Lecture 3: Water in Life Flashcards
Why do astrobiologists look for water when looking for extraterrestrial life?
Water is the most abundant molecule in organisms and cells and essential for life on Earth.
What percentage of body weight is typically composed of water?
50-75%
Where is most of the body water located within organisms?
in cells, specifically in the intracellular fluid.
What percentage of the volume in a typical cell consists of water?
75%
How long can you survive without eating?
weeks
What is the likely maximum duration for survival without drinking?
You aren’t likely to live more than 3-4 days without drinking.
Why is water important for life?
because of its unique structure and properties.
What are the structure and unique features of water?
Water is unique due to its:
A. Small size
B. Bent shape
C. Highly polar covalent bonds
D. Overall polarity
What are the four major properties of water?
- Is a very good solvent
- Is cohesive (sticks to itself) and adhesive (sticks to other components)
- Has a high capacity for absorbing energy before changing (ex: high boiling point)
- Decreases in density when cooled below 4oC (stats to float)
Why does water have those four major properties?
due to its structure and its ability to form a network of hydrogen bonds with other water molecules or other substances.
What are hydrogen bonds?
weak electrical attractions between the partially negative oxygen of one water molecule and the partially positive hydrogen of a different water molecule.
Besides water molecules, where else can hydrogen bonds form?
between a water molecule and another polar/charged group of a molecule.
How do hydrogen bonds compare in strength to covalent or ionic bonds?
not as strong as covalent or ionic bonds.
Why are hydrogen bonds extremely important in biology?
because they are common, and a large number of these bonds can form between substances, resulting in an overall strong interaction.
Why is water polar?
Would hydrogen bonding
be affected if the structure
of water was linear?
it wouldn’t be polar anymore = all of its properties lost
What is the maximum
number of hydrogen bonds that water can make?
4
Why do polar or charged molecules dissolve in water and non polar ones don’t?
*because water molecules can form a hydration shell around charged or polar molecule through hydrogen bonding. (and get in between the molecules of the compound)
Which molecule is most soluble in water? explain
Vitamin C since its a more polar molecule
Give me three biological significance of water relative to “being a good solvent”
explain cohesion versus adhesion
Give me three biological significance of water relative to “cohesion and adhesion”
Explain the transpiration in plants and what property of water allows this process.
Why can water resist change in temperature? aka absorb a lot of energy before it changes.
What is specific heat directly proportional to?
the molecule’s capacity for H-bonding
Give me three biological significance of water relative to “water’s capacity to resist change”
At what temperature is water at its highest density?
4oC
Interpret the graph
Why is water’s highest density at 4oC?
- Between 4oC and 0oC: hydrogen bonding increases when molecules slow down as temperature decreases; density decreases.
- at 0oC: ice forms when molecules further slow down and maximum hydrogen bonding forms a crystal lattice.
Give me three biological significance of water relative to “water’s capacity to resist change”
Give two other roles of water in life (other than related to its properties)
What is the average pH of these three solutions?
Soln 1: pH 7
Soln 2: pH 6
Soln 3: pH 8
Why is pH important in bio? What does the change in ion concentration affect? (3)
