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Block 0 > Cell Organelles > Flashcards

Cell Organelles Flashcards

1
Q

What does the cell/plasma membrane separate?

A

The external (extracellular) and internal (intracellular) environments

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2
Q

Cytosol (AKA Cystoplasm)

A

Intracellular gel like substance filled with proteins, lipids, sugars, nucleic acids, and organelles

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3
Q

What is the plasma membrane composed of?

A

Phospholipid bilayer and cholesterol

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4
Q

Phospholipid structure

A

Glycerol and phosphate (hydrophilic) head groups

Fatty acid tails (Hydrophobic)

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5
Q

Integral protein

A
  • Protein that spans both sides of the plasma membrane
  • Amphipathic
  • Can include: Receptors, Linkers, Transporters, Enzymes, and Structural Proteins
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6
Q

Peripheral protein

A

Proteins that are loosely associated with one side of the plasma membrane

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7
Q

What does it mean when a protein is glycosolated?

A

It has a sugar chain attached to it

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8
Q

What does it mean that the cell membrane is fluid?

A

The lipids and proteins of the cell membrane can move and rearrange on the cell membrane

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9
Q

Amphipathic

A

A molecule with both polar (hydrophilic) and non-polar (hydrophobic) properties

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10
Q

Saturated fatty acids

A

Each carbon in the chain is linked to the next with a single bond, and each carbon atom is “saturated” with hydrogen

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11
Q

Unsaturated fatty acids

A
  • Fatty acid with at least one carbon = carbon double bond

- Creates kinks in the tail, which increases fluidity and decreases stability of the cell membrane

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12
Q

Cholesterol

A
  • Large hydrophobic carbon ring structure
  • Small hydrophilic alcohol head group
  • Inserts between fatty acid tails of phospholipids in membrane
  • Increases membrane stability
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13
Q

What decreases membrane fluidity (increases stability)?

A
  • Longer fatty acid tails
  • More saturated fatty acids
  • More cholesterol
  • Lower temperatures
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14
Q

Glycolipids

A

Lipids with sugar chains added on the external membrane

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15
Q

Glycosylation

A

The process of adding sugar chains to lipids

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16
Q

Receptor proteins

A
  • Integral protein

- Binds to ligands at the cell’s surface –> changes the protein’s shape –> actives signals inside the cell

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17
Q

Linker proteins

A
  • Integral protein

- Connects cytoskeleton to the plasma membrane and external environment

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18
Q

Transporter proteins

A
  • Integral protein

- Pumps/channels that move molecules across the plasma membrane

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19
Q

Structural proteins

A
  • Integral protein

- Binds cells together into tissues

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20
Q

Glycocalyx

A
  • External glycoproteins/glycolipids
  • Funtions include:
    1. ) Cell attachment
    2. ) Protection from mechanical stress
    3. ) Protein scaffold or retainer
    4. ) Cell recognition
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21
Q

Lipid Rafts

A
  • Microdomains of membrane
  • High cholesterol and sphingolipids
  • Consolidate receptors and signaling proteins
  • Increases speed and efficiency of cell signaling at the cell’s membrane
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22
Q

Plasma Membrane Functions

A
  • Defines cell boundaries
  • Semi-permeable: restricts what enters/exits the cell
  • Establishes electro-chemical gradients
  • Cell-to-cell communication
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23
Q

How do the inner leaflet lipids differ from that of the outer leaflet lipids?

A
  • The amount of membrane protein will vary highly depending on the type of cell and its function
  • The outer leaflet will have glycolipids and higher amounts of Phosphatidylcholine (PC) and Sphingomyelin/sphingolipids (SM)
  • The internal leaflet has Phosphatidylserine (PS), Phosphatidylinositol (PI), and Phosphatidylethanolamine (PE)
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24
Q

Ribosomes structure

A
  • rRNA/protein complexes of 2 subunits
  • Prokaryotes: 50s and 30s subunits
  • Eukaryotes: 60s and 40s subunit
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25
Q

Ribosomes function

A

“Reads” messenger RNA (mRNA) to synthesize proteins (translation)

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26
Q

Free ribosomes

A
  • Free floating in the cytosol

- Synthesize proteins for the cystosol, mitochondria, nucleus, and peroxisomes

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27
Q

Membrane bound ribosomes

A
  • Bound to the rough ER

- Synthesize proteins for the ER, golgi, plasma membrane, lysosomes, or secretion

