Download - CELL CHEMISTRY IV Proteins & Nucleic Acids
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CELL CHEMISTRY IVProteins & Nucleic Acids
Plasma proteins that you must knowDeoxyribonucleic acid (DNA)
Ribonucleic acids (RNAs)
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Significance of Proteins in Physiology
• They are responsible for the unique structure and specific functions of cells
• They function as– Enzymes– Chemical messengers (hormones & neurotransmitters)– Carriers/Transporters (in blood and in cells) – Channels (in cell membranes)– Receptors for hormones & neurotransmitters – Immunity (vaccination)
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Know These Proteins and Their Respective Function!
• Hemoglobin:– Transports O2; Inside red blood cells; binds O2 reversibly
• Lactase:– Catalyzes hydrolysis of lactose into --- (what products?)
• Carbonic anhydrase:– Catalyzes synthesis of H2CO3 from CO2 and H2O
• Actin and Myosin:– For muscle contraction and relaxation; Interaction between these two generates forces that
cause movement• Albumin:
– Most abundant protein in plasma; Major role in plasma oncotic (or osmotic pressure)• Immunoglobulins (Ig) G, E
– Also called antibodies; Immunity (as in vaccination) and allergic reaction (IgE)• Keratin:
– Structural protein in cells, nails, hair• Ferritin:
– Intracellular storage of iron
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Some Facts on Proteins
• They are polymers of amino acids that are joined by peptide bonds.
• Each protein has a specific or unique amino acid sequence (AAS)
• The AAS determines the 3D structure and the function/s of a protein
• Questions– Peptide bonds are formed by what type of chemical reaction
---?– What enzyme catalyzes the synthesis of peptide bonds?– What organelle has this enzyme?
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More Facts About Proteins
• 3D structure that is maintained by hydrogen bonds and ionic bonds
• Function/s depend on 3D structure• Can be denatured (Denaturation) by
– A) extremes of pH– B) heat
• Questions:– Would denaturation affect the properties, structure and function
of a protein?– An example of denaturation in your kitchen?
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Hemoglobin: 3D Structure
• Notice 4 proteins interact to form a single structure (a quarternary structure).
• Hemoglobin is a multimeric protein
• What type of bonds stabilize the “globular” shape of hemoglobin?
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Some More Facts About Proteins
• There are thousands of proteins inside a cell• To synthesize proteins, cells need information
from a gene (genetic information)• A Gene is a sequence of nucleotides that has
information for the synthesis of a functional RNA or for a protein. in DNA molecule.
• The nucleotide sequence in a gene dictates the amino acid sequence of the protein or nucleotide sequence of functional RNA encoded in the gene
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Protein SynthesisStudy/Review Guyton Ch. 3
• To synthesize proteins, cells need:– Genetic information (Gene)– mRNA, tRNA– Ribosomes– Amino acids (20 different)– Energy
• The key events that you MUST review in any textbook of biology or college Anat & Physiol or in Guyton:1. Transcription (RNA synthesis)2. Translation (protein synthesis)3. Replication (DNA synthesis)
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Flow of Genetic information(Guyton Ch. 3)
• In all cells, the flow of genetic information is from: – Gene --> mRNA --> Protein
• Transcription– The enzyme RNA polymeraze catalyzes the synthesis of
phosphodiester bond between ribonucleotides.– The enzyme uses one of the two DNA strands as a template– Notice that DNA IS NOT CONVERTED TO RNA
• Questions• Given the nucleotide sequence: …-T A C G A A C C G A T-…
1. Write the sequence of the complementary strand?2. These two strands would be held together by what bonds?3. Assuming that the bottom strand (answer to #1 is the gene), write
the sequence of the transcribed mRNA?
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Nucleic Acids
Some Facts plus Some Illustrations
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Nucleic Acids• The nucleic acids are DNA and RNA• DNA is found in the nucleus and mitochondria• RNA is found in the cytoplasm• There are several types of RNA
– mRNA (m = messenger)– rRNA (r = ribosomal)– tRNA (t = transfer)
• They are all Polymers of nucleotides joined by ---? formed by what type of reaction?
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Composition of Nucleotide
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RNAs: Function of Each
• mRNA is a copy of the information in the gene.• tRNAs, in collaboration with ribosomes, translate the
message in the mRNA. Notice that during protein synthesis, a sequence of ribonucleotides is translated into a sequence of amino acids.– Each codon (a set of 3 consecutive ribonucleotides) of the
mRNA is a code for one amino acid in the protein. • rRNAs are structural component of ribosomes. They
function as enzymes (ribozymes) that catalyze the formation of peptide bonds.
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Be Able to Distinguish Amino Acid from Nucleotide
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DNA: Composition & Structure (1)
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DNA vs RNA (1)
• DNA– Found in the nucleus and mitochondria– Double stranded and shaped as twisted ladder– Contains the pentose deoxyribose– Contains the nucleotides A, T, G, C– In the double strand, A is structurally
complementary to T and G is complementary to C (A:::T, G:::C)
– RNA
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DNA: Composition & Structure (2)
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RNA vs DNA (2)
• RNA – Found in cytoplasm (cytosol, ribosomes)– Is single stranded– Contains the pentose ribose– Contains the nucleotides A, U, G, C– During transcription, DNA strand serves as
template for RNA synthesis and A is complementary to U, G is complementary to C. (A:::U, G:::C)
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Some Questions ??• Given the ….-5’-ACGTCACTCAGTGGATCA-….
1. Write the sequence of the complementary strand
• Assume that the 3’- strand (answer to 1 above) is the gene.
1. What is the sequence of the mRNA from that gene?2. How many codons are there in that (#2) mRNA?3. Write each codon on a separate line in your notes and for each
codon, write the sequence of the corresponding anticodon4. Which RNA has anticodons?5. What is the function of these RNAs (answer to #5) RNAs 6. According to the genetic code (consult Guyton Table 3.1), what is the
amino acid sequence of the peptide from that gene?