Topic 2 Plasma Membrane & Biological Molecules Flashcards
4 main elements that make up human body are?
- Oxygen
- Carbon
- Hydrogen
- Nitrogen
Function of the plasma membrane?
- Separates the cell from the surroundings
- controls the transport in/out of the cell
3 major macromolecules found in the plasma membrane are?
- Proteins
- Lipids
- Carbohydrates
Describe the Plasma Membrane Structure
Lipid bilayer
Fluid mosaic model:
Fluid: lipids and proteins within the membrane move > oil consistency = better movement
Mosaic: proteins of dif types are distributed throughout the membrane lipids
What is a chemical bond? What are 3 types of Chemical bond?
Link formed when atoms of REACTIVE elements combine into molecules
- Covalent: polar & nonpolar - share e-
- Hydrogen bonds
- Ionic bonds - transfer of e-
What is a covalent bond?
The sharing of an electron between molecules to complete the valence shell
What is meant by organic molecule?
Molecule containing carbon
What are functional groups? Provide some examples.
Groups of atoms on molecules that readily enter the chemical reactions to change the molecule, with hydrogen or carbon as the background atom
Ie Hydroxyl Carbonyl Carbonyl Amino Phosphate
What is electronegativity?
Measure of an atoms attraction for the electrons it shares in a chemical bond with another atom
UNEQUAL SHARING
Order the four most common atoms found in humans by highest electronegativity to lowest?
Oxygen
Nitrogen
Carbon
Hydrogen
How is there diversity in molecules based on the initial four?
The way the elements bond creates diversity:
Dif lengths, patterns types of covalent bond etc
Single vs double
Position of atoms around carbon
Formation of rings - branching patterns
Explain how water is partially charged.
Oxygen has ahigher pull for electrons (electronegativity) than hydrogen creating a partially negative side (near the oxygen atom) and a partially positive side (near the hydrogens)
How is the structure of the cell membrane beneficial?
The Inside of t he cell is 70% water and the outside environment is also made of water so having a phospholipid bilayer with hydrophilic heads allows the cell to interact with the environment
What is meant by polar and non-polar? What is the difference?
Polar: forms btwn atoms with dif electronegativity resulting in the unequal sharing of e-. Get a partial charge. hydrophilic molecules - interact with/ dissolve in water
Non polar: forms between atoms with similar electronegativities and results in equal sharing of e- hydrophobic - are excluded by water (don’t interact with water)
What is a hydrogen bond?
Bond that forms Btwn positively charged hydrogen atom within a polar covalent bond in one molecule and the negatively charged atom within a polar covalent bond in another molecule.
Ie two molecules interacting because of partially positive/negative charges
What are lipids commonly known as?
Fats and steroids
What are some functions of lipids?
- Energy, fuel
- Insulation/protection (myelin sheath)
- Major component of membranes
What is the typical lipid structure?
Carbon skeleton = hydrocarbon chain
With a functional group (hydroxyl , carboxyl)
What is the difference between amphiphilic and amphipathic molecules?
In reference to phospholipids: partially hydrophobic and partially hydrophilic
Two hydrocarbon chains attached to a glycerol would form what molecule?
A phospholipid
Difference between saturated and unsaturated fatty acids
Saturated Fatty acid chains lack double bonds in order to hold as many hydrogen molecules as possible
H h. H
H-c-c-c-h
H.h. H
Solid at room temp due to packing of straight molecules
Unsaturated: one or more double bonds creates a bend or kink in the fatty acid means more movement means liquid at room temp
What types of movement do the phospholipids on the cell membrane do?
Lateral movement occurs ~10^7 x per second
Flip flopping across the membrane is rare (about once a month) and is not spontaneous - requires energy and help from enzymes
How does temperature effect the cell membrane?
Decreasing temperature= reduces fluidity
Increasing temperature- increases fluidity
Why is fluidity increased with a temprrature rise?
Increase in kinetic energy results in an increase in fluidity making the membrane less stable. This creates holes where leakage occurs
How does decreasing temperature cause a reduction in cell fluidity?
Slows movement down. At extreme cold temperatures the cytoplasm can freeze and ice shards will puncture the membrane creating holes where leakage can occur
What is the “transition temperature”
Temperature that determines the freezing point of a cell.
Must bE above in order to function, but not high enough that the cell becomes too fluid and causing leaks
How does does the type of phospholipid effect membrane fluidity?
Unsaturated phospholipids are more fluid than saturated phospholipids because of the bent shape in the leg. Creates more space between the lipids
Shorter phospholipid chains are more fluid than long chains
How would a cell regulate its membrane fluidity in extreme temperatures?
By using enzymes to increase of decrease the saturation of the phospholipid and/or changing the length of the chain
What is the natural regulator of cell fluidity and how does it work?
Cholesterol
Large planar molecule inserted in the bilayer and regulates fluidity.
At cold temperature - hinders solidification
High temperature - decreases fluidity, reduces ‘melting’
What are the 3 major lipids?
- Phospholipids
- Sterols
- Fats (triglyceride)
What is the structure of a triglyceride and what is the function ?
Glycerol molecule with 3 fatty acids attached
Used for insulation and energy (myelin)
3 cellular examples of a macromolecule are:
Carbohydrates
Proteins
Nucleic acids
