Chapter 2,3,4,5,6 Flashcards
what are atoms?
building blocks of matter composed of atoms protons and neutrons
how do electrons determine atoms?
determines characteristic of atoms and behaviour, electron’s position indicates energy level
what is atomic number
represents # of protons in atom and specifies atom as a particular element
what is atomic mass
combined number of protons and neutrons in atom
what are isotopes?
atoms of same element but different atomic mass, neutron # differs
how are isotopes used?
due to radioactivity of some isotopes, used in carbon dating, medical purposes, radiotherapy, etc.
what are ions?
atoms that have lost or gained electrons
what are cations?
ions that lost electrons, positively charged
what are anions?
ions that gained electrons, negatively charged
what are covalent bonds?
bonds formed when two atoms equally share a pair of valence electrons
what is an atom’s valency?
of electrons an atom needs to gain/lose to complete its valence shell, # of covalent bonds an atom can form
what are valence electrons?
electrons found in an atom’s outermost shell
what are nonpolar bonds?
bonds where atoms share electrons equally
what are polar bonds?
bonds where atoms share electrons unequally, presence of dipole or partial charges
what are ionic bonds?
bonds that occur when two atoms are so unequal in their attraction for electrons that more electronegative ion strips away an electron from its partner resulting in complete ionic transfer
what are solvation spheres?
when ions are dissolved in water, they become surrounded by water molecules that are attracted to them
what are hydrogen bonds?
interaction of a hydrogen atom and a more electronegative atom
what do hydrogen bonds do in biological molecules?
they stabilize them
rank strength of bonds from least to greatest
hydrogen - ionic - polar covalent - nonpolar covalent
what are characteristics of water
cohesive behaviour, expansion upon freezing, ability to moderate temp, solvent
what is water’s cohesive behaviour?
water molecules have a tendency to stick together and to other polar molecules
how does water defy gravity and go to top of trees?
water acts as medium of transport, adheres to polar surfaces of cell walls, allows things to move without friction, adhesion to cell wall helps resist downward pull of gravity, pressure difference in plants pull water to top of tree
explain water’s expansion upon freezing
water is less dense as solid compared to liquid, ice has fewer water molecules than an equal volume of liquid water
what is water’s ability to moderate temp?
water resists large temp. changes because hydrogen bonds must break before water can change temp, billions of hydrogen bonds in water, water has high heat capacity
why is water a versatile solvent?
because of its polarity, water can dissolve more substances than any other liquid
Hydrogen bonds form between water molecules because the sharing of electrons is not equal between oxygen and hydrogen. When a water molecule is formed by two hydrogen atoms and one oxygen atoms, a polar covalent bond is formed. The larger more electronegative oxygen atom assumes a partial negative charge, attracting hydrogen from other water molecules which have a partial positive charge.
what is an element?
pure substances made with one type of atoms that cannot be broken down further
what elements are most abundant in living matter?
C H O N make up 96% along with Ca, P, S
what is a compound?
more than one type of atoms that can be further broken down via chemical reactions/purification into their elements
what is a molecule?
atoms held together by chemical bonds
what are ionic compounds?
ions held together by ionic bonds
the ability of other atoms to combine with other atoms is determined by what?
distribution of electrons in its valence shell
what does the number of valency electrons mean in an atom?
determines how reactive it is,
what is molecule stability?
when molecules tend to be more stable when they share enough electrons to fill valence shell
what are hydrophobic substances?
water-fearing, nonpolar
what are hydrophilic substances?
water-loving, polar
what are buffers?
substances that minimize concentration changes of H+ and OH- , most consist of a weak acid-base pair
how do buffers work?
reversibly work by either accepting or donation H+
what are organic compounds
molecules that contain carbon and are found/manufactured by organisms
why is carbon prevalent in organic compounds?
has 4 electrons in valence shell, behaves as if it has four unpaired valence electrons and can form 4 covalent bonds with other molecules
how are single and double bonds different?
double bonds are stronger and not free to rotate, have flat shape
what are isomers?
molecules with same chemical formula but different structures or spatial arrangements
what are structural isomers?
isomers that differ in covalent bond arrangement of carbon skeleton, minimum of 4 carbons in chemical formula to have structural isomers
what are geometric isomers?
isomers with same covalent bond arrangements but atoms differ in spatial arrangement
why can butan not form geometric isomers?
it only has single carbon bonds
what are enantiomers?
isomers that are mirror images of each other due to presence of chiral/asymmetric carbon, carbon is attached to 4 different types of groups
what are proteins?
most diverse class of macromolecules, act as structural support for cells, acts as catalysts to facilitate or speed up reactions
what does an amino acid generally look like?
central carbon covalently bonded to COOH group, NH2 group, hydrogen atom, and an R group
can amino acids form enantiomers?
yes except for glycine (R group is a hydrogen atom)
amino acid monomers are linked by a _________.
peptide bond
what are nucleic acids?
encodes genetic info in their nucleotide sequence
what are components of nucleic acids?
5-carbon sugar, phosphate groups, nitrogenous bases
adjacent nucleotide pairs are joined together by _________.
phosphodiester bonds
why does hydrolysis not occur spontaneously in nucleic acids?
lack of enzymes that facilitate or speed up hydrolysis reaction
sugars are linked together by a covalent _______.
glycosidic bond
what is empirical formula of carbs?
[CH2O]n
monosaccharides serve as what?
major source of energy for cells and as raw material for building molecules
what is starch?
storage polysaccharide used by plants for energy
what is cellulose?
structural polysaccharide and major component of plant cell walls
why can we digest starch but not cellulose
due to difference on two ring forms for glucose, enzymes recognize starch but not cellulose
what is glycogen?
storage form of glucose for animals
what are carbs on cell surfaces involved in?
cell to cell recognition
what are lipids?
hydrophobic nonpolar molecules not composed of any single monomers
what are major functions of lipids?
composing plasma membrane, energy storage and insulation
what are lipids constructed from?
triacyl glycerol/ triglycerides are constructed from glycerol and fatty acids
what kind of bonds are glycerol and fatty acids linked by?
ester linkages
what are saturated fatty acids?
max number of hydrogen atoms, no double bonds
what are unsaturated fatty acids?
one or more double bonds
what are cis-fats?
kink at each double bond, liquid at room temp
what are trans-fats?
no kink at double bonds, solid at room temp
why are cis-fats liquid but trans-fats solid?
kinked fatty acid chains prevent tight packing, attraction is weaker, requires less energy to melt
what are Van Der Waals forces?
temporary dipoles forms due to constant electron motion in fatty acid chains, regions of slight charges attracted or repelled by neighbouring molecules
what are phospholipids?
lipids with polar phosphate head that form semipermeable bilayer for cell membranes
what are steroids?
makes up cell membranes and strengthens them, all derived from cholesterol, functions as hormones
what are functional groups?
specific configuration of atoms commonly attached to carbon skeletons of organic molecules and are involved in chemical reactions
