Atoms, molecules, and life • An 18-th century chemists proved that all matter, living and nonliving is composed of particles called atoms, and discovery had a profound and permanent effect on the study of biology. In the decades that followed, biologists recognized that every organisms contains the same two dozen types of atoms arranged in different ways. The glorious diversity of life on our planet – the millions of kinds of plants, animals, fungi, and microbes could now be seen to stem from the myriad ways that specific atoms combine and interact. • A natural question arose from the pioneering work of Lavoisier and Dalton: are living things made up of the same elements as rocks, planets, and stars, or is our chemical makeup difference? Living things, it turns out, display a special subset of the 92 naturally occurring elements in the earth’s crust, but the elements occur in very different proportions. 98% of the atoms in the earth’s crust are the elements oxygen, silicon (Si), aluminum (Al), iron (Fe), calcium (Ca), sodium (Na), potassium (K), and magnesium (Mg), with the first three predominating
Transcript
Atoms, molecules, and life
•An 18-th century chemists proved that all matter, living and nonliving is composed of particles called atoms, and discovery had a profound and permanent effect on the study of biology. In the decades that followed, biologists recognized that every organisms contains the same two dozen types of atoms arranged in different ways. The glorious diversity of life on our planet – the millions of kinds of plants, animals, fungi, and microbes could now be seen to stem from the myriad ways that specific atoms combine and interact.•A natural question arose from the pioneering work of Lavoisier and Dalton: are living things made up of the same elements as rocks, planets, and stars, or is our chemical makeup difference? Living things, it turns out, display a special subset of the 92 naturally occurring elements in the earth’s crust, but the elements occur in very different proportions. 98% of the atoms in the earth’s crust are the elements oxygen, silicon (Si), aluminum (Al), iron (Fe), calcium (Ca), sodium (Na), potassium (K), and magnesium (Mg), with the first three predominating
• In a typical organisms, however, 99% of the atoms are the markedly different subset carbon, hydrogen, nitrogen and oxygen, with sodium and calcium, phosphorus (P), and sulfur making up most of the remaining 1%, plus a few other elements present in trace amounts. Biologists called the first ones – macro elements and the other – microelements. Microelements are present as ions in the structure of enzymes, vitamins and hormones. Other inorganic materials are water and mineral salts.•Biologists are not certain why the chemical subsets of living and nonliving things are so different, but they do know that atomic architecture determines the physical properties of elements and , in turn, the properties of living organisms.
Most frequent partners hydrogen, oxygen, and nitrogen
Hydrogen Oxygen Nitrogen Carbon
MineralsMineral Sources Function
Calcium (Ca) dairy products, dark green vegetables, legumes
bone and tooth formation, blood clotting, nerve and muscle function
Phosphorus (P)
dairy products, meat, grains
bone and tooth formation, acid-base balance, nucleotide synthesis
Sulfur (S) proteins part of some amino acids
Potassium (K)
meat, dairy products, many fruits and vegetables, grains
acid-base balance, water balance, nerve function
Chlorine (Cl) table salt acid-base balance, formation of gastric juice, nerve function, water balance
Sodium (Na) table salt acid-base balance, water balance, nerve function
Magnesium (Mg)
whole grains, green leafy vegetables
helps with ATP use
Minerals
Mineral Sources FunctionIron (Fe) meat, eggs, legumes, whole
grains, green leafy vegetablespart of hemoglobin, used in respiration
Functional GroupsHydroxyl -OH• alcohols• gives a compound
polar qualities• form hydrogen
bonds
Carbonyl -C=O• ketones and
aldehydes• found in most
sugars
Functional GroupsCarboxyl - COOH•organic acids•polar•gives a molecule acidic properties•key part of amino acids, the building blocks of proteins
Amino•-NH2
•called amines•gives a compound basic properties•key part of amino acids, the building blocks of proteins
Phosphate -PO4; organic phosphates•negative charge; hydrophilic•when it reacts with water energy is released; critical for many chemical reactions in the body
Functional Groups
Sulfhydryl -SH• called thiols• two of these
functional groups can interact to form sulfur bonds very important for maintaining the shape of proteins
Methyl -CH3
•methylated compounds•effects gene expression when it attaches to DNA•helps determine the function of some male and female hormones
Organic Chemistry• The study of compounds that contain
carbon• Can be very simple molecules or very
complex ones• Most organic compounds also contain
hydrogen
carbon can form covalent bonds with many different elements
Carbon: The Backbone of Life
•Although cells are 70–95% water, the rest consists mostly of carbon-based compounds•Carbon forms large, complex, diverse molecules
What is carbon’s valence?What does this mean?What are the shapes of organic compounds?
