Module 2: Biological molecules Flashcards
Explain the structure of water.
Covalently bonds. Unequal share of electrons so they move toward oxygen as it has a larger proton number/bigger atoms. Hydrogen are f+, oxygen are f-. Water is POLAR (unequal share of electrons) due to different charges over its surface. In polar bonds, electrons are shared, not lost. Hydrogen bonds are formed as the f- oxygen attracts the f+ hydrogen atom from a different water molecule. These bonds are weak compared to ionic or covalent. These give water lots of good properties.
What is water ionisation?
H+ and OH- ions formed is important for metabolic processes such as pH regulation.
Why does water have a high b.m.p?
Lots of hydrogen bonds require lots of energy to break.
Why does water make a good transport medium?
Liquid at room temp so doesn’t change state easily, providing a constant environment. Also due to adhesion and cohesion - water can rise up a narrow tube against the force of gravity (capillary action).
Define cohesion. Why does water have high cohesion?
Attraction between same substances (2 waters). They stick due to polarity/hydrogen bonding.
This property helps water to flow, water transported in xylem of plants.
Define adhesion. Why does water have high adhesion?
Attraction between different substances. Stick to others due to hydrogen bonding. Nutrients can be transported against gravity in plants ie capillarity.
Define latent heat. Why does water have high latent heat of evaporation?
Heat energy needed to change a substance from one state to the other, without changing temperature.
Because it takes a lot of energy to break the strong hydrogen bonds between water molecules, so lots of heat energy is used when water evaporates. It allows animals to cool themselves by sweating.
Why does water have high surface tension?
Due to highly cohesive forces, which require large amount of energy to break. Helps blood to flow through narrow vessels. Allows water to form a meniscus - insects can walk on water without sinking.
Define specific heat capacity and explain why water has a high specific heat capacity.
Energy needed to raise the temp of 1g of substance by 1 degrees C. Hydrogen bonds require a large amount of energy to break, so maintains homeostasis and a stable habitat.
Why is transparency important for water?
Light can pass through for photosynthesis and visibility in aquatic environments.
Explain why ice floats. Why is this important?
Water molecules are held further apart in solid form. Each H2O molecule forms 4 hydrogen bonds, making a lattice shape. Ice forms an insulating layer on top of water, so water below doesn’t freeze.
Water is a universal solvent. Why is that and how does it benefit?
Many solutes (amino acids) are also polar so the + and - attract ions in water. Important ions can dissolve in water in blood and be transported in the body.
Polar molecules are …
Hydrophilic as they dissolve easily in water.
Why is water difficult to compress?
Strong intermolecular forces between molecules. Provides support and turgidity in plant cells.
What is an inorganic ion?
Charged particles that aren’t part of the larger molecule and has no carbon (few exceptions). Typically derived from non-living sources.
