Organelles and the Cell membrane

Question 1

Nucleus:

Answer 1

Contains and protects DNA.
Surrounded by a double membrane (nuclear envelope) with embedded proteins for substance transport.

Question 2

Nucleolus:

Answer 2

Located within the nucleus.
Produces ribosome subunits from protein and RNA.

Question 3

Ribosomes:

Answer 3

Assemble polypeptide chains to form proteins.

Question 4

Mitochondria:

Answer 4

Known as the “powerhouse of the cell.”
Produces ATP during aerobic cellular respiration.
Contains its own DNA and ribosomes, and can divide independently.

Question 5

Plastids:

Answer 5

Membrane-bound organelles in plants and algae.
Chloroplasts: Perform photosynthesis.
Chromoplasts: Make and store pigments other than chlorophyll.
Amyloplasts: Store starch.

Question 6

Fluid Mosaic Model:

Answer 6

Describes the membrane as a fluid structure with proteins embedded in or attached to a bilayer of phospholipids.
Lipid and protein molecules can move laterally within the layer.

Question 7

Asymmetry:

Answer 7

The two sides of the membrane have different compositions and functions.
This allows the membrane to perform different functions on each side.

Question 8

Glycolipid:

Answer 8

A lipid with a carbohydrate attached, located on the exterior of the cell membrane.

Question 9

Glycoprotein:

Answer 9

A protein with a carbohydrate attached, also located on the exterior of the cell membrane.

Question 10

Phospholipids:

Answer 10

Have a hydrophilic (water-attracting) head and two hydrophobic (water-repelling) tails.
Form a bilayer in aqueous solutions.

Question 11

Embedded Molecules:

Answer 11

Embedded Molecules:
Membrane proteins and sterols (e.g., cholesterol).

Question 12

Sterols (e.g., cholesterol):

Answer 12

At high temperatures, they reduce fluidity by restraining lipid movement.
At low temperatures, they prevent lipids from packing tightly, maintaining fluidity.

Question 13

four functional categories of membrane proteins

Answer 13

Transport: Allow specific compounds to cross the membrane (e.g., channel proteins).

Enzyme Activity: Some proteins act as enzymes (e.g., those involved in cellular respiration).

Triggering Signals (Receptors): Bind to specific chemicals (e.g., hormones) to trigger changes inside the cell.

Attachment & Recognition: Serve as attachment points for the cytoskeleton and help in cell-cell recognition.

Question 14

Integral Proteins:

Answer 14

Integral Proteins: Embedded in the lipid bilayer, interacting with the hydrophobic core. Can span the entire membrane (transmembrane proteins).

Question 15

Peripheral Proteins:

Answer 15

Peripheral Proteins: Located on the surface of the membrane, not interacting with the hydrophobic core. Often found on the cytosol side.