Theme 1: Unity and Diversity Flashcards
1
Q
Water
Water as a solvent:
A
- makes up the fluid (cytoplasm) in all cells where all cellular reactions occur
- makes up the fluid inside all organelles in cells
- is found between cells of multicellular organisms (intercellular or tissue fluid)
- permits transport of substances into and out of cells
- is essential to blood and many other body fluids in humans and other organisms
- provides the medium in which all organisms in oceans, lakes and rivers live.
2
Q
Water
Structure of Water:
Molecular
A
- Hydrogen molecules are COVALENT BONDS
- H2O: POLAR COVALENT BOND
- Polarity of Covalent Bonding: Polarity of covalent bonding due to unequal sharing of electrons
- Hydrogen Bonding: Consequence of polar covalent bonding in water molecules
Oxygen has a slight - charge, Hydrogens have a slight + charge
3
Q
Cohesion
A
- Cohesion occurs when molecules of the same type are attracted to each other.
- Water molecules have a slightly positiveend and a slightly negative end. Whenever two water molecules are near each other, the positive end of one attracts the negative end of another - this is hydrogen bonding.
4
Q
Hydrogen Bonding
A
- Whenever two water molecules are near each other, and the positive end of one attracts the negative end of another
5
Q
Surface Tension
A
- Surface tension is a result of the absence of water molecules above the surface layer of a body of water.
- Water molecules at the surface exhibit a strong cohesive force with those nearby and below them, but there is no force pulling upwards.
- To pass through the water’s surface from above, this surface tension must be overcome or broken.
5
Q
Xylem: Cohesion
A
- Water moves as a “water column” in plant vascular tissues, primarily within xylem.
- Xylem functions like tiny straws inside the tree.
- Transpiration, the process of water evaporating from leaves, creates cohesion with xylem water, forming tension.
- Tension pulls water upward collectively in the xylem.
- Transpiration typically occurs through stomata on the underside of leaves.
- The lost water is replaced from the plant’s root system into the xylem.
5
Q
Adhesion
A
- Adhesion refers to the attraction between unlike molecules, often due to hydrogen bonding.
- Ex. Water molecules are attracted to cellulose molecules through hydrogen bonding; it involves different types of molecules.
5
Q
Xylem: Adhesion
A
- Water in the xylem demonstrates both cohesion and adhesion.
- Cohesion lifts each molecule when the water column is “pulled up.”
- Adhesion prevents the entire column from falling when not pulled up.
5
Q
Xylem: Stomata
A
- Water evaporates from small leaf openings called stomata, primarily found on the leaf’s underside, in a process called transpiration.
- This evaporation creates tension, a low-pressure area in the leaf and xylem tube.
- Water molecules’ polarity causes the entire water column to move towards the low-pressure area.
- The xylem in the leaf connects to that in the stem and root.
- As water moves upwards, it’s replaced by groundwater entering the root system.
5
Q
Water as a Solvent
A
- Water is called the “universal solvent” because it is capable of dissolving more substances than any other liquid.
- solutions w water as a solvent are aqaeous solutions
- polar solvent
5
Q
Hydrophilic molecules
A
- molecules that dissolve in water (water loving)
- soluble
- starch, salt, proteins
6
Q
Hydrophobic molecules
A
- molecules that do not dissolve easily in water (water fearing)
- Are insoluable and non-polar
- Ex. stereoid hormones (testorterone)
6
Q
Physical Properties of water
A
- Buoyancy
-Viscosity
-Thermal Conductivity
-Specific heat Capacity
6
Q
Buoyancy
A
-Tendency of objects to float or rise when submerged
- archimedes principle: when buoyancy force is stronger than the objects weight, object rises
- there is more pressuse in the water then in the air
6
Q
Viscosity
A
- Water’s resistance to an object moving through it
