Molecular Biology 2.2 - Water

Sodium chloride and transport in blood plasma:

-It is an ionic compound that is freely soluble in water. -dissolves to form sodium ions (Na+) and chloride ions (Cl-) which are carried in blood plasma.

How do water molecules arrange themselves when frozen?

A crystal lattice

Why is using water as an evaporative coolant an effective method of cooling the body?

Because water has a high latent heat of vaporization, so in the process of evaporation, a lot of heat is removed from the body and this cools it down.

What is a hydrophobic substance?

Substances that are insoluble in water although they dissolve in other solvents. Nonpolar molecules. All lipids are hydrophobic, including fats and oils. Ex. acetone.

What causes surface tension?

Surface tension is caused by the cohesive hydrogen bonding resisting an object trying to penetrate the surface of liquid water.

What is cohesion?

The binding together of two molecules of the same type. Ex. 2 water molecules.

What region of the brain controls sweat secretion?

The hypothalamus. It has receptors that monitor blood temperature and also receives sensory inputs from temperature receptors in the skin. If the body is overheated, the hypothalamus stimulates the sweat glands to secrete sweat.

What is a hydrogen bond?

The intermolecular force of attraction between water molecules. It is forms when a hydrogen atom in one polar molecule is attracted to a slightly negative atom of another polar molecule.

What do you call a substance that is insoluble in water?

immiscible/hydrophobic

What is more dense - liquid water or ice?

liquid water

What do you call a substance that is soluble in water?

miscible/hydrophilic

Which is more electronegative: oxygen or hydrogen?

oxygen

What do anti-diuretics do?

prevent dehydration

What type of bond is formed between the atoms in a water molecule?

single, covalent bonds.

Are hydrogen bonds weak or strong forces?

they are weak forces.

Hydrogen bonds explain the properties that make water useful to living organisms - true or false?

true

Which holds more oxygen - blood plasma at 37 ºC or blood plasma at 20 ºC?

20 ºC

How many binding sites does one hemoglobin protein molecule provide?

4

What percentage of the human body is made of water?

70%

What percentage of the lungs is made of water?

90%

What does blood plasma consist of?

95% water + other solutes

What is the chemical formula for water?

H2O

Explain the process of and reasons for sweat secretion in the body.

-The heat needed for the evaporation of water in sweat is taken from the tissues of the skin, reducing their temperature. -The sweat is carried along narrow ducts to the surface of the skin where it spreads out. -Sweat is secreted by glands in the skin. -Blood flowing through the skin is therefore cooled.

What happens when two nonpolar molecules are surrounded by water molecules and random movements bring them together?

-There is a slight attraction between the nonpolar molecules. -More hydrogen bonds form between the water molecules. *Water molecules are more attracted to each other than to the nonpolar molecules

Give examples of diuretics.

-caffeine -menstrual pain relievers -diet pills

Cholesterol and transport in blood plasma:

-cholesterol molecules are hydrophobic, apart from a small hydrophilic region at one end. -it is transported with fats in lipoprotein complexes, positioned in the phospholipid monolayer.

What properties of water make it useful to living organisms?

-cohesive properties -adhesive properties -thermal properties -solvent properties -density

Fat molecules and transport in blood plasma:

-entirely nonpolar -insoluble in water -they are carried in blood inside lipoprotein complexes -the hydrophilic phosphate heads of the phospholipids face outwards and are in contact with water in the blood plasma. -the hydrophobic hydrocarbon tails face inwards and are in contact with the fats.

What are some symptoms of dehydration?

-feeling of hunger, leading to overeating -daytime fatigue -short-term memory -difficulty focusing

Amino acids and transport in blood plasma:

-have both negatice and positive charges due to amine and acid groups. -they are all soluble in water, but level of solubility depends on the R group, some of which are hydrophilic, while others are hydrophobic. -is carried dissolved in blood plasma

List some benefits of water.

-helps ease joint pain -prevents constipation -flushes out disease-causing bacteria -increases metabolism -moisturizes skin

What are the thermal properties of water?

-high specific heat capacity -high latent heat of vaporization -high boiling point. -high latent heat of fusion

Oxygen and transport in blood plasma:

-nonpolar molecule -because of its small size, it dissolves in water, but sparingly -water becomes saturated with oxygen at relatively low concentrations -as the temperature of water rises, the solubility of oxygen decreases. -instead, hemoglobin in red blood cells provides binding sites for oxygen, greatly increasing the capacity of the blood for oxygen transport.

What are some other methods of cooling?

-panting in dogs and birds -transpiration (when water evaporates from plant leaves)

Glucose and transport in blood plasma:

-polar molecule -freely soluble in water (ring shape) -is carried dissolved in blood plasma

What are some habitats of methanogenic prokaryotes?

-swamps and other wetlands -the guts of animals (termites, sheep, cattle) waste dumps/landfills

List some functions of water.

