Cell and Organelles PDF

CELL Gulam Hekimoğlu, MD, PhD  What is a cell? The cell is the basic structural and functional unit of all living organisms. The body contains about 60 × 10¹² cells, 200 different types that vary greatly in size and shape What leads to the discovery of...

CELL Gulam Hekimoğlu, MD, PhD  What is a cell? The cell is the basic structural and functional unit of all living organisms. The body contains about 60 × 10¹² cells, 200 different types that vary greatly in size and shape What leads to the discovery of cells? All discoveries were made possible by advances in technology. Better microscopes can see smaller things. resolving power Around 1590, two Dutch lens manufacturers, Hans and Zacharias Janssen, invented the first compound microscope by combining two of their lenses in a tube.  Robert Hooke (1635- 1703) Slice of oak bark, piece of mushroom Honeycomb-like structures Cell, islet  1665- Micrography Published in the Royal Society This book, called Micrography, was the first important work on the microscope concerned with the study of small objects with a microscope.  View of cells under the microscope Anton Van Leeuwenhoek (1632-1723) - the first to see living cells. Improved design and muscle cells and bacteria can be seen. They called them "animal"  Robert Brown, Scottish botanist, best known for his descriptions of the cell nucleus and the constant motion of tiny particles in solution... 1831- cell nucleus, 1833- published  Development of Cell Theory In 1838 and 1839, a German botanist named Matthias Schleiden and a German zoologist named Theodore Schwann studied plants and animals under a microscope and discovered that plants and animals are both composed of cells.  In 1855, a Prussian (modern-day German) doctor named Rudolph Virchow developed the Cell Theory by sharing his ideas with two other scientists.  Cell Theory The ideas of these three men led to the creation of cell theory: These are the three main principles of cell theory. 1. All living organisms are made up of cells. 2. Cells are the most basic unit of life. 3. Cells come only from the division of pre- existing cells, that is, spontaneous cell formation does not occur.  Cell Diversity Cells within the same organism vary tremendously in the following areas: Dimension Shape Internal Organization  1. Cell size Female Egg - the largest cell in the human body; seen without the aid of a microscope. Most cells can only be seen with a microscope. Cells are too small  2. Cell Shape The diversity of shape reflects a diversity of functions. A CELL SHAPE DEPENDS ON FUNCTION. Conditions Cell - the smallest unit capable of continuing life processes. Unicellular - consists of only one cell Multicellular - consists of more than one cell Basic Cell Structures Cell Membrane - outer border Nucleus - control center Cytoplasm - the substance between the membrane and the nucleus Protoplasm, Cytosol Cell: The structural unit of all living organisms. 2 types of cells Prokaryotic: Primitive cells. Mixed metabolic and hereditary compounds. e.g. bacteria Eukaryotic: Most of the hereditary material is contained within the membrane- enclosed nucleus. plants and animal cells  Cell functions Arousal: responding to a stimulus Ability to forward the alert Contraction: shortening and changing shape Absorption: taking certain dissolved substances into the cell Secretion and excretion: removal of materials out of the cell Growth and reproduction Metabolism: breakdown of food materials coming into the cell  Cell components are two parts CYTOPLASMA: NUCLEUS: It is surrounded by a It is the part of the cell plasma membrane that carries the genetic (Plasmalemma) from the material, surrounded by the nuclear membrane. outside, and consists of Intense dark blue-black organelles and a matrix staining with hematoxylin- containing carbohydrate, eosin dye. lipid and pigment.  in the cytoplasm Water 75% Salts (such as K, Mg, phosphate, bicarbonate) Proteins Oils Carbohydrates vitamins Cytoplasmic organelles: Membraned organelles: Non-membraned Mitochondria organelles: Peroxisomes Endoplazmik retikulum Microfilaments Golgi complex intermediate filaments Lysosomes Ribosome secretory granules Centriole microtubules Inclusions: - Lipids - Glycogens - Pigments - Crystals  Plasma Membrane It separates the cytoplasm from the external environment. It consists of lipids, proteins, and carbohydrates.  Functions 1- It creates a selective barrier that regulates the passage of certain substances into and out of the cell. 2- It facilitates the passage of special substances through this barrier. 3- Executes the original recognition and editing function. In other words, it regulates the relationship of the cell with the environment.  Plasma Membrane Structure The most important feature is the lipid component. These are arranged in a double layer in the liquid medium.  Membrane lipids It is about 50% of the cell membrane mass. There are 3 main types: Phospholipids tend to be located around membrane proteins that bind and transport enzymes. -Cholesterol is the lipid that makes the membrane more stable -Glycolipids, located on the outer surface of the cell, are responsible for intercellular communication.  Functions of membrane proteins It attaches the filaments that make up the cytoskeleton to the cell membrane. It binds cells to the extracellular matrix. It moves molecules into or out of the cell. It plays a role as a receptor in intercellular chemical signaling. It has specific enzymatic activity.  Membrane Carbohydrates It is mostly located on the membrane surface, not in contact with the cytosol. On the cell surface it is called the glycocalyx.  