Ch 2 Assignment #3-Proteins, Nucleic Acids and ATP Name:_____________________Date:___________Period:___
Proteins (pp 38-41)
1. Describe the functions of proteins in cells.
• They transport molecules across the plasma
membrane
• One category of proteins, called enzymes,
catalyze cell reactions
• They provide structural support (for example,
keratin in nails and collagen in tendons and
ligaments)
• Some act as cell messengers, influencing
metabolic activity
2. Describe and draw the structure of an amino acid (Fig 2.22 p 40)
Proteins are composed of monomers of amino acids. Each amino acid
contains a central carbon atom bonded to
• an amino group
• a carboxyl group
• a hydrogen
• an R group that determines the type of amino acid it is
http://study.com/cimages/multimages/16/amino_acid_structure.png
3. Describe how a polypeptide is constructed from amino acids
Polypeptides are polymers of amino acids joined by
peptide bonds.
• Peptide bonds are polar covalent bonds,
allowing hydrogen bonding between
amino acids. This influences the threedimensional shape of proteins.
Fig 2.22 BC Bio 12
4. Draw and compare the four levels of protein structure (organization)
Primary structure: amino acid sequence
Secondary structure: polypeptide orientation,
such as alpha helix or beta pleated sheet
Tertiary structure: three-dimensional shape of a
polypeptide chain (protein). This shape is held
together by covalent, ionic, and hydrogen bonds
between R groups on different amino acids (for
example, disulfide linkage S−S between two
cysteine amino acids)
Quaternary structure: three-dimensional
arrangement of polypeptide chains for proteins
with two or more chains
https://upload.wikimedia.org/wikipedia/commons/a/a6/Protein-structure
5. Define denatured.
Denaturation (in biology) process of modifying the molecular structure of a protein (so
that it has an irreversible change in shape) Denaturation involves the breaking of many
of the weak linkages, or bonds (e.g., hydrogen bonds), within a protein molecule that
are responsible for the highly ordered structure of the protein in its natural (native)
state. Denaturation can be brought about in various ways—e.g., by heating, by
treatment with alkali, acid, urea, or detergents.
Nucleic Acids (pp 41-42)
1. What are the two types of nucleic acids?
*DNA (deoxyribonucleic acid), which carries the
genetic information of an organism
*RNA (ribonucleic acid), which consists of different
types of molecules such as mRNA, tRNA, and rRNA
2. Describe and draw the nucleotides that make both DNA and RNA.
Nucleic acids are polymers of nucleotides, which
contain a phosphate group, a pentose sugar, and a
nitrogen-containing base.
•
Nucleotides in DNA contain the
sugar deoxyribose and four
different types of bases: adenine
(A), thymine (T), guanine (G),
and cytosine (C).
• Nucleotides in RNA contain the
sugar ribose and the same bases as
DNA except uracil (U) replaces
thymine.
3. How does DNA structure differ from RNA structure?
https://cm.jefferson.edu/wordpress/wp-content/uploads/2014/01/pasted-graphic-11.jpg
BC Bio 12
4. How do the functions of DNA and RNA differ?
DNA stores and transfers genetic information
RNA directly codes for amino acids and acts as a messenger between DNA and
ribosomes to make proteins.
ATP (another function of nucleotides)
1. What is ATP?
ATP is a nucleotide that also acts as a source of energy
2. Draw and describe what happens to ATP when cells require energy? (Fig 2.26)
Energy is stored in the
chemical bonds of the
phosphates.
• Energy is released when the
bonds between phosphate
groups are broken
• Usually, the last phosphate is
cleaved to form ADP + Pi, and
energy is used for a reaction
http://home.comcast.net/~mjmayhew42/Biology%20notes/energy%20notes_files/image005.jpg
3. What are the functions of ATP?
• Chemical work: ATP supplies energy for
synthesis of macromolecules
• Transport work: ATP supplies energy used to
pump substances across the plasma membrane
• Mechanical work: ATP supplies energy for
processes such as muscle contraction and
flagella movement