MOLECULES OF LIFECHAPTER 2

GROUP 1

The universe is made up of matter which is anything that contains mass. Matter is composed of elements, substances which cannot be broken down by ordinary chemical means into simpler particles. An atom is the smallest unit of an element that retains the chemical properties of that element.

92 occurring elements, six are used in quantity by living organisms.

65%-oxygen(living matter) 18%-carbon 10%-hydrogen 3%-nitrogen 4%-phosphorus, sulfur, potassium, calcium, iron, magnesium, sodium, chlorine(other elements)

MOLECULE- the resulting substance when two or more atoms chemically combine.

EX: molecule of water, H2O, consist of two atoms of hydrogen bonded together to a single atom of oxygen.

THREE IMPORTANT CHEMICAL BONDS EXIST: IONIC BONDS COVALENT BONDS HYDROGEN BONDS

IONIC BONDS- an atom with a few electrons in its centremost orbital, may lose some to the outermost orbital of another atom that lacks a few electrons to complete its stable number.

ELECTRON DONOR- the atom that gives up its electrons.

-are usually the atoms with more than 4 electrons in their outermost orbital.

-ends up with more protons than electrons thereby becoming positively charged(+). ELECTRON ACCEPTOR- the atom receiving.

-are those with less than 4.

-ends up with more electrons than protons and becomes negatively charged(-). IONS- charged atoms.

COVALENT BONDS- atoms forming covalent bonds share electrons.

ex: water is a molecule formed by the covalent bonding of two atoms of hydrogen and one atom of oxygen.

Water molecule bonding

Water is a cohesive substance because hydrogen bonds

form between water molecules. The negatively

charged part of one molecule is

linked to the more positively portion of another molecule

by hydrogen bonds.

HYDROGEN BONDS- is formed when a hydrogen atom, essentially a single proton, acts as a bridge between two electrically negative atoms.

covalent bonding- has a slight negative charge in the oxygen atom

hydrogen atom- acquires a slight positive charge.

A weak hydrogen bond is formed when atom in one water molecule forms a hydrogen bond with the oxygen atom in another molecule until many water molecules bond together.

Large molecules held in proper shape by hydrogen bonds: structural protein DNA Enzymes Hemoglobin molecules

CHEMICAL REACTION- is a process by which the bonds between atoms are broken or formed resulting in different combinations of atoms or molecules.

EXERGONIC REACTION- when a chemical reaction gives off energy.

ENDERGONIC REACTION- when energy is needed for a chemical reaction.

-energy given off by exergonic reactions is often used to fuel endergonic reaction

CHEMICAL REACTIONS ARE IMPORTANT IN BIOLOGICAL SYSTEMS:

Oxidation-reduction Hydrolysis Condensation

IMPORTANT BIOLOGICAL MOLECULES

COMPOUNDS: WATER CARBOHYDRATES LIPIDS PROTEINS NUCLEIC ACIDS

Except for water, these compounds make up the organic substance of living organisms.

Organic compounds always contain carbon.

WATER- is the substance that makes possible life as we know it in here on earth. It is the biological medium here on earth and possibly on other planets as well.

Most cells are surrounded by water, and cells are about to 70-95% water. Three-quarters on earth’s surface is submerged in water. Most of this water is in liquid in form, but some of water exist as ice and vapor. Water is the only common substance to exist in the natural environment in all tree physical states of matter: solid, liquid, and gas.

As a compound, it is made up of two hydrogen atoms and one oxygen atom covalently bounded.

Oxygen part-slight negative charge

Hydrogen part- slight positive charge POLAR MOLECULE- such a molecule can form hydrogen bonds with other water molecules or with

molecules of other compounds.Water is effective in suspending small molecules such as: ions Sugars Amino AcidsDEHYDRATION- an effective method of food preservation.

-removal of water.

Another important property of water is its slowness in changing temperature. More heat is required to change water from solid, ice to liquid or liquid to gas compared with other known substances.

The cooling effect can be very important in maintaining homeostasis of of an organism.

Water enters into the many chemical reactions of cell.

The hydrolysis of a protein yields amino acids . Water also provides the medium for the

Chemical interaction of other biochemical molecules. The importance of water to living organisms can be better understood if we know that most living cells consists of 70-95% water.

PH of Solutions – common aquatic plants and animals generally live in a fairly narrow range of pH . Most of these organisms possess buffers which allow them to tolerate at least for a short time, water at a pH of six to nine .

buffer-is a substance that keeps the pH constant when small amounts of acid or alkali are added.

-they work to maintain a constant pH within an organism.

The internal pH of most living cells is close to seven .Even a slight change in pH can be harmful, because the chemical processes of the cell are very sensitive to the concentration of hydrogen and hydroxide ions .

Buffers in human blood, for example, normally maintain the blood pH very close to 7.4. A person cannot survive for more than a few minutes if the blood pH drops to 7 or rises to 7.8 ACIDS AND ALKALIS

-Acids are substances that release free protons in solution and have the pH of less than seven. Bases are substances that react with acids to form salts. Alkalis- bases that dissolve in water.

These molecules are proton acceptors, removing protons from aqueous(watery) solutions and so increasing the pH. Alkaline(or basic) solutions therefore have a higher concentration of ions than pure water and a pH greater than 7.

The pH of some aqueous solutions

• ph5- ten times higher than a solution at pH6.• A solution above 7 has a concentration of hydroxide ions 10x higher.

• A solution is pH9, has a concentration of hydroxide ions 10x higher than a solution at ph8.

• The ph scale is from zero(most acidic) to (most alkaline).

