Basic Structure of a Cell copyright cmassengale 1
Basic Structure of a Cell copyright cmassengale 1
CELL THEORY • All living things are made of cells • Cells are the basic unit of structure and function in an organism (basic unit of life) • Cells come from the reproduction of existing cells (cell division) 2
Number of Cells Organisms may be: • Unicellular – composed of one cell • Multicellular- composed of many cells that may organize into tissues, etc. copyright cmassengale 3
CELL SIZE Typical cells range from 5 – 50 micrometers (microns) in diameter 4
How Big is a Micron ( µ ) ? 1 cm = 10, 000 microns 1” = 25, 000 microns copyright cmassengale 5
Factors Affecting Cell Size • Surface area = L x W • Volume of a cell = L x W x H • Therefore, Volume increases FASTER than the surface area copyright cmassengale 6
Cell Size • When the surface area is no longer great enough to get rid of all the wastes and to get in enough food and water, then the cell must divide • Therefore, the cells of an organism are close in size copyright cmassengale 7
Cell Size Question: Are the cells in an elephant bigger, smaller, or about the same size as those in a mouse? About the same size, but … The elephant has MANY MORE cells than a mouse! copyright cmassengale 8
Multicellular Organisms • Cells in multicellular organisms often specialize (take on different shapes & functions) copyright cmassengale 9
Cell Specialization • Cells in a multicellular organism become specialized by turning different genes on and off • This is known as DIFFERENTIATION copyright cmassengale 10
Specialized Animal Cells Muscle cells Red blood cells Cheek cells 11
Specialized Plant cells Guard Cells Pollen Xylem cells copyright cmassengale 12
Types of Cells copyright cmassengale 13
Prokaryotes – The first Cells • Cells that lack a nucleus or membrane -bound organelles • Simplest type of cell • Single, circular chromosome • Includes bacteria copyright cmassengale 14
Prokaryotes • Nucleoid region (center) contains the DNA • Surrounded by cell membrane & cell wall (peptidoglycan) • Contain ribosomes (no membrane) in their cytoplasm to make proteins copyright cmassengale 15
Eukaryotes • Cells that HAVE a nucleus and membranebound organelles • More complex type of cells • Includes protists, fungi, plants, and animals copyright cmassengale 16
Eukaryotic Cell Contain 3 basic cell structures: • Nucleus • Cell Membrane • Cytoplasm with organelles copyright cmassengale 17
Organelles copyright cmassengale 18
Organelles • Very small (Microscopic) • Perform various functions for a cell • Found in the cytoplasm • May or may not be membranebound copyright cmassengale 19
Animal Cell Organelles Ribosome (attached) Ribosome (free) Nucleolus Nucleus Cell Membrane Nuclear envelope Mitochondrion Smooth endoplasmic reticulum Rough endoplasmic reticulum Centrioles Golgi apparatus copyright cmassengale 20
Plant Cell Organelles copyright cmassengale 21
1. Plasma Membrane • Composed of a constantly moving, double layer • Surrounds outside of ALL cells • Controls what enters or leaves the cell • We will discuss membranes a LOT after break Outside of cell Proteins Carbohydrate chains Cell membrane Inside of cell (cytoplasm) Protein channelcopyright cmassengale Lipid bilayer 22
2. Cell Wall • Supports and protects cell • Found outside of the cell membrane • In most prokaryotes, plants, and fungi copyright cmassengale 23
3. Cytoplasm of a Cell • Jelly-like substance enclosed by cell membrane • Provides a medium for chemical reactions to take place • Contains organelles to carry out specific jobs • Found in ALL cells cytoplasm 24
4. The Control Organelle - Nucleus • Controls the normal activities of the cell • Contains the DNA in chromosomes • Bounded by a nuclear envelope (membrane) with pores • Usually the largest organelle copyright cmassengale 25
Inside the Nucleus The genetic material (DNA) is found here DNA is spread out And appears as CHROMATIN in non-dividing cells DNA is condensed & wrapped around proteins forming as CHROMOSOMES in dividing cells copyright cmassengale 26
What Does DNA do? DNA is the hereditary material of the cell Genes that make up the DNA molecule code for different proteins copyright cmassengale 27
5. Ribosomes • Made of PROTEINS and r. RNA • “Protein factories” for cell copyright cmassengale 28
Ribosomes Can be attached OR Be free (unattached) in the cytoplasm copyright cmassengale 29
6. Mitochondrion (plural = mitochondria) • “Powerhouse” of the cell • Site of CELLULAR RESPIRATION (burning glucose) that generates cellular energy (ATP) • More active cells like muscle cells have MORE mitochondria • All eukaryotic cells have mitochondria copyright cmassengale 30
MITOCHONDRIA Made of a DOUBLE membrane Inner membrane is highly folded to increase surface area Has its own DNA copyright cmassengale 31
Interesting Fact -- • Mitochondria Come from cytoplasm in the EGG cell during fertilization Therefore … • You inherit your mitochondria from your mother! copyright cmassengale 32
7. Chloroplasts • Found only in producers (organisms containing chlorophyll) • Contains enzymes & pigments for Photosynthesis • Never in animal cells • Bacteria can be photosynthetic, but do not have chloroplasts copyright cmassengale 33
Chloroplasts • Made of a DOUBLE membrane • Inner membrane highly folded to increase surface area • Contains its own DNA copyright cmassengale 34
8. Cytoskeleton • Helps cell maintain cell shape • Also help move organelles around within the cell • Helps move the cell in environment • Made of proteins • Several sizes, like pipes, and copyright cmassengale 35
Cytoskeleton MICROTUBULES MICROFILAMENTS copyright cmassengale 36
Endomembrane System Includes nuclear membrane connected to ER connected to cell membrane as well as Golgi apparatus and vesicles copyright cmassengale 37
9. Endoplasmic Reticulum - ER • Network of hollow membrane tubules • Connects to nuclear envelope & cell membrane • Functions in Synthesis of cell products & Transport Two kinds of ER ---ROUGH & SMOOTH copyright cmassengale 38
9 a. Rough Endoplasmic Reticulum (Rough ER) • Has ribosomes on its surface • Makes membrane proteins and proteins for EXPORT out of cell copyright cmassengale 39
9 b. Smooth Endoplasmic Reticulum • NO ribosomes on its surface • Is attached to rough ER • Makes cell products that are USED INSIDE the cell, especially membrane pieces for organelles copyright cmassengale 40
10. Golgi Apparatus • Stacks of flattened membrane sacs • Receive products from ER on receiving side (cis face) • Vesicles with modified proteins pinch off the ends of shipping side (trans face) CIS TRANS Vesicle 41
Golgi Apparatus Modify, sort, & package molecules from ER for storage OR transport out of cell copyright cmassengale 42
11. Vesicles • Membrane sacs designed to transport materials • Pinch or bud off other membranes • At destination, fuse with other membranes copyright cmassengale 43
12. Vacuoles • Fluid filled sacks for storage • Small or absent in animal cells • Plant cells have a large Central Vacuole • No vacuoles in bacterial cells copyright cmassengale 44
12 a. Central Vacuoles • In plants, they store Cell Sap • Includes storage of sugars, proteins, minerals, lipids, wastes, salts, water, and enzymes copyright cmassengale 45
12 b. Contractile Vacuole • Found in unicellular protists like paramecia • Regulate water intake by pumping out excess • Keeps the cell from lysing (bursting) copyright cmassengale 46
13. Lysosomes • Contain digestive enzymes • Fuse with vesicles to break down food, bacteria, and worn out cell parts for cells • Programmed for cell death (AUTOLYSIS) 47
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