The cell Flashcards
What are the properties of the cell membrane?
Support- mechanical and chemical
Response to signals
Amphipathic
Fluidity
What are the membrane lipids?
Phospholipids
Glycolipids
Steroids
What do glycolipids do?
Provide membrane strength and a structural framework for the cell.
Gangliosidosis
Inappropriate development of the optic nerve due to the concentration of gangliosides not decreasing. This often is due to ineffective hexosamidases.
Scrambliosides
First step in apoptosis where enzymes redistribute the asymmetrical distribution of phosphoglycerides in the cell membrane.
What are the inner lipid players in the cell membrane?
Phosphatidylserine
Phosphotidyletholamine
What are the outer lipid players in the phospholipid bilayer?
Phosphatidylcholine
Sphingomyelin
What molecule has a hydroxyl head and a steroid ring that act to stabilize the lipid bilayer of a cell membrane despite temperature changes fluxuations?
Cholesterol
This component of cholesterol cements the phosphate head of the phospholipid.
The Hydroxyl component.
This disperses the hydrophobic tails of the phospholipid membrane.
The steroid ring of cholesterol.
This is in the external monolayer of the cell.
Glycocalyx
Covalently bonded with olgiosacchrides on the outer surface of the cell membrane to form a portion of the glycocalyx.
Glycolipids
Negatively charged to repel the negative charge of most bacteria.
Glycolipids
Characterized by lipid proteins caveolin and flotilin.
Lipid rafts
Nonpolar membrane protein
Glycine
Nonpolar lipid membrane
Alanine
Nonpolar lipid protein
Valine
Nonpolar lipid membrane
Leucine
Nonpolar membrane protein
Isoleucine
Nonpolar lipid protein
Methionine
Nonpolar membrane protein
Phenylalanine
Nonpolar membrane protein
Tryptophan
Nonpolar lipid protein
Proline
These proteins are hydrophobic and anchor the protein to into the cell membrane
Nonpolar lipid proteins
These proteins are hydrophilic and are located on the outer surface of the cell membrane interacting with the cytosol.
Polar lipid proteins
Polar lipid protein
Serine
Polar lipid protein
Threonine
Polar lipid protein
Threonine
Polar lipid protein
Tyrosine
Polar lipid protein
Tyrosine
Polar lipid protein
Asparagine
Polar lipid protein
Asparagine
Polar lipid protein
Glutamine
Characteristics of integral proteins
Folded
Well anchored
Found on the protoplasmic surface
Will leave impressions on the efface of the cell membrane
Arrhythmogenic Right Ventricular Cardiomyopathy
Genetic disorder characterized by distorted cell attachments within the desmosomes of cardiac cell muscle. This is typically a gradual unnoticed onset and diagnosed after death.
These cell membrane proteins are amphipathic with hydrophylic areas in an irregular coil and hydrophobic areas in a helix.
Integral proteins
Create pores to allow movement of water soluble substances
Integral proteins
Characteristics of peripheral proteins
More localized on the inner monolayer Associated with integral proteins Electron carriers Form part of the cytoskeleton Contribute as second messengers
Three types of lipid movements
Rotational
Lateral
Flip flop
Diffusion type that is restricted by association with the cytoskeleton
Lateral
This holds the cell membrane in place
Cytoskeleton
Main players in the cytoskeleton
Actin and Filament
Main players in the cytoskeleton
Actin and Filament
RBC protein that facilitates chloride/bicarb exchange
Band 3 proteins
RBC protein that provides mechanical support
Band 4.1 proteins
RBC protein that acts a stabilizer
Spectrin
RBC protein in the cytoskeleton
Actin
RBC protein that anchors Band 3 and Band 4.1
Ankrin Bridge
Functions of the gylcocalyx
Cell protection and insulation
Receptor sites for cell signaling
Cell attachment
Cell immunity
Interacts with the extracellular matrix to form the gylcocalyx
Glycolipids
Glycoproteins
Proteoglycans
Ig A protects cells
It is attracted to glycolipids and glycoproteins and it’s attachment increases the negative charge of the cell.
Proteins involved in cell attachment
Selectin
Integrin
Cadherin
Immunoglobulin super family
Junctions that significantly limit movement but can allow a very small amount of substances through based on size and charge (leaky).
Tight junctions
Anchoring junctions that are desmosomes or hemidesmosomes
Adherent junctions
These junctions form between cells, between the cell and the extra cellular matrix and both.