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28
Q

Rough Endoplasmic Reticulum (ER) structure

A
  • Network of membrane stacks

- Ribosomes dock at the surface

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29
Q

Rough Endoplasmic Reticulum (ER) function

A
  • Protein folding with chaperone proteins in the rough ER
  • Post-translational modification such as N-linked glycosylation and di-sulphide bonds
  • Fatty acid, cholesterol, and phospholipid synthesis
  • Quality control: misfolded proteins are tagged with ubiquitin and degraded by proteasomes
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30
Q

Describe the sequence of events of the Signal Recognition Particles (SRP)

A
  • Binds to signal peptide on new proteins and stops translation
  • Carries the ribosome and mRNA to the rough ER and binds to the translocator protein on the ER surface
  • Translocator forms a pore for the to be translated protein
  • Translation resumes and the new protein is extruded into the rough ER lumen
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31
Q

Smooth ER structure

A
  • No ribosomes

- More tubular shape

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32
Q

Smooth ER function

A
  • Synthesis of lipids and cholesterol
  • Detoxification (especially important in the liver)
  • Membrane production
  • Glycogen formation (formed and stored in the smooth ER)
  • Stores calcium ions (especially important in muscle tissue)
  • Steroid synthesis (especially important in endocrine tissues)
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33
Q

Golgi Apparatus structure

A
  • Usually near the nucleus
  • Series of membrane stacks called cisternae
  • Two sides:
    1. ) Cis-Golgi: closer to rough ER, entry point into the Golgi
    2. ) Trans-Golgi: further from ER, exit point out of the Golgi
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34
Q

Golgi Apparatus function

A
  • Sort proteins for shipping around cell
  • Further protein modification: Add (O-linked glycosylation), trim, or move sugars on proteins
  • Pack proteins into vesicles for secretion
  • Mannose-6-phosphate addition: special modification for lysosomal enzymes
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35
Q

Golgi Transport - Anterograde

A

COPII protein coated vesicles move from the rER –> Golgi –> Cis-Golgi –> Trans-Golgi

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36
Q

Golgi Transport - Retrograde

A

COPI protein coated vesicles moves from the Trans-Golgi –> Cis-Golgi –> rER

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37
Q

Golgi Transport - Transport to Endosomes and Cell Membrane

A

Clathrin protein coated vesicles bud off the trans-Golgi to endosomes and the cell membrane (secretion)

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38
Q

Constitutive Secretory Pathway

A

Protein vesicles continuously released from the Trans-Golgi to the cell membrane for release

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39
Q

Regulated Secretory Pathway

A

Vesicles storing products (secretory vesicles) wait for external signal before release

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40
Q

Mitochondria - Basic Structure

A
  • Rod/fiber/sphere shaped

- Double membrane with cristae folds

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41
Q

Mitochondria - Outer Membrane

A

Permeable to small molecules and ions

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42
Q

Mitochondria - Inner Membrane Folds: Cristae

A
  • Less permeable than outer membrane
  • Folds (cristae) increase surface area
  • Contains the electron transport chain (ETC) proteins
  • Contains ATP synthase for oxidative phosphorylation
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43
Q

Mitochondria - Intermembrane Space

A
  • Contains protons (H+)

- Contains cytochrome C

44
Q

Mitochondria - Matrix

A
  • Inside of the inner membrane
  • Enzymes for citric acid cycle (AKA Kreb’s or TCA cycle) and fatty acid oxidation
  • Has it’s own DNA/RNA: mitochondria self replicate
45
Q

Mitochondria - Function

A
  • Energy and heat production
  • TCA cycle and fatty acid oxidation produce ATP and NADH
  • NADH passes electrons through the ETC which pumps H+ into the intermembrane space
  • Protons flow through the ATP synthase protein to make to make ATP
  • These processes also produce heat
46
Q

Mitochondria and Apoptosis

A
  • Various stressors on the cell increase the permiability of the mitochondria membranes
  • This releases cytochrome c into the cytoplasm which is a major trigger for apoptosis
47
Q

Peroxisome structure

A
  • Small round organelles

- Single membrane

48
Q

Peroxisome function

A
  • Oxidation (breakdown) of long chain (18+ carbon) fatty acids into smaller pieces so that they can be metabolized for energy
  • This oxidation produces hydrogen peroxide (H2O2) which is highly reactive and can damage the cell
  • Peroxisomes contain catalase enzymes to break down H2O2 into water and oxygen
  • Peroxisomes also detoxify, and break down alcohol, methanol, and formaldehyde into harmless metabolites (especially important in the liver)
49
Q

