What is the key distinction between eukaryotes and prokaryotes?
Eukaryotes have an internal membrane system
What is important in cell communication, import/export of molecules, and cell growth and motility?
Plasma membrane
The plasma membrane is 40-80% lipids - what three types of lipids are included in this?
Phospholipids, cholesterol, and glycolipids
Fatty acids are hydrophobic, hydrophilic, or amphipathic?
Amphipathic (amphiphilic)Methyl group at one end (hydrophobic)Carboxyl group at the other (hydrophilic)
How many carbons do fatty acids such as stearic, oleic, and linolenic have?
18
Unsaturated fatty acids have one or more double bonds - does the cis or trans orientation make them kink?
Cis
Cholesterol is composed of
Rigid steroid ring (carbon rings), a non-polar hydrophobic tail, hydroxyl group head which is polar/hydrophilic (attracted to phosphate head of phospholipid)
Phospholipids are composed of
hydrophobic tail (usually one saturated/one unsaturated fatty acid with carboxyl group on each end), glycerol, and phosphate head
What is a glycolipid?
Carb that extends to the outside of the cell and is covalently linked to a lipid
What is a acylglycerol? Ex. Triglyceride/triacylglycerol
Glycerol with one or more fatty acids.
Phosphoacylglycerols
Fatty acid esters on carbons 1, 2 of glycerol, phosphate on carbon 3
Sphingomyelin is a type of phospholipid but its ______ is replaced with ________ and it has a _______ head group.
Glycerol, sphingosine, choline head group
What is the most common phospholipid in cell membranes?
Phosphatidylcholine
What're the 5 parts of a phospholipid
1. Hydrophilic head (ex. choline)2. Phosphate group3. Glycerol molecule4. & 5. Two hydrocarbon chains (sat or unsaturated FA tail)
T/F Most phospholipids contain two unsaturated hydrocarbon tail?
False. Most contain a saturated and an unsaturated hydrocarbon tail
Cholesterol (a sterol), a glycolipid, and a phospholipid are all hydrophobic/hydrophilic/amphipathic ?
Amphipathic
Fat molecules are fully hydrophobic/hydrophilic/amphipathic ?
Hydrophobic
Why is water dipole?
Total charge is zero but the positive and negative charges do not overlap (not symmetric)
Water can form hydrogen bones with itself/positive charged molecules/negatively charged molecules ?
All of the above (:
Lipids in water
Form either a surface film or spherical micelles (pure phospholipids form closed spherical liposomes in water)
Why do phospholipid bilayers spontaneously close in on themselves to form sealed compartments in water?
The sealed compartment is more energetically favorable
T/F Phospholipids in the membrane commonly move laterally, rotate, flex, and spontaneously flip?
False. All are true except spontaneously flip-flop rarely occurs
T/F The ratio of saturated:unsaturated phospholipids will influence the permeability and fluidity of the membrane
True. A membrane composed of completely saturated lipids will be dense and less fluid. One composed of completely unsaturated lipids will be very loose and fluid.
What does cholesterol do the cell membrane?
Fits into gaps between phospholipids and causes stiffening and strengthening of the cell membrane
3% of the plasma membrane is composed of this lipid with a carb head and lipid tail
Glycolipid
T/F Glycolipids are involved in cell-to-cell interactions?
TRUE
The main structure of the membrane
Lipids
Primary protein structure
Sequence/chain of amino acids
Secondary protein structure
Hydrogen bonding to form alpha-helix or beta-sheets
Tertiary protein structure
3-D structure created by a single protein
Quaternary
3-D structure of 2 or more polypeptide chains
Beta-barrel
Beta sheets twisting and coiling to form a closed barrel-like structure
What are integral membrane proteins?
Transmembrane and lipid-anchored proteins - would require disrupting the entire membrane to remove
Proteins usually cross membranes as ________, sometimes as ________
Alpha-helices, beta-barrels
T/F Eukaryotic cells are coated with carbohydrates
True. Oligosaccharides are attached to glycoproteins, glycolipids, and proteoglycans
Polypeptide backbone is hydrophilic/hydrophobic/amphipathic
Hydrophilic
In an alpha-helix structure, each oxygen of a carbonyl group of a peptide bone forms a hydrogen bond with the hydrogen atom attached to a nitrogen atom in a peptide bond ## number of amino acids farther along the chain
Four
T/F The hydrophobic AA side chains interact with hydrophobic hydrocarbon tails of phospholipids
TRUE
Roughly how many amino acids span the lipid bilayer as an alpha helix?
~20
While flip flopping in the plasma membrane is rare, this lipid can flip flop
Cholesterol
Two things that affect lateral diffusion?
