BILD 1: Exam #1

what are the 3 concepts of the cell theory definition of life?

• all living organisms are composed of one or more cells (structure-based definition)

• the cell is the basic unit of structure and organization in organisms

• cells arise from pre-existing cells

all cells have…

1. plasma membrane- an outer covering that separates the cell’s interior from its surrounding environment

2. cytoplasm- consisting of a jelly-like region within the cell in which other cellular components are found

3. DNA- the genetic material of the cell

4. ribosomes- particles that sythesize proteins

what are the two types of cells?

prokaryotes and eukaryotes

what are the characteristics/examples of prokaryotes?

• bacteria, anchaea

• no membrane-bound nucleus

• no membrane-bound organelles

• usually, single-celled

what are the characteristics/examples of eukaryotes?

• animals, plants, fungi, amoebas

• has membrane-bound nucleus

• has membrane-bound organelles

• usually bigger, often multi-cellular

what organelles are found in prokaryotes?

• dna (not in nucleus)

• ribosomes

what organelles are found in eukaryotes?

• dna (in nucleus)

• membrane bound organelles: chloroplasts, mitochondria, endoplasmic reticulum and golgi apparatus, lysosomes

what is the structure of viruses?

• proteins and RNA

• no ribosomes, no energy metabolism, do not grow independently of host cells

are viruses considered living things?

NO; viruses do not have a cell membrane-their outer shell is only made of proteins. they are not cells

what are all organisms composed of?

matter

what does matter consist of?

chemical elements in pure form and in combinations called compounds, each element consists of unique atoms

what are the characteristics of atoms?

• smallest unit of matter that retains properties of an element

• protons, neutrons, electrons

• basic building blocks of matter

• ex: hydrogen, oxygen, nitrogen

what are the characteristics of elements?

• elements consist of one type of atom and can be identified by their atomic numbers

• cannot be broken down to other substances by chemical reactions

what are molecules?

formed when two or more atoms join together by covalent bonds. can be the same atoms

what are compounds?

found when two different elements join together

how does a compound’s properties compare to those of the elements it is composed of?

a compound has characteristics (emergent properties) different from those of its elements

what are valence electrons?

those on the outermost shell/valence shell

what determines the chemical behavior of an atom?

mostly determined by the number of valence electrons

how to determine the valence/bonding capacity of elements?

usually the number of unpaired electrons

what does the the formation and function of molecules and ionic compounds depend on?

chemical bonding between atoms

what usually occurs with atoms with incomplete valence shells?

they can transfer valence electrons with other atoms

• these interactions usually result in atoms staying close together, held by attractions called chemical bonds

what is a covalent bond?

the sharing of a pair of valence electrons by two atoms

• the shared electrons count as a part of each atom’s valence shell

what is a single covalent bond (single bond)?

the sharing of one pair of valence electrons

what is a double covalent bond (double bond)?

the sharing of two pairs of valence electrons

what is electronegitivity?

the capability of an atom to attract electrons to itself

how does electronegativity affect attraction?

an atom with high electronegativity has a stronger attraction than an atom with low electronegativity

what determines polarity of covalent bonds?

difference in electronegativities

what forms nonploar covalent bonds?

occurs when two atoms share electrons equally because the electronegativity of both atoms is relatively equal

what forms polar covalent bonds?

occurs when one atom is more electronegative, and the atoms do not share the electron equally.

how do electrons interact with atoms that are more electronegative?

it has a stronger attraction for electrons, so electrons spend more time in the electron cloud of that atom

what causes partial charges on atoms/molecules?

unequal sharing of electrons

• the atom with the higher electronegativity will gain the partial negative charge.

what elements are most common in covalent bonds?

carbon, oxygen, nitrogen, and hydrogen

• essential for living organisms

• account for 96% of atoms in our bodies

what are sugars (glucose and fructose) held together by?

covalent bonds

what is an ionic bond?

a chemical bond that involves the transfer of electrons from one atom to another so that both atoms will be left with a full valence shell.

• the two resulting oppositely charged atoms of molecules are called ions

what are compunds formed by ionic bonds called?

salts

what are properties of salts?

• often found in nature as crystals

• most are stable when dry, but dissociate quite easily in water

what is the function of sodium ions?

used to help regulate blood volume and blood pressure

what is the function of chloride ions?

udes to help balance the pH of the body and to transmit nerve impulses

how are hydrogen bonds formed?

formed when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom

• usually oxygen or nitrogen

what do hydrogen bonds require?

1. a hydrogen with a partial positive charge due to it being covalently bonded to a much more electronegitive atom, such as O or N

2. a highly electronegitive terminal atom with a partial negative charge due to it being covalently bonded to a much less electronegative atom

3. both hydrogen-bonding functional groups must be within approximately an atomic diameter for the hydrogen bond to form

how are polar covalent bonds formed in water?

• covalent bonds are solid lines because they are within a molecule

• because of polar covalent bonds

how are hydrogen bonds formed in water?

• attraction between molecules

• partial + attracts partial - form polar bonds

what kind of compounds are hydrophilic?

• ionic compounds

• polar covalent compounds

• ex: salts, molecules with charges, and mostly polar covalent bonds

what kind of compounds are hydrophobic?

• nonpolar covalent compounds

• ex: oil, fats

what are van der waals interactions?

attractions between molecules that are close together as a result of these charges

how are electrons distributed in covalent, ionic, and hydrogen bonds?

