INTRODUCTION TO CELL STRUCTURE_LESSON.pptx

CELL

1. INTRODUCTION TO CELL STRUCTURE AND FUNCTION BIOCHEMISTRY

2. First to use the term “ cell ” (from cellula , Latin for “small room” like those in monasteries where monks lived.) Observed thin slices of cork under a microscope Noted a structure with many tiny compartments, comparing it to a honeycomb First recorded microscopic observation of cell structure Discovery of Cells Robert Hooke (1665)

3. “ Father of Microscopy ” Skilled lens maker – created simple microscopes First to observe: Microbes (ciliates, foraminifera, rotifers) Blood cells Living sperm cells Bacteria (from dental plaque, called animacules ) Discovery of Cells Antony van Leeuwenhoek (1670)

4. Significance Hooke : Introduced the concept of the “cell” Leeuwenhoek : First detailed observations of microorganisms Foundation for cell theory and modern microbiology

5. Theodor Schwann & Matthias Schleiden Development of the Cell Theory Proposed cells are the basic unit of all living things Proposed all cells come from preexisting cells Rudolf Virchow 1839 1858 Theodor Schwann Matthias Schleiden Rudolf Virchow

6. Modern Cell Theory All organisms are made up of one or more cells All life functions occur within cells All cells come from preexisting cells

7. What is a Cell? Basic unit of all living things Smallest unit that can carry out all life processes All organisms are made of one or more cells

8. What is a Cell? Cells perform similar functions: Transport materials Obtain and use energy Dispose of waste Reproduction Respond to the environment (Red Blood Cells) (Kidney cells ) (Food) (Amoeba) (Cell Division)

9. Common Parts of All Cells All cells, no matter their type, share some common structures. These include the cell membrane , cytoplasm , ribosomes , and DNA . These structures allow the cell to carry out essential life processes such as obtaining energy , building proteins , and storing genetic information.

10. Cell (Plasma) Membrane The cell membrane forms the physical boundary between the inside of the ce ll and its environment. It controls the movement of materials in and out of the ce ll , acting like the “skin” of the cell to protect its contents.

11. Cytoplasm The cytoplasm is the jelly - like substance that fills the inside of the ce ll. It consists of cytosol , a watery fluid that contains dissolved particles, and organelles , which are specialized structures that perform specific functions. The cytoplasm provides a medium for chemical reactions and supports the cell’s internal structures.

12. Ribosomes Ribosomes are small organelles found throughout the cytop lasm. They are the sites of protein synthesis, where the cell builds the proteins necessary for its structure, function, and regulation. Unlike other organelles, ribosomes are not surrounded by a membrane.

13. DNA D eoxyribo n uleic a cid DNA is the genetic material found in all cel ls. It contains the instructions needed to build proteins and RNA molecules and directs the cell’s activities. In eukaryotic cells , DNA is organized into linear chromosomes inside the nucleus , while in prokaryotic cells , DNA is circular and found in the cytoplasm .

14. Types of Cells There are two main types of cells: prokaryotic and eukaryotic . 1. Prokaryotic cells (Greek : pro – before; karyon – nucleus) lack a well defined nucleus and possess relatively simple structure. These include the various bacteria. 2. Eukaryotic cells (Greek : eu – true; karyon – nucleus) possess a well defined nucleus and are more complex in their structure and function. The higher organisms (animals and plants) are composed of eukaryotic cells.

15. Prokaryotic Cells Prokaryotic cells, such as bacteria , are usually unicellular and smaller than eukaryotic cel ls. They lack a nucleus, and their DNA floats freely in the cytoplasm. Many have a rigid cell wall for structural support, and some have a capsule that helps them stick to surfaces. Prokaryotes are found in a l most every environment on Earth and are believed to be the f ir st type of cells to exist.

16. Prokaryotic Cell

17. Eukaryotic Cells Eukaryotic cells are more complex and can be either single-celled or multicel lular . They have a nucleus that contains DNA organized into linear chromosomes, and a variety of membrane-bound organelles, each performing specific tasks. Eukaryotic cells are genera lly larger than prokaryotes and can carry out many more functions due to the ir complex internal organization.

18. Eukaryotic Cell

19. Prokaryotic Cell vs. Eukaryotic Cell

20. Two Main Types of Eukaryotic Cells

21. Cell (plasma) membrane It sep arates the int e rnal contents of the cell from its surrounding environment. Phospholipid structure : two fatty acid chains, a glycerol backbone, and a phosphate group. The plasma membrane regulates passage of substances (organic molecules, ions, water) to maintain internal conditions. Active transport: bringing in or removing certain substances. Passive transport: othe r compounds move without energy.

22. Cytoplasm The cytoplasm compr is es the contents of a cell between the plasma membrane and the nuclear envelope. Made up of: Organelles suspended in the gel-like cytosol, Cytoskeleton , and various chemicals Although 70–80% water, cytoplasm has a semi-solid consistency due to proteins. Other organic molecules present include: glucose, simple sugars, polysaccharides, amino acids, nucleic acids, fatty acids, and glycerol derivatives. Ions such as sodium, potassium, calcium, and others are also dissolved in the cytoplasm. Many metabolic reactions, including protein synthesis , occur in the cytoplasm.

