Chapter 13 Biochemistry: A Molecular View of

Life

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Biochemistry

• Chemistry of living things and life processes

• Cell: structural unit for all living things– Cell membrane defines cell and lets material flow

into and out of cell

• Plant cells: also have walls made of cellulose

• Animal cells: do not have cell walls

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Plant Cells

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Animal Cells

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Major Internal Structures

• Cell nucleus: contains material that controls heredity

• Ribosomes: carry out protein synthesis

• Mitochondria: produce energy

• Chloroplasts: only in plant cells– Convert solar energy into chemical energy

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Metabolism

• Series of coordinated reactions that keeps cells alive

• Catabolism: reactions that break down molecules for energy

• Anabolism: synthesize molecules of living systems

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Carbohydrates

• Sugars, starches, and cellulose

• General formula: Cx(H2O)y• Sugars: sweet tasting carbohydates

– Aldoses: aldehyde functional group– Ketoses: ketone functional group

• Monosaccharides: simplest sugars

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Polysaccharides

• Contain two or more monosaccharides

• Main energy storage system: starch

• Plants use them for cell walls: cellulose

• Both are polymers of glucose– Difference in way they are linked together– Determines chemistry

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Starch• Two kinds in plants

– Both made of glucose

• Amylose: straight chain

• Amylopectin: branched chain

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Glycogen

• Another kind of starch found in animals

• Made of glucose - branched chain

The structure of glycogen is similar to that of amylopectin, although the branches in glycogen tend to be shorter and more frequent

Allows more ends to undergo a more rapid hydrolysis to release glucose for energy requirement

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CELLULOSE

• A polymer of glucose molecules with beta linkage

• Beta linkage Does not allow for chain of molecules to coil Chains can align with one another to form fibers Fibers can lay down in a criss-cross pattern Hydrogen bonding Criss-cross pattern gives strength in many directions

• Cannot be digested by animals and therefore serves as dietary fiber to help regulate bowel movement

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Lipids• Defined by solubility

– Insoluble in water

• Fats are largest subgroup of lipids– Made up of fatty acids and glycerol

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Some Naturally Occurring Fatty Acids

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Saturated vs. Unsaturated Fats

• Saturated fats have no C=C bonds– Saturated with hydrogen

• Unsaturated fats have C=C bonds– May have more than one double bond– Can add more hydrogen to fats– React readily with iodine, bromine, and chlorine

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Iodine Number• Iodine Number: number of grams of

iodine consumed by 100 g of fat

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Proteins• Serve as structural

material for animals

• Required in all living cells

• Composed of carbon, hydrogen, oxygen, and usually sulfur

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Amino Acids

• Building blocks for polymers called proteins

• Contain an amino group, –NH2, and a carboxylic acid, –COOH

• Can form zwitterions: have both positively charged and negatively charged groups on same molecule

• 20 required for humans

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Peptide Bond• Connect amino acids from carboxylic

acid to amino group

• Produce amide linkage: -CONH-

• Holds all proteins together

• Indicate proteins by 3-letter abbreviation

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Sequence of Amino Acids• Amino acids need to be in correct order for

protein to function correctly

• Similar to forming sentences out of words

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Structure of Proteins

• Four organizational levels

• Primary structure: amino acid sequence

• Secondary structure: arrangement of chains around an axis– Pleated sheet– Alpha helix: right-handed helix

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Pleated Sheets

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Alpha Helix

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Tertiary Structure• Spatial relationships

of amino acids relatively far apart in protein chain

• Globular proteins: compact spherical shape

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Quaternary Structure

• Structure when two or more amino acid sequences are brought together

• Hemoglobin has four units arranged in a specific pattern

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Intermolecular Forces in Proteins• Hydrogen bonding

• Ionic bonds

• Disulfide linkages

• Dispersion forces

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Enzymes

• Biological catalysts produced by cells

• Nearly all are proteins

• Enormous catalytic power– Reactions occur at lower temperatures and

at higher rates

• Ordinarily highly specific

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Induced-Fit Model of Enzymes

• Explains how enzyme works

• Substrate: reacting substance

• Active site: where chemical reaction takes place and where substrate fits

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Cofactors

• Something other than polypeptide chain required by enzyme

• May be metal– Iron in hemoglobin

• May be organic cofactor– Coenzyme

• Apoenzyme: does not have cofactor

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Inhibition of Enzymes

• Lets cell control when an enzyme works

• Inhibitor binds to allosteric site

• Prevents substrate from binding

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Nucleic Acids• Serve as information and control center

of the cell

• Deoxyribonucleic acid (DNA) – Carries blueprint for proteins– Found in cell nucleus

• Ribonucleic acid (RNA)– Carries out protein assembly– Found in all parts of the cell

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Nucleotides

• Three components

• Sugar– Either ribose or deoxyribose

• Phosphate unit

• Nucleic acid– Purines: two fused rings– Pyrimidines: one ring

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Nucleotides• Four bases in DNA

• Pair up in a specific pattern

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DNA

• When all base pairs are paired up with second strand – form double helix

• Held together by hydrogen bonding

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RNA• Tends to form single strand

• May pair up with itself

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Genetic Information

• Chromosomes: hereditary material, concentrated in long threadlike bodies– 46 in humans– Made of protein and DNA

• Gene: basic unit of heredity– Section of DNA

• Genome is complete set of genes for an organism

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All humans have 46 chromosomes in each cell of their body, (23 pairs)

A chromosome is a rod shaped cell structure that directs the activites of a cell and passes on the traitsof a cell to new cells.

n : a threadlike body in the cell nucleus that carries the genes in a linear order

Facts about Chromosomes

-You have 23 pairs of chromosomes in every cell-Chromosomes are rod-shaped and can be found in the nucleus.-Prokaryotic cells are cells without nuclei.-Eukaryotic cells are cells with DNA and chromosomes.-Chromosomes are made of protein and DNA, which all escapes during the Chromosome's life.-The life of a Eukaryotic cell has two phases... mitosis and interphase.-Mitosis is cell division.-Interphase is the time between mitosis, in which the cell grows.-S phase is DNA duplication in a cell.-"G1" is the gap between mitosis and interphase.-"G2" is the time between S phase and mitosis-Chromosomes direct all activities of the cell, including growth and reproduction.-Chromosomes are responsible for passing traits of a cell to a new cell.-Chromosomes are made of nucleic acid.

Anyway, if you still don't get it. Think of chromosomes as an encyclopedia, chromosomes contain awhole lot of information. They give the cell their information, the way you get information from anencyclopedia. They could also be called instruction manuals, because the chromosomes know whattraits to pass on to a new cell when the cell divides. Chromosomes also oversee growth as well asreproduction, and other cell functions.

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Self-Replication

•Occurs every time a cell divides

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Transcription• Converts DNA code to RNA

• Must occur before protein synthesis

• Can make multiple copies to make multiple copies of the protein

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Translation• Converts code on RNA into protein

• Read using base triplet – Code for amino acids– Some redundancy

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Polymerase Chain Reaction (PCR)

• Method to rapidly amplify any DNA present in sample– Can use very small amounts of DNA

• Allows for genetic testing– Cut DNA into relatively small sizes– Amplify it to see any pattern

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Recombinant DNA

• Allows for addition of genes to organisms

• Make microorganisms produce useful drugs– All insulin is made this way

• Rapidly change genetics of plants

• Treat genetic disorders in humans

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End of Chapter 15