Liquid mosaic pattern Proteins with lipid and carbohydrate side chains are arranged in a mosaic form within the membrane. This structure formed by membrane lipids and proteins is called the liquid mosaic model. Carbohydrate extensions on the surface of the membrane form receptors. Transport into and out of cells (endocytosis, exocytosis) The plasma membrane is the site of exchange of substances between the cell and its environment. Some ions such as Na, K and Ca are actively transported through integral protein channels. Mass transport is done by plasma membranes. These are endocytosis (intake into the cell) and exocytosis (transport out of the cell).  endocytosis The cell membrane forms small pits, takes the filled fluid into the cell, and form pinocytosis vesicles.  pinocytosis Pinocytosis means the cell is drinking. In some cells they fuse with lysosomes, in others they move in the opposite direction, fuse with the plasma membrane and empty their contents out of the cell.  Receptor-mediated endocytosis There are receptors on the cell surface for many low-density substances. These are clustered in areas called coated pits. When the relevant molecule binds to its receptor, a vesicle is formed.  Phagocytosis Cell eating Large particles are taken into the cell. Bacteria, protozoa, fungi, injured cells and unnecessary extracellular formations are taken into the cell by cytoplasmic extensions (phagocytic vacuole), degraded by lysosomes.  Exocytosis It is the opposite of endocytosis. It is defined as the fusion of the membrane-enclosed vesicle with the cell surface and discharges its contents out of the cell. It is typical for the secretory cells to discharge their products.  Cell organelles Mitochondria Ribosomes Endoplazmik reticulum Golgi complex Lysosomes Peroxisome (microbody)  Mitochondria It is responsible for energy production. It is a rod or spherical organelle. The number varies according to the metabolic activity of the cell. It has two membranes.  Mitochondria Outer membrane. Inner membrane. The inner membrane makes folds called cristae. The inner membrane surrounds the matrix cavity.  Mitochondrial matrix It is filled with a fine granular material, rich in protein, and contains DNA and RNA. DNA is mitochondrial. It contains some enzymes.  Mitochondria in mitosis The mitochondria in the parent cell pass halfway through to the two daughter cells. Mitochondria can independently synthesize proteins.  Ribosomes They are free or attached to E.R. Performs protein synthesis Proteins to be used in the cell are synthesized in free ribosomes, and those to be secreted are synthesized in those attached to E.R.  Ribosomes They appear as dark basophilic stains on light microscope. They are stained with hematoxylin, methylene blue, toluidine blue. They are called Nissl bodies in neurons and basophilic bodies in other cells.  Endoplazmik reticulum There are two types, rough (granular) and smooth (ungranular). The definition of rough (granular) is due to the ribosomes in the membrane.  Endoplazmik reticulum Lipid and carbohydrate synthesis is carried out, Proteins are produced and separated from the cytoplasm, It is where changes take place in our proteins. The name of the reticulum is because it forms a network within the cell.  Rough (granuler) endoplazmik reticulum It is prominent in protein-secreting cells. Eg. Pancreatic acinar cell (digestive enzymes), Fibroblast (collagen), Plasma cells (immunoglobulin).  Granular endoplasmic reticulum Synthesize proteins: It can remain in the cell, It can be stored for release outside the cell, It can be used as a component of other membranes.  Smooth (ungranulated) Endoplasmic Reticulum Does not contain ribosomes Contains enzymes necessary for lipid and carbohydrate metabolism. Performs the detoxification process Stores calcium in muscle cells  Golgi complex Located close to the core Proteins and carbohydrates are packaged and sent to their destination. Hydrolytic enzymes are packaged (in the form of lysosomes)  Lysosomes They are membrane-enclosed vesicles, whose function is intracellular digestion and contain up to 40 hydrolytic enzymes. It is present in most cells but abundant in phagocytic cells (macrophage, neutrophil).  Peroxisome (microbody) Contains oxidases. They protect the cell by splitting hydrogen peroxide into water and oxygen. They are synthesized in free ribosomes. Cytoskeleton  Structural proteins of the cytoskeleton 1 – Microtubules 2 – Microfilaments (Actin filaments) 3 – Intermediate filaments  Microtubules It plays a role in the creation and maintenance of cell shape, It is involved in the intracellular movement of other organelles (mitochondria, vesicles). Axoplasm in neurons, melanin transport in pigment cells, chromosome movement in mitosis. It participates in the structure of centrioles, basal bodies, cilia and flagella.  Microfilaments It forms a reticulated layer with other proteins under the cell membrane. In all cells it is mainly actin, Contraction in muscle cells is mediated by actin and myosin organization. It takes part in the movement of cytoplasmic components. Takes part in endocytosis, exocytosis, cell movement  Intermediate filaments It is specific to cell types. Type between microtubules and microfilaments, Especially prominent along nerve cell extensions. Filament type Cell type Cytokeratins Epithelial cells Vimentin Mesenchymal cells Desmin Muscle cells Glial filaments Glial cells Neurofilaments Neurons Nuclear lamins Cell nuclei  Microtubule: yellow Actin : blue Nucleus : pink ( fluorescent light micrograph )