Basic Structure of a Cell 1 History of

Basic Structure of a Cell 1

History of Cells & the Cell Theory Cell Specialization 2

First to View Cells • In 1665, Robert Hooke • used a microscope to examine a thin slice of cork (dead plant cell walls) • What he saw looked like small boxes • Coined the term “cell” 3

Anton van Leeuwenhoek • In 1673, Leeuwenhoek (a Dutch microscope maker), was first to view organism (living things) • Leeuwenhoek used a simple, handheld microscope to view pond water & scrapings from his teeth 4

Beginning of the Cell Theory • In 1838, a German botanist named Matthias Schleiden • Studied plants • concluded that all plants were made of cells • Schleiden is a cofounder of the cell theory 5

Beginning of the Cell Theory • In 1839, a German zoologist named Theodore Schwann • Studied animals • concluded that all animals were made of cells • Schwann also cofounder of the cell theory 6

Beginning of the Cell Theory • In 1855, a German medical doctor named Rudolph Virchow observed, • Studied human diseases • Looked at cells dividing • He reasoned that all cells come from other pre-existing cells by cell division 7

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) 8

Discoveries Since the Cell Theory 9

ENDOSYMBIOTIC THEORY • In 1970, American biologist, Lynn Margulis, provided evidence that some organelles within cells were at one time free living cells themselves • Supporting evidence included organelles with their own DNA • Chloroplast and Mitochondria 10

Cell Size and Types • Cells, the basic units of organisms, can only be observed under microscope • Three Basic types of cells include: Animal Cell Plant Cell Bacterial Cell 11

Number of Cells Although ALL living things are made of cells, organisms may be: • Unicellular – composed of one cell • Multicellular- composed of many cells that may organize into tissues, etc. 12

Which Cell Type is Larger? Plant cell > _______ Animal cell > ______ bacteria _____ 13

CELL SIZE Typical cells range from 5 – 50 micrometers (microns) in diameter 14

How Big is a Micron ( µ ) ? 1 cm = 10, 000 microns 1” = 25, 000 microns 15

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! 16

Cells • Smallest unit that can carry out all the processes of life. • Why are cells so small? – Cells are small because a large surfaceto-volume ratio allows them to easily exchange food and wastes. 17

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 18

Simple or Complex Cells 19

Cells • All cells have at least 3 components in common. – Plasma (or cell) membrane – Genetic material (DNA) – Cytoplasm – Nucleus (only eukaryotes) 20

Prokaryotes – The first Cells • • • No nucleus No membrane-bound organelles DNA is not located in the nucleus DNA is circular Includes bacteria Simplest type of cell 21

Eukaryotes • Unicellular or multicellular • HAS a nucleus • HAS membrane-bound organelles • DNA located in nucleus • DNA is linear-double helix • Includes protists, fungi, plants, and animals • More complex type of cells 22

Two Main Types of Eukaryotic Cells Plant Cell Animal Cell 23

CELL MEMBRANE SEE HOW MEMBRANES FORM (also called plasma membrane) PHOSPHOLIPID BILAYER with PROTEINS Hydrophobic tails face in Hydrophilic heads face out • Composed of double layer of phospholipids and proteins • Surrounds outside of ALL cells • Controls what enters or leaves the cell(selectively permeable) • Living layer Outside of cell Carbohydrate chains Proteins Cell membrane Inside of cell (cytoplasm) Protein channel Lipid bilayer Membrane Image from: © Pearson Education Inc, Publishing as Pearson Prentice Hall; All rights reserved Phospholipid image from: http: //bioweb. wku. edu/courses/BIOL 115/Wyatt/Biochem/Lipid/P_lipid 2. htm

Cell Membrane in Plants Cell membrane • Lies immediately against the cell wall in plant cells • Pushes out against the cell wall to maintain cell shape 25

FLUID MOSAIC MODEL Click here to See Fluidity Molecules in cell membranes are constantly moving and changing Animation from: http: //www. sp. uconn. edu/~terry/images/anim/fluidmem. gif

CELL MEMBRANES • act as boundary • selectively permeable http: //vilenski. org/science/safari/cellstructure/cellmembrane. html ~ gases & hydrophobic molecules can pass through http: //www. d. umn. edu/~sdowning/Membranes/membrane. Images/jpegimages/diffusionmedium. jpg

