Exam 1 Flashcards
The number of ________ in an atom is always constant but the number of _______ can vary.
protons, electrons and neutrons
Mass number =
number of protons + neutrons
Atomic number =
number of protons
What are the most abundant elements found in organisms?
Hydrogen, carbon, nitrogen, oxygen, sodium, magnesium, phosphorous, sulfur, and chlorine
What is a covalent bond?
The sharing of electrons between atoms
How many bonds can carbon form?
4
How many bonds can oxygen form?
2
How many bonds can hydrogen form?
1
How many bonds can nitrogen form?
3 or 4
How many bonds can phosphorous form?
5
How many bonds can sulfur form?
2, 4, or 6
How many electrons can the third shell hold?
8 or 18
________ is the primary component of life on Earth.
Carbon
Carbon atoms in organic molecules are responsible for their overall _______.
shape
What is a nonpolar covalent bond?
When electrons are shared equally
What is a polar covalent bond?
When electrons are shared unequally
Electronegativity depends on what two factors?
number of protons and the distance between protons and the valence shell
What is the comparison of electronegativity between oxygen, nitrogen, carbon, sulfur, phosphorous, and hydrogen?
O>N>C-S-P-H
What is an ionic bond?
The gain or loss of an electron (due to electronegativity)
Water is ____.
polar
Water molecules form _______ _____.
hydrogen bonds
What are characteristics of hydrogen bonds?
Weak electrical attraction, no electron sharing, much weaker than covalent and ionic bonds, occurs between an H with a + charge and an atom with a - charge.
Why can many molecules dissolve in water?
Because they can form hydrogen bonds with the water molecules.
What shape does a water molecule have?
Bent
What are macromolecules?
Large, complex molecules (proteins, nucleic acids, carbohydrates, etc.)
A polymer is made up of _______.
monomers
Proteins are composed of ______ ______.
amino acids
What groups/atoms are in an amino acid?
Amino group, carboxyl group, hydrogen atom, a central carbon atom, and a side chain
What is an acid?
A molecule that can donate a proton
What is a base?
A molecule that can attract a proton
Does the amino group in proteins act as an acid or base?
base
Does the carboxyl group in proteins act as an acid or base?
acid
What is the side chain of glycine (Gly/G)?
a hydrogen atom
What are the characteristics of hydrophobic side chains?
nonpolar, does not contain O and N (except Trp)
What are the characteristics of hydrophilic side chains?
polar, have O and sometimes N, have a partial charge
If you see - it is an ______ side chain, if you see + it is a ______ side chain.
acidic, basic
What forms peptide bonds?
condensation (dehydration) reactions
What is a condensation (dehydration) reaction?
Monomer in, water out. A bond is formed and water is produced.
A peptide bond is similar to a _______ bond.
double
What group is on the N-terminus of a protein?
Amino group
What group is on the C-terminus of a protein?
Carboxyl group
What is the formula for a carboxyl group?
COOH
What is the formula for an amino group?
NH2
Proteins move because single bonds ________.
rotate
How many amino acids does a peptide (oligopeptide) contain?
less than 50
How many amino acids does a protein contain?
50 or more
A polypeptide can be a ______ or ______.
peptide, protein
What is the primary structure of a protein?
a unique sequence of amino acids
Changes (due to a mutation) in the primary structure of a protein can affect _______ _______.
protein function
What is the secondary structure of a protein?
Three-dimensional form of short amino acid sequences (a-helix or B-pleated sheets)
What type of bonding creates the secondary structure of protein?
Hydrogen bonding
What type of bonding forms the tertiary structure of proteins?
Hydrogen bonds, ionic bonds, hydrophobic interactions, and disulfide bonds
What is the tertiary structure of proteins?
A three-dimensional form of proteins comprised of multiple a-helices or B-pleated sheets
What is the quaternary structure of proteins?
When two or more proteins form a complex
What types of bonds form the quaternary structure of proteins?
Hydrogen bonds, ionic bonds, hydrophobic interactions, and disulfide bonds (same as tertiary structure)
What type of R group does cysteine have?
A sulfhydryl group (CH2-SH)
What is a dimer?
A complex of two proteins
What is a tetramer?
A complex of 4 proteins
How are proteins structures determined?
X-ray crystallography
What is the overall shape of a protein determined by?
