The bilayer is very thin and a phospholipids, which are amphipathic (dual functional ends). This refers to the hydrophilic head (orients toward the water) and hydrophobic tail (orients toward the middle/each other) Bilayer also has proteins.
Why are cell membranes asymmetrical?
Cell membranes are symmetrical: distinct "inside" and "outside" faces - different on each layer - not symetrical
Glcyolipid on outside (external)
Monolayer is seperate/different than another
Cholesterol equally in both up and bottom
The plasma membrane is reinforced by the...
cell cortex (inside)
Disorder increases when useful energy that could be used to do work is used as heat
Delta G measures...
the amount of disorder created in the universe
(2nd law)
How to get an unfavorable reaction to proceed?
Pair an unfavorable reaction with a favorable - as long as the total delta G is negative :)
What is used in the metabolic pathway to drive unfavorable reactions?
ATP
There is energy stored in the nucleoside triphophates used to make polymers...this means there is energy in the ....
energy in the phosphate bonds -->
assemble to make a polymer
Hydrolysis leads to breaking of water
Proteins are made of what
amino acids
Proteins are made of amino acids and are the ______ to our DNA
Instructions !
Proteins contain specific sequences of nucleotides that serve as coding for direction for how to synthesize proteins
= genes in the genome
Two ends of a polypeptide chain:
Amino (N) && Carboxyl (C)
Proteins folding involves:
A protein final 3D shape/configuration is stablized by ....
1) Noncovelent forces/bonds
2) Hydrophobic forces which help to fold proteins
- Membrane is filled with hydrocarbon so the outside is hydroPHOBIC
the inner core is hydroPHILIC
Protein Domain invovles :
an organizational unit, which is defined as any segment of a polypeptide chain that can fold independently into a compact, stable structure
Proteins have the ablity to bind specifically to other molecules as well as...
allowing proteins to as a catalyst, structural support, singal receptors
Proteins bind to a molecule called the ____
Proteins bind its ligand with high specify and high infinity
Proteins function by binding other
molecules: a ligand is the molecule a protein binds
Mechanisms enzymes have to increase the rate of the
reaction:
a)bring really close together (enzyme pulls the two substrates together)
b)creates a more favorable positive/negative
charged environment
c)straining bonds (force)
Lysosome: the classic enzyme
Natural Antibodic
- helps protect mouth, eyes from bacteria
Reaction medicates hydrolsis of polysaccharide in the cell wall of bacteria
Cell wall helps prevent trigger pressure from too much pressure
Feedback inhibition (you made enough, turns activity off)
Phosphorlation/Dephosphoryalation (+/- a Pi group)
Nucleotide Binding & Hydrolysis (GTP/ATP)
Allosteric
Roles of the Plasma Membrane:
- Fight delta G by creating order
- Mediates contct with the enviorment
- Mediates movement
Components of the Cell Membrane:
Lipids : phosolipid
sterols (cholesterol)
glycolipids (sugar fatty acid)
Protein
Major component of the cell membrane is the phospholipid, which is amphipathic meaning...
Amphipathic: hydrophilic head group orients toward the water, while hydrophobic tails orients toward each other
Phosphatidyl choline the the most common?
phospholipid
Integral proteins span the membrane with common motifs which are (name thee 2)
Alpha Helix: spiril
Beta Barrel: sheet wraps so much turns into tube
Experiment that lipids and proteins diffuse freely:
Mouse cells and human cells in a glass - shaken together...Would the mix? Yes
Proteins are fluid and can move
- Mobility
Describe the structure of a bilayer - why is it often called a fluid mosaic?
Different variety of components in the bilayer
Major component: phospholipids, which are amphipathic (dual fuctional ends)
Hydrophilic head (orients toward the water)
Hydrophobic tail (orients toward each other inside)
Bilayer also had proteins
Cell Membrane is asymmetric which refers to the "inside" and "outside" layer are different.
The different groups/heads on each side give rise to different functions.
Hydrophilic outside/ Phobic internally
Bilayer = ampathetic refers to membrane philic/phobic
Glycolipids = external monolater, while cholesterol is distrubuted equally both top and bottom.
