Question

critical thinking questions

1. list the three parts of the cell theory.

a.
b.

1. fill out this table comparing prokaryotes and eukaryotes.

	relative size	location of dna	organelles	example
eukaryotes			yes

1. explain how surface area limits cell size. why don’t most eukaryotic cells get bigger than 1mm?
2. explain the specific role or function of each of these types of membrane proteins.

a. channel protein -
b. receptor protein -
c. marker protein -

1. the cell membrane has selective permeability (is semipermeable). what types of molecules can pass through easily, and which cannot? give one example of each.
2. label the bilayer, a carbohydrate, the hydrophilic region, the hydrophobic region, and a protein in this diagram of the plasma membrane.

Explanation:

1. The three parts of cell theory are: all living organisms are made up of cells, the cell is the basic unit of life, and all cells come from pre - existing cells.
2. For prokaryotes, the location of DNA is in the nucleoid region (no true nucleus), and an example is bacteria. For eukaryotes, they are larger, DNA is in the nucleus, and an example is a plant or animal cell.
3. As a cell grows, its volume increases faster than its surface area. A large cell would have a low surface - area - to - volume ratio, limiting the rate of diffusion of nutrients in and waste out. So most eukaryotic cells don't get bigger than 1mm to maintain efficient transport.
4. a. Channel proteins form pores to allow specific molecules or ions to pass through the membrane. b. Receptor proteins bind to specific signaling molecules to initiate a cellular response. c. Marker proteins help cells recognize each other, like in immune responses.
5. Small non - polar molecules like oxygen can pass through easily. Large polar molecules like glucose cannot pass through easily without the help of transport proteins.
6. The bilayer refers to the phospholipid bilayer that forms the basic structure of the plasma membrane. Carbohydrates are often attached to proteins or lipids on the outer surface. The hydrophilic regions are the phosphate heads of the phospholipids which face the aqueous environments inside and outside the cell. The hydrophobic regions are the fatty - acid tails of the phospholipids that are in the interior of the bilayer. Proteins are embedded in or associated with the bilayer.

Answer:

1. a. All living organisms are made up of cells. b. The cell is the basic unit of life. c. All cells come from pre - existing cells.
2. Prokaryotes: Location of DNA - Nucleoid region (no true nucleus), Example - Bacteria. Eukaryotes: Relative Size - Larger, Location of DNA - Nucleus, Example - Plant or animal cell.
3. As cell grows, volume increases faster than surface area. Low surface - area - to - volume ratio limits transport, so cells stay small to maintain efficiency.
4. a. Form pores for molecule/ion passage. b. Bind signaling molecules to initiate response. c. Help cell recognition.
5. Can pass easily: Small non - polar molecules like oxygen. Cannot pass easily: Large polar molecules like glucose.
6. Bilayer - Phospholipid bilayer. Carbohydrate - Attached to proteins/lipids on outer surface. Hydrophilic region - Phosphate heads. Hydrophobic region - Fatty - acid tails. Protein - Embedded in or associated with bilayer.