3. Cell Membrane and Structure Composition

Question 1

Amino acid

Answer 1

• molecules that combine to form proteins
• Amino acids and proteins are the building blocks of life

Question 2

Charged/uncharged molecules meaning

Answer 2

any particle that contains more electrons than protons is said to be negatively charged

Question 3

Hydrogen Bond

Answer 3

interaction involving a hydrogen atom located between a pair of other atoms having a high affinity for electrons

Question 4

Lipid

Answer 4

any of various organic compounds that are insoluble in water

Question 5

Polar /unpolar molecules

Answer 5

Polar: Positive and Negative ends on some molecules

Question 6

Partial negative charge

Answer 6

the more electronegative atom is the one with the partial negative charge

Question 7

Partial positive charge

Answer 7

less electron-dense region

Question 8

Plasma Membrane

Answer 8

• a thin fatty film studded with proteins and coated with carbohydrates
• A living cell is a self-reproducing system of molecules held inside a container

Question 9

Functions of Plasma Membrane

Answer 9

• cell communication
  -import and export of molecules
  -cell growth
  -motility

Question 10

Amphipathic

Answer 10

• Molecules with both hydrophilic and hydrophobic parts
• All membrane lipids

Question 11

Phospholipids

Answer 11

• hydrophilic heads face water on both surfaces of the bilayer
• hydrophobic tails are all shielded from the water and lie next to one another in the interior

Question 12

How the hydrophobic and hydrophilic regions of phospholipids are involved in
membrane formation

Answer 12

Structure:
- Head: Hydrophilic, polar, attracted to water.
- Tails: Hydrophobic, nonpolar, repelled by water.

Membrane Bilayer:
-Spontaneous arrangement in aqueous environment.
- Forms a lipid bilayer, the basis of cell membranes.

Hydrophobic Tails:
-Cluster together to create a nonpolar interior.
Impermeable barrier to water-soluble molecules.

Hydrophilic Heads:
- Face outward, interact with watery surroundings.
- Maintain compatibility with both inside and outside of the cell.

Amphipathic Nature:
- Self-assemble into bilayer spontaneously.
- Driven by the need to minimize exposure of hydrophobic tails to water.

Membrane Fluidity:
- Influenced by phospholipid composition.
- Unsaturated fatty acids increase fluidity, saturated fatty acids lead to rigidity.

Protein Integration:
- Membrane proteins have hydrophobic regions.
- Embedded or associated with the lipid bilayer.

Question 13

How membrane fluidity can be regulated by the cell

Answer 13

Lipid Composition:
- Adjust phospholipid types.
- More unsaturated fats increase fluidity.

Cholesterol:
- Acts as a fluidity buffer.
- Maintains optimal conditions.

Temperature Sensing:
- Adjusts lipid composition with temperature changes.

Protein Influence:
- Membrane proteins impact fluidity.
- Affect lipid movement and arrangement.

Dynamic Membrane:
- Regulates lipid movement within the membrane.

Desaturation Enzymes:
- Produce enzymes for unsaturated fatty acids.
- Enhances fluidity as needed.

Adaptation:
- Cells alter lipid composition based on environmental changes.

Question 14

How new membrane are synthesized and matured

Answer 14

Lipid Synthesis:
- Cells produce lipids, especially phospholipids, in the endoplasmic reticulum (ER).

Phospholipid Assembly:
- Newly synthesized lipids are assembled into bilayers within the ER.

Vesicle Formation:
- Portions of the ER membrane form vesicles, transporting lipids.

Golgi Processing:
- Golgi apparatus modifies lipids and processes proteins.

Protein Integration:
- Membrane proteins are synthesized and inserted into the ER membrane.

Vesicle Budding:
- Vesicles containing modified lipids and proteins bud off from the Golgi.

Transport to Cell Membrane:
- Vesicles fuse with the cell membrane, incorporating new components.

Membrane Maturation:
Integrated lipids and proteins undergo modifications for maturation.

Lateral Movement:
- Components move laterally within the membrane, contributing to fluidity.

Endocytosis and Exocytosis:
- Membrane components are recycled or replaced through internalization and release.

Question 15

Differentiate between integral and peripheral proteins

Answer 15

Inegral proteins:
- exposed to aqueous enviornemnt on both sides of membrane
- used to transport molecules across membranes
- extend through the lipid bilayer (transmembrane,
associated with the lipid monolayer, or lipid-linked

Peripheral proteins:
- located on surface of membrane
- interact with integral membrane proteins or phospholipids

Question 16

How the movement of membrane components is restricted

Answer 16

• Lipid composition
• Cholestoral content
• Protein interactions
• Cytoskeleton Attachment

Question 17

Compare and contrast the three types of cell junctions found in animals

Answer 17

• Tight Junctions
• Desmosomes
• Gap Junctions

Question 18

Tight Junctions

Answer 18

Function:
-Forms a tight seal between adjacent cells.
- Prevents leakage of extracellular fluids and solutes between cells.

Structure:
- Proteins from adjacent cells interact to create a continuous barrier.
- Tight junctions are found near the apical surface of epithelial cells.

Location:
- Abundant in tissues where a strong barrier is essential, such as epithelial linings of the digestive tract.

Question 19

Desmosomes

Answer 19

Function:
- Provides mechanical strength and resilience to tissues.
- Anchors cells together and distributes tension or stress.

Structure:
- Connects the cytoskeletons of adjacent cells.
- Consists of cadherin proteins and linker proteins forming a dense structure.

Location:
- Common in tissues subjected to mechanical stress, such as skin and heart muscle.

Question 20

Gap Junctions

Answer 20

Function:
- Facilitates direct communication and exchange of small molecules between adjacent cells.
- Allows the passage of ions, metabolites, and signaling molecules.

Structure:
- Consists of connexin proteins forming channels (connexons) that align between adjacent cells.

Location:
- Found in various tissues where coordinated activity or signaling between cells is crucial, such as cardiac muscle.

Question 21

Do on paper

• Predict how removal of any components of the cell membrane affect its properties and
  function

-Design investigations to analyze the function of proteins and carbohydrates in cell
adhesion and cell recognition