Cell Membrane Truths:
1) Phospholipid bilayer spontaneously close in on themselves to form sealed compartments
2) Membranes serve as higly selective barriers in cells
3) Lipid Bilayer is 2 dimentional fluid
4)Membrane fluidity is essential for cells to live, grow, reproduce
Patch Clamp: recording used to monitor channel activity
Measure changes in electrical current – used to study ion movement and on channels measure how long current is open
It is important for a cell to avoid being torn apart by having an equal amount of + and - charges
What controls the concentration differences?
membrane transport proteins
lipid bilayer itself
What are cells permeable to?
Permeable: can move across – hydrophobic molecules – gas:CO2, O2
Hydrophobic molecules – small nonpolar
Steroid: hormones, gases (CO2,O2)
Small polar molecules (uncharged)
The interior of the lipid bilayer is hydrophobic, so that is what will diffuse the quickest and more readily.
Ion concentrations inside the cell vary differently from those outside
What are cells Impermeable to?
not able to pass through the lipid bilayer
Large polar molecules, glucose
Ions, charged molecules: H+, Na+, ATP, amino acid
Impermebles need/require transport proteins
Different types of proteins used to transport molecules across cell membranes include:
Channel: faster, allows molecules to move through selective for: size, charge
When open, continuous channel as molecules run through -- gated/discriminates
Carrier: slower, more specific, Highly specific, depends on bind sites
What influences the movement of substances across the membrane?
Size, Charge and polarity, specific roles
What is membrane potential and how does it work?
most cells have a voltage (charge)
Difference in potential exerts a force on any molecules that holds a charge
Inside (cytoplasmic side) = negative-ish
outside: more positive ish
Na and K in passive transport
Na+ is higher in concentration outside the cell as it tends to enter the cell if given the opprotunity, while K+ is higher in concentraion inside the cell and will try to rush out
Sodium- Potassium Pump is an example of Active Transport - How does it occur?
1) ATP driven Na+ binds to protein which stiumlates phosphorylation
2) Phosphorylation causes the protein concentration/shape to change
3) Change in shape expels Na+ out, K+ binds in
4) K+ binding in triggers release of a phosphate group
4) Loss of Pi, restores orignal conformation
5) K+ is released, Na+ sites are recycled
three ways cells carry about active transport:
1) Cotransporters: concentration gradient of one substance used to drive the active transport of another
2) ATP: couple uphill transport to hydrolysis of ATP
3) Light: energy uphill transport from light
Describe the Na+/K+ pump
ATP-driven Na+ pump (in animals cells) hydrolyzes ATP to ADP to transport Na+ out of the cell.
Proteins couple outward transports of Na+ with the inward transport of K+
Burns 30% of energy in cells (3 Na+ and 2 K+)
The Ca2+ pump :
Movement of Ca2+ is crucial to the cell membrane as calicum is used as a signaling messenger to triger intracellular events --> contraction of muscle cells in the sacroplasmic reticulum
Ca2+ levels have what affect, lead to what?
Ca2+ is released in our skeleltal muscles/contractions - when a muscle cell is stimulated Ca2+ rapidly floods from the sarcoplasmic reticulum
H+ pump (plants) vs. the Na+/K+ pump (animals)
electrochemical gradients of Na+ is generated by the Na+/K+ pump, used to drive active transport of solutes across the plasma membrane
ATP-driven Na+ pump in animals cells hyrdolized ATP to ADP to transport Na+ out of the cell
(Same Time) outward transport of Na+ and inward transport of K+
PLANT: H+ symport brings nutrients into cells, helps keep the pH of cytosol neutral, & pH of interior organelle acidic
Different types of proteins involved in vesicular transport?
Clathrin-coated vesicles transpot selected cargo from Golgi Apparatus to the outward secretary pathway
Clathrin assembles a basketlike network on the surface of membrane
Docking & Fusion invovles a class of proteins called SNAREs
v-snares interact with t-snares to force fusion of vesicles to target molecule, docking vesicle into place
Force of SNAREs winding together squeezes out any water molecules that remain trapped between the 2 membranes, allowing their lipids to flow together to form a continous layer
Describe the intermediate filaments of teh cytoskeleton:
- strong and dense stable ropelike
- good for dealing for mechinical stress
- non polar: end are not different
- keratin filaments: (skin/hair) epithelial cells - attach to desmosomes
- Nuclear Lamins: strengthen the nuclear envelope
Microtubles of the cytoskeleton : breifly describe
dynamic instablity (2nm)
microtubles are hollow which provide road ways for celluar material to move, microtubles are critical for cells division
Actin Filaments (thinest and most flexable)
Actine is a component of the cell cortex and allows cells to crawl as they pull forward
When myosin walks on actin = contraction
What are the specalized function for each of the filaments of the Cytoskeleton
is built on a framework of three types of proteins
Actin: cell movement
Microtubles: organize cytoplasm of cell; rail road track for motor proteins
Intermediate filaments: distrubute mechinacal strss across cells
K+ is kept inside the cell, but there are these leak
channels which randomly allow K+ to rush out.