Carbon Compounds•Carbon chains form the skeletons of most organic molecules•Carbon chains vary in length and shape
Organic compounds • Just as a novel is made up of words and words are made up of individual letters, the phenomenon we call life is written in a language of molecules and atoms. And just as atomic structure underlines the properties of molecules and compounds, the shapes and behaviours of biological (organic)molecules account for the physical characteristics and activities of living organisms.• The fundamental components of biological molecules • Carbon: the indispensable element While some biological molecules are small and relatively simple, many of the carbohydrates, lipids, proteins, and nucleic acids are macromolecules – extremely large molecules with molecular weights of about 10,000 Daltons or more. Most of the compounds that make up living things, however, share one thing in common: they contain carbon. In fact, life on earth can not be separated from carbon and its unique chemistry. Any compound that contains carbon and has molecule weight over 10,000 Daltons or more is called an organic compounds.
w ater
proteins
nucleic acids
carbohydrates
lipids
inorganic ions
Macromolecules• Large biological molecules
• Carbohydrates• Proteins• Lipids• Nucleic Acids
• Most made of chains of repeating units called polymers
• Lipids are a bit of an exception
•The unique structure of the carbon atom ultimately accounts for the great diversity of molecules in living things. Carbon’s unique properties allow it to bond with up to four other atoms and form the ring or chain skeletons of macromolecules. Macromolecules are polymers formed by linking of many monomers by means of condensation reactions. The splitting of polymers into their component monomers occurs through hydrolysis. •Macromolecules that are synthesized in the sell are called biopolymers. Biopolymers can be divided into homopolymers and heteropolymers. Homopolymers are built up of equal monomers and heteropolymers are built up of different monomers. Heteropolymers have structural and storage function the cells. These are for example polysaccharides. Heteropolymers are proteins and nucleic acids.•Organic compounds are four main types : carbohydrates, lipids, proteins and nucleic acids. All organisms are built up of these four types of organic compounds. This proves the unity of the origin of all living things on the earth.
fats, steroids, oils, waxes, etc
Some lipids make up the plasma membrane of cell membranes.
Fats are lipids that store energy
Lipids
Carbohydrates sources of stored energy• A carbohydrate is composed of C, H and O in the ratio 1:2:1 (CH2O). This
formula gives the group its name, “hydrate of carbon ”. Carbohydrates consist of a carbon backbone with various functional groups attached. The basic carbohydrate subunits are sugar molecules called monosaccharides (single sugar); they functions as monomers that can be joined together to form more complex disaccharides (two sugars) and polysaccharides (many sugars).
• Monosaccharides: simple sugars• Monosaccharides serve as energy sources for living tings and as
building blocks for carbohydrate polymers and other biological molecules. Each simple sugar has a structure based on a short carbon backbone. The monosaccharides glucose, fructose, and galactose are the most important carbohydrate monomers, since those units make up the complex carbohydrates in starch, wood, and other biological materials. These monomers are referred to as sugars and some do have a sweet taste. Fructose, for example, gives many of fruit their sweet flavour. Glucose is the universal cellular fuel, broken down by virtually all living things to release energy stored in its bonds.
Forming and Digesting Polymers
• Dehydration synthesis: process that bonds monomers together
• Hydrolysis: process that breaks polymers.
• Bonds based on functional groups at ends of monomers
• Enzymes speed this up.
Carbohydrate: molecule composed of carbon, hydrogen, and oxygen with simplified formula Cn(H20)n
raw materials for amino acids, fats- fuel source many isomers - end in –ose ring structure common when in water
The sub-unit (building blocks) of carbohydrates are single sugars, called monosaccharides.
