AP Biology
Quick Review:
Biochemistry
Everything you need
to know about
biochemistry for the
AP Biology Exam!
All About Water!
- Water is the best example of a polar molecule (the oxygen is the
more electronegative atom).
- The properties of water allow life to sustain on earth: cohesion
("water to water" sticking), adhesion ("water to other" sticking),
lower density as a solid, superb solvent, high specific heat, and
high heat of vaporization.
- Who can tell the importance of each property? Examples?
- Most of water's properties result from hydrogen bonding, a weak
attraction that occurs when an "electron" hungry atom (like
oxygen) attracts hydrogen atom's electrons. Remember, this
"bond" is extremely weak but essential for life.
- Water is prevalent in the body and is an apt environment because
the phospholipid bilayers of cell membranes spontaneously form
in water (this could not occur without water.
The Importance of Carbon
- The study of molecules and compounds containing carbon is
called "organic chemistry".
- Carbon atoms are versatile building blocks because they have four
valence electrons, allowing for four stable covalent bonds to be
made. This is why carbon is so prevalent in major
macromolecules in the body.
- There are four types of carbon compounds that are covered on the
exam: carbohydrates, lipids, proteins, and nucleic acids.
- Carbon compounds are complex molecules that are assembled
from smaller subunits (lipids are the exception because they are
composed of long hydrocarbon chains as opposed to smaller
monomers).
- OFF WE GO!
Carbohydrates
- Carbs are usually synonymous with sugars - simple or complex
- Composed of carbon, hydrogen, and oxygen atoms in a set empirical formula: (CH20)X;
the "X" stands for number of carbons (so obviously the number of carbons in carbs is
variable).
- What are carbs used as? Structural components, sources of short-term energy storage,
and raw materials.
-Three types of carbs: monosaccharides, disaccharides, and polysaccharides. Who can tell
the difference between them?
- Sugars are build like any other macromolecule, by dehydration synthesis and broken
down by hydrolysis.
- Sugars cost LITTLE ENERGY to build and can easily release energy (short term energy
storage remember!)
- Energy storage polysaccharides: glycogen and starch (which one do plants use?
Animals?)
- When used as building materials for organisms, polysaccharides can be cellulose or
chitin. Which organisms use which?
-It is important to know that polysaccharides can be highly branched as well as linear. With
that being said, why can't humans digest cellulose as expertly as some other
organisms?
Lipids
- Of the organic compounds, Lipids are the ones known for long-term
energy. They are composed of carbon, hydrogen, and oxygen but unlike
carbohydrates they have long chains of hydrocarbons.
-For the AP exam, it is vital to know these types of lipids: fats,
phospholipids, and steroids.
-What is the monomer of a lipid? Does anyone know?
-A fat or triacylglycerol is a glycerol (3C alcohol) and three fatty acid
tails. They are non-polar and hydrophobic and have 2x more energy
storage than carbohydrates because energy can be stored in the
hydrocarbons. Can anyone tell the difference between saturated and
unsaturated fats?
-Phospholipid is formed when combining a glycerol with 2 fatty acid
tails and a phosphate group (head). Can someone tell us how
phospholipids form a bilayer due to being hydrophobic and hydrophilic?
Lipids (Not even done yet D: )
-A steroid is a type of lipid that always has 4 fused carbon rings
and a functional group. Explain how a different structure here can have
a different function for the steroid (refer to hormones as an example).
-Cholesterol is found in animal cell membranes and is a precursor
of all other steroids. Why is it important that cholesterol be found in the
cellular membrane?
-BIG IDEA: How does the structure of the phospholipid bilayer affect
its function? (What characteristics does it have?).
Nucleic Acids
- These extremely complex molecules are the genetic materials for all living
organisms. They come in two colors: DNA and RNA.
- ALWAYS REMEMBER: DNA makes RNA makes PROTEINS. This will always
come back to bite you in the... uh, gluteus maximus later on.
- What are some differences between DNA and RNA? C'mon you know you
know it! T-t-today Junyah!
- The monomer of the nucleic acid is a nucleotide (NOT to be confused with a
nucleoside). What constitutes a nucleotide? Well, a sugar, phosphate, and
base of course! BUT that's not enough for the AP exam we're afraid. Who
can be more specific?
- The purine nucleotides are adenine and guanine and the pyrimidine
nucleotides are cytosine and thymine (and uracil in RNA).
- IMPORTANT CONCEPT: DNA replication is directional and based off a
system of copying a template, where each newly synthesized strand acts as
a template for the next copy.
Proteins
-YOUR INNER MANTRA: PROTEINS ARE EVERYWHERE AND DO
EVERYTHING!
-Proteins have many different jobs seeing as how there are so many different
proteins due to changes in structure therefore changes in function. Some
proteins are enzymes, some are structural proteins, some are used for cell
communication etc.
- The monomer of a protein is an amino acid. Amino acids are bonded together
by peptide bonds and therefore they form a polypeptide chain! Proteins can
be 1 or more polypeptide chains folded/bonded together. Makes sense now!
-Amino acid structure involves a central carbon, amino group, carboxyl group,
and an individual R group which does what again? How is this structure vs.
function? (think polar perhaps?) and this affects how amino acids interact?
-Proteins grow in a specific direction because DNA is directional and it
sequences proteins.. N-terminus = NH2 end, C-Terminus = COOH end.
(NCC= protein)
-
Proteins (Cont'd)
1. Primary Structure: correct order of amino acids in chain. A slight change in
the correct order can affect the protein's future function. How does this
apply to sickle cell anemia?
2. Secondary Structure: the "local folding" of the polypeptide. The local folding
is caused by interactions between adjacent amino acids through the
hydrogen bonds. This local folding results in either shape _______
or______.
3. Tertiary Structure: the whole molecule folds. Caused by interactions between
distant amino acids. The distant amino acids interact to form 3D structure by
hydrophobic interactions.
4. Quaternary structure: more than one polypeptide chain bounded together
and becomes a functional protein. It is caused by hydrophobic interactions.
-Protein denaturation is when a protein unfolds due to some factor or env.
_Chaperonin is a protein which does what?
-Protein models can be viewed using x-ray crystallography.
-
Enzymes
- Enzymes are proteins that lower the activation energy needed to initiate a
reaction - there are thousands upon thousands of specific enzymes.
- Enzyme vocabulary (let's see who can define): substrate, active site, inhibitor,
induced fit, competitive inhibition, allosteric inhibition, non-competitive
inhibition
- Enzymes are extremely specific and only react with specific substrates that
will fit into their active sites.
- Can anyone name some specific enzymes?
- IMPORTANT FREE-RESPONSE MATERIALS: factors affecting enzyme
action are enzyme concentration, substrate concentration, temperature, pH,
and salinity.
- Enzymes and metabolism are important topics, especially for free response
questions!
Functional Groups
-A functional group adds/changes the function
to a molecule.
Can you name the functional groups we have
learned this year?
Functional Groups
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