Chapter 2: Cells and organelles

Question 1

Phospholipid Membrane Permeability

Answer 1

• Small, uncharged, non polar molecules and hydrophobic molecules can freely pass across the membrane
• Polar molecules can pass as well only if they are small and uncharged.

Question 2

Membrane Protein Classification

Answer 2

• Peripheral: Loosely attached to one surface of the phospholipid bilayer.
• Integral: Embedded inside the lipid bilayer
• Transmembrane: Spans through both sides of the phospholipid bilayer and classified as a integral membrane protein.

Question 3

Channel Proteins

Answer 3

Passageway through membrane for hydrophilic substance which would be polar and charged.

Question 4

Recognition Proteins

Answer 4

Include Major-histocompatibility complex (MHC) on macrophages used to distinguish between self and foreign. They are glycoproteins due to oligosaccharides attached.

Question 5

Ion Channels

Answer 5

Allow passage of ions across membrane called gate channels in nerve and muscle cells, respond to stimuli

Question 6

Voltage-gated

Answer 6

Respond to difference in membrane potential

Question 7

Ligand-gated

Answer 7

Chemical binds and opens channel

Question 8

Mechanically-gated

Answer 8

Respond to pressure, vibration, temperature, etc.

Question 9

Porins

Answer 9

Allows passage of ions and small molecules. These aren’t specific but they are large passages. Molecules fit by diffusing through.

Question 10

Aquaporins

Answer 10

Increase the rate of H2O passing (Kidney and plant root cells).

Question 11

Transport Proteins

Answer 11

Move substances across membrane

 - In active transport, ATP is used to move substances 
      - Ex. Na+-K+ pump to maintain gradient.
 - Facilitated diffusion makes use of transport proteins but without the direct use of ATP.
 - Carrier protein are exposed to one side at a time whereas channels are exposed to both extracellular and intracellular environment.

Question 12

Passive Transport

Answer 12

Does not require the direct use of ATP.

Question 13

Adhesion Proteins

Answer 13

• Increases stability

- Attaches cells to neighbor cells and provide anchors for internal filaments and tubules.

Question 14

Receptor Proteins

Answer 14

Binding sites for hormones and other trigger molecules.

Question 15

Glycocalyx

Answer 15

Cells have an outer covering called the plasma membrane. This structure is a thin layer that separates the cell from the environment.

Question 16

Nucleus

Answer 16

Membrane enclosed organelle that contains most of its genetic material.

Question 17

Chromatin

Answer 17

Packaging structure of DNA around proteins in eukaryotes.

 - Heterochromatin= Tightly packed a DNA
 - Euchromatin= Loosely packed DNA

Question 18

Chromosomes

Answer 18

Tightly condensed chromatin that form when the cell is ready to divide.

Question 19

Nucleosomes

Answer 19

Basic units of DNA organized by 8 histones.

Question 20

Histones

Answer 20

Serve to organize DNA which coils up into a bundle.

Question 21

Nucleolus

Answer 21

Helps produces ribosomes inside the nucleus

Question 22

Nuclear Lamina

Answer 22

Dense fibrillar network inside the nucleus of eukaryotic cells. This provides mechanical support and helps regulate DNA replication, cell division, chromatin organization.

Question 23

Nucleoid

Answer 23

Irregular shaped region within the cell of a prokaryotes that contain all/most genetic material.
- Prokaryotes lack a nucleus

Question 24

Nucleoplasm

Answer 24

Cytoplasm of the nucleus