Range from small sugar molecules to the long starch molecules we consume in pasta and potatoes.
Key source of energy
found in most foods — especially fruits, vegetables, and grains
Disaccharides : sugars built of two monosaccharides
• Real diversity in shape and properties can arise when monosaccharide monomers are linked into larger molecules. Disaccharides are the common form in which sugar are transported inside plants. For example, glucose bonds to fructose to yield sucrose, or table sugar. Sucrose is abundant in the saps of sugarcane, maple trees, and sugar beets. Honey has also glucose and fructose. The predominant sugar in milk is lactose , galactose bonded to glucose. Maltose – two joined glucose subunits – gives barley seeds a sweet taste and their utility to the beer industry.
Formation of a disaccharide
Polysaccharides storage depots and structural scaffolds
•Living organisms form the long-chain carbohydrates called polysaccharides by linking large numbers of single sugars, or monosaccharides, into polymers. The most important polysaccharides are starch, glycogen, and cellulose. Other biologically significant polysaccharides include chitin, a major component of the shells of insects and crustaceans such as lobsters and crabs. Starch is the major nutrient reserve in most plants. Glycogen is a storage from for glucose in the living animal cells. It has a branched molecule which allows the rapid break down and release of energy that animals often require. Cellulose is polysaccharide as chitin and gives strength and rigidity to
plant cells and wood.
PolysaccharidesStarch- Helical (spiral) structureCellulose•long, straight chain, never branched•h-bonds between parallel polymers•makes fibers. Only some fungi and prokaryotes can digest cellulose (also symbionts: termites, cows, etc)•Glycogen (animals only) has many branches•Branched carbs better for rapid glucose release (more places for an enzyme to attack)
Lipids: energy interfaces, and signals• The second group of biological molecules, the lipids, makes
certain foods oily, keep us warm , and prevent the watery contents
of cells from leaking out. Lipids include the fats, such as bacon
fat, lard, and butter; the oils, such as corn, coconut, and olive oils;
the waxes, like beeswax and earwax; the phospholipids, which are
Important components of cell membranes; and steroids, including
certain vitamins, hormones, and cholesterol(the heart and blood
vessel cloggier ). Like carbohydrates, lipids can serve as energy
storage molecules or as waterproof coverings around cell.
Fats and oils are common compounds in animals and plants, and
the reason again is based on molecular structure. When an
organism burns stored fats or oils, more calories of heat energy
are released than when it burns an equivalent amount of sugar or
polysaccharide. When we consume more calories than we burn
our body stores the extra energy in concentrated form as fat.
• Waxes are a variation on oils. Their molecules are made up of a long – chain alcohol linked to the carboxyl group of a fatty acid. Large numbers of wax molecules packed together form a waterproof outer layer on the leaves of plants, the bills and feathers of some birds, and other structures in living organisms. Waxes serve as structural materials in honeycombs of beehives; and as protective coatings for the ear canal. The phospholipids contain nitrogen and phosphorus as well as the carbon, hydrogen, and oxygen atoms in fats and oils. Theseadditional elements give phospholipids their ability to maintain a cell’s waterproof boundary. The overall shape of a phospholipids molecule is something like a head with two long, thin tails streaming from the nape of the neck; the glycerol phosphate forms the hydrophilic head, while the fatty acid chains form the hydrophobic tails. The behaviour of phospholipids is rooted in this shape. Since the tails are hydrophobic and the head is hydrophilic the molecules have an ambivalent approach to water. This behaviour of phospholipids accounts for the structure of cell membranes, which are double – layered phospholipids barriers surrounding living cells.
•Steroids, the third type of lipids, are much less abundant in living cells than are fats, oils, and phospholipids, but they are no less important. Steroids are no polar and hydrophobic; they are insoluble in water, can dissolve in oils or in lipid membranes, and can move into and out many cells. Some steroids act, as vitamins, while others, such as estrogen and testosterone, are hormones. Cholesterol , another common steroid, has important beneficial effects on the fluidity of many cellular membranes. But this steroid, which is regularly manufactured in the body, may build up in the blood vessels and contribute to heart disease.
