A1.1 Flashcards
Water is required for…(2) due to (1)
Water was essential to the development of the first cells and remains essential as the medium in which life’s processes take place due to its solvent properties
Electronegativity
measure of how strongly the nucleus of an atom attracts the electrons it shares with another atom
Influenced by:
a) number of protons in the atom (more=stronger attraction)
b) number of orbital levels (more=creates more distance between nucleus and e-, decreases attraction)
Water molecules are…polar or nonpolar?
polar - O partial negative, H partial positive
hydrogen vs polar covalent bonds
hydrogen bonds break and reform rapidly between different molecules, whereas the polar covalent bonds break much less frequently
h bonds: between molecules
pc bonds: within molecules
Cohesion
‘like’ molecules are mutually attracted (pulls water together)
Examples of cohesion (2)(must know vascular)
- Vascular plants use cohesion to transport water up thin tubes called xylem - water evaporates from the surface of inner cell walls into air spaces in the leaf.
As water evaporates, they are replaced by water from within the cells. As more water molecules move from the xylem into the leaf, tension is transmitted down a continuous column of water molecules all the way to the root.
- Water striders
Adhesion
attraction between water + other things
Capillary action and adhesion + example (1)
water is pulled through narrow tubes and space as a result of cohesion and adhesion, occurring when adhesion is greater than cohesion (pulls it up until it’s above a “water line”)
xylem cellulose fibres that compose the cell wall pull water into the spaces between them to prevent dehydration of plant
Physical properties of water
- Buoyancy is a force that counteracts the force of gravity.
- Viscosity is resistance to flow and is related to how much energy is needed to change the shape of a liquid.
- Thermal conductivity is the ability of a substance to transfer heat when there is a temperature difference. Water has a high thermal conductivity compared with other liquids (except liquid metals). Air has a much lower thermal conductivity than water.
- Specific heat capacity is how much energy is needed to raise the temperature of a substance. Water has a high specific heat capacity. Air has a much lower specific heat capacity than water.
What is the most likely original source of water on Earth?
asteroids/comets
What feature of liquid water makes it the focus of the search for extraterrestrial life
Water can dissolve the building blocks of life as well as the enzymes that catalyse the reactions that make up metabolism.
DNA
deoxyribonucleic acid
What type of biological macromolecule is DNA?
DNA is a type of biological macromolecule called a nucleic acid.
Nucleic acids are essential for genetic information storage and transfer.
What are nucleic acids made of?
Nucleic acids are chains of repeating monomers called nucleotides.
Nucleotides consist of a sugar, a phosphate group, and a nitrogenous base.
How do nucleotides join to form nucleic acids?
Nucleotides join together to form the nucleic acid polymer by a condensation reaction called polymerisation.
This process involves the removal of water to link nucleotides.
What is the role of DNA in living organisms?
DNA is the genetic material of all living organisms.
It carries the instructions for the development, functioning, growth, and reproduction of organisms.
True or False: Viruses are considered living organisms.
False
Viruses are infectious agents that require a host to replicate and are classified as non-living.
What type of genetic material do some viruses use?
Some viruses use RNA as their genetic material.
An example is the SARS-Cov-2 virus, which caused the recent pandemic.
components of dna/rna nucleotides
pentose sugar, nitrogenous base, phosphate group
dna and rna synthesis direction
5’ -> 3’ (sugar phosphate bonding)
2 types of nitrogenous bases
Purines have 2 rings
Pyrimidines have 1 ring