Its primary structure
Structure defines ______.
function
_______ are the most versatile large molecules in the cell.
Proteins
What is the formation of the tertiary and quaternary structure of proteins called?
Protein folding
Protein folding is often _______.
Spontaneous
A folded molecule is often more __________ _____ than the unfolded molecule.
energetically stable
What is an unfolded protein called?
a denatured protein
What proteins help some proteins fold correctly in cells?
Chaperones
Why do high temperatures lead to protein unfolding?
High temperatures break bonds
What environmental conditions determine protein folding?
Temperature, ion concentration, and pH
What breaks proteins back down into amino acids?
Hydrolysis (water in, monomer out)
What monomers comprise nucleic acids?
nucleotides
What makes up a nucleotide?
Phosphate group, nitrogenous base, and a 5-carbon sugar
Which carbon in deoxyribose is lacking an oxygen atom compared to ribose?
C2
Which is larger: purine or pyrimidines?
Purines
Which nitrogenous bases are purines?
Guanine and adenine
Which nitrogenous bases are pyrimidines?
Cytosine, Uracil, and Thymine
The nitrogenous is bonded to which carbon in the 5-carbon sugar?
C1
What is the abbreviation for monophosphates, diphosphates, and triphosphates?
_MP, _DP, _TP
What goes in front of nucleotides with deoxyribose?
the letter “d”
What forms nucleic acids (type of linkage)?
Phosphodiester linkage
How is a phosphodiester linkage formed?
A condensation reaction between C3 of the 5-carbon sugar and phosphate
What is the 5’ end?
Then end with an unlinked 5’ phosphate
What is the 3’ end?
The end with an unlinked 3’ hydroxyl
What direction are nucleotide sequences written in?
5 ——> 3
What is used for DNA and RNA synthesis?
Nucleoside triphosphates
Are DNA and RNA acids or bases?
acids
What type of charge does DNA and RNA have?
A negative charge
What is the secondary structure of DNA stabilized by?
hydrogen bonding
What if the half life of DNA?
521 years
What is the secondary structure of RNA?
a double stranded region forming a helix, and and single stranded region forming a loop
What is the tertiary structure of RNA?
When secondary structures fold into more complex shapes
What can RNA function as?
a catalytic molecule
What are ribozymes?
Enzyme-like RNAs
What type of carbohydrate is sugar?
sucrose
What type of carbohydrate are wood and cotton?
cellulose
Milk contains what type of carbohydrate?
lactose
What is a carbohydrate?
Organic compounds with the empirical formula (CH20)n
What functional groups are found in carbohydrates?
carbonyl group, hydroxyl group, and a hydrogen atom
What is a monosaccharide?
simple sugars, monomers
What are examples of monosaccharides?
glucose, galactose, fructose, ribose, and deoxyribose
What are disaccharides made up of?
two monomers
What is sucrose?
glucose+fructose
What is lactose?
glucose+galactose
What are oligosaccharides?
polymers made from 3-10 monosaccharides
What is a polysaccharide?
A polymer made from many monosaccharides
What are examples of polysaccharides?
starch, glycogen, cellulose, chitin, and peptidoglycan
What do monosaccharides differ in?
The number of carbon atoms present, and the arrangement and number of their hydroxyl groups
What is a monosaccharide with 3 carbons called?
a triose
What is a monosaccharide with 5 carbons called?
a pentose
What is a monosaccharide with 6 carbons called?
hexose
What do glucose and galactose differ in?
The configuration of their hydroxyl groups at C4 (glucose = OH over H, galactose = OH under H)
Hexokinase will interact with _______ but never _______.
glucose, galactose
What do many monosaccharides form in aqueous solutions?
ring structures
a-glucose and B- glucose differ in?
The configuration of their hydroxyl groups at C1 (a-glucose = OH on bottom, B-glucose = OH on top)
Are carbohydrates hydrophobic or hydrophilic?
hydrophilic
What produces polysaccharides?
The condensation of monosaccharides
What type of linkage forms polysaccharides?
glycosidic linkage (condensation reaction)
When B-galactose and B-glucose link together, ______ is flipped.
B-glucose
What forms maltose?
a-glycosidic linkage
What forms lactose?
