Discovery of cells Cells 1st discovered

in 1665 by Robert Hooke

Viewed dead cork cells with simple light microscope

Discovery of cells 1st live cells seen

by Anton van Leeuwenhoek

Cell Theory About 150 years

after 1st observations, scientists developed cell theory

Three parts of the theory:

1) All living things are composed of one or more cells

2) Cells are the basic units of structure and function in an organism

3) Cells come only from the reproduction of existing cells

Cell Diversity Size

Lots of variation in size; from bacteria to eggs. Some giraffe nerve cells can be 6.5 feet long!

However, most are microscopic

Cell Diversity Although there is

variation, most cells are microscopic

Cells are limited by their surface area to volume ratio

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Cell Diversity Shape

Shapes of cells vary according to their function

“form follows function”

Cell Diversity Shape

Shapes of cells vary according to their function

“form follows function

Internal Organization Internal structures of

cells are called organelles

Organelles perform specific functions of the cells

Two types of cells Prokaryotes

(bacteria) lack membrane bound organelles

Eukaryotes have membrane bound organelles

We will only study eukaryotes in this course(ZOO ONLY)

Organelles

Cell membrane Membrane must

regulate what wastes and nutrients leave or enter the cell

Because of this the membrane is said to be selectively permeable

Organelles Structure

Made of a bilayer of lipids and proteins

Proteins and lipids move, creating a fluid mosaic

Composition of membrane varies according to cell function

Organelles Cytoplasm

Located between cell membrane and nucleus

Jelly-like substance in which other organelles are located

Organelles Mitochondria

Large organelles located in cytoplasm

Manufactures ATP

Organelles Mitochondria

Have double membrane

Have own DNA Has lead scientists to

believe that mitochondria evolved as symbionts with another cell

Organelles Ribosomes

Most numerous organelle in the cytoplasm

No membrane. They consist of proteins and RNA.

Important in production of proteins in the cell.

Organelles

Ribosomes 2 kinds

Those in cytoplasm produce proteins used in the cytoplasm. They are “free floating” in the cytoplasm

Those attached to the endoplasmic reticulum produce proteins for the membrane and those to be exported from the cell

Organelles Endoplasmic

Reticulum (ER) Made up of

membranous tubules and sacs.

Cellular highway for molecules to move from one area of the cell to another

Organelles Endoplasmic

reticulum Rough ER--dotted

with ribosomes. Lot of rough ER in cells that produce proteins to be exported from the cell or inserted into the membrane

Organelles Endoplasmic reticulum

Smooth ER--not covered with ribsomes

Responsible for synthesis of steriods in glands, regulation of calcium in muscles, and breaking down of toxins in liver

Organelles Golgi apparatus--

Processing, packaging, secreting organelle of the cell. Like ER, is a network of membranes

Organelles Lysosomes--

Small spherical organelles that enclose certain enzymes within membranes (digestive and breaking down types)

Organelles Cytoskeleton

Network of long protein strands in the cell.

Provide the cell with support and structure

Move organelles around the cell

Organelles Cilia

Hair like organelles that extend from cell surface

Assist in cellular movement

Ex: moving unicellular organisms through water

Lining respiratory tract to move particles to throat for swallowing

Organelles Flagella

Similar to cilia, though fewer in number

Propel cells though solution

Made of microtubules similar to those of the cytoskeleton

Organelles Nucleus

Contains genetic material of the cell and directs most of it’s activity

Organelles Nucleus

Nuclear matrix--similar to cytoskeleton

Double membrane--called nuclear envelope

Chromatin--fine strands of DNA and protein

Organelles Nucleus

Chromosomes--chromatin that coils and packs densely prior to reproduction

Site where DNA is copied into RNA. RNA is exported from nucleus and made into proteins

Organelles Nucleus

Has at least one spherical area called nucleolus. This area synthesizes and partially assembles ribosomes.

Multicellular Organization--tissues In most multicellular

organisms, cells combine to form tissues

Tissue-group of cells that carries out a specific function

Tissue Examples Epithelial tissue--

closely packed cells that cover the surface of things such as skin or lining of the nose

Tissue examples Connective tissue--

loosely scattered arrangement of cells that serves to support and link together other tissues.

Multicellular organization--organs Organs--several types

of tissues that interact to perform a specific function

Example-stomach. Made up of

epithelial tissue(lining) Muscle tissue

(movement) Connective tissue (holds

it all together) All work toward one

function; digestion

Multicellular organization: organ systems Organ systems-

groups of organs that carry out a set of related tasks Example: stomach is

part of the digestive systems which also includes the mouth, esophagus, small and large intestines, and other organs.

Evolution of multicellularity Fossil evidence suggests

that the first life on Earth was unicellular, prokaryotic organisms similar to bacteria

Eukaryotes though to have evolved through symbiosis with prokaryotes (mitochondria have their own DNA and membranes--they could have originally been symbionts inside another cell!)

Evolution of Multicellularity Eventually some

unicellular organisms started to live together in colonies. Over time, certain cells began to specialize in certain functions. Eventually, this lead to the development of tissues

What to know for quiz Cell theory Why cells are small Organelles and their

function Multicellular

organization Evolution of

multicellularity