, transcriptionally active.

Front 6

Nucleolus

Back 6

Contains the genes that synthesize rRNAs. The intensity of the nucleolus results from the ribosomes in the process of assembly.

Front 7

Chromatin

Back 7

Complex of DNA, histones, and nonhistone proteins in eukaryotic cells. The material of which chromosomes are made.

Front 8

Histones

Back 8

One of a group of small abundant proteins rich in positively-charged amino acids that form the nucleosome with the DNA of eukaryotes.

Front 9

Nucleosome

Back 9

Consists of the core histones:
1. H2A
2. H2B
3. H3
4. H4

The linker histone H1, and DNA loop.

Front 10

Territories of the nucleus

Back 10

Two copies of each chromosome occupy the same relative positions in the nucleus.

Front 11

Nuclear transport in ribosome assembly

Back 11

1. Ribosomal proteins are made in the cytoplasm and brought into the nucleolus
2. Assembled ribosomal subunits are exported to the cytoplasm

Front 12

3 major types of RNA transcribed from DNA

Back 12

1. Ribosomal RNA (used to make new ribosomes
2. Messenger RNA (codes for proteins)
3. transfer RNA (one tRNA representing each amino acid used during translation to make polypeptide chains out of mRNA)

Front 13

Substances moved in and out of nucleus and directions they move in

Back 13

1. Nuclear proteins (histones, transcription factors) move into the nucleus
2. Ribosomal proteins and subunits move into and out of the nucleus
3. mRNAs, tRNAs move out of the nucleus
4. Ions, ATP, molecules freely diffuse in and out of the nucleus

Front 14

Structure of nuclear envelope

Back 14

Two membranes with nuclear pore complexes forming openings.

Front 15

How does the nuclear pore complex differ from the ER and mitochondrial protein import processes?

Back 15

The nuclear pore can allow large sizes of macromolecules in and can transport completely folded proteins and large complexes.

In the ER and mitochondria, only unfolded proteins are small enough to cross the membrane.

Front 16

Targeting sequence for nuclear import.

Back 16

Nuclear localization sequence

Front 17

Targeting sequence for nuclear export

Back 17

Nuclear export sequence

Front 18

Karyopherin

Back 18

Recognize targeting signals and move proteins in and out of the nucleus.

Front 19

Importin

Back 19

Imports proteins into the nucleus then releases its target and recycles back to the cytoplasm.

Front 20

Exportin

Back 20

Exports proteins out of the nucleus, dissociates and recycles back to the nucleus.

Front 21

Role of Ran in nuclear import

Back 21

Ran/guanosine diphosphate is present in high concentration in the cytoplasm whereas Ran/guanosine triphosphate is in high concentrations in the nucleus.
1. When importin brings a protein into the nucleus, RAN/GTP binds and releases importin and the imported protein and moves the importin to the cytoplasm
2. In the cytoplasm GTP is cleaved to GDP releasing importin back into the cytoplasm.

Front 22

What is the relationship between splicing and export of a newly transcribed mRNA?

Back 22

If you inhibit splicing you also inhibit export of the mRNA.

Front 23

What is a way that HIV takes advantage of nuclear localization?

Back 23

HIV viral proteins contain nuclear localization sequences allowing viral nucleoprotein complexes to be actively imported into the nucleus of non-dividing cells.

Export of viral mRNA also uses host machinery.

Front 24

Perinuclear cistern

Back 24

The space between the inner and outer nuclear membranes.

Front 25

What types of proteins are transcribed on free ribosomes?

Back 25

Proteins that will remain in the cytoplasm.

Front 26

What types of proteins are transcribed on bound ribosomes?

Back 26

Proteins that will go to lysosomes, are secreted by the cell, or will be embedded in the plasma membrane.

Front 27

ER signal sequence

Back 27

Directs the ribosomal complex to the ER membrane.

Stretches of ~20 hydrophobic amino acids that allow the polypeptide to span the lipid bilayer as a helix.

Front 28

Signal recognition particle

Back 28

Binds to the sequence and brings it to the signal recognition particle receptor on the surface of the ER.