EFFECTS OF ACIDS ON LIVING ORGANISMS. The bodies of living organisms can tolerate only a limited pH

range. A slight change in pH can be harmful because molecules in cells are very sensitive to concentrations of protons and hydroxide ions.

Acid precipitation has a pH of less than five. The increased acidity is caused mainly by fumes from burning

fossil fuels reacting with water in the atmosphere to form acids of sulphur and nitrogen.

Acid precipitation refers to rain, snow, or fog more acidic than pH 5.6.

oThe effects of acids in lakes and river and the other sources of water is a serious environmental problem; considering the dependence of all life on water.

o The effects of acid precipitation on plants pose problems to other living organisms.

oPlants are made susceptible to pests and diseases and can die.

Acidic gas emissions cause acid rain

• Carbohydrates play an important role in energy transformation in cells. They are form by plant cells during photosynthesis. Carbohydrates store energy that can be released by cellular respiration to fuel cell functions. Starch and cellulose are large, complex molecules of carbohydrates.

CARBOHYDRATES-composed of simple sugars called MONOSACCHARIDES that are link together.

GLUCOSE- is a monosaccharide that place a role in energy transformations. Other monosaccharide are fructose and ribose.

Monosaccharide- composed of carbon, hydrogen and oxygen atoms in which there are always twice as many hydrogen atoms as oxygen atoms.

CX(H2O)Y-this formula represents a monosaccharide in which the x and y can be any number.

Monosaccharides are building blocks of more complex sugars.

DISACCHARIDE- When two monosaccharides are chemically united.

A molecule of water is formed whenever two monosaccharide molecules bond together. This is an example of a condensation reaction.

POLYSACCHARIDES- when carbohydrate molecules are made up of more than two simple sugars.

Polysaccharides-formed by the same process that forms disaccharides and can be broken down into many simple sugar components by hydrolysis.

Starch and Glycogen-polysaccharides composed of bands of long chains.

POLYSACCHARIDE CHAINS(polymers)-contain hundreds or thousands of simple carbohydrate molecules.

The three very important polysaccharides in living things, namely: STARCH-the storage form of glucose in plants. CELLULOSE-the most abundant material in plant cell walls. GLYCOGEN-the primary form of glucose storage in animals cells.

Starch and Glycogen-used as sources of food by animal cells, but cellulose is not digestible by most animals. PROTEIN- are large, complex molecules composed mainly of carbon,

hydrogen, oxygen, and nitrogen.

ENZYMES- proteins serving as catalysts.

There are about twenty different amino acids that form a great number of proteins.

In the process, one molecule of water is formed which is the process of dehydration synthesis.

A peptide bond is a type of covalent bond. POLYPEPTIDES-short chains of amino acids. LEVELS OF PROTEIN STRUCTURE- the specific sequence of amino acids in a

protein constitutes the protein primary structure. The primary structure determines the fundamental nature of the polypeptide.

When a chain of amino acids twists into a helix, the protein molecule is shaped like a coiled spring. The coiling is the secondary structure of the protein. A molecule hemoglobin in human blood is composed of four sub-units and

hence called a “super protein”. A hemoglobin cannot work without iron, and iron cannot work without the

protein.

LIPIDS-lipids are organic compounds that function as concentrated food storage materials, as structural components of cells, and as regulatory chemicals.

Examples of it are:

• Lipids are fats, oils, waxes, phospholipids, steroids, and cholesterol.

The molecule of a simple fat is composed of four building blocks: One molecule glycerol bonded to three fatty acid molecules. The bond s are formed by removing water molecules in dehydration

synthesis. The digestion of fats by hydrolysis separates the molecules of fatty

acids from the glycerol molecules through the addition of three molecules of water.

Saturated fats solidify fat room temperature and every carbon atom in the chain of the fatty acids is bonded to four different atoms.

OILS-unsaturated fats, are liquid at room temperature.CHOLESTEROL- saturated fats are easily converted to the complex

lipid.

The accumulation of cholesterol in the walls of arteries reduces blood flow and increases blood pressure. This condition is called Atherosclerosis.

FUNCTIONS OF FATS AND OILS: HEAT INSULATION-being a poor conductor of heat, mammals

increase their adipose (fat) tissues in winter to reduce heat loss. SHOCK ABSORPTION- delicate mammalian organs such as kidneys

have relatively thick layers of fat around them. BUOYANCY-many single-celled aquatic animals produce an oil

droplet for buoyancy in water.

DIETARY FAT- source of fatty acids and of phospholipids. PHOSPHOLIPIDS-form a major part of the plasma membrane

including the myelin sheath around nerve fibers that allows the rapid conduction of nerve impulses.

Phospholipids consist of glycerol. NUCLEIC ACID-are the key to translating genetic information into

cellular function. It is found in living things. They are made of very large molecules (macromolecules) due to the linking of small units that are repeated over and over again.

NUCLEOTIDES-the nucleic acids of all living organisms differ in the sequence of units.

NUCLEIC ACIDS ARE MADE UP OF THREE COMPONENTS: PHOSPHATE, SUGAR, AND NITROGEN CONTAINING BASES

• TWO MAIN KINDS OF NUCLEIC ACIDS: RIBONUCLEIC ACID(RNA)- nucleic acids containing

ribose sugar. DEOXYRIBONUCLEIC ACID(DNA)-contains deoxyribose,

a sugar with one less oxygen atom. DNA-is the genetic material inherited from parents.

-a chemical substance of genes. GENE-unit of inheritance that programs the amino acid

sequence of a polypeptide that form the protein. RNA and DNA- play important roles in protein synthesis.

Reported by group 1: Jiamie Catam-isan

Rose Ann Postrero

Karen Sumalinog

Janice Urot