Bio 2 Flashcards
cell membrane
Barrier to the
outside, controls
flow in/out of cell
DNA
Contains universal code of life –facilitates heredity
Ribosomes
Where proteins are made – facilitates metabolism and cell function
Molecules
are groups of atoms held together in a stable association
Electronegativity determines an atom’s attraction for
the electrons
non-polar covalent bond: 0-0.4
polar covalent bond: 0.4-2
Ionic bond: >2
Polar covalent bonds result from
uneven sharing of electrons
In a polar covalent bond, one atom is more electronegative.
– Unequal sharing of electrons causes a partial positive or
negative charge for each atom or molecule
Water has four key properties
– Water is “sticky”
– Water is an excellent solvent
– Water moderates temperatures
– Ice (solid water) floats
cohesion
Water molecules form hydrogen bonds with each other, resulting in an attractive force
adhesion
Polarity also allows water to attract other polar molecules though
Water is an excellent solvent because it is polar
Water is an excellent solvent for charged and polar
substances
- Charged and polar protein parts
- Small alcohols
- carbohydrates
Water is a poor solvent for nonpolar substances
- Non-polar gases
- Aromatic groups
- Long hydrocarbon chains
PH scale
Acidic= 1-6
Neutral= 7
Base= 8-14
Acids
are molecules that can split apart in water and release hydrogen ions (H+)
Bases
are molecules that split apart in water and release hydroxide ions (OH-)
Maintaining correct pH is important for organisms
- The pH of different cellular compartments, body fluids, and organs is tightly regulated in a process called acid-base homeostasis
- There must be a system in place to ensure pH is
maintained at the desired level - buffers are substances that resist extreme changes in pH
- take up excess hydrogen or hydroxide ions
Buffers are essential for acid-base
homeostasis
- Keep the organism healthy and cellular
components working properly - if something goes wrong with the pH balance, organism can develop acidosis or alkalosis
- both are detrimental and potentially deadly
- The most common buffer system in humans is the bicarbonate/carbonic acid buffer system in blood
Catabolic pathways
involve the breakdown of nutrient molecules into
usable forms (building blocks). In this process, energy is either stored in molecules for later use, or released as heat.
Anabolic pathways
build new molecules out of the products of catabolism, and these pathways typically use energy. The new molecules built via anabolic pathways (macromolecules) are useful for building cell structures and maintaining the cell
Lipids
- Energy storage
- protective membrane
- communication
Carbohydrates
- Energy storage
- structural support
- communication
Nucleic Acid
Contain genetic information
Proteins
- communication
- transport
- chemical breakdown of substance
- structural support
Most macromolecules are polymers
Polymers consist of many similar or identical building blocks linked by covalent bonds
Biopolymers are made by condensation reactions (also known as dehydration reactions)
- Monomers connected together a covalent bond
- Water is lost in the process
- Energy is required
- Special enzymes are needed
Biopolymers can be broken down via
hydrolysis
Hydrolysis adds a watermolecule, breaking a bond
All cellular macromolecules are carbon-based because carbon atoms are the most versatile building blocks that combine together to form very diverse molecules
Carbon atoms can form 4 covalent
bonds with many elements, including H, O, P, S, N
Carbon is also allotropic
Structural isomers
Molecules with the same molecular formula have different bonding patterns and atomic organization
Geometric isomers
cis isomer: The two Xs are on the same side.
trans isomer: The two Xs are on opposite sides.
Enantiomers
- isomers that are mirror images of each other
– to be an enantiomer, a molecule must have at least four different atoms or groups connected to a central carbon
There are four essential macromolecules that build up cells
- polysaccharides
- Fats, lipids, membranes
- Protein
- Nucleic acid
