BTEC HND in Applied Sciences Unit 4: Cell Biology Introduction to Cell Biology Ms Sasini Wijewarna Bsc(Hons)Microbiology-India Msc in Bioinformatics(UOC-Reading) All right reserved ® by AIBS Cell Biology • Cell biology is the study of cell structure and function, and it revolves around the concept that the cell is the fundamental unit of life. • All living things, including humans, animals, and plants, are made of cells. • Focusing on the cell permits a detailed understanding of the tissues, organs, organ systems, and organisms that cells compose. • Cell biology can be divided into many subtopics, including the study of cell metabolism, cell communication, cell cycle, and cell composition. All right reserved ® by AIBS Levels of Organization of Living Things • Before you begin to study the different structures and functions of the human body, it is helpful to consider its basic architecture; that is, how its smallest parts are assembled into larger structures. • It is convenient to consider the structures of the body in terms of fundamental levels of organization that increase in complexity: atoms, molecules, macromolecules (e.g. carbohydrates, lipids, proteins, and nucleic acids), organelles, cells, tissues, organs, organ systems, and organisms. • It is also important to realize that humans and other living organisms interact with one another and the environment as the hierarchy of biological organization continues upward from organisms to populations, communities, ecosystems, and the biosphere. All right reserved ® by AIBS All right reserved ® by AIBS • The cells in complex multicellular organisms are organized into tissues, groups of similar cells that work together on a specific task. • Organs are structures made up of two or more tissues organized to carry out a particular function, and groups of organs with related functions make up the different organ systems. • At each level of organization—cells, tissues, organs, and organ systems—structure is closely related to function. For instance, the cells in the small intestine that absorb nutrients look very different from the muscle cells needed for body movement. The structure of the heart reflects its job of pumping blood throughout the body, while the structure of the lungs maximizes the efficiency with which they can take up oxygen and release carbon dioxide. All right reserved ® by AIBS • How do you define life/living things? • What are the characteristics that you think all living things share? All right reserved ® by AIBS Definition of Living Things • Living things are the organism, that is alive. • They are made up of a small unit of the structure known as cells, which form tissues. • Different tissues, in turn, combine to form organs and when all these organs function together as an integrated unit, called as an organ system, which functions in something that has a life. • They are human beings, plants, insects, birds, animals, fungi, bacteria, algae, protozoa, etc. There are some traits which are common in all living things, which are: • Grow and develop, with time. • Respire to release energy. • Require nutrition • Excrete to eliminate waste. • Reproduce to give birth to the new organism. • Respond to the external environment. • Adapt themselves to the changing conditions. All right reserved ® by AIBS Definition of Non-Living Things • Non-living things refer to those things, which are not alive, i.e. the characteristic of life is absent, in them. • They do not show any trait of life, such as Reproduction, growth and development, respiration, metabolism, adaptation, responsiveness, movement, etc. • They are created or produced from non-living materials, such as wood, plastic, iron, metals, leather, cotton, etc. All right reserved ® by AIBS https://www.youtube.com/watch?v=tjm8WLMWq6Q All right reserved ® by AIBS Cells • The basic structural and functional unit of cellular organization is the cell. • Within a selective and relative semi permeable membrane, it contains a complete set of different kinds of units necessary to permit its own growth and reproduction from simple nutrients. • All organisms, more complex than viruses, consist of cells, yet they consist of a strand of nucleic acid, either DNA or RNA, surrounded by a protective protein coat (the capsid) • Cells have many parts, each with a different function • Some of these parts, called organelles, are specialized structures that perform certain tasks within the cell • Based on the number of cells it contain, organisms are of two types All right reserved ® by AIBS • On