The key to every biological problem must finally be sought in the cell, for every living organism is, or at some time has been, a cell. E.B. Wilson, 1925

Why Study Cell Biology?

Cells are Us

Cells are Us

Cilia on a protozoan Sperm meets egg

Cells are Us

A person contains about 100 trillion cells. That’s 100,000,000,000,000 or 1 x 1014 cells.

There are about 200 different cell types in mammals (one of us).

nerve cell

Red and white blood cells above vessel-forming cells.

CELL SIZE

• Smallest cell in the human body is the sperm cell

• Largest cell in the human body is the egg cell

Most cells are small

1. Surface to volume ratio: cell has to be small enough to get– Waste out

– Nutrients in

2. The nucleus can only control a certain size cell

Robert Hooke

• Used a microscope to look at small object and coined the term “cells”

• They looked like little boxes that monks lived in called “cells”

Anton von Leewenhoek

• FIRST person to OBSERVE and DESCRIBE MICROSCOPIC ORGANISMS and LIVING CELLS.

• Matthias Schleiden : “plants are made of cells”

• Theodor Schwann : “Animals are made of cells”

Schleiden

Schwann

The Cell Theory

1. All living things are made of cells.

2. Cells are the basic unit of structure and function

3. New cells come from preexisting cells.

*cells are different shapes and sizes based on their function

The cell theory (proposed independently in 1838 and 1839) is a cornerstone of biology. Proposed by Rudolph Virchow

A Sense of Scale and Abundance – Bacteria on the Head of a Pin

Two Fundamentally Different Types of Cells

Us vs. Them -Eukaryotes and Prokaryotes

• Organisms whose cell contain a nucleus and other membrane bound organelles are called EUKARYOTES

• Organisms whose cells never contain (or lack) a nucleus and other membrane bound organelles are called PROKARYOTES

Major Divisions of the Eukaryotic Cell

1. NUCLEUS

2. CYTOPLASM

3. CELL MEMBRANE

A rat liver cell (with color enhancement to show organelles)

It’s Crowded In There

An artist’s conception of the cytoplasm - the region of a cell that’s not in the nucleus or within an organelle.

A micrograph showing cytoskeleton (red), ribosomes (green), and membrane (blue)

It’s Crowded In There

Animal and Plant Cells Have More Similarities Than Differences

Cellular Anatomy

We’ll start by seeing what role these parts play in making and moving proteins.

The Nucleus

•Control center of the cell

•Surrounded by a nuclear envelope with pores

•DNA is in the form of chromatin which condenses down into chromosomes

Ribosomes and the Endoplasmic Reticulum

Ribosome

• Ribosomes Are Not Surrounded by a membrane. They are the site of PROTEIN SYNTHESIS (Production or Construction) in a cell.

The Rough Endoplasmic Reticulum

Protein movement (transport)

Protein synthesis (about half the cell’s proteins are made here).

Studded with ribosomes

Smooth ER

• SMOOTH ER IS NOT Covered with RIBOSOMES and processes LIPIDS and CARBOHYDRATES. The Smooth ER is involved in the synthesis of steroids in gland cells, the regulation of calcium levels in muscle cells, and the breakdown of toxic substances by liver cells.

Cystic Fibrosis

Click here to see the article.

Golgi Apparatus

• Processing, Packaging and Secreting Organelle of the Cell that is made of flattened SAC

                             

The Lysosome

Recycling cellular components

Functions:

Digesting food or cellular invaders

The Lysosome

This bacterium about to be eaten by an immune system cell will spend the last minutes of its existence within a lysosome.

Many Diseases are Caused by Lysosome Malfunction

Cellular Anatomy

The Mitochondrion

Think of the mitochondrion as the powerhouse of the cell.

Both plant and animal cells contain many mitochondria.

Mitochondrial Diseases

Mitochondria and Health

Animal vs. Plant Cells – Chloroplasts Are a Big Part of the Difference

Cells In a Leaf

The Chloroplast

Think of the chloroplast as the solar panel of the plant cell.

Only plants have chloroplasts; they perform photosynthesis

Two Other Unique Features of Plant Cells

The central vacuole may occupy 90% of a plant cell.

A Consequence of Cell Walls – the Great Strength of Woody Plants

The Central Vacuole Controls Turgor Pressure

Flaccid – no water

Turgid – full of water

Cellular Anatomy

The name is misleading. The cytoskeleton is the skeleton of the cell, but it’s also like the muscular system, able to change the shape of cells in a flash.

Maintains the shape of the cell

Aids in movement

The Cytoskeleton

An animal cell cytoskeleton

A Cytoskeleton Gallery

A white blood cell using the cytoskeleton to “reach out” for a hapless bacterium.

The Cytoskeleton in Action

The Cytoskeleton in Action

Cilia on a protozoan Beating sperm tail at fertilization

Smoker’s cough is due to destruction of cilia linking the airways.

Cell membrane

• The Cell Membrane is a complex barrier separating the cell from it's external environment. The "Selectively Permeable" Membrane regulates what passes into and out of the cell.

Cell Wall

• Plant cells have a cell wall. A Cell Wall DOES NOT REPLACE the Cell Membrane; Cells with WALLS also have a CELL MEMBRANE.  Plant Cells are covered by a Rigid Cell Wall that lies Outside the Cell Membrane.