Chapter 7: Chapter 7: Cell Structure Cell Structure and Functionand Function

7-1: Life is Cellular• The Discovery of the Cell

– Robert Hooke coins the term “cell” to describe sections of cork that he sees through his microscope in 1665.

Left: Hooke’s cork cells

Right: cork cells by electron microscope

7-1: Life is Cellular

Around the same time Anton van Leeuwenhoek finds “animacules” in pond water.

7-1: Life is Cellular

This leads to the Cell Theory:1. All living things are composed of cells.

2. Cells are the basic unit of living things.

3. New cells are produced from existing cells.

7-1: Life is Cellular

• Cells come in all shapes and sizes– a typical cell is 5-50 micrometers in diameter– smallest cells (bacteria) are 0.2 micrometers across– Biggest cells (ex: amoeba) can be 1000 micrometers

across – visible with the naked eye Diatom Amoeba

Check out this interactive to get an idea of the scale of cells…

• http://learn.genetics.utah.edu/content/begin/cells/scale/

How big is an e-coli bacteria?

Which is bigger the influenza virus or hepatitis?

7-1: Life is Cellular

Two Broad Categories of Cells

• Prokaryotes and

Eukaryotes– Greek roots

• “pro-” means first or before• “eu-” means true• “-karyon” means kernel

– Both types have cell membranes and DNA– Prokaryotes are much smaller than eukaryotes– Prokaryotes vastly outnumber eukaryotes

White Blood Cell attacking Bacteria

7-1: Life is Cellular

Prokaryotes• No nucleus

(DNA is free-floating in the cytoplasm)

• Bacteria are

prokaryotes

Streptococcus bacteria

7-1: Life is Cellular

Eukaryotes• Contains nucleus

(DNA is contained within the nucleus)

• Single-celled organisms and all multicellular organisms

• Often perform specific functions

White blood cell among red blood cells

7-2: Eukaryotic Cell Structure

• How is a cell like a factory?– Organelles perform specific, repetitive tasks

• “Organelles” means little organs

Organelles inside a cell

7-2: Eukaryotic Cell Structure

Nucleus– Contains DNA (instructions for making

proteins)– Control center for cellular activities– Nuclear anatomy

• Nuclear envelope (porous)• Chromatin (DNA attached to proteins)

– Chromatin becomes chromosomes during cell division

Muscle cells: Nuclei are

stained purple.

7-2: Eukaryotic Cell Structure

Ribosomes– Made of RNA and proteins– Ribosomes make proteins (important!)

• Use amino

acids to make

chains that form

proteins

7-2: Eukaryotic Cell Structure

Endoplasmic Reticulum– Lipid components of cell membrane and

proteins that get exported from the cell are made on the endoplasmic reticulum

– Two types of ER• Smooth ER – synthesis of membrane lipids and

detoxification of drugs• Rough ER

– Called “rough” because of ribosomes on surface– proteins bound for export are chemically modified

7-2: Eukaryotic Cell Structure

Golgi Apparatus (AKA Golgi Body)

– It’s a stack of membranes (like pancakes)– Final touches on proteins after they leave the

endoplasmic reticulum, before they leave the cell– Lysosomes are made by the Golgi apparatus

7-2: Eukaryotic Cell Structure

Protein

Synthesis

7-2: Eukaryotic Cell Structure

Lysosomes– Made by the

Golgi apparatus– Contain

digestive

enzymes –

garbage men

of the cell

7-2: Eukaryotic Cell Structure

Vacuoles– Saclike structures that store materials like

water, salts, proteins, and carbohydrates– Prominent feature of plant cells

7-2: Eukaryotic Cell Structure

Mitochondria– Power HousePower House of the cell

– Energy from glucose is converted into energy that organelles can use

– Inherited from your mother

7-2: Eukaryotic Cell Structure

Chloroplasts– Organelles of photosynthesis (found in plants

and other photosynthetic organisms)– Contain green pigment, called chlorophyll

7-2: Eukaryotic Cell Structure

Organelle DNA– Mitochondria and Chloroplasts have their own DNA!?

American biologist Lynn Margulis has suggested that these organelles are descendants of ancient, independent prokaryotes. The ancestors of modern-day eukaryotes may have developed symbiotic relationships with such prokaryotes millions of years ago.

Mitochondrion Prokaryote

Endosymbiotic theory

7-2: Eukaryotic Cell Structure

Cytoskeleton– A network of protein filaments that help to

support eukaryotic cells (also help some cells to move)

– Composed primarily

of microfilaments and

microtubules

Microfilaments in red Microtubules in

green