Lysosome structure

A
  • Round membrane organelles
  • Filled with enzymes
  • Low pH (due to proton pumps in membranes)
50
Q

Lysosome function

A
  • Mannose-6-phosphate modification targets proteins to lysosome
  • Degrade macromolecules
  • Degrade pathogens
  • Degrade organelles (Autophagy)
51
Q

Endocytosis

A
  • The uptake of substances through the membrane
  • Three main types:
    1. ) Pinocytosis
    2. ) Receptor-Mediated Endocytosis
    3. ) Phagocytosis
52
Q

Pinocytosis

A
  • Type of endocytosis
  • “Cell Drinking”
  • Update of fluids and small particles
  • Occurs continually for most cells
  • Calveolae: vase shaped indentations formed by protein called caveolin which works with the cholesterol/lipid content of the membrane to pinch of the calveolae. This is the most common type of pinocytosis which is used to continuously and nonselectively uptake fluid from the environment.
53
Q

Receptor-Mediated Endocytosis

A
  • Specific type of endocytosis where uptake is aided by receptors
  • Allows cells to selectively ingest compounds
  • Clathrin-Coated Vesicles: formed when receptors are bound and clathrin proteins adhere to the membrane
54
Q

Phagocytosis

A
  • Type of endocytosis
  • “Cell Eating”
  • Uptake of large structures or cells
  • Actin-mediated: pseudopods extend out from the membrane to surround the target, which is mediated by actin.
  • Critical in immune functions: used by Macrophages and Neutrophils
  • Vesicles are called phagosomes which often merge with lysosomes
  • Can also be receptor-mediated
55
Q

Exocytosis

A
  • Release of substances through the cell membrane

- Releases waste products or other products such as hormones or neurotransmitters

56
Q

Endosome

A
  • Temporary sorting center that vesicles enter

- Slightly lower pH separates receptor from cargo

57
Q
  • In exocytosis, vesicles fuse to membranes via what?

- What must be present to mediate fusion?

A
  • SNARE proteins

- Ca2+ ions which allow binding of the fusion proteins

58
Q

What is needed for neurotransmitter release?

A
  • High enough concentration of calcium ions (CA2+)
59
Q

What are the three categories of cytoskeleton components?

A
  1. ) Microfilaments (Largest)
  2. ) Intermediate filaments (Intermediate)
  3. ) Microtubules (Smallest)
60
Q

Microtubules (MT) general information

A
  • Composed of tubulin dimers
  • Largest component of the cytoskeleton
  • GTP for assembly
  • Over time GTP is hydrolyzed to GDP which causes the subunits to become less stable
  • Polar structures: new tubulin at the (+) end, (-) end is embedded in MT organizing center (MTOC)
  • MTs grow out from center towards cells periphery
  • Forms tracks for moving cellular structures throughout the cell
61
Q

Microtubule Organzing Center (MTOC)

A
  • Also called the Centrosome
  • Is a pair of 2 centrioles
  • A centriole is composed of 9 MT triplets
  • Located close to the cell nucleus
  • Stabilizes (-) end of MT
  • Initiates formation of new MT
  • Very important for mitosis and formation of cilia/flagella
62
Q

What causes an MT to rapidly break down and shrink?

A

When enough of the tubulin subunits hydrolyze GTP to GDP which reduces binding affinity

63
Q

What can stabilize MTs?

A

Binding of specialized proteins can stabilize MTs at certain lengths and prevent depolymerization

64
Q

Microtubule functions

A
  • Maintain cell shape
  • Form tracts for intracellular transport
  • Form core of cillia/flagella
  • Important for cell migration
  • Form mitotic spindle during cell division
65
Q

Intermediate Filaments (IF)

A
  • Mid sized components of the cystoskeletal
  • Non-polar
  • Structurally very stable, no enzymatic activity
  • Self-assembling
66
Q

Types of intermediate filaments

A
  1. ) Desmin - in muscle cells
  2. ) Keratin - in epithelial cells
  3. ) Neurofilaments - in neuronal cells
  4. ) GFAP - in glial cells
  5. ) Vimentin - in mesenchymal cells (fibroblasts, endothelial cells, macrophages)