• covalent- shared

• ionic- transferred

• hydrogen- not shared nor transferred

what is the solvent of life?

water

what constitutes a solution?

a liquid that is a completely homogeneous mixture of substances

what is the solvent?

the dissolving agent of a solution

what is the solute?

the substance that is dissolved

what is an aqueous solution?

water is the solvent

why do hydrophilic substances have an affinity to water?

when an ionic compound is dissolved in water, each ion is surrounded by a sphere of water molecules called a hydration shell

what are hydrocarbons?

organic molecules consisting of only carbon and hydrogen

• can undergo reactions that release a large amount of energy

what molecules make up prokaryotes and eukaryotes?

• carbohydrates

• proteins

• nucleic acids

• lipids

what is a polymer?

a molecule consisting of an infinitely long chain of similar building blocks called monomers

how does a dehydration reaction occur?

when two monomers bond together through the loss of a water molecule

• the synthesis of carbohydrate and protein polymers

how are polymers disassembled?

hydrolysis; a reaction that is essentially the reverse of the dehydration reaction

• the breakdown of carbohydrate and protein polymers

what is the function/purpose of nucleic acids?

store, transmit, and help express hereditary information

what are the two types of nucleic acids?

• deoxyribonucleic acid (dna)

• ribonucleic acid (rna)

what provide for dna replication?

dna provides for its own replication

explain the process of gene expression

dna directs synthesis of messenger rna and, through mrna, controls protein synthesis

what do two dna molecules together form?

a double helix

what makes up the rail of a double helix?

phosphate and sugar

what makes up half step of double helix?

nitrogenous base

what is the structure of dna?

there are four bases, which can be in any order on a stand (T,G,C,A)

true or false: the sequence of bases along a DNA or polymer is unique for each gene, and does not change the double helix shape

true

whata does pairing a purine with a pyrimidine result in?

uniform width consistent with double helix structure

what kind of bonds hold stair steps (bases) together?

hydrogen bonds

what os antiparallel structure of dna?

the backbones run in opposite 5’-3’' directions from each other

what are chargaff’s rules of base pairing in dna?

• the base composition of dna varies between species

• in any species the number A and T bases equal the number of G and C bases is equal

what does the rna monomer consist of?

• sugar is ribose (with an OH)

• bases can be adenine (A), uracil (U), guanine (G), cytosine (C)

• U pairs with A

what does a dna monomer consist of?

• sugar is deoxyribose (with an H)

• bases can be adenine (A), thymine (T), guanine (G), cytosine (C)

is rna double or single stranded?

single-stranded

where can complementary pairing occur in rna?

between two rna molecules or between parts of the same molecule

what does the OH instead of an H mean in rna?

• rna can take a variety of shapes

• it can base-pair with itself and with dna but it can take other shapes too

• OH is more chemically reactive, so different rnas can have different functions

what are some example functions of rna?

• carry genetic information

• bind and regulate the function of dna

• bind to other molecules and carry them around

what consists of the backbone of proteins? what is its function?

ALWAYS THE SAME

+NH3-CH-COO-

• how amino acid links to other amino acids to form a peptide

what is the structure/function of an amino acid side chain?

• structure: variable (always attached to the alpha carbon)

• function: its chemistry give proteins their shape and function

what is the amine group of an amino acid?

NH2 or NH3+

• binds to the carboxyl of another amino acid

what is the alpha carbon of an amino acid?

• will always be bound to: the carboxyl, the amine, and the side chain

what is the carboxyl group of an amino acid?

• COO- or COOH

• binds to the amine of another amino acid

what are the types of chemistry of amino acids?

• nonpolar

• polar

• acidic (- charged)

• basic (+ charged)

what kind of bonds join together amino acids?

peptide bonds (covalent bonds)

what does a functional protein consist of?

one or more polypeptides precisely twisted, folded, and coiled into a unique shape

what determines a protein’s three dimensional structure?

the sequence of amino acids

what does a protein’s function depend on?

its ability to recognize and bind to some other molecule

what is the primary structure of proteins?

• sequence of amino acids

• determined by inherited genetic information

what is the secondary structure of proteins?

• coils and folds

• results from hydrogen bonding between repeating constituents of the polypeptide backbone

• side chains not involved

what is the tertiary structure of proteins?

• shapes a strand’s overall 3-D shape

• hydrogen bonds, ionic bonds, hydrophobic interactions, van der waals interactions

• strong covalent bonds called disufide bridges may reinforce the proteins structure

what are disulfide bridges?

• one special type of bond that can be involved in tertiary (and quarternary) structure

• occurs when the sulfurs in side chains of two cysteine amino acids interact to form a covalent bond

what is the quaternary structure of proteins?

• same kind of side chain interactions as tertiary structure: disulfide bridges, hydrogen bonds, hydrophobic interactions, ionic interactions

• Difference: side chains are on different polypeptides

what is the one class of large biological molecules that does not include true polymers?

lipids

what is the unifying feature of lipids?

they mix poorly, if at all with water

what do lipids mostly consist of?

hydrocarbon regions

what are the most biologically important lipids?

fats, phospholipids, steroids

what are the functions of lipids?

• storing energy

• make membranes to make compartments around and within cells

• insulation

what is the structure of a phospholipid?

• two fatty acids and a phosphate group re attached to glycerol

• the two fatty acid tails are hydrophobic, but the phosphate group and its attachements form a hydrophilic head

phospholipids in water:

• the heads will contact the water (polar)

• the tails will contacts each other and not the water (nonpolar)

what consitutes a phospholipid bilayer?

• double layered sheets called bilayers

• hydrophobic facing interior

• forms a boundery between the cell and external environment

what are amphipathic molecules?

molecules containing hydrophobic and hydrophilic regions