Topic 1: Eukaryotic Cell Ultrastructure

Question 1

Cell Theory (5 principles)

Answer 1

1. The cell is the basic unit of life that carries out all the essential processes of life that makes the organism a living entity.
2. All organisms are made up of cells.
3. All cells arise from pre-existing cells through cellular division.
4. The cell contains information (in the form of hereditary materials/DNA) which is used as instructions for growth, development and functioning.
5. The cell is the functional unit of life in which chemical reactions that maintain life takes place within it.

Question 2

Eukaryotes

Answer 2

(inclusive of all plants and animals) the cell of a eukaryote possess a true nucleus containing genetic materials (DNA), enclosed within the nuclear envelope

Question 3

Prokaryotes

Answer 3

(inclusive of bacteria and archaea) the cell of a prokaryote lacks a true nucleus; genetic material is not enclosed within the membranes but lies freely in the cytoplasm

Question 4

Ultrastructure of Eukaryotic Cells

Answer 4

A generalised eukaryotic cell has at least three major structural features that makes up the protoplasm (living matter in the cell)

1. Cell surface membrane
2. Nucleus
3. Cytoplasm:
   - Cytosol (fluid component; aqueous solution of various essential ions; soluble organic compounds such as sugars and amino acids; and soluble proteins, many of which are enzymes)
   - Cytoskeleton (network of fine strands of globular proteins; support the cell and maintain its overall shape)
   - Organelles (subcellular components which carries out specific functions to maintain the cell or a multicellular organism; may or may not be membrane-bound)

Question 5

Nucleus

Answer 5

Structural Features:
1. Largest organelle, spherical or ovoid in shape
2. Surrounded by a double membrane known as nuclear enveloped: i) outer membrane is continuous with the endoplasmic reticulum; ii) inner membrane is in contact with the contents of the nucleus
3. Nuclear envelope is perforated nuclear pores
4. Nearly all the cell’s DNA (organised into chromosomes) is found here
5. One or more nucleolus within the nucleoplasm

Functions:
1. Control of cellular activities by regulating protein and enzyme synthesis
2. Nuclear division is the basis of cellular replication
3. Nucleolus is responsible for synthesis and partial assembly of ribosomes

Question 6

Cell surface membrane

Answer 6

Structural Features:
1. Basic structure: Phospholipid bilayer with the hydrophobic tails on the interior of the membrane, and the hydrophilic heads on the exterior
2. Each phospholipid is made up of a glycerol molecule attached to a phosphate group and two fatty acid chains
3. Additional components include: Cholesterol, glycoproteins, glycolipids, transport/carrier proteins