-transportation of nutrients and waste -lubricates and cushion joints and organs -involved in biochemical reactions (metabolism) -helps maintain body temperature (perspiration) -gives cells their shape

Suggest why cytoplasm or blood made with water would be better for living things than cytoplasm or blood made from methane.

A cytoplasm of water can dissolve lots of proteins, and salts which are essential for life. The reactions of metabolism happen in solution, and can't happen unless they dissolve. Blood transports lots of substances including oxygen and nutrients, hormones and antibodies. Many of these molecules would not dissolve in methane.

Define a diuretic

A substance that prevents the kidneys from taking back water, leading to frequent urination.

Define homeopathy

A system for treating illnesses that uses very small amounts of substances that would, in larger amounts, produce symptoms of the illnesses in healthy people.

Define pseudoscience

A system of theories, assumptions, and methods wrongly regarded as scientific.

What is methane (CH4)?

A waste product of anaerobic respiration in certain prokaryotes that live in habitats where oxygen is lacking. Is nonpolar and cannot form hydrogen bonds. Can be used as a fuel, but when in the atmosphere, it is a greenhouse gas.

Why is adhesion a useful property to living organisms?

Also useful for water transport in cells. When water is being sucked through the xylem vessel, hydrogen bonds allow adhesion between the water molecules and the cellulose of the xylem wall. This is called capillary action.

What does it mean for water to have a high latent heat of vaporization?

Because hydrogen bonds must be broken to change the temperature of water, it takes a lot of heat to evaporate it. This makes water an effective evaporative coolant. Ex. sweating.

What is a hydrophilic substance?

Describes substances that are chemically attracted to water/soluble in water. Only polar molecules. Includes substances that water adheres to. Ex. sodium ions, chloride ions, cellulose, glucose.

What is water intoxication?

Drinking too much water. It dilutes the sodium in the blood and brain and can lead to death.

What are lipoprotein complexes?

Groups of molecules with a single layer of phospholipid on the outside and fats on the inside. There are also proteins in the phospholipid monolayer - hence the name lipoprotein.

What happens when a nonpolar molecule is surrounded by water molecules?

Hydrogen bonds form between the water molecules. There are no hydrogen bonds between the nonpolar molecule and the water molecule.

What does it mean for water to have a high specific heat capacity?

Hydrogen bonds restrict the motion of water molecules, and increases in temperature require hydrogen bonds to be broken. Hence, the amount of energy needed to raise the temperature of water is relatively large. This means water's temperature remains relatively stable, making it a thermally stable habitat for aquatic organisms.

What makes water molecules polar?

It involves unequal sharing of electrons. The hydrogen atoms have a partially positive charge and the oxygen atom has a partially negative charge.

Why is cohesion a useful property to living organisms?

It is useful for water transport in plants. When water is sucked through the xylem vessels of plants, its molecules are not separated (due to hydrogen bonding). Hence, water can be pulled from the roots all the way to the top of the tree.

Why is water's density useful to living organisms?

It's density means that it can support the mass of organisms that would be too large on land. They can float or swim in water.

Which has a lower boiling point - water or methane?

Methane

How does water act as a solvent to polar molecules?

The polar attraction of large quantities of water molecules interrupts ionic bonds, and causes dissociation of the atoms. The water molecules then form shells around the ions, preventing them from clumping together and keeping them in a solution. Ex. sodium ions (Na+) end up being surrounded by the negative oxygen regions of water molecules and the chloride ions (Cl-) are surrounded by the positive hydrogen region of water molecules.

What is "memory of water"?

The purported medicinal properties present in the ultra-dilute solutions used in homeopathic remedies.

What are hydrophobic interactions?

They are the forces that cause nonpolar molecules to join together in groups when in water.

What does it mean for water to have a high latent heat of fusion?

This means that a lot of energy has to be lost to change water into ice. This makes a stable habitat for aquatic organisms, particularly those living in beneath the oceans.

Which has a higher latent heat of vaporization - water or methane?

Water

Which has a higher specific heat capacity - water or methane?

Water

Why is water's solvent property important to living organisms?

Water dissolves polar molecules. It is an excellent solvent. This allows waste and nutrients to be moved around by blood (95% water) in the veins and arteries and enables trees to transport gases and other solutes. Also, substances dissolved in water can react with one another. Ex. cytoplasm is the site of metabolism.

Compare the cohesive ability of water and methane.

Water molecules are held together by relatively strong hydrogen bonds, so water molecules display strong cohesion. Methane molecules are held together by van der Waals forces (the weakest), hence they display weak cohesion.

Why is the high boiling point of water useful to living organisms?

Water's high boiling point means that it is liquid over a broad range of temperatures (0º to 100º). This is the temperature range found in most habitats on Earth.

What is adhesion?

When hydrogen bonds form between water and other polar molecules, causing water to stick to them.

Are water molecules bent or linear?

bent