Cell Biology - SUMMARY

Week 1

What are taxonomic ranks and what is the highest taxonomic rank?

Taxonomic ranks are used to classify all living organisms into categories based on their similarities. The Domain is the highest taxonomic rank, which is divided into three groups: Bacteria, Archaea, and Eukaryota.

What are the key differences between the three domains of life (Bacteria, Archaea, and Eukaryota)?

• Bacteria: Single-celled prokaryotes with 70s ribosomes, no membrane-bound organelles, and cell walls made of murein.

• Archaea: Single-celled prokaryotes that look like bacteria but have genes/protein synthesis and RNA polymerase more similar to eukaryotes, ether-linked membrane fatty acids, and no murein in their cell walls.

• Eukaryota: Organisms with one or more eukaryotic cells, membrane-bound organelles (like nuclei and mitochondria), ester-linked membrane lipids, and larger 80s ribosomes.

What are the key structural features that distinguish plant cells from animal cells?

Plant cells have a rigid cellulose cell wall, chloroplasts for photosynthesis, and a large central vacuole that maintains turgor pressure. Animal cells lack a cell wall (allowing flexible, rounded shapes), lack chloroplasts, have numerous small non-permanent vacuoles, and contain centrioles and lysosomes.

What is the composition of a fungal cell wall compared to plant and bacterial cells?

Fungal cell walls are made of chitin. (Plant cell walls are made of cellulose, and bacterial cell walls are made of murein).

What is the function of the nucleus and its internal structures?

The nucleus stores genetic material (DNA/chromosomes) and controls cell activities via mRNA production for protein synthesis. The nucleolus manufactures ribosomal RNA and assembles ribosomes. Nuclear pores allow large molecules like mRNA to pass out of the nucleus

How is the structure of mitochondria adapted for aerobic respiration?

Mitochondria have a double membrane where the inner membrane folds into cristae, providing a large surface area for the attachment of enzymes and ATP synthase needed for ATP production during respiration. The matrix contains proteins, lipids, and DNA to control the production of its own proteins

What are the roles of chloroplasts and their internal compartments?

Chloroplasts harvest sunlight to carry out photosynthesis. Grana (stacks of thylakoids containing chlorophyll) provide a large surface area for the first stage of photosynthesis. The stroma is a fluid-filled matrix containing enzymes where the second stage of photosynthesis occurs

What is the functional difference between Rough ER and Smooth ER?

Rough Endoplasmic Reticulum (RER) is studded with 80s ribosomes and provides the site for protein synthesis and transport. Smooth Endoplasmic Reticulum (SER) lacks ribosomes and is responsible for the synthesis, storage, and transport of lipids and carbohydrates

What are the functions of the Golgi apparatus and lysosomes?

The Golgi apparatus modifies, labels, and packages proteins and lipids from the ER (forming glycoproteins and lysosomes). Lysosomes are single-membrane vesicles containing digestive enzymes (like lipases, proteases, and lysozymes) used for digestion, innate immunity, and cell recycling

What is the hierarchical organisation of living organisms from cells to systems?

• Cell: Basic unit of life (e.g., muscle cell).

• Tissue: Group of similar cells working together (e.g., muscle tissue).

• Organ: Structure of at least two tissue types (e.g., heart).

• Organ System: Group of organs working together (e.g., circulatory system

How do cells become specialised during development?

All cells originate from mitotic divisions of a fertilised egg and contain the exact same genes. Cells specialise by switching specific genes on (expressing them) or off, altering their organelle content and structure to best suit their specific function

What are "housekeeping genes"?

Genes that are expressed in all cell types because they code for proteins required for essential everyday cellular processes, such as DNA replication and respiration.

What are the main characteristics of viruses?

Viruses are acellular, non-living entities that contain DNA or RNA, can mutate and evolve, and can only replicate inside a living host cell using host machinery and viral attachment proteins.

What are the phases of the cell cycle (Interphase)?

• G1 Phase (Growth): Cell contents excluding chromosomes are duplicated.

• S Phase (DNA Synthesis): Each chromosome is duplicated into sister chromatids.

• G2 Phase (Growth & Preparation): Cell double-checks duplicated chromosomes for errors and makes repairs.

What happens during the four stages of mitosis?

• Prophase: Chromosomes condense, nuclear envelope breaks down, and spindle fibres form from centrioles.

• Metaphase: Sister chromatids align along the equator (metaphase plate) of the cell.

• Anaphase: Centromeres divide, and spindle fibres pull sister chromatids apart toward opposite poles.

• Telophase & Cytokinesis: Nuclear envelopes reform, chromosomes uncoil into chromatin, and the cytoplasm divides to form two genetically identical daughter cells.