Lipid rafts and the cytoskeleton
Lipid rafts
Affects membrane fluidity and protein trafficking. Ordered, tightly packed but float freely in lipid bilayer. Rich in cholesterol and sphingolipid, contain proteins
What is a caveolae?
A type of lipid raft that is a flask-shaped invagination of the plasma membrane. Many proteins and lipids are found in high concentration here. As a lipid raft it affects membrane fluidity, etc.
T/F The plasma membrane is reinforced by the underlying cell cortex
TRUE
In human RBC what forms the cell cortex?
A spectrin meshwork attached to plasma membrane proteins and made of spectrin and actin molecules linked together
Where does membrane assembly begin?
In the ER
What enzyme transfers phospholipids across ER bilayer?
Scramblases
What enzyme catalyzes the transfer of SPECIFIC/SELECTIVE phospholipids to cytosolic monolayer of the Golgi membrane?
Flippases
Phospholipids and glycolipids are symmetrically/asymmetrically distributed in the lipid bilayer of eukaryotic plasma membrane?
Asymmetrically
T/F The outer nuclear membrane of the nucleus is contiguous with the endoplasmic reticulum
TRUE
T/F The nuclear membrane is a since membrane
False. It is a double membrane system
Does the nucleus contain all of the enzymes and other proteins required for metabolism of the DNA?
Yes
Purpose of fibrillar centers of nucleolus
Contains DNA loops containing rRNA genes, RNA polymerase I and transcription factors
Purpose of fibrillar material
rRNA transcription
Purpose of granular material
sites of ribosome assembly
Nucleolus function
Ribosomal biogenesis, makes cell-cycle regulator proteins, disappears during mitosis
What are NORs
Nucleolar organizing regions in human chromosomes 13, 14, 15, 21, 22. Contained repeated genes encoding for 18s, 28s, 5.8s ribosomal RNA
Can large molecules diffuse freely through nuclear pores?
No, they need a nuclear localization signal (NLS) and are actively and specifically transported in/out. Small polar molecule ions can diffuse passively though
% Protein/ % rRNA in ribosomes
40% protein and 60% rRNA
Describe the ribosomal large subunit
60s in weight, 50 different proteins, 28S, 5.8S, 5S ribosomal RNA
Describes to ribosomal small subunit
40s in weight, 30 different proteins, 18S rRNA
Rough ER function
Production (RNA to protein), folding, quality control and dispatch of some proteins; modifications including glycosylation
Smooth ER function
Largely associated with lipid manufacture and metabolism, steroid/hormone production, chemical/drug detox, glycosylation
In the liver, what part of the cell is glycogen stored in?
Smooth ER
What is essential for reconstitution of nuclear membrane in late mitosis?
ER
Golgi cis face faces the membrane or the RER
Faces RER - receives proteins from RER
Functions of cis Golgi network
1. Phosphorylation of lysosomal glycoproteins2. Translation3. Segregation4. Signal removal5. Beginning of glycosylation
Functions of medial Golgi
Saccharide chains of glycoproteins are modified, sulfation
Functions of trans Golgi
Packing, condensing, storing, final proteolysis, specific distribution of proteins
T/F All mitochondrial proteins are encoded by mitochondrial genome?
False. Some are encoded by mitochondrial genome, others are encoded by the nuclear genome
T/F Mitochondrial DNA is responsible for its own reproduction and protein synthesis
True.
Where do lysosomes come from?
They bud off the Golgi apparatus
What are 3 special properties of the lysosome membrane?
1. ATP driven proton [H+] pump to maintain low pH (4.5-5.5)2. Glycoprotein coat rich in carbohydrates on the inner surface to protect its own enzymes from hydrolyzing it3. Transporter channels that transport break-down products
What cells are particularly susceptible to damage caused by mutations in genes that encode lysosomal hydrolyses
neurons
Tay-Sachs & Gaucher's disease
Lysosomal storage diseases caused by a failure to produce an enzyme needed to break down lipids
Mucopolysaccharidoses 1 (MPS-1)
Lysosomal storage disease caused by a failure to synthesize an enzyme needed to break down proteoglycans like heparan sulfate
I-Cell Disease (inclusion cell disease)
Lysosomal storage disease caused by a failure to "tag" (phosphorylate) all of the hydrolytic enzymes that're supposed to be transported from the Golgi apparatus to the lysosomes - they're secreted from the cell instead
Peroxisomes contains what kind of enzymes?
Oxidases and catalases
What to peroxisomes oxidize?
Very long chain fatty acids
Peroxisomes regulate levels of _____ in the cell?
Regulates hydrogen peroxide levels for killing pathogens (make and degrade H2O2 and other ROS)
Where do peroxisomes come from?
They bud off from the ER