Front 29

Signal peptidase

Back 29

Cleaves the signal sequence as the protein is strung through the ER membrane.

Front 30

Stop transfer sequence

Back 30

Required for the insertion of membrane proteins into the endoplasmic reticulum membrane.

Front 31

Asparagine-linked glycosylation

Back 31

Most proteins in the ER lumen undergo this N-linked glycosylation which helps in correct protein folding.

Front 32

Protein disulfide isomerase

Back 32

Catalyzes the oxidation of free sulfhydryl groups to form disulfide bonds. This aids in correct protein folding.

Front 33

Glycosylphosphatidylinositol (GPI) anchor

Back 33

A GPI anchor acts as a sorting signal to direct these membrane proteins to special regions of the plasma membrane (caveolae).

Front 34

Chaperones

Back 34

Help fold proteins that enter the ER. Often part of the hsp70 family.

Front 35

Role of smooth endoplasmic reticulum in the liver.

Back 35

Detoxification. It contains some of the membrane-bound enzymes used to degrade certain hormones and to neutralize noxious substances.

Front 36

Major function of smooth ER in all cells

Back 36

Synthesis of lipids:
1. Phospholipids
2. Cholesterol

Front 37

Three ways that lipids synthesized on the smooth ER reach other membranes in the cell

Back 37

1. Vesicles bud off and move along cytoskeletal elements by motor proteins to other membranes with which they fuse
2. Diffuse to the rough ER which is continuous with the smooth ER
3. By transfer proteins to organelles like the mitochondria that dont receive vesicles from the ER

Front 38

Phospholipid transporting protein

Back 38

Carries phospholipids to another membrane.

Front 39

Flippase

Back 39

Moves phospholipids from one side of the bilayer to the other.

Front 40

What role does smooth ER play in the testis?

Back 40

Steroid synthesis and lipid metabolism.

Front 41

Loss-of-function disorder

Back 41

Occurs when an aberrant protein is made and cleared efficiently so resulting in an loss of that protein's function in the cell.

Front 42

Gain-of-toxic-function disorder

Back 42

Occurs when an aberrant protein is made and cannot be cleared so accumulates in the cell causing damage.

Front 43

What does the most common mutation (Phe508) do to the CFTR in Cystic Fibrosis.

Back 43

The CFTR protein can still function normally, but because it is slightly misfolded it is trapped in the ER and then degraded.

Front 44

Gain-of-toxic function in alpha1-antitrypsin disease

Back 44

Accumulation of undegraded mutant protein in hepatocytes can lead to cirrhosis of the liver.

Front 45

Loss-of-function in alpha1-antitrypsin disease

Back 45

Its hindered secretion is responsible for lung disease.

Front 46

What are the steps in a misfolded protein getting destroyed by the cell?

Back 46

1. Persistent interaction with the chaperone is fruitless and N-linked sugar is edited causing it to be sent towards degradation
2. Protein is dislocated from the ER lumen to the cytoplasm
3. N-linked sugar is removed by N-glycanase
4. Protein is tagged with ubiquitin
5. Protein is degraded by proteasome

Front 47

What signal causes ER retention of native proteins?

Back 47

KDEL sequence
Lysine, aspartic acid, glutamic acid, leucine

Front 48

How does tetanus toxin work?

Back 48

It cleaves receptors used for the movement of synaptic vesicles in inhibitory neurons blocking secretion and leading to convulsive contractions (only stimulatory neurons are functioning).

Front 49

Botulinum toxin

Back 49

Cleaves receptors causing neurons to be unable to release acetylcholine at the neuromuscular junction, leading to descending paralysis from the cranial nerves to the extremities.

Front 50

How does a lysosome prevent itself from destroying itself?

Back 50

Special coating on the interior of lysosomal membrane preventing the acid hydrolases from digesting its own membrane components.

Front 51

What signal targets a protein to lysosomes?

Back 51

A mannose 6-phosphate group is added to the N-linked sugar on the protein.

Front 52

What is the default pathway if no other signal is added to the vesicle?

Back 52

Constitutive secretion

Front 53

What is the default pathway for proteins if they are not edited along the way?

