CHAPTER 3 The Molecules of Cells Life’s structural and functional diversity results from a great variety of molecules A relatively small number of structural patterns underlies life’s molecular diversity

Organic Compounds  Always contain carbon  Tend to be large & complex  A carbon atom forms four covalent bonds ( this allows carbon to form many different chemical compounds)  Carbon skeletons vary in many ways Carbon skeletons vary in length. Skeletons may be unbranched or branched. Skeletons may have double bonds, which can vary in location Skeletons may be arranged in rings

Cells make a huge number of large molecules from a small set of small molecules Most of the large molecules in living things are macromolecules called polymers –Polymers are long chains of smaller molecular units called monomers (building blocks) –A huge number of different polymers can be made from a small number of monomers –SIZE: monomer< polymer< macromolecule

Molecules of Life Put C, H, O, N together in different ways to build living organisms What are bodies made of? –carbohydrates sugars & starches –proteins –lipids –nucleic acids DNA, RNA

Why do we eat? We eat to take in more of these chemicals –Food for building materials to make more of us (cells) for growth for repair –Food to make energy calories to make ATP ATP

How do we make these molecules? We build them!

Building large molecules of life Chain together smaller molecules –building block molecules = monomers Big molecules built from little molecules –polymers

Small molecules = building blocks Bond them together = polymers Building large organic molecules

Building important polymers sugar – sugar – sugar – sugar – sugar – sugar nucleotide – nucleotide – nucleotide – nucleotide Carbohydrates = built from sugars Proteins = built from amino acids Nucleic acids (DNA) = built from nucleotides amino acid amino acid – amino acid – amino acid – amino acid – amino acid –

How to build large molecules Dehydration Synthesis –building bigger molecules from smaller molecules –building cells & bodies repair growth reproduction + ATP

Making and Breaking of POLYMERS Cells link monomers to form polymers by dehydration synthesis (building up) Short polymer Unlinked monomer Removal of water molecule Longer polymer

Example of synthesis amino acidsprotein amino acids = building block protein = polymer  Proteins are synthesized by bonding amino acids

Making and Breaking of POLYMERS Polymers are broken down to monomers by the reverse process, hydrolysis (hydro ~ add water; lysis ~ to split) Addition of water molecule

How to take large molecules apart Hydrolysis ~Digestion –taking big molecules apart –getting raw materials for synthesis & growth –making energy (ATP) for synthesis, growth & everyday functions + ATP

Example of digestion starchglucose ATP Starch is digested to glucose

1. CARBOHYDRATES They range from small sugars to large polysaccharides Poly~ many Sacchar ~ sugar Mono ~ one Di ~ two

Monosaccharides are the simplest carbohydrates Monosaccharides are single-unit sugars (building blocks) These molecules typically have a formula that is a multiple of CH 2 O Monosaccharides are the fuels for cellular work

Sugars = building blocks Names for sugars usually end in –glucose –fructose –sucrose –maltose OH H H HO CH 2 OH H H H OH O glucose C 6 H 12 O 6 sucrose fructose maltose -ose

Cells link single sugars to form disaccharides Monosaccharides can join to form disaccharides, such as sucrose (table sugar) and maltose (brewing sugar)

Polysaccharides are long chains of sugar units polymers of hundreds or thousands of monosaccharides linked by dehydration synthesis Function as –Energy storage Starch (plants) Glycogen (animals) – Structure Cellulose (plants cell walls) (fiber in diet) Chitin ( insects)

Digesting starch vs. cellulose starch easy to digest cellulose hard to digest enzyme

Cellulose Cell walls in plants –herbivores can digest cellulose well –most carnivores cannot digest cellulose that’s why they eat meat to get their energy & nutrients cellulose = roughage –stays undigested –keeps material moving in your intestines

Helpful bacteria How can cows digest cellulose so well? –BACTERIA live in their stomachs & help digest cellulose-rich (grass) meals Eeeew… Chewing cud?

Lipids composed largely of carbon and hydrogen –They are not true polymers –They are grouped together because they do not mix with water (Nonpolar)

Lipids Examples –fats –oils –waxes –hormones sex hormones –testosterone (male) –estrogen (female)

Lipids Function: –energy storage very concentrated twice the energy as carbohydrates! –cell membrane –cushions organs –insulates body think whale blubber!