B-glycosidic linkage
What breaks down polysaccharides?
hydrolysis ( water in, monomer out)
What polysaccharides are made of glucose?
glycogen, starch, and cellulose
Cellulose =
(B1 –> 4) linked glucose units
What do glycogen and starch do?
store and provide energy in cells
Why do glycogen and starch provide energy in cells?
They have a lot of C-H and C-C bond, high potential energy bonds. When they are broken, energy is released.
Glycogen is a _______ molecule.
Branched
Which is more branched: glycogen or starch?
glycogen
Starch is produced by ________, while glycogen is produced by ________.
Plants, animals
Where is glycogen stored?
In the liver
What does an organism do when it need energy?
- glycogen or starch are hydrolyzed to glucose
- cells break down glucose through a series of reactions (respiration)
- released energy is captured through synthesis of ATP (adenosine triphosphate)
What forms cells walls?
cellulose
What makes up a bacterial cell wall?
peptidoglycan
What makes up fungi cell walls and insect exoskeletons?
Chitin
What are characteristics/ roles of a cell wall?
- outside of the plasma membrane
- very rigid and cage-like
- responsible for cell shape
- prevents osmotic bursting
- protects from other organisms
In a cell wall, many ______ molecules aligned along each other are joined by ______ ______.
cellulose, hydrogen bonding
What is the most abundant molecule on earth?
cellulose
In fungi cell walls and insect exoskeletons, many _______ molecules are aligned along each other and joined by ______ _____.
chitin, hydrogen bonding
What is chitin similar to? What type of linkage does it have?
glucose, B1–>4 glycosidic linkage
What type of linkage does peptidoglycan have? What bonds hold it together?
B1–>4 glycosidic linkage, hydrogen bonds
What carbohydrates are structural carbohydrates?
cellulose, chitin, peptidoglycan
What do carbohydrates do? (5 things)
- store chemical energy
- provide fibrous structural materials
- serve as precursors to larger molecules
- indicate cell identity
- make proteins more stable
Which carbohydrates serve as precursors to larger molecules?
glucose, galactose, fructose
Which carbohydrates indicate cell identity and make proteins more stable?
glycoproteins
How do glycoproteins indicate cell identity?
They display informations on the outer surface of cells
What is each spike on a spike protein made of?
Three intertwined proteins
What are lipids?
Carbon containing compounds found in organisms.
What are lipids mostly made of?
C-C and C-H bonds
Are lipids polar or nonpolar?
nonpolar
Are lipids hydrophobic or hydrophilic?
Largely hydrophobic
What are the three most important types of lipids found in cells?
Triacylglycerols, phospholipids, and steroids
What do tracylglycerols do?
Store energy through fats and oils
What do phospholipids do?
Make membranes
What do steroids do?
Found in membranes, vitamins, and hormones
What are the key building blocks of lipids?
Fatty acids
What do fatty acids contain?
A carboxyl group and a hydrocarbon chain
Fatty acids are __________.
Amphipathic ( have polar and nonpolar parts)
Amphipathic salts of fatty acids spontaneously form ________.
micelles
Does a saturated fatty acid have double bonds?
No
Does an unsaturated fatty acid have double bonds?
yes
What do double bonds in fatty acids cause?
Kinks in the tails
What does monounsaturated mean?
one double bond
What does polyunsaturated mean?
many double bonds
What does a triacylglycerol consist of?
A glycerol linked by ester linkages to three fatty acids
How do fats form?
Via dehydration reacts (Ester linkages)
What are tricylglycerols from animals called? Plants?
fats, oils
What does the melting point of triacylglycerols depend on?
The number of double bonds in their tails
Are oils saturated or unsaturated?
unsaturated
Are fats saturated or unsaturated?
saturated
What is the function of oils in plants?
Serve as an energy reserve in seeds
What is a phospholipid made of?
glycerol, two fatty acids, and a polar group (has phosphate)
Amphipathic phospholipids spontaneously form ______ ______.
lipid bilayers
Eukaryotic cells have many _________.
membranes
Phospholipids bilayers have selective ________.
permeability
What types of molecules have the highest permeability?
Small, nonpolar molecules
What types of molecules have the lowest permeability?
