Organelles

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Cell Structure & Function

OUTLINE : 

OUTLINE CELL 1. The Discovery of Cell 2. Modern Cell Theory 3. Cell Types 3.1. Eukaryotic and Prokaryotic Cells 4. Cell Membrane 5. Transport Mechanisms 6. Cell Wall 7. The Cytoplasm and Cell Organelles

INTRODUCTION : 

INTRODUCTION People have studied living things since ancient times. But nobody knew that living things were made up of cells until the microscope was invented. Today we know the cell as the most elementary unit of life. Some organisms consist of only a single CELL. Others are composed of many billions of cells

Examples of Cells : 

Examples of Cells Amoeba Proteus Plant Stem Red Blood Cell Nerve Cell Bacteria

The Discovery of the Cell : 

The Discovery of the Cell 1590 – Jansen 1665 – Robert Hooke 1650 - 1700 - Anton Van Leewenhoek 1838 - A. Schleiden 1839 - T. Schwann 1840 - Purkinje 1855 - Virchow

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CELL TYPES CELL TYPES Each cell has special structures called organelles. Each of them carries out a special function within the cell. Today cells are divided into two groups depending on the presence of membrane-bound organelles. 1) Prokaryotic Cells 2) Eukaryotic Cells

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PROKARYOTIC CELLS Have no membrane-bound organelles but have lots of ribosomes around DNA Genetic material is in cytoplasm Have a single-circular DNA Ribosomes are 70S Size 0.5-5 micrometer Have mesosomes in aerobic species In photosynthetic prokaryotes, chlorophyll is found in cytoplasm

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EUKARYOTIC CELLS Have membrane-bound organelles Their genetic material is packaged in nucleus They have linear chromosomes made of DNA and proteins (histones). Ribosomes are 80S Size 20 micrometer Examples are protists, fungi, plants, animals.

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ANIMAL CELL

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Section 7-2 Figure 7-5 Plant and Animal Cells Go to Section: Animal Cell Nucleus Nucleolus Cell Membrane Cytoplasm

Eukaryotic Cell Organelles and Function : 

Eukaryotic Cell Organelles and Function Nucleus Nickname: “The Control Center” Function: holds the DNA Parts: Nucleolus: dark spot in the middle of the nucleus that helps make ribosomes

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Section 7-2 Figure 7-5 Plant and Animal Cells Go to Section: Animal Cell Nucleus Nucleolus Ribosomes Cell Membrane Cytoplasm

Eukaryotic Cell Organelles and Function : 

Eukaryotic Cell Organelles and Function Ribosomes Function: makes proteins Found in all cells, prokaryotic and eukaryotic

Eukaryotic Cell Organelles and Function : 

Eukaryotic Cell Organelles and Function Endoplasmic Reticulum (ER) Nickname: “Roads” Function: The internal delivery system of the cell

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Section 7-2 Figure 7-5 Plant and Animal Cells Go to Section: Animal Cell Nucleus Nucleolus Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum Cell Membrane Cytoplasm Ribosomes

Endoplasmic Reticulum : 

Endoplasmic Reticulum 2 Types: Rough ER: Rough appearance because it has ribosomes Function: helps make proteins, that’s why it has ribosomes Smooth ER: NO ribosomes Function: makes fats or lipids

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Section 7-2 Figure 7-5 Plant and Animal Cells Go to Section: Animal Cell Nucleus Nucleolus Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum Ribosomes Golgi Complex Cell Membrane Cytoplasm

Eukaryotic Cell Organelles and Function : 

Eukaryotic Cell Organelles and Function Golgi Complex Nickname: The shippers Function: packages, modifies, and transports materials to different location inside/outside of the cell Appearance: stack of pancakes

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Section 7-2 Figure 7-5 Plant and Animal Cells Go to Section: Animal Cell Nucleus Nucleolus Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum Ribosomes Golgi Bodies Cell Membrane Cytoplasm

Eukaryotic Cell Organelles and Function : 

Eukaryotic Cell Organelles and Function Lysosomes: circular, but bigger than ribosomes) Nickname: “Clean-up Crews” Function: to break down food into particles the rest of the cell can use and to destroy old cells

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Section 7-2 Figure 7-5 Plant and Animal Cells Animal Cell Nucleus Nucleolus Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum Ribosomes Golgi Bodies Mitochondria Cell Membrane Cytoplasm

Eukaryotic Cell Organelles and Function : 

Eukaryotic Cell Organelles and Function Mitochondria Nickname: “The Powerhouse” Function: Energy formation Breaks down food to make ATP ATP: is the major fuel for all cell activities that require energy

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Animal Cell Nucleus Nucleolus Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum Ribosomes Golgi Bodies Mitochondria Cell Membrane Cytoplasm

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Now let’s talk about structures only found in PLANT Cells!!

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Section 7-2 Figure 7-5 Plant and Animal Cells Go to Section: Plant Cell Vacuole

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Organization of Cells: Groups of cells similar in structure and function form tissues. A group of tissues working together to perform a special function form an organ. A group of organs working together to perform a special function form a system. Several systems together form an organism.

The Cell Membrane : 

The Cell Membrane Cell biologists now accept a working model of cell membrane, Fluid-Mosaic Model of the cell membrane. Singer-Nicolson proposed fluid-mosaic structure in 1972. According to the model cell membrane is composed of two layers of phospholipids and many variable proteins disposed through it.

