The History of the Cell Theory(click)

The Path to the Cell Theory

1500’sFirst magnifying lenses used in Europe to look at the quality of cloth

1665Robert Hooke – used a microscope to look at a thin slice of cork (bark from an oak

tree) and saw what looked like small boxes - First to name them cells (because they looked like the small rooms that monks lived

in called “cells”)

Advancements in Cell Biology and Imaging Quality

1838Matthias Schleiden – concluded that all plants were made of cells

Cofounders of the Cell Theory

Rudolf Vichow –Cells come from pre-existing cells.

1858

The Basic Cell Theory

• All living things are composed of cells. • Cells are the basic units of structure and function in living things. • New cells are produced from existing cells.

Discoveries since the Cell Theory

• 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

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Modern Cell Theory

• With advancements and more studies in science the following additions have been added onto the Cell Theory:

• Energy Flow occurs within cells. • Metabolism

• Cells contain hereditary information that is passed on from cell to cell during cell division

• DNA• All cells are basically the same in chemical composition in organisms of similar

species.

The Cell Membrane:

• “Skin” that surrounds cell• Selectively permeable• Phospholipid bilayer• Many cell organelles have membrane

Cytoplasm (Cytosol)• The liquid inside the cell• Helps to support cell

structures• Provide protective buffer

Cytoskeleton

• gives a cell shape• holds organelles inplace• Lets cell move in space by

contracting and expanding (microfilaments made of protein actin).

• Holds organelles in place and anchor nucleus (intermediate filaments)

Mitochondrion• The “powerhouse” of the cell• Double-membrane• Has its own DNA and ribosomes• Use chemical energy from

primarily sugar to make the energy for the cell to do various metabolic tasks.

• The main molecule that provides chemical energy is adenosine tri-phosphate (ATP).

NUCLEUS• The control center of cell• Source of genetic information• Instructions for protein

production which controls cell functioning.

• Almost always near center of cell.

NUCLEOLUS

• Dark area in center of nucleus• Makes materials for ribosomes• Defective nucleoli evident in

Parkinson’s and Huntington’s diseases.

Endoplasmic reticulum

• Attached to the nucleus by its membranes.

• Two parts: the smooth endoplasmic reticulum (SER) and the rough endoplasmic reticulum (RER).

• SER releases lipids, such as hormones, that are used both in the cell and in other cells.

• RER looks rough because it is studded with ribosomes and functions in making proteins.

Golgi Apparatus

• Modifies proteins by adding signaling sugars onto surface of protein.

• Unmodified protein arrives at Golgi inside a transport vesicle.

• Fuses with Golgi and is modified as it travels through Golgi

• Golgi membrane pinches off with modified protein inside.

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Golgi Apparatus

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Golgi Animation

Materials are transported from Rough ER to Golgi to the cell membrane by VESICLES

Protein Targeting & Disease

• Different types of proteins are housed in different parts of the cell where they can carry out their specific functions.

• Other proteins are secreted. • If proteins end up in the wrong

place or don’t get to the right place this can lead to abnormal cell function and/or serious diseases.

Perioxisomes

• Vesicles that contain oxidative enzymes

• Breaks down fatty acids, some amino acids, and toxic hydrogen peroxide.

• Look similar to lysosomes but bigger

• Found near mitochondria and chloroplasts while lysosomes can be found anywhere in the cell.

Found in many Animal Cells - Centrioles• Organize the spindle during cell

division. • Consist of 9 groups of

microtubules; each group has three microtubules.

• Therefore there are 27 microtubules in one centriole.

• Centrioles are always arranged perpendicular to each other.

Found in many Animal Cells -Flagella

• 9 + 2 arrangement of microtubules

• Used for cell movement

Found in many Animal Cells -Cilia

• Similar in structure to the flagella, but they tend to be shorter

• 9 + 2 arrangement of microtubules• Found in groups on the cell surface. • In single-celled organisms, they are

used to move the cell. • In the human body, used to move

substances across the cell surface (e.g. cilia can be found on cells lining the trachea. These cells help to move mucus and trapped particles away from the lungs.

Found in animal cells - Lysosomes

• Recycling centers of cell. • Contain hydrolytic enzymes which break

nutrient particles into smaller pieces so that other organelles can use these fragments as a source of energy.

• They destroy bacteria and organic debris that enter cell from extracellular fluid.

• Break down damaged organelles, freeing components for re-use.

• Rarely found in plant cells because the central vacuole fulfills the recycling function in plant cells.

Found only in plant cells: Cell wall

• Surrounds the outside of a plant’s cell membrane

• Attaches cells to neighboring cells. • The wall is made of a rigid

polysaccharide called cellulose • Gives plant cells shape and structure . • It prevents cell from bursting when too

much water is available (e.g. rainy seasons).

• Turgor pressure is pressure that water puts on cell wall

Chloroplast

• Contains the molecule chlorophyll.

• Traps light energy for the plant and converts it to chemical energy (sugar).

Found only in plant cells: Central Vacuole• Found near the middle of the

cell. • Stores water and other materials

in these storage tanks, keeping them separate from cytosol.

• Central vacuoles perform the same functions as lysosomes, breaking down nutrients and organelles into usable energy components