Cells: The Basic Units of LifeSection 1: The Diversity of Cells

What is a cell? The smallest unit that can perform all the

processes necessary for life.

Brainstorm with your neighbor what you think some of those processes are?

Why do you think cells weren’t discovered until the mid-1600’s

Answer: That was when the microscope was invented.

Possibilities: growing, reproducing, taking in nutrients, getting rid of waste, performing specialized functions (heart cells, nerve cells)

Scientists who first discovered and defined cellsFirst person to describe cells

First person to discover single-celled organisms, different blood cells and bacteria.

People who wrote the 3 parts of the cell theory

Robert Hooke

Anton van Leeuwenhoek

Schleiden/Schwann/Virchow

Robert Hooke Drawing

The Cell Theory All organisms are made of cells

The cell is the basic unit of all living things

All cells come from existing cells

Cell Size Most cells are small.

Big cell example: chicken egg yolk The surface area-to-volume ratio limits size

If cell volume is too big then the surface area will be too small for sufficient nutrient and waste transfers.

Equation: Surface area ÷ volume

Challenge question: What is the surface area-to-volume ratio of a cube whose sides are 2 cm long?

Cell parts All cells have the following even though

they have different functions and different shapes

1) Cell Membrane2) Cytoplasm3) Organelles4) Genetic material

Cell Membrane & Cytoplasm Cell Membrane

Protective layer that covers the cell’s surface

Acts as a barrier Controls materials going in and out of the

cell Cytoplasm

The fluid inside the cell

Organelles Structures that have specific functions

in the cell. Different types of cells have different

organelles Examples: nucleus, ribosomes,

mitochondria, endoplasmic reticulum, chloroplasts

Genetic Material All cells have DNA (deoxyribonucleic acid)

Genetic material passed from parent to new cells

Contains information needed to make new cells

Controls the activities of the cell Is enclosed in the nucleus is some cells

Two Basic types of cells

Prokaryotes: cells without a nucleus

Eukaryotes: cells with a nucleus

Prokaryotes Two groups

Eubacteria(or just plain bacteria) Most common World’s smallest cells

Archaebacteria Same in many ways to bacteria Some organelles are different Can live where no other

organism can (hot springs or deep ocean volcanic vents)

Eukaryotes All living things that are not prokaryotes

are eukaryotes Are the largest cells (10x larger than

bacteria) Have a nucleus Can be single-celled organisms

Examples: amoebas and yeasts Often are multicellular organisms

Examples: animals or plants

Review question 1Who was the first person to describe cells?

A) Louis Pasteur

B) Charles Darwin

C) Robert Hooke

D) Isaac Newton

Review question 2Which of the following is NOT part of the cell theory?A. All organisms are made of cells

B. The cell is the basic unit of all living things

C. All cells are the same shape

D. All cells come from existing cells

Review question 3Which cell part acts as a protective barrier?

A. Cell Membrane

B. Cytoplasm

C. Organelles

D. Genetic material

Review question 4Which type of cell has a nucleus?

A. Prokaryote

B. Eukaryote