Look at the organelles in your packet and choose 2 that you know. Star them. Write down a word or two about their function. *Give One Get One copyright cmassengale 28

Organelles: What you should know 29

Organelles • Very small (Microscopic) • Perform various functions for a cell • Found in the cytoplasm • May or may not be membranebound 30

Animal Cell Organelles Nucleolus Nuclear envelope Rough endoplasmic reticulum Golgi apparatus Ribosome (attached) Ribosome (free) Cell Membrane Mitochondrion Smooth endoplasmic reticulum Centrioles 31

Plant Cell Organelles 32

Image from: http: //faculty. stcc. tn. us/jiwilliams/labprojectsmenu. htm CYTOPLASM (Between nucleus and cell membrane) • Jelly-like substance enclosed by cell membrane • Provides a medium for chemical reactions to take place • Helps give cell its shape • Includes organelles that carry out specific functions • Includes water, salt, organic molecules, and organelles • Found in ALL cells CYTOSOL-semi-fluid “goo” Image from: http: //vilenski. org/science/safari/cellstructure/cytoplasm. html

The Control Organelle – Nucleus (Brain) • Surrounded by DOUBLE membrane called a (Nuclear envelope) • Nuclear pores-allow molecules in & out • Controls the normal activities in the cell • Contains the DNA in chromosomes • Usually the largest organelle • “Brain or Boss” • Control center for two processes: Replication (DNA → DNA) Transcription (DNA → RNA) 34

Inside the Nucleus The genetic material (DNA) is found DNA is spread out And appears as CHROMATIN in non-dividing cells DNA is condensed & wrapped around proteins forming as CHROMOSOMES in dividing cells 35

What Does DNA do? DNA is the hereditary material of the cell Genes that make up the DNA molecule code for different proteins, those proteins make us who we are- brown hair, etc. 36

NUCLEOLUS Dark spot in nucleus • Produces ribosomal RNA • Assembles ribosomes (RNA & proteins) • Image from: http: //lifesci. rutgers. edu/~babiarz/histo/cell/nuc 3 L. jpg http: //universe-review. ca/I 09 -08 -RNA. gif

Nuclear Envelope • Double membrane surrounding nucleus • Also called nuclear membrane • Contains nuclear pores for materials to enter & leave nucleus • Connected to the rough ER Nuclear pores 38

Cytoskeleton • Helps cell maintain cell shape • Anchors organelles • Made of proteins • Microfilaments are threadlike & made of ACTIN • Microtubules are tubelike & made of TUBULIN 39

Centrioles • Found only in animal cells • Paired structures near nucleus • Made of bundle of microtubules • Appear during cell division forming mitotic spindle • Help to pull chromosome pairs apart to opposite ends of the cell 40

CENTRIOLES/MITOTIC SPINDLE Made of MICROTUBULES (Tubulin) Image from: http: //www. coleharbourhigh. ednet. ns. ca/library/organelle_worksheet. htm

Mitochondrion (plural = mitochondria) • “Powerhouse” of the cell • Generate cellular energy (ATP) • More active cells like muscle cells have MORE mitochondria • Both plants & animal cells have mitochondria • Site of CELLULAR RESPIRATION (burning glucose) 42

MITOCHONDRIA Surrounded by a DOUBLE membrane Has its own DNA Folded inner membrane called CRISTAE (increases surface area for more chemical Reactions) Interior called MATRIX 43

Interesting Fact -- • Mitochondria Come from cytoplasm in the EGG cell during fertilization Therefore … • You inherit your mitochondria from your mother! 44

What do mitochondria do? “Power plant” of the cell Burns glucose to release energy (ATP) Stores energy as ATP 45

Endoplasmic Reticulum – ER (Roadways) • Network of hollow membrane tubules • Helps to move materials throughout the cell • Connects to nuclear envelope & cell membrane • Functions in Synthesis of cell products & Transport Two kinds of ER ---ROUGH & SMOOTH 46

Rough Endoplasmic Reticulum (Rough ER) • Has ribosomes on its surface • Makes products for use outside of the cell • Proteins are made by ribosomes on ER surface • They are then threaded into the interior of the Rough ER to be modified and transported 47

