2.2 Water

IB Molecular Biology from MaritNy on Quizlet

What's covalent bond?

• Chemical bond
• Share of one or more electrons in pair - between atoms

What's peptide bond?

• Covalent bond
• Joins amino acids, at carboxyl group of 1 amino acid to the amino group of another amino acid
• Release of molecule of water

What's hydrogen bond?

• Weak bond
• Caused by electrostatic attraction, between positive and negative charge of molecules
  OPPOSITES ATTRACTIONS

Structure of water molecule?

Why is water a polar molecule?

• Oxygen: 8 protons
• Hydrogen: 1 proton
  -Oxygen attract electrons more strongly - become negative/ Hydrogen comes positive.

+Bonded by covalent bond, slight potential charge, becomes polar

Formation of hydrogen bonds between water molecules?

• Water molecules associate by weak hydrogen bonds
  -Hydrogen bonds: generally weak, form and break easily

What's adhesion?

Attraction between water molecules and other molecules
+format attract to polar or charged molecule

What's cohesion?

Attraction between water molecules and itself
+by formation of hydrogen bond

Examples of cohesion?

E.g. easier for water transport inside the plants, stick together, it creates a bigger single water molecule

Examples of adhesion?

E.g. Help water to be 'pulled' up the xylem easier. it stick towards the inner linings of the xylem

Why is water a good solvent?

Able to dissolve many organic/inorganic substances that are charged/polar.

+Has polar attraction, large quantities can interrupt ionic bonds - cause dissociation of atoms

Example of solvent properties of water benefits organisms?

Oxygen dissolves into moist layer lining the alveoli before diffusing from alveoli to blood, in human body.

3 thermal properties of water that are useful to organisms

1. High specific heat capacity
2. High heat of vaporization (hard to change state of water, energy is required)
3. High heat of fusion, temperature of water remains stable

+Useful: Heat lost from leaves for evaporation, prevent overheat & denature

Why it is important for mammals to control their body temperature?

Mammals are made up of 70% of water, including the blood - carries important substances around the body

How sweating is used as a mechanism to cool the body?

When sweats evaporates, its able to cool down the body - so the blood vessels and skin are cooled.

+keep constant temperature of animals in hot temperature habitats

What molecules are hydrophilic?

Ionic and polar molecules, b.c it has negative and positive charges - allow them to dissolve in water, substances that water adheres to e.g. cellulose

What molecules are hydrophobic?

Non-polar, Non-ionic molecules are hydrophobic. b.c. doesn't have charges

Link between hydrophilic molecules and water properties?

Hydrophilic molecules adheres to water.
Adhesion happens when water molecules stick to other type of molecules - through hydrogen bond.

Examples of hydrophobic molecules and a solvent they can dissolve into?

E.g Lipids dissolved in solvents like acetone

Glucose: Hydrophilic or Hydrophobic?

Hydrophilic

Amino Acids: Hydrophilic or Hydrophobic?

Hydrophilic

Cholesterol: Hydrophilic or Hydrophobic?

Both

Fats: Hydrophilic or Hydrophobic?

Hydrophobic

Oxygen: Hydrophilic or Hydrophobic?

Hydrophilic

Sodium Chloride: Hydrophilic or Hydrophobic?

Hydrophilic

Properties of glucose and how its transport in the blood?

• polar molecules
• easily soluble
  -carried by blood plasma

Properties of Amino Acids, and how its transport in blood?

• opposite charges
• soluble in water, polar molecule
• R group determines degree of solubility
  +can be all: polar, non-polar, charged
  +Carried by blood plasma

Properties of Fats, and how its transport in blood?

• big, non-polar molecules
  -insoluble in water

+carried in lipoprotein complexes, in plasma

Properties of Cholesterol, and how its transport in blood?

• hydrophobic, apart from small hydrophilic region
  -NOT easily dissolved in water

Properties of Sodium Chloride, and how its carried in blood?

• ionic compound
  -free: soluble in water
  -dissolve to form Sodium and Chloride Ions

+Carry in blood plasma

Properties of Oxygen, how its carried in blood?

-non-polar molecules (attract opposites)
-soluble in water
-temp. increases, solubility increases
-water gets saturated w/ oxygen @ low concentrations

+carried by hemoglobin, has 4 binding sites

Physical properties of Methane?

• light, colorless at room temp
• non-polar molecules only dissolve in non-polar substance (no opposite charges)
• low density and leant heat of vaporisation than water
  -low m/b point

Physical properties of Water?

• polar molecules
• density of 1 & s.h.c higher than methane (4.2)
• m.p at 0(ºc) b.p at 100(ºc)
• higher latent heat of vaporization than methane, thus harder to change state from liquid-solid, more energy requires
• hydrogen bonds, good coolant

Why the physical water and methane are different - while same molecular mass?

Water: form polar molecules w/ hydrogen bonds between water and oxygen.
-required heat energy to break H bonds, liquid at high temp.