Section 8.1 Life is Cellular

Standard

• LS1.1 Compare and contrast existing models, identify patterns, and use structural and functional evidence to analyze the characteristics of life. Engage in argument about the designation of viruses as non-living based on these characteristics.

• LS1.2 Evaluate comparative models of various cell types with a focus on organic molecules that make up cellular structures.

I can…

• LS 1.2 I can develop comparative models of major cell types (prokaryotic and eukaryotic).

Key Questions

1. What are the main points of the cell theory?

2. How do microscopes work?

3. How do prokaryotic and eukaryotic cells differ?

Vocabulary

• Cell

• Cell theory

• Cell membrane

• Nucleus

• Eukaryote

• Prokaryote

The Discovery of the Cell

• The smallest living unit of any organism is a cell.

• 1500s in Europe- eyeglass makers combined several glass lenses to magnify small objects • They had built the first true microscopes

The Discovery of the Cell

• 1665 in England- Robert Hooke used an early microscope to look at a nonliving thin slice of cork, a plant material

• saw thousands of tiny empty chambers

• Called the chambers “cells”

The Discovery of the Cell

• ~1665 in Holland- Anton van Leeuwenhoek used a single-lens microscope to observe pond water• saw tiny living organisms

• 1838 in Germany- botanist Matthias Schleiden concluded all plants are made of cells

• 1839 in Germany- biologist Theodor Schwann concluded all animals are made of cells

• 1855 in Germany- physician Rudolph Virchow concluded that new cells are produced only from the division of existing cells

The Cell Theory

1. All living things are made up of cells.

2. Cells are the basic units of structure and function in living things.

3. New cells are produced from existing cells.

Compound Light Microscope

• Allows light to pass through a specimen and used two lenses to form an image

• Light limits the resolution (because light waves are scattered as they pass through)

• Produce clear images of objects only to 1000x magnification

1. Objective lens• Located just above the specimen

• Enlarges the image of the specimen

2. Ocular lens• Magnifies the image still further

Compound Light Microscope

Compound Light Microscope

• Most living cells are nearly transparent.

• Chemical stains or dyes are used to make cells and their parts visible.

• Fluorescent labels can be attached to certain molecules within a cell. Dyed Skin Cells

Electron Microscopes

• Use beams of electrons focused by magnetic fields

• Offer much higher resolution than light microscopes

• Can be used to study cell structure that are one billionth of a meter

• Samples must be placed in a vacuum

• Researchers must chemically preserve their samples

• Used only to examine nonlivingcells and tissues

Transmission Electron Microscope (TEM)

• Explore cell structures and large protein molecules

• Beams of electrons pass throughthin samples

• Samples must be cut into extremely thin slices

• Images often appear flat and 2D

Scanning Electron Microscope (SEM)

• Pencil-like beam of electrons is scanned over the surface of a specimen

• Samples do not need to be cut into thin slices

• Produce 3D images of the surface

SEM showing neurons (nerve cells)

Yeast Cell micrographs from different microscopes

Cell Size

Typical cells range from 5-50 micrometers.

Cells

• ALL cells, at some point in their lives, contain DNA.

• ALL cells are surrounded by a thin flexible barrier called a cell membrane.

• Cells fall into two main categories, depending on whether or not they contain a nucleus- large membrane-enclosed structure that contains genetic material in the form of DNA.

PROKARYOTIC CELLS

• No nucleus

• No membrane-bound organelles

• Generally smaller and simpler

• Ex. Bacteria

EUKARYOTIC CELLS

• Nucleus

• Membrane-bound organelles

• Generally larger and more complex

• Highly specialized

• Ex. Plants, animals, protists, fungi

Section 8.1 Exit Ticket

1. What is a cell? What are its components?

2. What are the differences between a prokaryotic cell and eukaryotic cell?

The End ☺