Download Metabolic Processes

y Both anaerobic and aerobic processes begin with y
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glycolysis.
Glycolysis is the break up of the glucose.
Glycolysis is a series of enzyme‐catalased reactions that break down 6‐carbon glucose molecules into 3‐
carbon pyrovate acid molecules.
Glycolysis occurs in the cytosol
It does not require oxygen (anaerobic)
y Three main events:
y 1. Glucose is phosphorylated by the addition of two phosphate groups, one at each end of the molecule. y 2. The 6‐carbon glucose molecule is split in two 3‐carbon molecules.
y 3. The electron carrier NADH is produced, ATP is synthesized and two 3‐carbon pyruvic acid molecules result. The electrons contain a lot of energy . To keep this energy in a form that cell can used ,t hey are passed in pairs to molecules of the hydrogen carrier NAD+ NAD+ + 2H— NADH + H+ y NADH + H+ must be able to y Under anaerobic conditions, has deliver electrons to electron transport chain.
nowhere to unload electrons and cannot accept electrons from NADH.
y Presence of oxygen.
y Oxygen acts as the final electron acceptor at the end of the electron transport chain.
y The chain continue processing electrons and recycling NAD+
y As an alternative, NADH + H+ can give its electrons and hydrogen back to pyruvic acid and form lactic acid.
y The build up of lactic acid, inhibits glycolysis, and ATP production declines. This is an example of cramping muscles during exercise.
y If enough oxygen is available, the pyruvic acid generated by glycolysis continue the aerobic pathways.
y These reactions include:
y Synthesis of acetyle coenzyme A or Acetyl CoA
y The citric acid cycle y Electron Transport Chain
y The aerobic conditions produces water, carbon dioxide and 36 ATP molecules per glucose.
y Everything starts with the pyruvic acid produced by glycolysis moving from cytosol to mitochondria.
Glycolysis
The steps of Glycolysis
y It begins when 2‐ carbon acetyl Co A molecule combine with a 4 carbon oxaloacetic acid molecule to form the 6 carbon cytric acid and Co A.
y The CoA can be used many times and changed to oxaloactic acid. The cycle repeats as long that pyruvic acid is supplied.
y The citric acid has 3 important consequences:
y 1. One ATP is produced for each citric acid molecule in the cycle.
y 2. For each citric acid molecule, eight hydrogen atoms with high energy electrons are transferred from NAD and ther leated FAD
y As the carbon citric acid reacts to form 4‐ carbon axloacetic acid, two carbon dioxide are produced.
y The carbon dioxide produced by acetyl CoA and the cirric acid cycle dissolves in the cytoplasm, diffuses from cell and enters blood stream
y NADH and FADH2 generated by glycolysis and the citric acid cycle now hold most of energy contained n the original glucose molecule.
y In order to change this energy into ATP synthesis, high energy electrons are handed off to the electron transport chain, which is a series of enzyme complexes that carry and pass electrons along from one to another.
y These complexes do the folds of mitochondria.
y The electron transport chain passes each electron along gradually lowering the electron’s energy level.
y Neither glycolysis nor the citric acid cycle uses oxygen y
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directly, though they are part of aerobic metabolism of glycose.
Instead, the final enzyme gives up a pair of electrons with two hydrogen atoms ions and an atom of oxygen to form a water molecule.
Metabolic processes are interconnected and allows a molecule to pass one pathway or another one.
Excess glucose, may enter anabolic carbohydrate pathways and be storage to form glycogen. Glycogen is produced by liver and muscle mostly. During meals, the glycogen gets stored in liver, between meals the glucose is released by the liver.
y The rate of each metabolic reaction is regulated by enzymes that catalyzes each of the steps.
y The first enzyme in the reactions is the one that affects the reaction rate. The rate limiting enzyme.
y Often the product of metabolic pathways inhibits the rate limiting regulatory enzyme. This is a negative feedback. y Because enzymes control the metabolic processes, cells must have information for producing specialized proteins.
y The information that instructs a cell to synthesize a particular protein is held in the sequence of building blocks of DNA (Deoxyribose nucleic acid), the genetic material.
y The correspondence between an unit of DNA info and a particular amino acid is the genetic code.
y Children get the genetic info from DNA molecules of y
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their parent’s sex cells.
Chromosomes are cell structures that carry DNA.
The portion of the DNA molecule that contains the genetic information for making a particular protein is called gene.
The complete set of genetic instructions in a cell constitutes the genome.
