Check your Progress-BC Biology 12
Chapter 2
Check your Progress 2.4 p 33 Organic Molecules
1. Explain why organic molecules are considered the molecules of
life?
Organic molecules always contain Carbon and Hydrogen and
Carbon allows the molecules to form a large variety of organic
molecules found in living organisms. It can covalently share
electrons with up to four other atoms or with other carbon atoms.
A hydrocarbon chain can form rings and specific combinations of
bonded atoms (functional groups) attached to the carbon chains
always react in the same way (See chart on p 33)
2. Compare and contrast dehydration and hydrolysis reactions
Dehydrations reactions: chemical reactions that join /bond
monomers together to form polymers. An –OH group (hydroxyl)
and an –H (hydrogen atom) are removed (essentially, a water
molecule is removed) Dehydration synthesis needs energy to
break bonds (endergonic)
Hydrolysis reactions: the opposite of a dehydration reaction.
Polymers are degraded (broken down) into monomers when the
components of water are added. (see Fig 2.11 , p 33) Hydrolysis
releases energy (exergonic)
Check your Progress 2.5 p 35 Carbohydrates
1. Identify the structural element that all carbohydrates have in
common.
C-H-OH is the atomic grouping that is characteristic of
carbohydrates. (the ratio of H to O atoms is 2:1 (eg. Glucose has
22 H’s and 11 O’s)
2. Explain why starch in plants is a source of glucose for our bodies
but cellulose in plants is not.
Starch can be hydrolyzed into glucose and stored in the liver as
glycogen. Cellulose the glucose units are joined by a different
linkage than found in starch or glycogen. The oxygen is
alternating in an up/down orientation and the bond between the
glucose units prevents us from breaking the bonds. Cellulose
passes through our guts as fibre that helps to scrape out
intestines, lowers blood pressure and helps us absorb water.
Check your Progress-BC Biology 12
Chapter 2
Check your Progress 2.6 p 38 LIPIDS
1. List the two types of lipid molecules found in the plasma
membrane of living cells
Phospholipids Phospholipids look similar to triglycerides except they
have 2 fatty acid tails instead of 3. Instead, it has a phosphate group
(group with P and N) that is polar. Therefore, the phosphate end is polar
(hydrophilic) and the fatty acid chains are non-polar (hydrophobic)
Cholesterol is a steroid that is found in the plasma membrane. Steroids
have a backbone of four fused carbon rings. Each one differs in the
arrangement of the atoms in the rings and the type of functional groups
attached to them.
2. Explain how the presence of a double bond in an unsaturated fatty
acid affects whether that substance is liquid or solid.
Unsaturated fatty acids have double bonds between carbon atoms
wherever the number of hydrogens is less than two per carbon
atom. This causes a bending of the fatty acid and the molecules
can slip and slide past one another.
Check your Progress 2.7 p 41 Proteins
1. List some of the functions of proteins.
a)Structure and support (keratin in hair and nails, collagen in the
ligament, tendons and skin)
b)enzymes are proteins in the body speed up chemical reactions
c) hormones are protein messengers that influence the workings
in cells (metabolism)
d) actin and myosin are proteins that allow movement in our
muscles
e) proteins transport molecules to where they are needed (like
hemoglobin in red blood cells carries oxygen) and act as carriers
to transport molecules into and out of the cell. Some form
channels that allow substances to enter and exit cells.
f) antibodies are defensive proteins in blood and body fluids that
combine with foreign substances to prevent infection from
destroying cells or disrupting the balance in an organism
(homeostasis)
Check your Progress-BC Biology 12
Chapter 2
2. Describe the structure of an amino acid
Amino acids have a central CARBON atom bonded to a hydrogen
atom and three functional groups (one group is an amino group –
NH2 and another is an acidic group –COOH. The third group is an
R group, which can very from having a single carbon to being a
complicated ring structure)
3. Compare and contrast the four levels of protein structure
Primary: linear sequence of amino acids joined by peptide bonds
through dehydration synthesis (peptide bond see p 38, polar C-O
in one aa bonds to N-H of another aa)
Secondary: Hydrogen bonding between amino acids causes the
polypeptide to form an alpha helix (a coil) or beta pleated sheets.
Tertiary: Due in part to covalent bonding between R-groups, the
polypeptide folds and twists, giving it a globular shape
Quaternary: when two or more polypeptides join to form a single
protein.
Check Your Progress 2.8 p 45 Nucleic Acids
1. Describe the structure of nucleic acids
Two types: Deoxyriboneucleic acids (DNA; see p 42, Fig 2.24) and
ribonucleic acids (RNA).
DNA (double stranded Helix) and RNA (single stranded, no Helix)
are polymers (Chains) of nucleotides.
A nucleotide has 3 subunits (see p 41 Fig 2.24)
1. a sugar
2. a phosphate
3. a nitrogen-containing base
(DNA has the sugar “deoxyribose” and RNA has the sugar
“ribose”)
There are four different bases that raise the pH of a solution:
Adenine: has 2 rings “purine”
Guanine: has 2 rings “purine”
Cytosine: has one ring “pyramidine:
Thymine (in DNA only): has one ring “pyramadine” or Uracil (in
RNA only)
2. Describe how energy is stored in ATP (adenosine triphosphate)
Check your Progress-BC Biology 12
Chapter 2
ATP is the “universal currency” of cells” and is a high energy
molecule with; It is a nucleotide composed of adenosine (a 5carbon sugar “ribose” with the nitrogen containing base
“adenine”) and three phosphate groups (called a triphosphate).
When cells require energy, ATP undergoes hydrolysis (break
down big molecule to small ones using water), producing ADP
with (P) with the release of energy (see Fig 2.26, p 44) Energy is
stored in the chemical bonds of the phosphates and the last two
phosphate bonds are unstable and easily broken. Energy released
=7.3 kcal/mol
It can be used for chemical work (supplies energy to make
macromolecules), transport work (supplies energy needed to
pump substances across plasma membrane of cells or for
conduction of nerve impulses) and mechanical work (provides
energy to permit movement). ATP can also be rebuilt by adding a
P to ADP and removing water)
See page 45 (fig 2.27 ) for a look at the reactions creating ATP and
breaking down into ADP+P