K is positive keeping the inside positive but when it rushes out (+) rushing out, the inside turns more negative (-) also when K+ leaves to the outside, the
outside becomes more positive
A chemical reaction that occurs spontaneously must have
negative delta G
TRUE
Hydroxyl groups decrease the solubility of sugars in water
FALSE
Antibodies are proteins produced by the immune system in
response to foreign molecules
TRUE
A decrease in saturation of fatty acids tails in lipid
bilayer would increase the fluidity of the membrane
TRUE
Glycolipids contain sugars as part of the hydrophilic head
group of the molecule
TRUE
The hydrophobic amino acids of a transmembrane protein would
be found largely in the interior of the folded proteins
FALSE
Intertwined alpha helices can form a coiled-coil
TRUE
Lipids in the lipid bilayer readily flip flop in the
monolayer to the other
FALSE
A lipid-linked membrane protein would be considered a
peripheral membrane protein
FALSE it would be an integraL
Both fatty acids and polysaccharides can be important energy
stores in the cell
TRUE
Entropy of a system is a measure of the system’s disorder
TRUE
Protons and electrons are found in the atomic nucleus of an
atom.
FALSE
Hydrocarbon molecules are polar molecules
FALSE
Nucleotide hydrolysis allows motor proteins to produce large
movements in the cells
TRUE
The distribution of elements in the earth’s crust is very
similar to the tissue of an animal
FALSE
Robert Hooke first identified cells in a piece of cork in
1665
TRUE
Competitive inhibition of protein function involves binding
of another molecule at a separate site other then the active site
FASLE
Cholesterol fills spaces between neighboring phospholipids
making the membrane more flexible
FALSE
Two atoms that engage in a polar covalent bond will equally
share a pair of electrons
FALSE
Allosteric proteins have two or more conformational states
TRUE
Prokaryotic cells contain internal membrane bound
compartments called organelles
FALSE
ENZYMES
Highly specific for the substrate they bind
Speed up the rate of the reaction by lowering AE of a
reaction
An enzyme’s Km value indicated how effectively the enzyme
binds to its substrate
Hydrolase is a general term fora group of enzymes that catalyze a hydrolytic
cleavage
PROTEINS
Can be classified into families in which members share a 3D
shape/amino acid sequence
Two identical polypeptides that assemble together as a
larger protein complex would be considered a heterodimer
Many proteins are composed of separate functional domains
Three types of bonds which stabilize the structure of
cytosolic protein
Hydrogen bond
Ionic bond
Van der Waals Forces
Proteins:
Proteins are held together by peptide bonds
Each type of protein has a unique amino acid sequence that
determines both its 3D shape and biological activity
Refolding of an unfolded polypeptide is termed renaturation
Binding site of a protein contains specific amino acids that
form a set of noncovalent bonds only with certain ligands
Carbohydrates:
Contain C, H, and O = (CH2O)n
Disaccharides are two covalently linked sugar monomers
Long chains of sugar molecules called polysaccharides are
important storage forms of energy and serve as structural material in cells
Smaller oligosaccharides can be covalently linked to lipids
to form glycolipids
Fatty Acids
Largely Hydrocarbon length 14-24
Addition of shorter fatty acid increases fluidity
Unsaturated fatty acids have one or more double bonds which
form by removal of hydrogen atoms
ATP
Serves as energy carrier
ATP hydrolysis to ADP and Pi provides energy to drive
reactions
ATP formed through reaction that release energy such as
oxidative breakdown of foods
Energy:
Living organism use energy to create order
1st Law of Thermo, energy can only be transferred
not destroyed
Cells obtain energy by oxidation of organic molecules
The primary source of energy for most living organism is the