The nucleotides are the building blocks of nucleic acids.
y A nucleotide consist of :
5 carbon sugar (ribose or deoxyribose)
A phosphate group
One nitrogen base They join by a pattern with hydrogen bonds, alternating sugars and phosphate groups and forming the backbone of the DNA or RNA structure
y DNA is formed by two strands pointing in opposite directions, called antiparallel
y A DNA molecule is sleek and symmetrical because the bases pair in only two combinations, maintaining a constant width in the structure.
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y Adenine ( 2 ring structure) join Thymine ( 1 ring structure)
y Guanine ( 2 ring structure) join Cytosine ( 1 ring structure) These are called complementary base pairs.
y DNA is a double stranded‐ twisted molecule.
y An individual DNA molecule may be millions of pairs y
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long.
In the nucleus, DNA is wound around complexes proteins called histones. To form chromatin.
Genetic code specifies the correct sequence of amino acids in the polypeptide chain
Every amino acid is represented by a triplet codon
(ATT)
The sequence of amino acids create a particular protein.
y The sequence of nucleotides in a DNA molecule dictates the sequence of amino acids of a particular protein and indicates how to start or stop protein synthesis.
y This method of storing information for protein synthesis is the genetic code.
y Because DNA molecules are in the nucleus and protein synthesis occurs in cytoplasm, and because the cell must maintain a copy of the genetic material at all times, RNA molecules transport the genetic instructions from nucleus to cytoplasm
DNA
RNA
y RNA (ribonucleic acid) molecules differ from DNA molecules in different ways:
y Single stranded
y Nucleotides contain sugar ribose
y Contain Uracil instead of Thymine
y Three types of RNA: y mRNA (messenger RNA)
y tRNA (transfer RNA)
y rRNA (ribosomal RNA)
DNA
RNA
y Location: Part of y
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chromosomes
Sugar: Deoxyribose
Structure: Double stranded
Nitrogen bases: Cytosine, Guanine, Adenosine and Thymine
Types : one type
Function: Contain genetic code for proteins synthesis, replicate prior mitosis
Location: Cytoplasm
Sugar: Ribose
Structure: Single stranded
Nitrogen bases: Cytosine, Guanine, Adenosine and Uracil
y Types: mRNA, tRNA and rRNA
y Function: mRNA transcribes DNA info. tRNA carries aminoacids to mRNA. rRNA
provides structure and enzyme activity.
y It is done in two processes:
y Transcription‐ inside nucleus
y Translation‐ Cytoplasm
Transcription
Translation
y In the nucleus
y RNA polymerase binds to DNA y In cytoplasm.
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molecule
RNA polymerase moves along strand of DNA forming a complementary strand
When RNA polymerase reaches the end of the gene, new mRNA molecule is released
DNA molecule rewinds and close helix
mRNA molecules enters cytoplasm.
y A ribosome bind to mRNA
y tRNA wigh complementary anticodon
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brings its amino acid to ribosome.
A second tRNA brings next aminoacid to ribosome
tRNA is released.
The process is repeated and a chain of amino acids is formed
Chaperone proteins help amino acids to fold to form protein
The completed protein molecule is released and mRNA, ribosome and tRNA are recycled.
y DNA replication is the process that creates an exact copy of DNA molecule. It occurs during interphase
y As replication begins, hydrogen bonds break, unwinding the DNA.
y When the DNA is uncoiled, some nucleotides bases are exposed and DNA polymerase knit together the new sugar phosphate back of the DNA.
y Two complete DNA molecules result, each one with one original and an new strand.
y The genetic information in chromosomes is enormous.
y DNA has to be replicated many times to get rid of errors, and produce a high degree of accuracy.
y When a mistake in the replication of DNA occurs is called mutation.
y Origin of mutations:
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During DNA replication a base may pair incorrectly
Extra bases may be added
Sections of DNA may be deleted
Sections of DNA may be moved to another molecule region.
y Cell detect damage in their DNA molecules and use repair enzymes to clip out defective nucleotides in a single DNA strand, and restores original DNA structure.
y Effects of mutation:
y If a mutation alters a base in second position, the substitute amino acids is similar, and the protein does not change enough to alter its function.
y One protection against mutation is that a person has two copies, so if one is mutated, the other can work normally.
y If the mutation occurs in the DNA of an adult may be not be noticed, but if it is in an embryo is going to rise to a lot of problems.
y Mutations may occur spontaneously if a chemical (mutagen) alters the DNA. Example UV light.
y A type of disorder called an inborn error of metabolism occurs when a mutation alters an enzyme. This alters the human being Phenylketonuria (PKU) unable to synthesize phenilanine ( amino acid)