Biology Summative number 3

Water and the functions essential for life.

1. Metabolism: aqueous solutions are liquid → allowing enzymes and substrate to move and collide aiding in metabolism.

2. Nutrition: Digestion and photosynthesis both require water as it either occurs in water or require water in the reactants.

3. Growth: Cytoplasm, more specifically cytosol is aqueous → for a cell to grow it must absorb more water via osmosis.

4. Reproduction: Fetus is supported by amniotic fluid (aqueous solution) and sperm must swim through water to get to the egg.

5. Response to stimuli: Na+ and K+ ions are dissolved which are required for nerve impulse and hormones travel through the blood.

6. Excretion: urine is an aqueous solution and waste gases require a moist surface.

7. Homeostasis: Blood plasma and tissue fluid are both aqueous solutions and both are maintained to create optimum conditions within the body.

Cohesion Examples

• Strong pulling forces, tensions, are exerted to suck water up to the tops of the tallest trees in tubular xylem vessels.

• The surface of pond water on ponds is used as habitat for many insects. The surface doesn’t break however because of the cohesion of the water molecules.

Adhesion Examples

• Polar substances such as cellulose in plant walls form hydrogen bonds with water. Cell walls therefore tend to remain saturated with water and draw more water from the nearest supply if they have become unsaturated due to evaporation.

• Capillary action is water being drawn through narrow spaces because it adheres to the surfaces of the spaces. Water moves through pores in dry soils by this process because the solids in the soil (humus) and particles of the sand, silt and clay are hydrophilic. The water can move upwards.

Properties of water in reference to the black-throated loon and ringed seal.

• Buoyancy: solids float in fluids if the density is lower.

  • Black-throated loon → It is more dense than air so it must beat its wings to stay airborne

  • Ringed seal → Its density is close to that of sea water, hence, it can float easily.

• Viscosity: resistance to flow of a fluid due to cohesion between the molecules.

  • Black-throated loon → Air has a low viscosity so less resistance when moving.

  • Ringed seal → Sea water is 50 times more viscous, so the seal has to overcome much more resistance when it swims through water.

• Thermal conductivity: the ability of a material to transfer heat

  • Black-throated loon → Better insulator, poor conductor → can stay warm

  • Ringed seal → Water is a great conductor, the seal may struggle to stay warm; hence, adapting to have blubber and adipose tissue to insulate itself.

• Specific heat capacity: the quantity of heat needed to raise the temperature of a gram of material by one degree.

  • Black-throated loon → Air has a low specific heat capacity so terrestrial habitats change much more because of temperature.

  • Ringed seal → High specific heat capacity, the habitats are more thermally stable.

What two factors aid in retaining water in liquid form on Earth?

• Gravitational force

• Intensity of sunlight due to distance from the Sun keeps the Earth below 100˚C and mostly above 0˚C.

Goldilock’s Zone

The range of distances from a star that keep temperatures between 0 and 100˚C.

Unity of Life

All livings things are made of molecules and genes are the instructions of doing so. All living organisms have DNA as their genetic material.

Parts of Nucleotide + Differences between DNA and RNA

• Pentose sugar with 5 carbon atoms in a ring

• Phosphate

• A nitrogenous base, A, C, T or U, G

• Purines = A and G → 2 rings

• Pyrimidines = T, C, U → 1 ring

• A and T or U = 2 Hydrogen bonds

• C and G = 3 Hydrogen bonds

Which bonds are which?

Bonds in between a nucleotide are covalent. Bonds between the phosphates and sugars are esters → phosphodiester bonds. It is a condensation reaction.

5’ to 3’?

5 carbon (the phosphate) to 3 carbon. In a DNA double helix, the strands are antiparallel so one is 5’ to 3’ and the other is the opposite.

Roles of complementary base pairing

1. DNA Replication → sequences of bases in DNA can be copied accurately, so the genetic information of a cell can be passed on to daughter cells.

2. Transcription → RNA can be made with the same base sequence as one of the two strands of a DNA molecule. mRNA carries the base sequence of a protein-coding gene to the ribosome.

3. Translation → a base sequence can be used to determine the amino acid sequence in a polypeptide. mRNA carries a codon. Each tRNA has the anticodon. Ribosomes link codons to anticodons via complementary base pairing.