23. Cytoskeleton The cytoskeleton is a network of protein fibers in the cytoplasm that: Maintains cell shape Secures organelles in place Allows cytoplasm and vesicles to move Enables unicellular movement

24. Cytoskeleton Three types of cytoskeletal fibers: Microfilaments (actin filaments) Thinnest fibers Move cellular components (e.g., during cell division) Maintain microvilli structure in absorptive cells Responsible for muscle contraction

25. Cytoskeleton 2. Intermediate filaments Intermediate diameter Structural support: maintain cell shape, anchor organelles Example: Keratin strengthens hair and nails

26. Cytoskeleton 3. Microtubules Thickest fibers; hollow tubes Can dissolve and reform quickly Guide organelle movement Pull chromosomes during cell division Structural component of cilia and flagella (arranged as 9+2)

27. Centrosome Region near the nucleus in animal cells Microtubule-organizing center Contains pair of centrioles (perpendicular cylinders of 9 triplets of microtubules) Replicates before cell division to help pull chromosomes Function is not essential: cells without centrioles and plant cells can still divide

28. Flagella (singular = flagellum) Flagella and Cilia Long, hair-like structures extending from the plasma membrane Used to move the entire cell (e.g., sperm, Euglena) Typically one or a few per cell Short, hair-like structures, many per cell Cover the entire surface of the plasma membrane Functions: Move entire cells (e.g., Paramecium) Move substances along cell surfaces: Respiratory tract: move mucus and trapped particles toward throat Cilia (singular = cilium)

29. Nucleus Prominent organelle: Typically the largest organelle in a cell Function: Houses the cell’s DNA (chromatin) and directs ribosome and protein synthesis Control center of the cell

30. Nucleus Nuclear Envelope: Structure: Double-membrane (inner and outer phospholipid bilayers) Pores: Control passage of i ons, molecules, and RNA between nucleoplasm and cytoplasm

31. Nucleus Chromatin and Chromosomes: Chromosomes: DNA + proteins, linear in eukaryotes Chromatin: Unwound form of DNA during growth/maintenance phases Humans: 46 Visibility: Chromosomes are visible only during cell division

32. Nucleus Nucleolus: Darkly stained area within the nucleus Function: Aggregates ribosomal RNA and proteins to assemble ribosomal subunits Subunits are transported through nuclear pores into the cytoplasm

33. Endoplasmic Reticulum (ER) It is a network of interconnected membranous tubules that extends throughout the cytoplasm. It plays a central role in synthesizing, modifying, and transporting molecules within the cell.

34. Endoplasmic Reticulum (ER) The ER has two main types, each with distinct functions: Rough ER (RER) Studded with ribosomes on its cytoplasmic surface Modifies and folds proteins synthesized by the ribosomes Prepares proteins for transport to other organelles or for secretion outside the cell Smooth ER (SER) Lacks ribosomes on its surface Synthesizes lipids, including phospholipids and steroids Involved in detoxification of harmful substances and storage of calcium ions in some cells (e.g., muscle cells)

35. Endoplasmic Reticulum (ER) The lumen (also called the cisternal space) is the hollow interior of the ER tubules where proteins and lipids are temporarily stored and processed. The ER membrane is a phospholipid bilayer embedded with proteins and is continuous with the nuclear envelope, allowing direct transfer of molecules between the nucleus and ER. Overall, the ER serves as a manufac turing and distribution system for the cell, linking the nucleus, ribosomes, Golgi apparatus, and other organelles to maintain cellular function.

36. Golgi Apparatus is a series of flattened membranous sacs that sort, modify, package, and distribute proteins and lipids. Structure: Receiving face: Near the ER, receives transport vesicles containing proteins and lipids Releasing face: Opposite side, sends vesicles to other cell regions or the plasma membrane

37. Lysosomes The cell’s “garbage disposal”, breaking down proteins, polysaccharides, lipids, nucleic acids, and worn-out organelles. Digest food and recycle organelles.

38. Vacuoles Vesicles and Vacuoles Larger than vesicles Membrane does not fuse with other cellular components Smaller than vacuoles Membrane can fuse with other cellular components to deliver contents Vesicles

39. Ribosomes Responsible for protein synthesis in the cell Free ribosomes: Clusters or single dots floating in the cytoplasm Bound ribosomes: Attached to the cytoplasmic side of the plasma membrane or endoplasmic reticulum Made of large and small subunits, forming enzyme complexes for protein synthesis Found in nearly all cells; smaller in prokaryotes Especially high in immature red blood cells to synthesize hemoglobin for oxygen transport

40. Mitochondria Often called the “pow erhouses” or “energy factories” of the cell. Produce ATP(adenosine triphosphate), the cell’s main energy molecule, through cellular respiration (breakdown of glucose) Membranes: Phospholipid bilayers with embedded proteins

41. Mitochondria Structure: Oval-shaped, double-membrane organelles Contain their own DNA and ribosomes Inner membrane folds = cristae → increase surface area Mitochondrial matrix: Space inside cristae, involved in respiration

42. Peroxisomes Small, round organelles encl osed by a single membrane. Carry out oxidation reactions to break down fatty acids and amino acids Detoxify harmful substances, such as alcohol, drugs, and poisons, especially in liver cells

43. Peroxisomes Work cl osely with mitochondria and ER for lipid metabolism Critical in detoxification pathways and protecting the cell from oxidative damage

44. SHORT QUIZ What is the basic unit of life? Who discovered cells by looking at cork under a microscope? What type of cell has no nucleus — prokaryotic cell or eukaryotic cell? Which structure controls what enters and leaves the cell? In which type of cell is the DNA found inside a nucleus?

45. THANK YOU

46. 3.3 Eukaryotic Cells – Concepts of Biology – 1st Canadian Edition REFERENCES