a1.1- water Flashcards
why is water a medium for life
- first cells originated in water
- where most life processes occur
physical properties [9]
- high specific heat capacity
- takes a lot of energy to break H+ bonds - high latent heat of vaporisation
- good coolant
- good solvent
- medium for metabolic reactions - transport medium
- dissolves nutrients, gases and waste products - dense
- can support the mass of large and small organisms
- ice is less dense: life on top and below - buoyancy
- float - viscosity
- thermal conductivity
organisms in water examples x2 [3]
black-throated loon
1. oiled feathers- water has greater thermal conductivity than air
2. large wings- generate lift in less buoyant air
3. hydrodynamic- reduce drag against viscosity
ringed seal
1. low density blubber- increases buoyancy
2. insulating blubber- reduce heat loss
(higher specific heat capacity, temperature is more stable)
3. streamlined shape: against viscosity
why is water polar
- due to unequal sharing of electrons
- imbalance of charges
- hydrogen bonding due to polarity
*bonds diagram
reason for cohesion of water molecules + application
due to hydrogen bonds
1. transport of water under tension in xylem
2. use of water surfaces as habitats- surface tension
adhesion of water to material that are polar + application
Attraction to charged or polar surfaces (such as cellulose cell walls) allows water to flow in opposition to gravitational forces (capillary action)
solvent properties of water
- hydrophilic molecules dissolve in water
- most enzymes catalyse reactions in aqueous solution
- some functions of cells depend on them being hydrophobic and insoluble
origin of water
- from extra-planetary objects
- ice asteroids maybe from asteroid belt
- other asteroid knocks out asteroid belt- to us
- large asteroids at least few hundred kilometers so it would still be ok after ozone
reasons for water retention [2]
- earths gravity prevents water form escaping the planet
- temperature is cool enough to condense water
relationship between the search for extraterrestrial life and the presence of water
- universal solvent
- important for transport medium within a cell
adhesion
water molecule is able to stick to other polar or charged molecules via the formation of polar associations
cohesion
- ability of like molecules to stick together
- forms h bonds
hydrophilic
- water loving
- polar
- charged
examples of hydrophilic substances [2]
- glucose
- minerals
hydrophobic
- repels water
- non-polar
- non-charged
examples of hydrophobic substances [2]
- fat
- oil
goldilocks zone
- habitable zone
- range of distance form a star with the right temperatures for water to remain liquid
signs of water in space
spectroscopy
- analyses the wavelengths of light emitted or absorbed by a substance
- used to detect the presence of water molecules in space
other factors that contribute to look for extraterrestrial life
- carbon
- nitrogen
- suitable temperature
phospholipid bilayer
hydrophilic head
- glycerol and a phosphate molecule
hydrophobic tail x2
- fatty acid (hydrocarbon) chains
properties of the phospholipid bilayer
- held together by weak hydrophobic interactions between the tails
- individual phospholipids can move within the bilayer: allows fluidity and flexibility
- spontaneous breaking and reforming of membranes (endocytosis / exocytosis)
fluid-mosiac model
fluid– the phospholipid bilayer is viscous and individual phospholipids can move position
mosaic– phospholipid bilayer is embedded with proteins, resulting in a mosaic of components
osmolarity
measurement of solute concentration of a solution
what property allows for the presence of ions, sugars, amino acids and proteins in sweat
solvent properties