Lipids include fats, Fats are lipids whose main function is long term energy storage Other functions: –Insulation in higher vertebrates –“shock absorber” for internal organs A triglyceride molecule consists of one glycerol molecule linked to three fatty acids Fatty acid

Saturated & Unsaturated fats fatty acids of unsaturated fats (plant oils) contain double bonds –These prevent them from solidifying at room temperature Saturated fats (lard) lack double bonds –They are solid at room temperature

Saturated vs. unsaturated saturatedunsaturated

Phospholipids, waxes, and steroids are lipids Phospholipids are a major component of cell membranes –heads are on the outside touching water “like” water –tails are on inside away from water “scared” of water –forms a barrier between the cell & the outside

Other lipids in biology Waxes form waterproof coatings Steroids are often hormones

Other lipids in biology Cholesterol (Steroid) ( only in animal cells) –good molecule in cell membranes –make hormones from it including sex hormones –but too much cholesterol in blood may lead to heart disease

Connection: Anabolic steroids Anabolic steroids are usually synthetic variants of testosterone Use of these substances can cause serious health problems

PROTEINS : Multipurpose molecules essential to the structures and activities of life Make up 50% of dry weight of cells Contain carbon, hydrogen, & oxygen PLUS nitrogen and sometimes sulfur Proteins are involved in –cellular structure –movement –defense –transport –Communication Monomers are called amino acids

collagen (skin) Proteins insulin Examples –muscle –skin, hair, fingernails, claws collagen, keratin –pepsin digestive enzyme in stomach –insulin hormone that controls blood sugar levels pepsin

Proteins are made from just 20 kinds of amino acids Proteins are the most structurally and functionally diverse of life’s molecules –Their diversity is based on different arrangements of amino acids –R- variable group- which distinguishes each of the 20 different amino acids

Amino acids can be linked by peptide bonds to form polymer Cells link amino acids together by dehydration synthesis The bonds between amino acid monomers are called peptide bonds Dehydration synthesis Amino acid PEPTIDE BOND Dipeptide

A protein’s specific shape determines its function A protein consists of polypeptide chains folded into a unique shape –The shape determines the protein’s function –A protein loses its specific function when its polypeptides unravel

A protein’s specific shape determines its function A protein can change in response to the physical and chemical conditions Alterations in pH, salt concentration, temperature, or other factors can unravel or denature a protein Some proteins can return to their functional shape after denaturation -renature

NUCLEIC ACIDS : Information molecules 1. DNA (deoxyribonucleic acid) contains the instructions used to form all of an organism’s proteins. 2. RNA (ribonucleic acid) forms a copy of DNA for use in making proteins. They ultimately control the life of a cell

DNA Nucleic Acids Function: –genetic material stores information –genes –blueprint for building proteins »DNA  RNA  proteins transfers information –blueprint for new cells –blueprint for next generation proteins

NUCLEIC ACIDS The monomers of nucleic acids are nucleotides –Each nucleotide is composed of a sugar, phosphate, and nitrogenous base Phosphate group Sugar Nitrogenous base (A)

NUCLEIC ACIDS The sugar and phosphate form the backbone for the nucleic acid Nucleotide Sugar-phosphate backbone

Nucleotide chains Nucleic acids –nucleotides chained into a polymer DNA –double-sided –double helix –A, C, G, T RNA –single-sided –A, C, G, U phosphate sugar N base phosphate sugar N base phosphate sugar N base phosphate sugar N base strong bonds RNA

DNA Double strand twists into a double helix –weak bonds between nitrogen bases join the 2 strands A pairs with T –A :: T C pairs with G –C :: G –the two strands can separate when our cells need to make copies of it –The sequence of the four kinds of nitrogenous bases in DNA carries genetic information weak bonds

DNA Stretches of a DNA molecule called genes program the amino acid sequences of proteins –DNA information is transcribed into RNA, a single-stranded nucleic acid –RNA is then translated into the primary structure of proteins

Watson and Crick … and others… 1953 | 1962