Anchorage junctions
These attachments can be heterophilic or homophilic
Stable cell attachments
These junctions are typically homophilic and use intermediate junctions and cadherins to connect cells and the extracellular matrix.
Desmosomes
Characteristics of desmosomes
Visualized as rivets
Cystoskeleton: actin
CAM: cadherin
Note a homophilic desmosome would involve cadherin to cadherin interactions
Characteristics of hemidesmosomes
Connect the cytoskeleton to the extra cellular matrix
Cytoskeleton: actin
CAM: Integrin
Characteristics of adherin junctions
Combination of hemidesmosome and desmosome Provide morphological diversity Can be seen as streaks, spots or bands Cell to cell: cadherin Cell to extracellular matrix: integrin
This protein is not involved in adherin junctions
Actin
Communication/GAP junction
This junction facilitates spontaneous impulses in individual cells so they will act as a unit.
Communicating/GAP junxtion
These junctions allow cells to share cytoplasmic contents- not organelles, but ions and electrical current.
Examples of Communicating/GAP junctions
Brain, heart, smooth muscle and highly proliferating cells
Type of communicating/GAP junction
Intercalated disk- allow the heart cells to behave as a functional syncytium.
Composition of intercalated disk
Macula adherins- desmosome, fascia adherins and a communicating GAP junction
Protein involved in a communicating or GAP junction
Connexin
Structure of connexins
Connexon (Communicating or GAP junction)
Example of cells that use connexins to make connections for their communicating or GAP junction
Interstitial Cells of Cajal
Interstitial Cells of Cajal
Highly proliferating cells located in the GI tract
These toxins can destroy a tight junction
E coli, Staph, C. dif, parasites and hook worms
Functions of tight junctions
Barrier to each body compartment
Act as a barrier
Regulate the amount of water and solute movement
Proteins found in tight junctions
Occludens
Property is limited by tight junctions
Osmosis
Cell Adhesion Molecule plentiful on WBC that participate in phagocytosis. Used by both macrophages and monocytes.
Selectins
Act as ligands, bind to ligands can participate in paracrine autocrine or juxtacrin functions
Cell Adhesion Molecules CAM
Cell Adhesion Molecules
Selectins
Integrins
Cadherins
Immunoglobulin Super Family
Organelles
Subcellular component with a membrane that resembles the cell membrane in structure and function
Vacuoles
Structures with membranes that are not lipid bilayer
Cytoplasm
Electrolytes and solutes that form a colloidal substance, can also be called cell matrix, cytosol or cell ground substance
Nucleus
Protective container for the cells DNA. DNA never leaves the nucleus but messages (mRNA) can be sent to other parts of the cell.
Ribosomes
Smallest organelles found in all cells. Build proteins by putting together long chains of amino acids according to mRNA, thousands in each cell.
Mitochondria
Powerhouse of the cell. Converts glucose to ATP.
Cell Membrane
Controls what molecules are allowed in and out of the cell. Also known as plasma membrane. Made up of phospholipids that form the outer barrier of the cell.
Cytoplasm
Cytosol, the liquid that fills cells and contains proteins and dissolved ions that are involved in many cell reactions.
Vacuole
Membrane enclosed sac that can be filled with anything the cell needs to be kept separate, can store food, water etc.
Golgi body
Receives products from the endoplasmic reticulum and adds their final modifications. Sorts these products and sends them to their final destinations.
Lysosome
A membrane enclosed bag of digestive juices. Breaks down large molecules and old cell parts into their components to be recycled to build new cell parts.
Primary lysosome has not used it’s enzymes. A secondary lysosome has used it’s juices and is activated when fusing with a phagosome.
Rough Endoplasmic Reticulum
Large folded membrane system studded with ribosomes. Ribosomes build proteins and the endoplasmic reticulum helps to fold or modify them. Products are then shipped to the Golgi.
Smooth Endoplasmic Reticulum
Large folded membrane system that puts together lipids. Is also important for making new membranes.
Microtubules
Long tubes or cord like structures that provide cells internal structure and allow movement. Other organelles are anchored to the network called the cytoskeleton. Microtubules work together in muscle contraction and the movement of cilia and flagella.
Have a positive end and a negative end.
Negative is toward the center of the cell, positive is toward the cell membrane.
Dynein moves materials outside in and kinesin moves molecules inside out.
Endoplasmic Reticulum
Reticulated organelle with a large lumen for protein processing (modification and synthesis).
