Eukaryotic Structure & Function

Question 1

Describe the structure and function of the nucleus.

Answer 1

Structure: Large, membrane-bound organelle containing genetic material (DNA).

Function: Stores DNA, regulates gene expression, and coordinates cell activities.

Question 2

Describe the structure and function of the nucleolus.

Answer 2

Structure: Dense, spherical region inside the nucleus.

Function: Produces ribosomal RNA (rRNA) and assembles ribosome subunits.

Question 3

Describe the structure and function of chromatin.

Answer 3

Structure: DNA + histone proteins, loosely packed in non-dividing cells.

Function: Stores genetic information and regulates gene access for transcription.

Question 4

Describe the structure and function of the nuclear envelope and nuclear pores.

Answer 4

Nuclear envelope: Double membrane surrounding the nucleus, controls material exchange.

Nuclear pores: Openings in the envelope allowing RNA and proteins to move in/out.

Question 5

Compare free ribosomes and bound ribosomes.

Answer 5

Free ribosomes – Float in cytoplasm; synthesize cytosolic proteins (e.g., enzymes).

Bound ribosomes – Attached to rough ER; synthesize membrane & secretory proteins.

Question 6

Describe the structure and function of the rough ER.

Answer 6

Structure: Network of membranes studded with ribosomes.

Function: Synthesizes proteins for secretion or membrane integration.

Question 7

Describe the structure and function of the smooth ER.

Answer 7

Structure: Tubular membranes lacking ribosomes.

Function: Lipid synthesis, detoxification, calcium storage.

Question 8

Describe the structure and function of the Golgi apparatus.

Answer 8

Structure: Stacked, flattened sacs (cisternae).

Function: Modifies, sorts, and packages proteins for secretion or membrane use.

Question 9

Describe the structure and function of the lysosome.

Answer 9

Structure: Membrane-bound sac containing digestive enzymes.

Function: Breaks down macromolecules, old organelles, and pathogens.

Question 10

Describe the structure and function of the peroxisome.

Answer 10

Structure: Small membrane-bound organelle containing oxidative enzymes.

Function: Breaks down fatty acids and detoxifies hydrogen peroxide (H₂O₂).

Question 11

Describe the structure and function of the mitochondria.

Answer 11

Structure: Double-membrane organelle with inner folds (cristae) and its own DNA.

Function: Produces ATP through cellular respiration.

Question 12

Describe the structure and function of the cytoskeleton.

Answer 12

Structure: Network of microfilaments, intermediate filaments, microtubules.

Function: Maintains shape, aids intracellular transport, enables movement.

Question 13

Describe the structure and function of the extracellular matrix (ECM).

Answer 13

Structure: Meshwork of proteins (collagen, elastin, fibronectin) and glycoproteins.

Function: Provides structural support and cell signaling.

Question 14

Provide examples of cytosolic, membrane, and secretory proteins.

Answer 14

Cytosolic proteins: Actin (cytoskeleton), glycolytic enzymes (metabolism).

Membrane proteins: Ion channels (Na⁺/K⁺ pump), receptors (insulin receptor).

Secretory proteins: Insulin, antibodies, digestive enzymes.

Question 15

What is the role of the signal sequence in proteins destined for the rough ER?

Answer 15

A short amino acid sequence directs ribosomes to bind to the rough ER.

Ensures that secretory & membrane proteins enter the endomembrane system.

Question 16

Describe diseases caused by lysosome malfunction.

Answer 16

1. Tay-Sachs disease – Missing enzyme causes lipid accumulation in neurons.
2. Gaucher’s disease – Defective enzyme leads to fatty substance buildup.
3. Pompe disease – Inability to break down glycogen, affecting muscles.

Question 17

Describe features of specialized cell types.

Answer 17

• Ovum (egg) – Large, nutrient-rich for early embryo development.
• Sperm – Tail (flagellum) for mobility; mitochondria for energy.
• Muscle cell – Long, multinucleated; contains actin & myosin for contraction.
• Adipose (fat) cell – Stores triglycerides for energy and insulation.
• RBCs (red blood cells) – No nucleus, packed with hemoglobin for oxygen transport.
• WBCs (white blood cells) – Contain lysosomes to digest pathogens.
• Liver cell – Detoxifies chemicals; high amounts of smooth ER & peroxisomes.
• Neuron – Long axons for signal transmission; myelin sheath for speed.
• Tracheal epithelial cell – Cilia to trap debris and move mucus.
• Bone cell – Secretes collagen and minerals to maintain bone structure.
• Intestinal epithelial cell – Microvilli to increase surface area for absorption.
• Ovary (endocrine cell) – Secretes hormones (estrogen, progesterone).