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Chapter 1

KIN217 Chapter Notes - Chapter 1: Red Snapper, Dna Replication, Thx

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Monica Vesely

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Chapter 1: Biochemistry and the Unity of Life
-Goals of biochemistry
oTo understand what it means to be alive at the molecular level
oTo understand the effects of molecular manipulations on the life the organism leads
-Biochemical research has found that organisms are remarkably uniform at the molecular level
-Jacques Manond Anything found to be true of [the bacterium] E.coli must also be true of
-This uniformity indicates that all life has arisen from a common ancestor
Living Systems Require a Limited Variety of Atoms and Molecules
-Three elements make up 98% of the atoms in an organism – Hydrogen, Carbon and Oxygen
-After hydrogen and oxygen, carbon is the next most-common element in living organisms
-Most large molecules in living systems are made up predominantly of carbon because of the
element’s ability to form strong bonds
-Fuel molecules are made entirely of carbon, hydrogen and oxygen
-Biological fuels react with oxygen to produce carbon dioxide and water
-Combustion provides the energy to power the cell
There are Four Major Classes of Biomolecules
oConstructed from 20 amino acids linked by peptide bonds
oForm unbranched polymers which fold into precise three-dimensional structure
oProteins serve as signal molecules and as receptors for signal molecules
oReceptors covey to the cell that a signal has been received and initiates the cellular
oProteins play structural roles, allow mobility and provide defenses against environmental
oProteins serve as catalysts (enzymes)
-Nucleic Acids
oAre the information keepers of the cell
oStores and transfers information
oContain instructions for all cellular functions and interactions
oThey are liner molecules
oThey are constructed form only four nucleotides
oA nucleotide is made up of a 5C sugar, either a deoxyribose or a ribose, attached to a
heterocyclic ring structure called a base and at least one phosphoryl group
oThere are two types of nucleic acid: deoxyribonucleic acid and ribonucleic acid
oDNA is constructed from four deoxyribonucleotides, differing in their bases; Adenine
(A), Cytosine (C), Thymine (T) and Guanine (G)
A interacts with T and C with G
oDNA in all higher organisms exists as a double-stranded helix
oRNA is a single stranded form of nucleic acid
oSome regions of DNA are copied as a special class of RNA molecules called messenger
oMessenger RNA is a template for the synthesis of proteins
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oUnlike DNA, mRNA is often broken down after use
oRNA is not like DNA in two ways
The base thymine is replaced by the base uracil
The sugar component of the ribonucleotides contain an additional hydroxyl
oMuch smaller than proteins or nucleic acids
oNot polymers made from repeating units
oHave a dual chemical nature:
Partly hydrophilic and the part made up of one or more hydrocarbon chains is
Allows lipids to form barriers that delineate the cell and the cellular components
oHydrocarbon chains cannot interact with water and instead interact with those of other
lipids to form a battier or membrane
oThe water-soluble components interact with the aqueous environment on either side of
the membrane
oLipids store energy
oThe hydrophobic component of lipids can undergo combustion to provide energy
oLipids are signal molecules
oImportant fuel source for most living creatures
oMost-common carbohydrate fuel is the simple sugar glucose
oGlucose is stored in animals as glycogen, which consists of many glucose molecules
linked end to end
oIn plants, the storage form of glucose is starch
oCarbohydrate chains can be highly branched
oPlay important roles in helping cells to recognize one another
The Central Dogma Describes the Basic Principles of Biological information Transfer
-The scheme that underlies information processing at the level of gene expression was first
proposed by Francis Crick in 1958
DNA ---- replication----> DNA ----Transcription-----> RNA ---Translation----> Protein
-Crick called this scheme the central dogma: Information flows from DNA to RNA and then to
-Moreover that DNA can be replicated
-DNA constitutes the heritable information --> the genome
-This information is packaged into discrete units called genes
-The collection of genes determines the physical nature of the organism
-When a cell duplicates, DNA is copied and identical genomes are present in newly formed
daughter cells
-A group of enzymes called DNA polymerase catalyze the replication process
-Transcription makes genes accessible by turning one form of DNA into another form RNA
-RNA polymerase catalyzes the reaction of transcription
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