Science Fair Announcements

Semester 1:Assessed items (i.e. where an A is earned)

1. Background research paper (Due Jan 6th )

2. Final/Formal Lab Report (Due Jan. 20th)

Includes a short classroom presentation on results.

Semester 2:Assessed items (i.e. where an A is earned)

1. Tri-fold board (due Feb 14th)

2. Presence at Science Fair (evening, Feb. 22nd)

What do you know about cells?

• On the “Cell Structure and Function” handout provided fill out each of the boxes in the What I Know column – These answers should be based on what you

have learned in previous classes

Introduction to Cells

7.1 Life is Cellular

• Discovering the Cell:• It was not until the invention

of the microscope that cells were discovered

• Robert Hooke used an early compound microscope to examine cork– Noticed that there were empty

“rooms” that he called cells

Cell History• Anton van Leeuwenhoek

observed pond water• Matthias Schleiden said all

plants are made of cells• Theodor Schwann said all

animals are made of cells• Rudolf Virchow said that

new cells can only be made from the division of existing cells

Cell Theory

• The cell theory states that:– All living things are made

up of cells– Cells are the basic units

of structure and function in living things

– New cells are produced from existing cells

Exploring the Cell: Microscopes

• Most microscopes use lenses to magnify the image of an object by focusing light or electrons

• Light microscopes– The type used in our yeast lab is called a

compound light microscope– Light typically passes through specimen and

two lenses– Limited to magnification of up to 1000 times

Light Microscope

Microscopes continued

• Another problem with light microscopes is the most tissues are transparent

• Staining and dyes are used to see cells clearer– In some cases these are

used to track molecules as they are made

Microscopes continued

• Electron Microscopes:– Allows scientist to view things smaller than 1

millionth of a meter– Use beams of electrons that are focused by

magnetic fields– Two major types: transmission and scanning– Can only be used on nonliving cells and tissues– “false color” often added to electron

micrographs

Electron micrograph examples

Cell characteristics

• Despite the variety seen in cell shape and size- all cells at some point in their lives contain DNA

• All cells are surrounded by a cell membrane which is a thin flexible barrier

• Cells can be categorized based on the presence of the nucleus– Nucleus: large membrane enclosed structure that

contains genetic material in the form of DNA and controls many of the cells activities

Prokaryotes and Eukaryotes• Eukaryotes are cells that enclose their

DNA in nuclei• Prokaryotes are cells that do not separate

their genetic material within a nucleus– Generally smaller and simpler– Bacteria are prokaryotes

7.2 Cell Structure• Regular patterns in eukaryotic cells• Two major parts: nucleus and cytoplasm

– Cytoplasm: portion of cell outside of nucleus– Prokaryotes have a cytoplasm, but no nucleus

• There are many parts to this cell factory– The structures are called organelles because

they act like specialized organs

Cell as a factory

• Different organelles can be compared to the machines and assembly lines of a factory

The Nucleus

• Main office/ control center of factory

• The nucleus contains nearly all the cell’s DNA and, with it, the coded instructions for making proteins and other important molecules

• Surrounded by a nuclear envelope made of 2 membranes

• Chromosomes• Nucleolus

Organelles that store, clean up and support

• Many cells contain large, saclike, membrane enclosed structures called vacuoles– Vacuoles store materials

like water, salts, proteins and carbohydrates

– In plants, vacuole is filled to increase rigidity

Organelles that store, clean up and support

• Almost all eukaryotic cells contain smaller membrane enclosed structures called vesicles– These transport materials

between organelles and to and from the cell surface

Organelles that store, clean up and support

• Lysosomes break down lipids, carbs and proteins into smaller pieces that the rest of the cell can use– Also break down old

organelles– Small organelles filled with

enzymes

Organelles that store, clean up and support

• The cytoskeleton is a network of protein filaments that helps the cell maintain its shape and is involved in movement– Acts like conveyor belts

to transport materials– Microfilaments and

microtubules

Microfilaments and Microtubules

• Microfilaments are threadlike structures made up of actin protein– Form extensive networks

for support– Help cell move

Microfilaments and Microtubules

• Microtubules are hollow structures made up of tubulin proteins– Maintain cell shape– Form mitotic spindle– Help build projections of cell

surface called cilia and flagella

– Centrioles are also made of tubulin and are located near the nucleus to help organize cell division (in animal cells only)

Organisms that build proteins

• Proteins are assembled on ribosomes• Proteins that are made on rough

endoplasmic reticulum are transported around and out of cell

• Golgi apparatus modifies, sorts and packages proteins and other materials from the endoplasmic reticulum for storage or to be released from the cell

Questions?