Molec Cell: Ch. 2 pt. 2

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The Molecules of Cells pt. 2

Biology

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49 Terms

1
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The information in DNA and RNA is conveyed…
by the order of the bases.
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DNA is made up of __. The bases are on the __, joined by __ btween _____ base pairs
DNA is made up of two polynucleotide chains. The bases are on the inside, joined by hydrogen bonds between complementary base pairs.
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Complementary base pairing
one strand of DNA (or RNA) to act as a template for synthesis of a complementary strand.
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Nucleic Acids
self-replication
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The information carried by and ___ directs _____ of specific ______, which control __________.
The information carried by DNA and RNA directs synthesis of specific proteins, which control most cellular activities.
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Other important nucleotides include:
* ATP
* some act as signaling molecules within cells
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_______ are the most diverse of all macromolecules.
Proteins
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Each cell contains ______ different proteins.
Each cell contains several thousand different proteins.
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Proteins direct _______.
Proteins direct virtually all activities of the cell.
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Functions of proteins include:
* structural components
* transport and storage of small molecules (O2)
* Transmit information between cells (protein hormones)
* Defense against infection (antibodies)
* Enzymes
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Proteins are polymers of _____.
Proteins are polymers of 20 different amino acids.
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What does each amino acid consist of?
* *a* carbon bonded to a carboxyl group (COO-)
* amino group (NH3+)
* hydrogen
* distinctive side chain
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Amino acids are grouped based on what? What are some examples?
Amino acids are grouped based on characteristics of the side chains:

* Nonpolar side chains
* polar side chains
* side chains with charged basic groups
* acidic side chains terminating in carboxyl groups
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What are some basic amino acids?
* Lysine (Lys) K
* Arginine (Arg) R
* Histidine (His) H
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What are some acidic amino acids?
* Aspartic Acid (Asp) D
* Glutamic Acid (Glu) E
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How to join the amino acids?
Peptide bonds
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Polypeptides
chains of amino acids, hundreds or thousands of amino acids
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What are the on the ends of a polypeptide?
* One end of a polypeptide terminates in an *a* amino group (N terminus)
* Other ends in an *a* carboxyl group (C terminus)
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What do amino acid sequences define?
characteristics of proteins
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What did Frederick Sanger do in 1953?
Worked out the amino acid sequence for insulin
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How are protein sequences now deduced from?
Sequences of mRNAs
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Complete amino acid sequences of over _____ proteins have been established.
100,000
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Insulin consists of____. The side chains of three pairs of ___ are joined by _______.
Insulin consists of two polypeptide chains. The side chains of three pairs of cysteine residue are joined by disulfide bonds.
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How are the sequences are amino acids in a protein determined by?
the order of nucleotide bases in a gene
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Proteins also have distinct ________ that are critical to their ____.
Proteins also have distinct 3D conformations that are critical to their function.
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The shape and functions of proteins are determined by….
The shape and functions of proteins are determined by their amino acid sequences.t
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What did Chirstian Anfinsen do?
* demonstrated the importance of the 3D structure.
* disrupted proteins by treatments such as heating, which breaks non-covalent bonds (denaturation)
* demonstrated the importance of the 3D structure.
* disrupted proteins by treatments such as heating, which breaks non-covalent bonds (denaturation)
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All the information required to specify the correct 3D conformation of a protein is contained in its ___ _____ ___ ____.
All the information required to specify the correct 3D conformations of a protein is contained in its primary amino acid sequence.
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Primary Protein Structure
the sequence of amino acids in the polypeptide chain
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Secondary Protein Structure
Regular arrangement of amino acids within localized regions

* Two common types:
* *a* helix
* *B* sheet
* both are held together by H bonds between CO and NH groups of peptide bonds
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Tertiary Protein Structure
The folding of the polypeptide chain due to interactions between side chains of amino acids in different regions of the chain
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Domains
The basic units of tertiary structure; are folded 3D structures usually containing between 50-200 amino acids
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What are the 3 critical determinants of tertiary structure?
* Hydrophobic amino acids: in the interior of the protein
* Hydrophilic amino acids: on the surface - interact with water
* Loop regions - connect the elements of secondary structure
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Where are the critical determinants of tertiary structure?
They are on the surface of folded proteins, where the polar components of the peptide bonds form H bonds with water or with the polar side chains of hydrophilic amino acids.
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Quaternary Protein Structure
Interactions between different polypeptide chains in proteins composed of more than one polypeptide.
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Hemoglobin is composed of…
4 polypeptide chains
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A fundamental role of proteins is to act as…
enzymes
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Enzymes
Catalysts that increase the rate of all chemical reactions in cells
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What would happen to most biological reactions without enzymes?
They would be so slow that they would not occur.
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What are the two fundamental props of enzymes?

1. Increase rate of chemical reactions **without themselves being consumed** or permanently altered.
2. **Increase reaction rates** without altering the chemical equilibrium between reactants and products.
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When a substrate (s) is converted to a product (P), the chemical equilibrium between S and P is determined by…
the laws of thermodynamics
the laws of thermodynamics
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If an enzyme is present, the conversion is ___ , but the equilibrium is ___.
If an enzyme is present, the conversion is accelerated, but the equilibrium is unaltered.
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Equilibrium is determined by…
the final energy states of S and P
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The substrate must first be converted to a higher energy state, the…
transition state
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activation energy
energy requires to reach the transition state
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Enzymes…
reduce the activation energy
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What are enzyme-substrate complexes (ES)?
It is when enzymes bind their substrates to form an enzyme-substrate complex.
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Active site
Where the substrate binds to a specific region of the enzyme
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The substrate is converted to ___ while bound to the ____ ____, then _____.
The substrate is converted to product while bound to the active site, then released.