Chemical Composition of Living Matter

What is the nature of matter?

Anything that takes up space and has mass, made up of elements that cannot be broken down by chemical reactions.

What is a compound?

A substance consisting of two or more different elements combined in a fixed ratio.

Which elements make up about 96% of human body weight?

Oxygen (65.0%), Carbon (18.5%), Hydrogen (9.5%), Nitrogen (3.3%).

Which elements make up about 4% of human body weight?

Calcium (1.5%), Phosphorous (1.0%), Potassium (0.4%), Sulfur (0.3%), Sodium (0.2%), Chlorine (0.2%), Magnesium (0.1%).

What are trace elements?

Elements required by an organism in only minute quantities, making up less than 0.01% of body weight.

Who proposed the concept of atoms in the 5th Century B.C.?

Democritus.

What does the word 'atom' mean in Greek?

Uncuttable.

What are the three major subatomic particles?

Neutrons (no charge), Protons (positive charge), Electrons (negative charge).

What is the atomic number of an element?

The number of protons in an atom of that element.

What is the mass number of an atom?

The sum of the number of protons and neutrons in the nucleus of an atom.

What are isotopes?

Different atomic forms of the same element that have the same number of protons but different numbers of neutrons.

In what physical states does water exist in the natural environment?

Solid (ice), liquid, and gas (vapor).

How much of most cells is made up of water?

About 70-95%.

How long can humans typically survive without water?

About a week.

What shape does a water molecule resemble?

A wide V, with two hydrogen atoms joined to an oxygen atom by single covalent bonds.

Why is water considered a polar molecule?

Because it has opposite charges at each end; the oxygen region has a partial negative charge and the hydrogen regions have partial positive charges.

What is cohesive behavior in water?

The hydrogen bonds in water molecules hold the substance together, contributing to the transport of water and nutrients in plants.

What is adhesion in the context of water?

The ability of water to stick to cell walls by hydrogen bonds, helping to counteract gravity.

What is surface tension?

A measure of how difficult it is to stretch or break the surface of a liquid, exemplified by water striders.

What is water's specific heat?

1 cal/gm/°C.

How does water's high specific heat affect temperature?

It allows large bodies of water to absorb and store heat, stabilizing ocean temperatures and creating favorable environments.

What is the significance of water in the evolution of life on Earth?

Life began in water and evolved there for 3 billion years before spreading onto land.

What is evaporation?

The transformation from a liquid to gas.

How much heat is needed to evaporate 1g of water at 25⁰C?

About 580 calories.

What is evaporative cooling?

It occurs when liquid evaporates, causing the surface of the remaining liquid to cool down.

What is unique about water's density when it freezes?

Water is less dense as a solid (ice) than as a liquid, which is why ice floats.

What effect does ice have on bodies of water?

Floating ice insulates the liquid water below, preventing it from freezing and allowing life to exist beneath the frozen surface.

What is a solution?

A liquid that is a completely homogenous mixture of two or more substances.

What is a solvent?

The dissolving agent of a solution.

What is a solute?

The substance that is dissolved in a solution.

What is an aqueous solution?

A solution in which water is the solvent.

What does hydrophilic mean?

Substances that have an affinity for water.

What does hydrophobic mean?

Substances that do not have an affinity for water and tend to repel it.

What is a colloid?

A stable suspension of fine particles in a liquid.

What is an acid?

A substance that increases the hydrogen ion (H+) concentration of a solution and removes hydroxide ions (OH-).

Give an example of a strong acid.

Hydrochloric acid (HCl).

What is a base?

A substance that reduces the H+ concentration of a solution and increases OH- concentration.

Give an example of a strong base.

Sodium hydroxide (NaOH).

What is the pH range of battery acid?

pH 1.

What is the pH of human blood?

Very close to 7.4, which is slightly basic.

What is a buffering system?

Substances that minimize changes in the concentrations of H+ and OH- in a solution.

What is the carbonic acid-bicarbonate buffering system?

A buffering system that consists of an acid and a base in equilibrium with each other.

What are salts?

Compounds formed by ionic bonds, often found in nature as crystals.

What happens to ionic bonds in salt when dissolved in water?

The ionic bonds become weaker as each ion is partially shielded by its interaction with water molecules.

What are monosaccharides?

The simplest carbohydrates, also known as single sugars.

What is the most common monosaccharide?

Glucose (C6H12O6)

What classification is based on the location of the carbonyl group in monosaccharides?

Aldose (aldehyde sugars) and Ketoses (ketone sugars).

What are the three types of monosaccharides based on the length of their carbon skeletons?

Trioses (3-carbon), Pentoses (5-carbon), Hexoses (6-carbon).

What are the primary functions of monosaccharides like glucose?

They serve as major fuel for cellular work and nutrients for cells, and their carbon skeletons are raw materials for synthesizing other organic molecules.

What are disaccharides?

Double sugars consisting of two monosaccharides joined by a glycosidic linkage.

Give examples of disaccharides and their components.

Maltose (2 glucose), Sucrose (glucose + fructose), Lactose (glucose + galactose).

What are polysaccharides?

Macromolecules, polymers made of a few hundred to a few thousand monosaccharides joined by glycosidic linkages.

What are the two types of polysaccharides?

Storage polysaccharides and structural polysaccharides.

What is starch and where is it stored?

A storage polysaccharide in plants, stored as granules in plastids.

What is glycogen and where is it primarily stored?

A storage polysaccharide in animals, mainly stored in liver and muscle cells.

What is cellulose?

A major component of the tough walls that enclose plant cells.

What is chitin and where is it found?

A structural polysaccharide used by arthropods for exoskeletons and found in fungal cell walls.

What are lipids?

Hydrophobic compounds that include fats, phospholipids, and steroids.

What are the two smaller molecules that fats are constructed from?

Glycerol and fatty acids.

What is the difference between saturated and unsaturated fats?

Saturated fats are for energy storage, while unsaturated fats cushion vital organs and insulate the body.

What is the structure of phospholipids?

They have a hydrophilic head (phosphate group) and hydrophobic tails (hydrocarbons).

What is the role of steroids in the body?

Many hormones are steroids produced from cholesterol, which is crucial for animals.

What are nucleic acids?

Biomolecules that enable living organisms to reproduce their complex components across generations.

What is the primary function of DNA?

It serves as the genetic material inherited from parents.

What is RNA and how does it differ from DNA?

RNA consists of a single polynucleotide chain and contains ribose sugar.

What are the different types of proteins based on their functions?

Enzymatic, Structural, Storage, Transport, Hormonal, Receptor, Contractile/Motor, and Defensive proteins.

What is the function of enzymatic proteins?

They regulate metabolism by acting as catalysts that speed up chemical reactions.

What is an example of a storage protein?

Ovalbumin.

What is the role of transport proteins?

They transport other substances, such as hemoglobin transporting oxygen.