Chemistry (Cliff Notes) Flashcards
What is an ionic bond?
a bond shared between two atoms when electrons are transferred from one atom to another (ie: Na+Cl-)
What is a covalent bond?
A bond that forms when electrons between atoms are shared
What is a non polar covalent bond?
A bond that forms when electrons between atoms are shared EQUALLY (ie: O2)
What is a polar covalent bond?
A bond that forms when electrons between atoms are shared UNEQUALLY (ie: H2O)
How many electrons are shared in a single covalent, double covalent, and triple covalent bond respectively?
2, 4, 6
What is a hydrogen bond?
A hydrogen bond is an IMF so considered a weak bond between molecules. They form when a H+ in one molecule is attracted to a (-) on another molecule. Water molecules are held together by hydrogen bonds.
Why does water make an excellent solvent?
Because of it’s polar covalent bonds that can interact with ionic substances and separate them into ions.
Why are non polar covalent molecules hydrophobic?
Nonpolar covalent substances are hydrophobic because they lack charged poles (because the electrons are shared equally), and cannot interact with the poles of the polar water molecules
Why does water have a high heat capacity?
Because is changes temperature very slowly with changes in its heat content, and a large amount of energy is required to warm water or even freeze water.
Why does ice float?
The hydrogen bonds between water molecules become more rigid and water molecules are separated - this is why water expands as it freezes. The crystal lattice that is formed is also known as ice, which is less dense, and therefore floats.
Does water have strong cohesion? Why or why not?
Water does have strong cohesion because of the hydrogen bonds between water molecules - the polarity in these bonds allows for attraction between like substances
Does water have high or low surface tension? Why?
The strong cohesion of water results in a high surface tension, that is firm enough to allow many insects to walk upon it without sinking
Does water have strong adhesion?
Yes. It can act as sort of a binding agent between two unlike substances (Like wetting your finger so you can turn the page of a book)
What is cohesion?
The attraction between like substances
What is adhesion?
The attraction of unique substances
Explain the capillary action of water
Because water has strong adhesion, it adheres to the walls of narrow tubing or to absorbent solids, demonstrating capillary action
What is an organic molecule?
Molecules that have carbon atoms
What is a macromolecule?
Large organic molecules that may consist of hundreds or thousands of atoms, and are usually polymers.
What is a polymer?
Molecules consisting of a single unit (monomer) repeated many times
What does a functional group do to organic molecules?
It gives an organic molecule a particular property, such as acidity or polarity, depending on the functional group added.
What is a monosaccharide?
The simplest kind of carbohydrate consisting of a single molecule such as glucose or fructose.
What are the two forms of glucose?
alpha-glucose and beta-glucose
What is a disaccharide?
A carbohydrate consisting of two sugar molecules joined by a glycosidic linkage through a condensation, more specifically, a dehydration reaction.
What are the two monosaccharides that make up sucrose?
Glucose + Fructose=sucrose (table sugar)
What are the two monosaccharides that make up lactose?
Glucose + Galactose=Lactose (sugar in milk)
What are the two monosaccharides that make up maltose?
Glucose + Glucose
What is a polysaccharide?
A polymer of monosaccharides.
What is starch?
It is a polysaccharide of repeating units of alpha-glucose used as an energy storage molecule in plant cells
What is glycogen?
It is a polysaccharide of repeating units of alpha-glucose used as an energy storage molecule in animal cells
What is the difference between starch and glycogen if they are both polysaccharides of alpha-glucose?
Starch has a structure that is coiled and unbranched or long and branched; whereas glycogen are short and highly branched
What is cellulose?
A polymer of beta-glucose molecules. It is used as a structural molecule in the walls of plant cells and is the major component of wood
What is chitin?
A polymer of beta-glucose molecules, but different from cellulose because each beta-glucose molecule has a nitrogen-containing group attached to the ring. Chitin serves as a structural molecule in the walls of fungus cells and the exoskeletons of insects, other arthropods, and mollusks
What is the composition of triacylglycerol?
Glycerol + 3 fatty acids
What is a saturated fatty acid?
Single bond between each pair of carbon atoms, with 2 hydrogens on each carbon, except for the last carbon which has 3 (“saturated with hydrogen”)
What is a monounsaturated fatty acid?
A Fatty acid with one double bond
What is a polyunsaturated fatty acid?
A fatty acid with two or more double bonds
What is a phospholipid?
Looks like a lipid, except one of the fatty acid chains is replaced by a phosphate group. This phosphate head is the hydrophilic portion of the molecule, and the two fatty acid chains are the hydrophobic portion of the molecule - thus making a phospholipid amphipathic. Phospholipids are often oriented in a sandwich-like formation because of its amphipathic nature.
How is a steroid characterized, and what are some examples of it?
It is characterized by a backbone of four inked carbon rings. Examples include cholesterol, and certain hormones like testosterone and estrogen
What are the 5 groups of proteins according to their function?
Structural, storage, transport, defensive, enzymes.
