Unit 2 Bio Quiz

Name the property of water that allows salt and water to mix. Explain why it is important in cells.

Water is an excellent or "universal" solvent that keeps polar and charged substances dissolved inside organisms. The first benefit of high solubility is that dissolved substances are easier to transport across the cell and around the body. The second benefit is that because individual dissolved molecules are available to participate in reactions (think about surface area), the chemical reactions in our cells-our metabolism- occurs at a fast enough rate to keep us alive.

2 examples of integral proteins

1. channel protein - provides a gate through the membrane for water, ions, etc. 2. receptor - has a binding site for specific hromones and relays the signal to cytoplasm

5 special properties of water

1. high heat capacity 2. universal solvent 3. cohesion 4. adhesion 5. low density of ice

3 parts of the fluid mosaic model + functions

1. phospholipid bilayer - has tails forming a hydrophobic core that waterproofs and seals the cell 2. cholesterol - moderates membrane fluidity 3. proteins - float in lipid bilayer a.) integral proteins - go all the way through the membrane b.) peripheral proteins - are embedded in the membrane but do not go through

structure of water

2 slightly positive hydrogen atoms, 1 slightly negative oxygen atom

Name the special properties that bring water to the top of plants. Explain how this works.

Both adhesion and cohesion are required for water to ascend a plant. Hydrogen bonds between water and the walls of polar xylem vessels in the stem create adhesion. Cohesion of these water molecules at the sides with water molecules closer to the middle allows water in the center to be pulled up the vessel, eventually to the leaves.

Name the special property that keeps lakes from freezing solid. Explain.

Ice is less dense than liquid water. Water exposed to cold air at the surface of a lake can freeze but will remain at the top because ice floats in water. If the cold air persists, the lake might freeze over, creating a layer of ice that insulates the cold air above from the water below where aquatic plants and animals survive the winter.

Name the special property that allows some insects to walk on water. Briefly explain.

Insects can walk on top of water if the water molecules stick together well enough to prevent the insect's feet from pushing down into the water, so this phenomenon is due to cohesion. Cohesion at the surface is also called surface tension.

Name the membrane component that is amphipathic. Explain in what way that component is amphipathic.

Phospholipids are amphipathic because their heads (glycerol and phosphate) are hydrophilic, and their tails (two fatty acid chains) are hydrophobic. It's more of an AP Biology word, but we all need to remember the importance of phospholipids and their properties.

Name the special property that makes it easier for organisms to maintain a moderate body temperature. Briefly explain.

Water's high specific heat (or high heat capacity, or high specific heat capacity) moderates body temperature because a large amount of energy would need to be gained or lost to change our body temperature only a small amount. This property makes regulation (or homeostasis) easier to manage.

describe the bonds within the water molecule and between water molecules that give rise to the five special properties.

Within a water molecule, the bond between oxygen and hydrogen is a polar covalent bond, meaning that the electrons spend more time closer to the O. Oxygen with its partial negative charge (δ-) forms a weak bond called a hydrogen bond with the H's of other water molecules because of their partial positive charge (δ+). The H's likewise form hydrogen bonds with the O's of other water molecules. H-bonds can form the same way between water and other polar molecules. Similar weak attractions form between water and charged particles.

special property of water + definition + why + benefit: high heat capacity

definition: it takes a LOT of energy transferred to achieve a small temperature change why: each water molecule forms 3" hydrogen bonds with other water molecules; a lot of energy is required to break those hydrogen bonds benefit: we are 60-70% water and naturally resistant to temperature change, decreasing our need for shivering and sweating

special property of water + definition + why + benefit: universal solvent

definition: most polar and charged substances dissolve well in water why: polar water molecules surround every solute particle, with the oxygen facing positive charges; hydrogen facing negative charges benefit: nutrients and wastes are efficiently transported to and from cells

special property of water + definition + why + benefit: adhesion + cohesion

definition: water sticks to polar and charged substances why: the oxygen is attracted to anything with a positive/partial positive charge and the hydrogen is attracted to anything with a partial negative/negative charge benefit: in xylem vessels in plants, water molecules form hydrogen bonds with the xylem wall (adhesion). Those water molecules pull up on water molecules beneath them with hydrogen bonds (cohesion). water is transported from roots to leaves with no energy cost.

Explain the fluid mosaic model

fluid - the cell membrane is fluid bc the lipids and proteins float in constant motion mosaic - all of the different types of proteins in the cell wall are like a mosaic, where everything is different, but it all works together to create the whole

structure of the cell membrane

fluid mosaic model

example of peripheral proteins

peripheral proteins on the cytoplasm side connect to cytoskeletal fibers to support the cell membrane

function of the cell membrane

selective permeability, protects and supports cell, and helps cells communicate with other cells