the basis of internal organization and architecture, all cells can be subdivided into two major classes, ▪ prokaryotic cells ▪ eukaryotic cells • Cells which have the unit membrane bound nuclei are called eukaryotic, whereas cells that lack a membrane bound nucleus are prokaryotic. • Besides the nucleus, the eukaryotic cells have other membrane bound organelles (small organs) like the Endoplasmic reticulum, Golgi complex, Lysosomes, Mitochondria, Microbodies and Vacuoles. • The prokaryotic cells lack such unit membrane bound organelles. All right reserved ® by AIBS Cell theory All right reserved ® by AIBS Discovery of the Cell • The cell was first discovered and named by Robert Hooke in 1665 • He observed very thin slices of bottle cork and discovered a multitude of tiny pores that he named "cells“ • As the cells Hooke observed were actually dead, he was actually observing cell walls and empty space All right reserved ® by AIBS All right reserved ® by AIBS Discovery of the Cell • Anton van Leeuwenhoek made better lenses for microscopes and was the first person to observe living cells • He is commonly known as the “Father of Microbiology” and considered to be the first microbiologist • He was able to discover tiny animals in pond water • He called them “animalcules,” or little animals All right reserved ® by AIBS Discovery of the Cell • In 1838, German botanist, Matthias Schleiden concluded that all plants are made up of cells • In 1839, German physiologist and zoologist, Theodor Schwann, who was a close friend of Schleiden, stated that all animal tissues are composed of cells • In 1858, Rudolf Virchow, German physician, concluded that “All cells only arise from pre-existing cells” All right reserved ® by AIBS Cell Theory • The ideas of all three scientists — Schwann, Schleiden, and Virchow — led to cell theory, which is one of the fundamental theories unifying all of biology • Cell theory states that: ▪ All organisms are made of one or more cells ▪All the life functions of organisms occur within cells ▪ All cells come from already existing cells All right reserved ® by AIBS All right reserved ® by AIBS https://www.youtube.com/watch?v=4OpBylwH9DU Modern Cell Theory • Modern Cell Theory contains 4 statements, in addition to the original Cell Theory: ▪ The cell contains hereditary information(DNA) which is passed on from cell to cell during cell division ▪ All cells are basically the same in chemical composition and metabolic activities ▪ All basic chemical and physiological functions are carried out inside the cells (movement, digestion, etc.) ▪ Cell activity depends on the activities of sub-cellular structures within the cell(organelles, nucleus, plasma membrane) All right reserved ® by AIBS Cell diversity and classification All right reserved ® by AIBS Cell Diversity and Classification • Cells within the same organism show enormous diversity in 1. Number 2. Size 3. Shape 4. Internal organization All right reserved ® by AIBS Cell Number • Cell Number: The number of cell present in organism is varies from a single cell in unicellular organism to many cell in multi cellular organism. • Number of cells in an organism varies significantly based on various factors • In some organisms, the body is made up of single cell (unicellular) • In some organisms, the body is made up of many cells (multicellular) • The number of cell in multicellular organism usually remains correlated with the size of organism and, therefore, a small sized organism has a less number of cells in comparison to large sized organism. • Number of cells increases up to certain period of life and such increase ceases afterwards All right reserved ® by AIBS Cell Size • Cells differ greatly in their sizes • Cell size is measured in micrometers (μm) • A typical eukaryotic cell is 10 to 100 micrometers (μm) in diameter, while most prokaryotic cells are only 1 to 10 μm in diameter All right reserved ® by AIBS https://www.youtube.com/watch?v=wuXSEOKNxN8 All right reserved ® by AIBS • Surface area to volume ratio limits cell size • Surface area → The total area of the outer surface of an object • Volume → The amount of space an object takes up • The larger the cell, the smaller the SA/V ratio • The smaller the ratio, the less efficient the cell is as the cell membrane is too small to take in enough nutrients for the large volume • Small cells have more surface area than a large cell for a given volume of cytoplasm • Therefore, in order to build large organisms, they must be built up from small cell subunits All right reserved ® by AIBS • A cell can be flat and thin instead of cube-like • A cell can have the same volume but a bigger surface area (Ex: Neurons) • A cell can increase surface area by having folds in the cell membrane (Ex: Specialized gut cells found in the small intestine) All right reserved ® by AIBS Cell shape • Prokaryotic cells come in many different shapes and sizes that you can see under a microscope. • A description of the shape of a cell is called the cell morphology. • The most common cell morphologies are cocci (spherical) and bacilli (rods). • The illustration shows these common cell morphologies. All right reserved ® by AIBS Cell Shape • The activities of each cell are reflected in the range of cell shapes observed in prokaryotes and eukaryotes, supporting the structurefunction connection prevalent throughout life. • Each cell type has developed a form that is most closely associated with its function. • Depending on the purpose, the cell takes on a number of forms. Cells come in a variety of forms, including: • Skin cells i. These skin cells have a flat surface. ii. They are a protective body cover with a flat form that allows them to cover a large area. All right reserved ® by AIBS • Muscle cells i. Muscle cells are long, thin, and elongated. ii. Muscle cells expand and contract, and their long and thin structure aids in this process. All right reserved ® by AIBS Cell Shape Bone Cells Kidney Cells Internal Organization • All cells have a plasma membrane and contain genetic material • In some cells, the genetic material is housed in a membrane-bound space called the nucleus • Cells can be divided into two classes based on the presence or absence of a nucleus: - Prokaryotes - Eukaryotes All right reserved ® by AIBS What are Prokaryotic Cells ? • Unicellular organisms which don’t have membranebound organelles like nucleus and mitochondria are referred to aspro karyotic cells. • These organisms are divided into two groups depending on the comp onents of the cell wall: Bacteria and Archaea. • In prokaryotes, the cell membrane encloses watersoluble proteins, DNA and metabolites in the cytoplasm. They do not possess separate compartments, but microco mpartments act as primitive organelles which arecreated by protein s hells. All right reserved ® by AIBS What are Eukaryotic Cells? • Eukaryotes are complex organisms with a nucleus and other organelles enclosed in a plasma membrane. • Here are the primary components of eukaryotic cells. • Nucleolus: The nucleolus is the part of the nucleus where ribosomal RNA is produced. • Cell wall: The cell wall, also called the cytoskeleton, provides the structure that enables cell division. • Mitochondria: They are responsible for energy production; hence, they are known as the cell’s powerhouse. • Endoplasmic reticulum: It plays a role in protein maturation and transportation. • Vesicles and vacuoles: They are membrane-bound sacs aid in transportation and storage. • Many eukaryotes also have the Golgi apparatus, chloroplasts, and lysosomes. • Most eukaryotes undergo sexual reproduction resulting in offspring with genetic material, a mixture of the parents’ genome. In this process of sexual recombination, genetic variation is generated. All right reserved ® by AIBS https://www.youtube.com/watch?v=RQ-SMCmWB1s All right reserved ® by AIBS Generally much smaller (1 to 10 μm in diameter) lacks a true nucleus and membrane-bound organelles Carry ribosomes (70s) Most bacteria are surrounded by a rigid cell wall made out of peptidoglycan, (carbohydrates and small proteins) It provides an extra layer of protection, helps the cell maintain its shape and prevents dehydration Reproduces through binary fission, a process which simply splits duplicated DNA into separate cells Fimbriae are used for attachment to host cells and other surfaces Flagella act as rotary motors to help bacteria move Generally much larger (10 to 100 μm in diameter) They contain true nucleus and membrane bound organelles Carry larger ribosomes (80s) A number of membranebound organelles How do plant and animal cells differ? • Both plant and animal cells are eukaryotic, so they contain membrane-bound organelles like the nucleus and mitochondria. • However, plant cells and animal cells do not look exactly the same or have all of the same organelles, since they each have different needs. For example, plant cells contain chloroplasts since they need to perform photosynthesis, but animal cells do not. All right reserved ® by AIBS All right reserved ® by AIBS Thank You All right reserved ® by AIBS