Fluid-Mosaic Model : 

Fluid-Mosaic Model Phospholipids play important structural and functional role in cell membrane. A phospholipid consists of a glycerol molecule attached to two fatty acids, and to a phosphate group. The lipid bilayer is very impermeable to ions and polar molecules. Water is an exception and is able to pass in and out of the cell through lipid bilayer with ease.

MEMBRANE PROTEINS : 

MEMBRANE PROTEINS 1) INTEGRAL PROTEINS: They have regions that are inserted into the hydrophobic regions of the lipid bilayer and are firmly bound to membrane. 2) PERIPHERAL PROTEINS: They usually bind to exposed regions of integral proteins.

Functional Groups of Plasma Membrane Proteins: : 

Functional Groups of Plasma Membrane Proteins: a) Cell Adhesion Proteins attach membranes of adjacent cells and may serve as anchoring points for cytoskeletal elements. b) Protein Channels allow transfer of small molecules

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c) Transport Proteins allow selective passage of essential molecules d) Receptor Proteins bind external signal molecules (like hormones). e) ATP-driven Pumps actively transport ions from one side to another. f) Membrane-bound enzymes may have active sites located on either side or in the interior of the membrane

The functions of the plasma membrane as follows: : 

The functions of the plasma membrane as follows: It protects the cell and gives shape to the cell. It separates the cell from surrounding environment. It regulates the passage of materials into and out of the cell. It receives information that permits the cell to sense changes in its environment and respond them. It communicates with neighboring cells and with the organism as a whole.

Permeability of the Cell Membrane : 

Permeability of the Cell Membrane The cell membrane doesn't permit the passage of every kind of molecule selectively (=semi) permeable. It maintains homeostasis. Small molecules like H2O, CO2, glucose, amino acid, lipid-soluble molecules (=alcohol, ether, chloroform, etc.) can pass easily. Large molecules (=starch, glycogen, protein, etc.) can not pass through the cell membranes

TRANSPORT MECHANISMS : 

TRANSPORT MECHANISMS I. Passive transport mechanisms (No energy (ATP) is used)a) Simple diffusionb) Facilitated diffusionc) Osmosis II. Active transport III. Bulk transporta) Endocytosis (pinocytosis, phagocytosis)b) Exocytosis

PASSIVE TRANSPORT MECHANISMS : 

PASSIVE TRANSPORT MECHANISMS A) Simple diffusion: The movement of molecules of a substance from an area of higher concentration to an area of lower concentration due to random movement of individual particles is called diffusion . It will continue until particles are evenly distributed in equal concentrations.

Factors affecting the rate of Diffusion: : 

Factors affecting the rate of Diffusion: Concentration gradient; Size of the molecules; Temperature; Solubility; Pressure; Charged or uncharged condition:

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B) Facilitated Diffusion : (Carrier - Mediated Diffusion) Transport of glucose, urea and glycerol is done by facilitated diffusion. For the transport of these molecules, there're channel - like proteins; known as PERMEASES C) Osmosis: Movement of water molecules from a region of high water concentration to a region of low water concentration through a semi - permeable membrane.

ACTIVE TRANSPORT MECHANISM : 

ACTIVE TRANSPORT MECHANISM The movement of materials across a cell membrane requires the expenditure of cellular energy (ATP), the process is called active transport. Active transport usually involves the movement of materials against a concentration gradient. That is, materials move from the area of lower concentration to the area of higher concentration.

BULK TRANSPORT MECHANISMS : 

BULK TRANSPORT MECHANISMS a) ENDOCYTOSIS: A part of the cell membrane forms a sac or vesicle around the particles. The vacoule is released into the cytoplasm. The process requires energy (ATP). i. Phagocytosis (cell eating): For example, white blood cells ingest bacteria. ii. Pinocytosis (cell drinking): For example, cell takes in needed solute dissolved in tissue fluid.

EXOCYTOSIS : 

EXOCYTOSIS b) EXOCYTOSIS: Many substances are exported from cells in vesicles formed by golgi bodies and endoplasmic reticulum. This process is called exocytosis.

Eukaryotic Cell Organelles and Function : 

Eukaryotic Cell Organelles and Function Vacuoles Function: stores water This is what makes lettuce crisp When there is no water, the plant wilts

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Section 7-2 Figure 7-5 Plant and Animal Cells Go to Section: Plant Cell Vacuole Chloroplasts

Eukaryotic Cell Organelles and Function : 

Eukaryotic Cell Organelles and Function Chloroplasts Function: traps energy from the sun to produce food for the plant cell Green in color because of chlorophyll, which is a green pigment

Chloroplasts : 

Chloroplasts

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Section 7-2 Figure 7-5 Plant and Animal Cells Go to Section: Plant Cell Vacuole Chloroplasts Cell Wall

Eukaryotic Cell Organelles and Function : 

Eukaryotic Cell Organelles and Function Cell Wall Function: provides support and protection to the cell membrane Found outside the cell membrane in plant cells

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Plant Cell Vacuole Chloroplasts Cell Wall Nucleolus Nucleus Rough ER Smooth ER Golgi Bodies Mitochondria Ribosomes Cytoplasm

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