Cool note: This can be used to determine the origin of cancer cells that have metastasized

67
Q

Intermediate Filament function

A
  • Maintain cell shape
  • Provide mechanical strength to cells and tissues
  • Form nuclear lamina (helps form the outer boundary of the nucleus)
  • Reinforce cell-to-cell junctions
  • Major component of skin/hair (Keratin)
68
Q

Actin Microfilaments general information

A
  • Smallest component of the cytoskeleton
  • Flexible
  • Composed of actin
  • ATP binding causes assembly
  • ATP hydrolyses to ADP causing less binding affinity and reduced stability
  • Polar: actin subunits add to the (+) end, subunits are lost quicker at the (-) end
  • Can be stabilized by capping proteins
  • Can be cross-linked together to form mesh
69
Q

Actin Microfilaments function

A
  • Structural support to cell membrane
  • Important in cell migration
  • Helps form filapodia: cell surface projections that appear during movement of cells
  • Form core of microvilli
  • Forms ring structure in cytokinesis during cell division
  • Movement of the human body: thin filaments of muscle
70
Q

Kinesin

A
  • Microtubule Motor
  • Anterograde: moves towards the (+) end
  • Particularly important for transporting neurotransmitters
71
Q

Dynein

A
  • Microtubule Motor
  • Retrograde: moves towards the (-) end
  • Particularly important for transporting neurotransmitters
72
Q

Myosin

A
  • Actin motor
  • Hydrolyze ATP to move toward the (+) end of actin microfilaments
  • Myosin II is responsible for muscle contraction
73
Q

Cilia general information/structure

A
  • Surface projection
  • Axoneme: core of cilia made of 9 doublet MT and 2 central MT
  • Basal body: forms MTs
  • Motile structures: Dynein motors link adjacent doublets, movement towards basal body bends the cilia
74
Q

Cilia function

A
  • Moves substances across surface of cells (ex. moving mucus out of the lungs)
  • Celia of the female reproductive tract move the (egg) oocyte
  • Flagella of sperm are similar to cilia
75
Q

Primary Cilia

A
  • Non-motile cilia
  • Found on most cells
  • Have sensory proteins to transmit information about the surrounding cells and fluid
  • Ex. Sense fluid flow (kidney tubules and ducts of glands)
76
Q

Kartegener syndrome

A
  • AKA Primary cilia dyskinesia
  • Cilia Disorder
  • Cilia lack dynein arms and thus become non-motile
  • Mucus builds up in the lungs (frequent respiratory infections and/or sinusitus)
  • Infertility
  • Possible situs inversus (reversal of right/left organ placement during development)
77
Q

Microvilli general information/structure

A
  • Surface projection (shorter than cilia)
  • Epithelial cells (especially in the digestive tract)
  • Core composed of actin microfilaments
  • Non-motile
  • Bend/flex
78
Q

Microvilli function

A
  • Expand surface area for absorption of material (important for digestion)
79
Q

Nucleus structure/general information

A
  • Largest organelle
  • Control center of the cell
  • Contains the cell’s DNA
80
Q

DNA codes for what?

A
  • Every protein of every cell in your body

- DNA –> RNA –> Protein

81
Q

Chromatin

A

DNA wrapped around histone proteins

82
Q

Chromosomes

A
  • More tightly condensed DNA

- Only visible during cell division

83
Q

Euchromatin

A
  • Type of chromatin
  • DNA loosely wrapped around the histone proteins
  • Easy to transcribe
  • Regularly transcribed
84
Q

Heterochromatin

A
  • Type of chromatin
  • DNA tightly wrapped around histone proteins
  • Hard to transcribe
  • These segments of DNA are turned off (not expressed)
85
Q

Histone modifications

A
  • Controls the tightness of DNA wrapping around histones
  • Acetylation loosens DNA wrapping
  • Methylation tightens DNA wrapping
  • These changes are called epigenetic changes
86
Q

Nuclear Envelope structure/general information

A
  • Contains the nucleus
  • Double membrane (outer and inner phospholipid bilayer)
  • Outer layer is continuous with the rough ER
  • Nuclear pores
87
Q

Nuclear pores

A
  • Protein complexes of the nuclear envelope that shuttle compounds in and out of the nucleus
  • Permeable to small molecules
  • Large particles are carried by importin and exportin proteins
88
Q

