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P & A Notes Chap. 4

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P & A Notes Chapter 4

February 07, 2011

Chapter 4 

* Metabolic processes are occurring even when the organism is at rest. (basal metabolic rate)

Anabolic metabolism:
* Allows for growth and repair
* It involves the buildup of large molecules from
smaller ones.
*It uses or requires energy.
*Water is given off.

C6 H12 O6 + C6 H12 O6 ----> C12 H22 O11 + H2O

* Anabolic metabolism is also called dehydration synthesis due to the production of a larger molecule (synthesis) and the loss of water from existing molecules (dehydration).

Catabolic metabolism:
*Digestion is an example.
* It involves the breakdown of large molecules into
smaller ones.
*It gives off energy.
*It uses water.

C12 H22 O11 + H2O ----> C6 H12 O6 + C6 H12 O6

* Catabolic metabolism is also called hydrolysis
because water is consumed & energy is given off.

Enzymes - aid metabolic reactions. They are proteins that lower the energy needed to start these reactions. (activation energy) They also speed up the reaction. Enzymes are needed in small amounts because they are reused.
Enzyme / Substrate Interaction

* Enzymes are specific, they act only on a particular substrate.
The enzyme attaches to its specific substrate forming the enzyme - substrate complex. After the reaction a product is released and the enzyme, which is unchanged may attach to a new substrate.

*3 kinds of energy
1. potential (glucose)
2. activation (enzymes lower)
3. kinetic (energy released)

DNA

DNA: holds the information the cell needs to produce enzymes that control all metabolic processes......all life processes....growth, repair, maintenance, development...

* Children look like the parents because genetic information is passed to the children in the form of DNA through the sex cells.

* The portion of DNA that is needed to produce one kind of protein is called a gene.

* The basic building block for the nucleic acids (DNA and RNA) is the nucleotide. Each nucleotide consists of a 5 carbon sugar (ribose or deoxyribose), a phosphate group, and an organic base. (see page 83)

* the organic base of a DNA nucleotide can be one of four kinds...adenine (A), thymine (T), cytosine (C) and guanine (G)....so there is only four kinds of nucleotides an adenine nucleotide, a thymine nucleotide, etc.

*Adenine will bond only to thymine.

*Cytosine will bond only to guanine.

A DNA strand with the base sequence A, G, T, C would have a complimentary strand of T, C, A, G.

* It is the arrangement of these base pairs that encodes or “programs” the genetic information held in DNA.

* The shape of DNA is double helix.

* The information in a DNA is used to produce protein.

* A protein can be made of up to 20 different amino acids. (page 86 table 4.1)

* To produce a certain protein the amino acids have to be arranged in a particular sequence in the polypeptide chain. ( this is determined by the arrangement of the base pairs.)

RNA

RNA molecules:
* Contain ribose sugar are... single stranded, and have uracil (U) nucleotides in place of thymine.

* Messenger RNA (mRNA) - carries the information in a gene’s base sequence from he nucleus to the cytoplasm.

* Transfer RNA (tRNA) - correctly aligns amino acids along mRNA to form proteins.

* Ribosomal RNA (rRNA) - It moves along the mRNA showing tRNA where to place the amino acids.

Protein synthesis:
(Includes both Transcription & Translation)

Transcription:

* The enzyme RNA polymerase attaches to a DNA at the start of a gene. Other enzymes in the nucleus pull apart the DNA exposing the gene.

* RNA polymerase moves along the exposed gene attaching mRNA nucleotides to the complementary DNA nucleotides.

* When RNA polymerase reaches the terminal signal at the end of the gene, the mRNA is complete and it releases the new mRNA molecule.

*DNA zips back shut.

( Amino acids are represented by groups of 3 nucleotides on the DNA. The complementary set of 3 mRNA nucleotides is called codon.)

* Once formed mRNA moves out of the nucleus into the cytoplasm and attaches to a ribosome. This is where translation begins.

( There are 20 different amino acids used in our body, so there is 20 different kinds of tRNA. tRNA serves as guides in the cytoplasm to direct amino acids to mRNA.
The set of 3 nucleotides of tRNA that match-up with mRNA codons are called anticodons.)

Translation

* A ribosome binds to the mRNA at the start codon.

* A tRNA with the complementary anticodon attaches to the ribosome and the amino acid it carries is held until a second tRNA binds to the next codon the amino acids are joined by a peptide bond and the first tRNA is released.

* This is repeated again and again as the ribosome moves along the mRNA.

* When the ribosome reaches the stop codon the protein is complete. It is then released, and transported to where it is needed.

DNA replication (see page 89)
why?

when?

how?

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