Back 53

Constitutive secretion

Front 54

What enzyme is missing in Tay-Sach's disease?

Back 54

Hexosaminidase A which breaks down glycolipids in the lysosomes.

Front 55

Signal sequence for mitochondrial import

Back 55

It is an alpha helix with positively charged residues on one side and nonpolar residues on the opposite face.

Front 56

TOM complex

Back 56

Translocator of the outer membrane

Front 57

TIM complex

Back 57

Translocator of the inner membrane

Front 58

OXA complex

Back 58

Mediates insertion into inner membrane.

Front 59

Use of chaperone proteins in mitochondrial protein targeting.

Back 59

Chaperone proteins maintain protein in the partially unfolded position to allow it to be fully strung into the mitochondria.

Front 60

Two ways to get something into the inner membrane

Back 60

1. Matrix acts as an intermediate and you send it out through OXA complex
2. There can be a second signal that acts like a stop transfer sequence

Front 61

TIM22

Back 61

Specialized complex for the translocation of multipass membrane proteins.

Front 62

Story of the traveler in the mitochondria

Back 62

Tom either can have a ticket and go through Tim23 to the matrix, or bribe Tim22 to let him into the inner membrane.

After he is in the matrix he has to have a special ticket to get the hot german girl Oxa to let him into the inner membrane space.

The Homeboys that reside in the matrix are only allowed to get past Oxa if they get a ticket.

Front 63

What are electron-dense paracrystalline structures in peroxisomes?

Back 63

Urate oxidase

Front 64

Functions of peroxisomes

Back 64

1. Oxidation of fatty acids and other lipids
2. Oxidation of purines, amino acids, hydroxy acids, and other metabolites
3. Biosynthesis of cholesterol, bile acids, ether based lipids
4. Contain large amounts of catalase which can convert excess hydrogen peroxide into water

Front 65

What are the two import signals into peroxisomes?

Back 65

1. PTS1 - found in most matrix proteins, the three final C-terminal amino acids are Ser-Lys-Leu. Signal not cleaved after translocation
2. PTS2 - found in a subset of matrix proteins within the first 20-30 amino acids. Signal can be cleaved

Front 66

Steps in peroxisomal matrix protein import

Back 66

1. Binding of protein or complex by PEX5
2. Transport
3. Docking on peroxisome
4. Translocation through PEX complex
5. Receptor recycling

Front 67

Hypothesis on why peroxisomes can import huge complexes but no translocation channel has been visualized.

Back 67

After bringing a protein or complex into the peroxisome, the translocation channel is rapidly disassembled to prevent proteins from being able to escape.

Front 68

Phagocytosis

Back 68

Cell eating (large particles)

Front 69

Pinocytosis

Back 69

"cell drinking" or fluid phase

Front 70

Receptor mediated endocytosis

Back 70

Active uptake of external and plasma membrane proteins

Front 71

Transcytosis

Back 71

Cells that line certain cavities will move substances from one side to another.

Front 72

How are bacteria and damaged cells recognized and engulfed by the immune system?

Back 72

IgG antibodies are released and bind to epitopes on the antigen. The Fc receptors are recognized by the plasma membrane of macrophages and neutrophils initiating phagocytosis.

Front 73

Clathrin coated pits

Back 73

Clathrin is located under receptors and helps form the endosome that brings substances into the cell.

Front 74

Transcytosis

Back 74

The uptake of a substance from one domain of the plasma membrane and the delivery of that substance to another domain of the plasma membrane.

Front 75

Caveolae

Back 75

A GPI anchor is used to form buds.

Front 76

Use of transcytosis in the mammary gland

Back 76

1. Secreted IgA enters the mother's mammary duct and are released into the milk
2. Maternal IgA travels to the infant's small intestine
3. Maternal IgAs bind to Fc receptors on apical surface
4. The receptor and IgAs are internalized and put into infant's blood stream
5. Provides immunological protection

Front 77

Autophagy

Back 77

Protein trafficking distinct from plasma membrane that leads to lysosomal degradation. It is how cells destroy their own organelles.