Nuclear Envelope function

A
  • Separates the DNA from the cytoplasm

- Controls what enters and exits the nucleus (generally: RNA exits, proteins enter)

89
Q

Nuclear Lamina structure/general information

A
  • Immediate beneath the nuclear envelope
  • Composed of lamin intermediate filaments
  • Scaffold for DNA and transcription proteins
90
Q

Nucleolus function

A
  • Where ribosomal RNA (rRNA) is made and ribosomes are assembled
91
Q

Nucleus functions

A
  • Stores genetic information
  • RNA transcription and gene expression
  • DNA synthesis and cell division
92
Q

Necrosis definition

A
  • Accidental cell death
  • Caused when the cell is severely damaged (oxygen deprivation, certain chemical agents, microbial infections, extreme temperatures, nutrient loss, physical trauma, etc.)
93
Q

Necrosis process

A
  • The membrane loses integrity
  • The cell swells: the leaking membrane allows water and solutes to flow into the cell
  • The cell lysis (rupture of the cell membrane)
  • The cell debris damages neighboring cells
  • Immune cells are recruited to the are and cause inflammation
  • This inflammation can damage neighboring cells and lead to even more cell death
94
Q

Apoptosis definition/general information

A
  • Programmed cell death
  • Does not cause inflammation
  • Carried out by specialized proteins called caspases
95
Q

Physiologic Apoptosis

A
  • Normal process of the body
  • Occurs during embryonic development (ex. removes finger webbing)
  • Also occurs with old cells
  • Self reactive immune cells are also destroyed so that they don’t damage your body
96
Q

Pathologic Apoptosis

A
  • Defense mechanism
  • Destroys cells that accumulate too many DNA mutations
  • Can also destroy cells infected by viruses
97
Q

Apoptosis process

A
  1. ) Cell shrinks
  2. ) Nucleus condenses (becomes pyknotic) and then fragments in a process called karyorrhexis
  3. ) Membrane forms bubbles and phosphatidylserine flips to the extracellular leaf which acts as a signal for the cell to be consumed
  4. ) The cell breaks down into small pieces called apoptotic bodies which are phagocytosed by surrounding cells and immune cells
98
Q

Caspses

A
  • Specialized protease enzyme that initiate and execute apoptosis
  • Cuts other proteins at asparagine residues in their peptide sequence
99
Q

Proteases

A

Enzyme that breaks down proteins and peptides

100
Q

Initiator Caspases

A
  • Caspase 8 and 9
  • Initiates apoptosis
  • Once activated, actives more caspase 9, activates executioner caspses, and creates apoptosis cascade
101
Q

Executioner Caspases

A
  • Caspases 3, 6, and 7
  • Cleave cytoskeleton
  • Activate DNAse which degrades DNA in the nucleus
102
Q

Apoptosis: Intrinsic (Mitochondrial) Pathway

A
  • Regulated by BCL2 family of proteins
  • General path: Cell injury –> BID sensor –> BAX/BAK –> Holes in mitochondria –> Releases Cytochrome C –> Initiates Caspase 9 –> Apoptosis
103
Q

BCL2 and BCL-XL

A

Anti-apoptosis proteins

104
Q

BID

A
  • Apoptosis sensor protein
  • Monitors the cell for different types of stress (DNA damage, protein misfolding, loss of growth factors)
  • Regulates which BCL2 proteins are active (pro or anti-apoptosis)
105
Q

BCL2 Family Control Pathway

A

Part of the intrinsic pathway of apoptosis and includes:

  • BCL2 and BCL-XL (anti-apoptosis)
  • BID (sensor)
  • BAK/BAX (pro-apoptosis)
106
Q

BAK/BAX

A
  • Pro-apoptosis proteins
  • If cell stress is high enough they initiate apoptosis by opening holes in the mitochondrial membrane which allows Cytochrome C to be released into the cytoplasm which binds to the APAF-1 protein to form the apoptosome complex which then activates Caspase 9 to start apoptosis
107
Q

Apoptosis: Death Receptor (Extrinsic) Path

A
  • Initiated by external signal, often delivered by specialized immune cells such as Natural Killer (NK) cells to prevent the spread of pathogens or cancer
  • General path 1: FAS receptor protein binds to ligand –> Leads to activation of Caspase 8 –> Apoptosis
  • General path 2: Tumor Necrosis Factor (TNF) 1 binds to its receptor –> Leads to activation of Caspase 8 –> Apoptosis

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