Biology Chapter 1: Cell Structure and Function

Lecture 1: Introduction: Evolution of Cells and Classification of Organisms

• The lecture is about the evolution of cells and classification of organisms.
• The lecturer is Dr. Leonid Nikitenko.
• Contact email: [email protected]
• Module code: 441287 Cell Structure and Function.
• Date of lecture: 24/09/24
• Level 4 module.
• The class size is 150 students
• The teaching team comprises 6 members whose percentages range from 1% to 90%.

Module 441287 Cell Structure and Function

• The module aims to provide insight into the evolution and classification of organisms.
• The module will cover a brief overview of cell structure and the roles of individual organelles in cell function.

Cell: The ∞ quest for knowledge

• The lecture aims to present a comprehensive overview of cells, addressing questions like 'Why?', 'What?', 'How?', 'Who?', and 'Where?'
• A quote from Lewis Carroll is provided: "That depends a good deal on where you want to get to."
• There is a Canvas discussion section available for further interaction

Lecture Aims

• The lecture aims to educate on aspects of cell evolution and organism classification.
• A brief overview of cell structure and the function of individual organelles will be discussed.

What is Cell?

• A cell is the basic functional, structural, and biological unit of all living organisms.
• Other definitions include a small room in which a monk lives, a microprocessor architecture, or a prison cell.
• Diagrams of a cell and its parts, such as the nucleus, plasma membrane, endoplasmic reticulum, ribosomes, mitochondria, Golgi apparatus, lysosomes, vacuoles, microfilaments, microtubules, intermediate filaments, peroxisome are discussed

Overview: Cells - The Fundamental Units of Life

• All organisms are composed of cells.
• A cell is the most basic unit of life
• All cells are related through descent from previous cells.
• Cell structure is closely related to its function.

Cell: The basis/foundation and diversity

• Cells form a fundamental basis for organism development and existence, displaying intricate diversity.
• Diagrams of various stages in developmental processes, including zygote, blastula, gastrula, and organismal structure are shown.
• The development of organisms from simple to complex is shown.

Multicellular Organisms and Various Cell Types

• A single genome can give rise to multiple different cell types and tissues
• Differential gene expression leads to differential cell signalling pathways in multicellular organisms.

From cell to tissues, organs, organ systems and organism

• Focuses on the hierarchical organization from cells to organisms, highlighting the continuous process in multicellular life forms.
• Diagrams illustrating the progressive levels of organization from cells to tissues and culminating in organ systems and complete organisms are presented in the lecture.

Various multicellular organisms and models

• Various multicellular organisms and models, such as fish, human beings and mice etc., are presented to illustrate the variety and diversity in the animal kingdom, which highlights the complexity of the variety in cell types and structures of organisms.
• Diagrams of cells and their structures and various organisms.

The Three Domains of Life

• Life is categorized into three domains: Bacteria, Archaea, and Eukarya.
• Within Eukarya, there are different kingdoms like Animals, Fungi, and Protists.
• Images of the organisms and diagrams are shown.

Hierarchical Classification

• A hierarchical system classifying organisms from species to domain is depicted.
• A specific example of the American black bear (Ursus americanus) is used to illustrate the hierarchical levels.

Cell Evolution: A Brief History of (Cell) Time

• The first organisms were single-celled.
• Fossils of bacteria-like organisms are at least 3 billion years old.
• Evidence presented for a common ancestor of all life forms, showing common features, such as common biochemical building blocks, common patterns of metabolism, and common genetic code

Example: Presence of common cellular structures

• Examples of common cellular structures, such as cilia from paramecium and windpipe cells, are discussed.
• Microscopic images of these structures are presented for reference
• The size of a cilium is given using electron microscope

Comparing Prokaryotic and Eukaryotic Cells

• Comparing features of prokaryotic and eukaryotic cells is presented
• Basic features in cells are compared from prokaryotic to eukaryotic, highlighting fundamental cell structures

Sizes of the cells and organelles

• A comparison of the sizes of different cells and organelles is presented with images.

Common features of Prokaryotes and Eukaryotes

• Cells share fundamental features: plasma membrane, semifluid substance (cytosol), chromosomes, and ribosomes

Prokaryotes and Eukaryotes

• Images of typical rod-shaped bacteria and mammalian cells are shown.

Exploring Eukaryotic Cells

• Various eukaryotic cells, including animal cells and fungal cells, and their components, such as yeast cells budding are shown.

Cells with Chloroplasts

• Specific images of plant and protistan cells showing chloroplasts, cell walls, and other specific features are shown.

Specific cell types (Spermatozoa)

• Diagrams of spermatozoa are presented.
• The structure of a sperm cell is described (oval head and tail).

