1.1 water1
Post on 03-Apr-2018
228 Views
Preview:
TRANSCRIPT
-
7/28/2019 1.1 water1
1/35
CHAPTER 1:
MOLECULES OF LIFE
1.1 WATER
1.2 CARBOHYDRATES
1.3 LIPIDS
1.4 PROTEINS
1.5 NUCLEIC ACIDS
-
7/28/2019 1.1 water1
2/35
-
7/28/2019 1.1 water1
3/35
-
7/28/2019 1.1 water1
4/35
Explain the structure of water
molecule. Describe the properties of water and
its importance.
OBJECTIVES
1.1 WATER
-
7/28/2019 1.1 water1
5/35
ROLES OF WATER
solvent for polar molecules
medium for exchange of
respiratory gases
medium for enzymatic reactions
-
7/28/2019 1.1 water1
6/35
ROLES OF WATER
external fertilization
external media for aquaticorganisms
secrete waste products
locomotion
foodresources
-
7/28/2019 1.1 water1
7/35
wide V-shaped structure 1 oxygen atom
2 hydrogen atoms
covalent bonds
STRUCTUREOF WATER MOLECULE
bond angle: 104.5
-
7/28/2019 1.1 water1
8/35
Polar molecule
opposite ends of water moleculehave opposite charges
oxygen: partial negative charge;
hydrogen: partial positive charge; +
Polarity allows water molecules to formhydrogen bonds with each other
STRUCTUREOF WATER MOLECULE
-
7/28/2019 1.1 water1
9/35
STRUCTUREOF WATER MOLECULE
-
7/28/2019 1.1 water1
10/35
Formation of hydrogen bond
hydrogen atoms of one water molecule
by hydrogenbonds
attracted to
oxygen atoms ofnearby watermolecules
STRUCTUREOF WATER MOLECULE
-
7/28/2019 1.1 water1
11/35
but strong enough to hold watermolecules together
hydrogen bonds are weaker thancovalent bonds
Hydrogen bond
each molecule will form hydrogen
bond to a maximum of four watermolecules
STRUCTUREOF WATER MOLECULE
-
7/28/2019 1.1 water1
12/35
STRUCTUREOF WATER MOLECULE
-
7/28/2019 1.1 water1
13/35
Has high specific heat
capacity
Has low viscosity
Has high latent heat ofvaporization
As universal solvent
Has high surface tension Has maximum density at 4C
PROPERTIES OF WATER
-
7/28/2019 1.1 water1
14/35
due to its polarity: water asuniversal solvent for ions and polarmolecules e.g. Na+ Cl
1. AS UNIVERSAL SOLVENT
oxygen regions are attracted topositively charged sodium
hydrogen regions are attractedto negatively charged chloride
-
7/28/2019 1.1 water1
15/35
surroundsodium andchloride
separate
and avoidthem fromeach other
-
7/28/2019 1.1 water1
16/35
solvent for most solutes
BIOLOGICAL IMPORTANCE
provides an aqueous mediumfor biochemical reactions
serves as the bodys major
transport medium e.g. in bloodcapillaries and xylem
-
7/28/2019 1.1 water1
17/35
2. HAS LOW VISCOSITY
due to hydrogen bonds betweenwater molecules continuouslyform, break and reform
-
7/28/2019 1.1 water1
18/35
as lubricant
BIOLOGICAL IMPORTANCE
i.e. lubricates movement ofsubstances
Water molecules can moves easilyand flow with less friction throughnarrow blood vessel
e.g: peristaltic movement of foodbolus in esophagus
-
7/28/2019 1.1 water1
19/35
3. HIGH SPECIFIC HEAT CAPACITY
DEFINITION
large amount of heat energy(in J @ cal)
that must be absorbed @ lost for1g of substance (water molecule)
to change its temperature by 1C
specific heat capacity for water
= 4200 J kg-1
C-1
-
7/28/2019 1.1 water1
20/35
-
7/28/2019 1.1 water1
21/35
BIOLOGICAL IMPORTANCE
stabilize ocean temperature
provide constant environment
in the sea for aquatic organisms tolive
act as heat buffer
prevent large fluctuation inbody temperature of terrestrialorganisms
-
7/28/2019 1.1 water1
22/35
4. HIGH LATENT HEAT OF VAPORIZATION
DEFINITION
large amount of heat energy mustbe absorbed by 1g of water molecule
to turn liquid water into water vapour
latent heat of vaporization for water
= 540 cal g-1
hydrogen bond between water moleculesmake it difficult for them to be separated
and vaporized
caused by breakdown of hydrogen bond
-
7/28/2019 1.1 water1
23/35
BIOLOGICAL IMPORTANCE
evaporation of water in sweat on skin,
or in transpiration from green leaves
or panting in animals e.g. dog
causes the cooling effect
because the escapingmolecules take a lot of energy
with them
-
7/28/2019 1.1 water1
24/35
COHESIVE AND ADHESIVE FORCE
cohesive force: force of attractionbetween the same molecule
e.g. between water molecules
adhesive force: force of attractionbetween water molecule with theother molecule
e.g. between water moleculesandwall of xylem vessels
-
7/28/2019 1.1 water1
25/35
Upward movement of water from rootsthrough xylem vesselsadhesion and cohesion creates
capillary actionas water evaporates from leaves,cohesion of water within xylemvessel drawn upwards from roots
adhesion of water to wall of xylemvessel resist the downward pull ofgravity
PHYSIOLOGICAL ROLE #1
-
7/28/2019 1.1 water1
26/35
-
7/28/2019 1.1 water1
27/35
5. HIGH SURFACE TENSION
Surface tension is related to cohesiveforces between water molecules
Surface tension is a measure of how
hard it is to break the surface of a liquid
PHYSIOLOGICAL ROLE #2
-
7/28/2019 1.1 water1
28/35
arrangement of water moleculeson the surface bonded by
hydrogen bond with watermolecules underneath form a skinlike layer at the surface
p one molecule is
attracted by adjacentmolecules
-
7/28/2019 1.1 water1
29/35
surface tension allows insects to walkon the water surface e.g. water skater
BIOLOGICAL IMPORTANCE
-
7/28/2019 1.1 water1
30/35
6. MAXIMUM DENSITY AT 4C
at 0
C, liquid water transforms into ice (solid)
ice is less dense than liquid water at 4C
Ice floats in liquid water because hydrogenbonds in ice are more ordered, making ice
less dense
-
7/28/2019 1.1 water1
31/35
-
7/28/2019 1.1 water1
32/35
BIOLOGICAL IMPORTANCE
ice floats; act as insulator
to prevent ponds, lakes, oceansfrom freezing
thus, allow life to exist underthe floating ice
-
7/28/2019 1.1 water1
33/35
CONCLUSION
All living organisms require WATER morethan any other substance
Most cells are surrounded by water, andcells themselves are about 70-95%water
QUESTION
-
7/28/2019 1.1 water1
34/35
QUESTION
Give TWO significances of hydrogenbonding in water molecules.
QUESTION
-
7/28/2019 1.1 water1
35/35
QUESTION
Why must water absorb relatively largequantity of heat in order to change itstemperature? [1 mark]
To break hydrogen bond
top related