Major events in the in the lumen of the ER
Protein sorting
Protein trafficking
Protein modification
Major events outside of the lumen of the ER
Translation
Transcription
Steps of protein synthesis in the RER
External stimuli acts on a ligand (receptor) and forms the ligand receptor complex. The ligand receptor complex is internalized and will associate with the CREB.
CREB Interaction
Cyclic AMP will act as a second messenger and activate a dormant kinase along with ATP. CAMP and ADP-P will phosphorylate protein kinase A.
CAMP and phosphorylated protein kinase A will form the Cyclic AMP Response Element Binding (CREB)
CREB will enter the nucleus.
Events between CREB entering the nucleus and mRNA leaving the nucleus for the Rough Endoplasmic Reticulum
The CREB will locate the structural gene and bind to the response element on said gene. The ligand will leave the CREB unit to be recycled in the cell.
The response element will bind with the CREB to produce transcription factors and RNA polymerase.
RNA polymerase will copy the information in the structural gene and produce mRNA.
mRNA will enter the ribosomes.
Amino Acids are also located in ribosomes.
Synthesis of codons (mRNA) and anticodons (tRNA)
mRNA and tRNA will combine to pick appropriate amino acids- translation.
Amino acids will be added to the incomplete polypeptide.
The synthesized protein will be inserted into the membrane of the ER for modification in the lumen by a signal recognition receptor on the RER.
These unfold the protein in the RER lumen
Cytoplasmic chaperones
This does not require a signal recognition molecule
A free ribosome
Signal peptidase
Catalyzes the cleaving of the signal recognition particle and dissolves the ribosome
Post translational translocation
Occurs in free ribosomes
Translation ends before translocation occurs
Cotranslational translocation
Occurs as the protein is being carried into the lumen of the RER on the attached ribosomes.
Protein trafficking
Follows the cleaving of the signal recognition particle and is the formation of a transport protein channel
Process by which young proteins are stabilized
Modification
How is modification done?
Formation of disulfide bridges and glycosylation
Disulfide bridges
A linear protein with cysteine is acted on by disulfide isomerase to form a disulfide bonds. This brings molecules closer together and changes the structure of the protein.
Oxidation of reduced cystein in the lumen of the RER
Oxidation reaction with disulfide isomerase and cystein that lead to the formation of disulfide bridges and change the shape of the protein,
Glycosylation
Addition of a glycan (sugar) to a newly synthesized protein with enzyme oligosaccharide transferase.
N-linked glycosylation
The nitrogen in asparagine is added by oligosaccharide transferase in the RER.
O-linked glycosylation
This is not exclusive to the RER
The hydroxyl group (OH) of serine and threonine are acted on by oligosaccharide transferase in the RER, Golgi, cytosol and nucleus.
Glypation
The glycan (sugar) is added by oligosaccharide transferase to a phospholipid and a protein.
C- linked glycosylation
Oligosaccharide transferase binds mannose to the indole ring of tryptophan.
Mannose is a pathogen recognition receptor on a macrophage.
Phosphoglycosylation
Glycan is added to serine through a phosphodiester bond by oligosaccharide transferase.
Events that stabilize a protein in order to send it to the Golgi Apparatus
Protein is stabilized in the RER disulfide isomerase forming disulfide bridges with cystein and oligosaccharide transferase adding sugars through glycosylation.
Golgi apparatus
Structure within the cell that finishes protein processing and releases the finished product.
Antegrade transport
Perfect protein is escorted to the entry face of the Gogli apparatus for further processing by COP II (coatomer protein)
Retrograde transport
A protein with a defect is escorted from the entry face of the Gogli apparatus back to the RER with chaperone protein COP I (Coatomer protein I)
Structure of the Gogli Apparatus
Entry face
Middle: transgolgi stalk and medial stalk
Exit face which releases secretory vesicles
Exocytosis
How secretory vesicles with differing protein concentrations will leave the Golgi apparatus.
Constitutive exocytosis
Exocytosis at the Golgi apparatus where secretory vesicles of differing proteins are release without a stimulus.
Regulatory exocytosis
Exocytosis at the Golgi apparatus that requires a stimulus for the release of secretory vesicles of differing protein concentrations.
Membrane redistribution
Occurs when proteins are released from the Golgi apparatus via constitutive or regulatory exocytosis to be incorporated back into the cell.
These proteins can be incorporated back into the cell, cell membrane or various organelles.