Cell Organelles

• Diagrams illustrating various cell organelles and their respective functions, such as nucleus, rough and smooth endoplasmic reticulum, golgi apparatus, mitochondria, peroxisomes, and chloroplast

Cell Membrane

• The cell membrane's functions include protection, maintaining cellular integrity, and providing a selective barrier; allowing interaction with other cells and offering flexibility.
• A detailed diagram of the cell membrane structure is shown (hydrophilic head, hydrophobic tail, cholesterol, phospholipids, glycoprotein, etc.).

Vacuoles: Diverse Maintenance Compartments

• Food vacuoles are formed by phagocytosis.
• Contractile vacuoles help in pumping out excess water in freshwater protists.
• Central vacuoles are found in plant cells, playing roles in storage and water balance
• Images of these structures from plants and protists.

The Nucleus: Information Central

• The nucleus is a conspicuous organelle housing the cell's DNA.
• It houses chromosomes, containing most of the cell's genes, and the nuclear envelope.
• A diagram of the nucleus structure is presented.

The Endomembrane System

• The endomembrane system regulates protein traffic and performs metabolic functions within the cell, including the endoplasmic reticulum, Golgi apparatus, lysosomes, and exosomes
• An overview of functions of different component of endomembrane system is presented with images.

Ribosomes: Protein Factories

• Ribosomes, the protein-synthesizing machinery in the cell, consist of two subunits.
• Ribosomes are found both in the cytosol and attached to the endoplasmic reticulum and nuclear envelope.

Mitochondria and chloroplasts change energy from one form to another

• Mitochondria are sites for cellular respiration, generating ATP.
• Chloroplasts are found in plants and algae, carrying out photosynthesis.
• Peroxisomes are oxidative organelles.

The Evolutionary Origins of Mitochondria and Chloroplasts

• Mitochondria and chloroplasts have similarities with bacteria, being enveloped by a double membrane, having free ribosomes and circular DNA, and growing and reproducing somewhat independently in cells.

The Endosymbiont theory

• Explains the origin of mitochondria and chloroplasts through endosymbiosis
• It suggests that early eukaryotic cells engulfed nonphotosynthetic or photosynthetic prokaryotic organisms.
• Explanation and diagram of the evolutionary process.

Extracellular components and connections between cells help coordinate cellular activities

• Extracellular components and connections enable coordination in multicellular organisms.
• Examples include cell walls of plants, the extracellular matrix (ECM), and intercellular junctions.

The Cell: A Living Unit Greater Than the Sum of Its Parts

• Cells depend on the integrated functioning of various structures and organelles; for example, a phagocytic cell like a macrophage depends on the coordinated efforts of cytoskeleton, lysosomes, and the plasma membrane
• The interactive nature of the cell parts and structures to create the complete cell function is explained

The summary (I)

• The lecture aims to provide insight into the evolution and classification of organisms.
• The lecture will cover a brief overview of cell structure and the role of individual organelles in cell function.

The summary (II)

• All organisms are made up of cells.
• A cell is the simplest unit of life.
• All cells are related by descent from earlier cells
• Cell structure directly correlates to cellular function.

The summary (III)

• The eukaryotic cell's genetic instructions are housed in the nucleus and carried out by ribosomes
• The nucleus is described as the control centre of the cell and the chromosomes as the genetic material housed within
• The ribosomes synthesize proteins

The summary (IV)

• The endomembrane system regulates different cellular activities including protein traffic and various metabolic functions.
• The system involves specific components like the endoplasmic reticulum, Golgi apparatus, and lysosomes
• Detailed functions of each component are described.

The summary (V)

• Mitochondria and chloroplasts were originally bacteria, and these organelles convert energy from one molecular form to another within cells.
• Mitochondria carry out cellular respiration, while chloroplasts perform photosynthesis.

Further Reading

• Recommended textbooks for further study of cell biology (Molecular Biology of the Cell and Essential Cell Biology).

Home work: How do cells move?

Amoeboid Movement

Cytoplasmic Streaming

Cilia and Flagella

Dynein "walking"

Actin/myosin "walking"/motors

How to study Cell Structure and Function?

• Review material regularly to prepare for exams
• Check lecture material against aims and questions

Frequently Asked Questions

• Key questions related to the lecture material ('Why?', 'What?', 'How?', 'Who?', and 'Where?') are presented.
• A contact email address is provided for students with further questions or for additional discussion inquiries.

Take home message

• The module content and materials are available for the students to learn about cells.

This quiz explores the fundamental concepts of cell biology, including the definition of cells, their structures, and functions. It covers the relationship between various cell types, the role of the extracellular matrix, and the similarities between prokaryotic and eukaryotic cells. Test your knowledge on these essential topics!