What is a protein?
A polymer of amino acids joined together by peptide bonds (chain is a polypeptide or peptide)
What is the primary structure of a protein?
describes the order of amino acids, using 3 letters to represent each amino acid
What is the secondary structure of a protein?
3D shape resulting from H-bonding between amino and carboxyl group of adjacent AA. This produces spiral (alpha helix) or folded plane that looks like pleats (beta pleated sheets). Proteins whose shape is donated by these two patterns often from fibrous proteins.
What is the tertiary structure of a protein?
3D shape often dominating the structure of globular proteins. This is a result of H-bonding between R groups of AA and Ionic bonding between R groups of AA.
What is the hydrophobic effect that occurs in the tertiary structure of a protein?
When Hydrophobic R groups move toward the center of the protein (away from the water in which the protein is usually immersed)
How are turns of AA chain maintained in the tertiary structure of a protein?
The formation of disulfide bonds when the sulfur atom in the AA Cys bonds to the Sulfur atom in another Cys (forming cystine). This disulfide bridge helps maintain turns in the AA chain.
What is the quaternary structure of a protein?
Describes a protein that is assembled from two or more separate peptide chains. The globular protein hemoglobin, for example, consists of four peptide chains that are held together by H-bonding, interactions among R groups, and disulfide bonds.
What is DNA?
(Deoxyribonucleic acid), a molecule consisting of 3 parts, a nitrogenous base, a 5-carbon sugar (ribose), and a phosphate group. DNA is a polymer of nucleotides.
What are the four DNA nucleotides?
- Adenine (Purine)
- Guanine (Purine)
- Thymine (Pyrimidine)
- Cytosine (Pyrimidine)
What is a pyrimidine?
Single-ring nitrogenous bases
What is a purine?
Double-ring nitrogenous bases
Describe what makes the two strands of the DNA helix antiparallel
One strand is arranged from 5’»3’ direction, that is, it begins with a phosphate group attached to the fifth carbon of deoxyribose (5’ end) and ends where the phosphate of the next nucleotide would attach, at the third deoxyribose carbon (3’ end). The adjacent strand is oriented in the opposite, of 3’»5’ end
Name 3 ways RNA is different from DNA
- Sugar in RNA is ribose, not deoxyribose
- Thymine does not occur in RNA, and replace by Uracil which pairs with Adenine
- RNA is usually single-stranded and does not form a double helix as it does in DNA.
What causes a chemical reaction to take place?
Reacting molecules (or atoms) must first collide and then have sufficient energy (activation energy) to trigger the formation of new bonds.
Is a catalyst required for a reaction fo happen?
No, reactions may occur spontaneously, but a catalyst accelerates the rate of the reaction by lowering the activation energy required for the reaction to take place.
Is a catalyst consumed in the reaction?
No, it does not undergo a chemical change itself, so it can be used over again.
What is metabolism?
Chemical reactions that occur in biological systems. Metabolism includes the breakdown of substances (catabolism), the formation of new products (synthesis, anabolism), or the transferring of energy from one substance to another.
What is chemical equilibrium?
This describes a condition where the rate of the reaction in the forward direction equals the rate in the reverse direction and, as a result, there is no net production of reactants or products.
What determines the net direction of metabolic reactions?
The concentration of reactants and end products
What is an enzyme?
A globular protein that act as catalysts (activators or accelerators) for metabolic reactions.
What affects the efficiency of an enzyme?
Temperature and pH. In the human body, temperatures above 104 F can cause enzymes to become denatured, losing their 3D shape as H-bonds and peptide bonds break.
Pepsinogen is activated only at low pH
What is a cofactor?
Nonprotein molecules that assist enzymes.
What is ATP? How does it used in metabolic reactions?
Adenosine Triphosphate is a common source of activation energy for metabolic reactions. through breaking the last bond and giving up this energy. This results in ADP and ATP can be reassembled through phosphorylation when ADP is combined with a phosphate group.
What is an allosteric enzyme?
An enzyme with two kinds of binding sites, one for a substrate and another for an allosteric effector
What is an allosteric effector?
One that acts on the allosteric site of the enzyme. An effector can be either an activator (induces the active form of the enzyme), or an inhibitor (induces the inactive form of the enzyme)
What is feedback inhibition?
The end product of a series of reactions acts as an allosteric inhibitor, shutting down one of the enzymes catalyzing one of the series of reactions
What is competitive inhibition?
A substance that mimics the substrates and competes for occupation of the active site of an enzyme. This occupation of the active site displaces the substrate and prevents the enzyme from catalyzing the substrate.
What is noncompetitive inhibition?
A substance that inhibits the action of the action of the enzyme by occupying a site other than the active site. This disables enzymatic activity. Many toxins and antibiotics are noncompetitive inhibitors.
What is cooperativity with regard to enzyme function?
In cooperatively, an enzyme becomes more receptive to additional substrate molecules after one attaches to the active site. This can occur in an enzyme with two or more subunits, each having its own active site.