Smooth Endoplasmic Reticulum • Smooth ER lacks ribosomes on its surface • Is attached to the ends of rough ER • Makes cell products that are USED INSIDE the cell • Makes membrane lipids (steroids) • Regulates calcium (muscle cells) • Destroys toxic substances (Liver) 48

Endomembrane System Includes nuclear membrane connected to ER connected to cell membrane (transport) 49

Ribosomes • Made of PROTEINS and r. RNA • “Protein factories” for cell • Join amino acids to make proteins • Process called protein synthesis 50

Ribosomes Can be attached to Rough ER OR Be free (unattached) in the cytoplasm 51

Golgi Bodies/Apparatus/Complex • Stacks of flattened sacs • Have a shipping side (trans face) and receiving side (cis face) • Receive proteins made by ER • Transport vesicles with modified proteins pinch off the ends CIS TRANS Transport vesicle 52

Golgi Bodies Look like a stack of pancakes “UPS” of cell Modify, sort, & package molecules from ER for storage OR transport out of cell 53

Golgi Animation Materials are transported from Rough ER to Golgi to the cell membrane by VESICLES Animation from: http: //www. franklincollege. edu/bioweb/A&Pfiles/week 04. html See a Golgi movie

EVERYTHING’S CONNNECTED!

Lysosomes - membrane-bound vesicles containing digestive enzymes Breaks down • food • unwanted cell parts • bacteria • helps in APOPTOSIS “programmed cell death” See lysosomes in action:

“PROGRAMMED CELL DEATH” APOPTOSIS Embryo development Cell maintenance Signal to self destruct lost in cancer cells http: //www. mgm. ufl. edu/images/bharfe/image 3. jpg http: //research. yale. edu/ysm/images/78. 3/articles-apoptosis-cells. jpg

Cilia & Flagella • Made of protein tubes called microtubules • Function in moving cells, in moving fluids, or in small particles across the cell surface • Cilia are shorter and more numerous on cells • Flagella are longer and fewer (usually 1 -3) on cells 58

What’s the Difference Cilia- Many and short Flagella- Few and long 59

Vacuoles • Fluid filled sacks for storage • Small or absent in animal cells • Plant cells have a large Central Vacuole • No vacuoles in bacterial cells • In plants, they store Cell Sap • Includes storage of sugars, proteins, minerals, lipids, wastes, salts, water, and enzymes 60

VACUOLES can store WATER http: //www. biology 4 kids. com/files/cell_vacuole. html

Freshwater organisms have contractile vacuoles to control excess water in cells (HOMEOSTASIS) http: //www. microscopy-uk. org. uk/mag/imgjun 99/vidjun 1. gif

Chloroplasts • Found only in producers (organisms containing chlorophyll) • Use energy from sunlight to make own food (glucose) • Has own DNA • Double Membrane • Contains thylakoid sacs with chlorophyll for photosynthesis • Never in animal or bacterial cells 63

WHAT’S SPECIAL ABOUT PLANT CELLS? • • Cell wall HUGE vacuoles Chloroplasts No centrioles

Cell Wall • Nonliving layer • A rigid layer that lies outside of the cell membrane • Supports and protects cell • • Found in plants, fungi, & bacteria Plants: Cellulose makes it “sturdy” Bacteria: have peptidoglycan Made of chitin in Fungi Cell wall 65

WHAT’S DIFFERENT ABOUT BACTERIAL CELLS? • Cell wall • NO NUCLEAR MEMBRANE • DNA is circular • No membrane bound organelles http: //www. eurekascience. com/ICan. Do. That/bacteria_cells. htm

WHICH IS BIGGER? Plant cell Animal cell bacteria _________ > ___________

DIFFERENCES IN ANIMAL CELLS, PLANT CELLS, AND BACTERIA ANIMAL CELL PLANT CELL BACTERIA Eukaryotes Prokaryotes Cell membrane Nuclear membrane NO cell wall Cell wall made of CELLULOSE Cell wall made of PEPTIDOGLYCAN Has ribosomes DNA in multiple chromosomes DNA is a single circular ring CYTOSKELETON Small vacuoles Really big vacuole NO vacuoles Has lysosomes Few lysosomes NO lysosomes Has centrioles NO chloroplasts Chloroplasts NO chloroplasts SMALLER size SMALLEST size NO nuclear membrane

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