Ions
Do lipid bilayers with short and unsaturated hydrocarbon tails have higher or lower permeability and fluidity?
higher
Do lipid bilayers with long and saturated hydrocarbon tails have higher or lower permeability and fluidity?
lower
What type of structure does a steroid have?
a bulky, four-ring structure
What is the most abundant steroid in animals?
cholesterol
What is the function of cholesterol?
reduces membrane permeability, precursor of vitamin D, and a precursor for several hormones
Cholesterol does not exist in ______.
plants
What does the quickness of molecule movement across membranes depend on?
The structure of fatty acid tails, the number of cholesterol molecules in the bilayer, and temperature
How does temperature affect permeability?
Higher temperature = more movement
Phospholipids are in _______ ______ motion.
constant lateral
What do plasma membranes allow for?
For cells to create an internal environment that is much different from an external one.
What do other cell membranes allow for?
compartmentalization
What does the existence of membrane lead to the formation of?
concentration gradients
What is a concentration gradient?
A difference in solute concentrations across a barrier
Why do molecules cross membranes?
Molecules and ions move randomly (diffusion), net movement from high-concentration regions to low concentration regions, spontaneous process (requires no energy input)
When does equilibrium occur?
When the molecules or ions are randomly distributes (no more net movement)
How does water move across lipid bilayers?
Water moves from regions of low solute concentration to regions of high concentration
What is osmosis?
The movement of water across a selectively permeable membrane
What is passive diffusion?
Movement of molecules across membranes along their concentration gradients
What is a hypotonic solution to outside?
When there is less of a solute within a cell and more outside
What is a hypertonic solution to outside?
When there is more of a solute within a cell and less outside
What is an isotonic solution to outside?
When the solute is evenly distributed
What happens when a cell is hypotonic to the outside?
The cell shrinks
What happens when a cell is hypertonic to the outside?
It swells with water and bursts
What is a peripheral membrane protein?
The portion of the protein on the outside of the membrane
What is an integral membrane protein?
The portion of a protein inside of the membrane
What allows biologists to view membrane proteins?
Freeze-fracture preparations
Proteins can be ________.
amphipathic
What proteins can integrate into lipid layers?
Amphipathic proteins
What are the two mechanisms of membrane transport?
Diffusion and facilitated diffusion (passive diffusion)
What is aquaporin?
facilitated diffusion, water channel, passive transport along its electrochemical gradient, allows for osmosis
What is active transport?
Transport against the electrochemical gradient
What do channel proteins do?
Aid in facilitated diffusion
What does each channel protein have?
A specific structure that allows only a particular type of ion or small molecule to pass through it
What direction(s) can a molecule move through a channel?
Both directions
What do gated proteins do?
Regulate movement through membrane channels: open or close in response to a signal
What are the two types of gated proteins?
Voltage-gated and ligand-gated (extracellular ligand)
How does a potassium channel work?
When the inside of the membrane is negatively charges relative to the outside, the channel is closed (gate blocks ions from entering channel). If membrane charge asymmetry is reversed, channel opens (filter only allows K+ ions to pass).
How do carrier proteins work?
They change shape during the transport process, a glucose transporter named GLUT-1 increases permeability to glucose. Carrier proteins are slower than channels.
What are the steps of glucose diffusion with GLUT-1?
- Unbound protein outside of the cell
- glucose binding
- conformational change
- release
Is the movement of substances through channel and carriers passive or active?
Passive
What is passive transport powered by?
diffusion along an electrochemical gradient
What factors affect facilitated diffusion?
The difference in the concentration of solutes between the two sides of the membranes, the number of channels/carrier proteins available on the plasma membrane, the affinity of the channel/carrier protein for its substrate molecule
What are pumps?
Membrane proteins that transport molecules across the membrane against the electrochemical gradient. Requires energy in the form of ATP
What are the steps of Na+/K+ pump?
- unbound protein
- sodium binding
- shape change
- release
- unbound protein
- potassium binding
- shape change
- release
What percentage of ATP generated by your body is used by the Na+/K+ pump?
30%
What does the Na+/K= pump do?
It establishes an electrochemical gradient in animal cells
What does an H+ pump do?
Establish an electrochemical gradient in bacterial, yeast, and plant cells
What does the electrochemical gradient allow for?
secondary active transport, or co-transport
What are antiporters?
Channel that move two ions in opposite directions
What are symporters?
Channels that move two ions in the same directions
