If all living things need water to survive… Why do you think the runner reacted so negatively when given water during her marathon?

7.1 Life is Cellular The key to how organisms live and function is found in cells. Let’s see what you remember or already know about cells…

Pre-Test … What do you know? The smallest unit considered “alive” is… T / F: All cells contain genetic material called DNA DNA is found in this centralized structure within a cell called the ______________ All cells are surrounded by a thin, flexible barrier called __________________________ Scientists didn’t know about cells until (THIS) was invented in the late 1500’s.

6. T / F: All cells have the same basic structure and function 7 6. T / F: All cells have the same basic structure and function 7. T / F: Most plants and animals are multi-cellular (made of many cells) 8. An example of a unicellular (one-celled) organism is _________________.

Pre-Test Answers Anyone get 100% ? A cell True Nucleus Cell membrane Microscope False Bacteria Anyone get 100% ?

CELLS The building blocks of living things Some organisms are made of 1 cell Unicellular (bacteria) Some organisms are made of many cells Multi-cellular (plants, animals)

Discovery of the Cell Invention of microscope led to discovery of cells! 1665 – Robert Hooke, Englishman – used microscope to observe piece of cork Made of many tiny compartments, like rooms in a monastery called “cells” Anton van Leeuwenhoek - using a microscope, found organisms in pond water, drinking water, and even his mouth

Types of Microscopes (p.192) Light microscopes – can see cells and cell structures – use stains Can be magnified up to 500x Electron microscopes (2 types) Scanning electron microscope – produces dramatic 3D images - Have 3750x magnification 2. Transmission electron microscope – samples are cut in thin slices, making a flat 2D image - Have 4375x magnification

Transmission Electron Microscope (TEM) Light Microscope Transmission Electron Microscope (TEM) Scanning Electron Microscope (SEM) Light microscopes use stains to add color to cells Electron microscopes use the computer to add color

What do all cells have in common? Cells are many different shapes and sizes But all cells have a _______________ – thin, flexible barrier that surrounds the cell - All living things are made of cells Cells are the basic unit of structure and function of living things New cells are produced from existing cells cell membrane The Cell Theory

How are cells different? Cells fall into 2 broad categories, based on the presence or absence of a _________ _________ = large, membrane-enclosed structure that contains genetic material called DNA Prokaryotes (bacteria) Eukaryotes (animals, plants) nucleus Nucleus

2 Categories of Cell Types Prokaryotes Eukaryotes No nucleus (DNA floats freely) Unicellular Small and simple Some swim or glide along surfaces Nucleus (contains DNA) Multi-cellular Large and complex

Is a virus a cell? Is it alive? No, it is not a cell, and it is not alive Viruses are nonliving particles Made of proteins, nucleic acids (DNA or RNA), and sometimes lipids (fats) Can ONLY reproduce by infecting living cells (remember cell theory?)

Structure of Viruses Many shapes and sizes – All very small – need what type of microscope …? Viruses have a protein coat called a capsid Bacteriophages – virus that infects bacteria Once inside bacteria, it makes many copies of itself Breaks open and infects other cells