A Tour of the Cell

• Anton Van Leeuwenhoek (1600’s)

• Credit for the first microscope

• Looked at pond water and saw “wee beasties”

Robert Hooke• Observed plant

stems, wood, and cork (1600’s)

• Saw all the tiny chambers and called them CELLS

• What cell part did Hooke observe?

• Cell Wall

Robert Brown (1833)

• Observed that cells had a dark structure within plant cells

• Brown observed the nucleus and stated that all cells have nuclei (at this time no one knew that the nucleus has DNA)

Matthias Schleiden (1838)• Stated that all plants

are made of Cells

• Made many observations of plants around the area

Theodor Schwann (1839)• Stated that all animals are made of

Cells

• Observed many animal tissues

Rudolf Virchow (1855)• Stated that all cells come from pre-

existing cells• Cells arise from the division of pre-

existing cells

The Cell Theory

Microscopes Provide the Windows to the World of the Cell

The Cell Theory• All living things are

composed of cells

• Cells are the basic unit of structure and function in living things

• All cells come from pre-existing cells

A Prokaryotic Cell

Figure 7.1 The size range of cells

The SizeRange ofCells

Cell SizesAverage Animal Cell – 15 microns

Average Plant Cell – 40 microns

Average Eukaryotic Cell :10-100 microns

Average Prokaryotic Cell: 1-10 microns

An Electron Microscope

Geometric Relationships Explain Why Most Cells Are Microscopic

Overview of an Animal Cell

Human Cheek Cells

Overview of a Plant Cell

Onion Epithelial Cells

Animal Cell’s Cell Membrane

Cell or Plasma Membrane

•“Fluid Mosaic” Model• Lipid Bilayer (made of phospholipids)•Proteins embedded throughout•Semi-permeable or Selectively Permeable

Cell Wall• provides support to the

perimeter of plant cells, some protists, and bacterial cells

The Plasma Membrane

The Nucleus and Its Envelope 

Nuclear Envelope/Membrane

•Double Membrane that surrounds the nucleus•Lined with pores•Supported by nuclear lamina

Nucleolus•Inside the nucleus•Site of ribosome and rRNA synthesis

Ribosomes

Endoplasmic Reticulum (ER)

Endoplasmic Reticulum(ER)

•Rough ER •Intercellular transport of materials, particularly proteins; site where proteins leave ribosomes and are chemically modified

Smooth ER• breaks down toxic substances, • regulates Ca levels, • synthesizes steroids and other lipids

The Golgi Apparatus

Golgi Apparatus•Modifies proteins and other substances from the ER for export from the cell

Lysosomes

Lysosomes•Digest cellular waste and foreign substances•Breakdown of lipids, carbohydrates, and proteins

The Formation and Functions of Lysosomes

Plasma membrane expandsby fusion of vesicles; proteinsare secreted from cell

Transport vesicle carriesproteins to plasma membrane for secretion

Lysosome availablefor fusion with anothervesicle for digestion

4 5 6

Nuclear envelope isconnected to rough ER, which is also continuous

with smooth ER

Nucleus

Rough ER

Smooth ERcis Golgi

trans Golgi

Membranes and proteinsproduced by the ER flow in

the form of transport vesiclesto the Golgi

Nuclear envelop

Golgi pinches off transport Vesicles and other vesicles

that give rise to lysosomes and Vacuoles

1

3

2

Plasmamembrane

• Relationships among organelles of the endomembrane system

Figure 6.16

Peroxisomes•Contain an assortment of enzymes that perform such roles as detoxification of alcohol, breaking down of fatty acids•Produces H2O2 in the process

Peroxisomes

The Chloroplast, Site of Photosynthesis

Plastids•May be called chromoplasts or leukoplasts•Store starch, fat or contain pigments suchas chlorophyll or carotenoids to capture energy from the sun

The Mitochondrion

MitochondrionSite of cellular respirationand synthesis of ATP,a source of chemical energy for the cell

The Plant Cell Vacuole 

Vacuoles•Store water, salts, proteins, carbohydrates, or enzymes

The Cytoskeleton

Cytoskeleton•Protein strands that give the cell its shape and size•Helps organize the location of organelles and their activities

There are three main typesof fibers the make up the cytoskeleton: 1) Microtubules 2) Microfilaments 3) Intermediate Filaments

Microtubules•Are made of the protein tubulin•Shape and support the cell•Are responsible for the separation of chromosomes during cell division

Centrosome Containing a Pair of Centrioles

Centrioles•Appear during mitosis in animal cells; are composedof nine sets of triplet microtubules in a ring

Centrosome•Area from which the centrioles radiate during mitosis

Figure 7.24 Ultrastructure of a eukaryotic flagellum or cilium

Ultrastructure of a Cilium or flagellum

Cilia and Flagella•In eukaryotes, a specializedarrangement (“9 + 2”) of microtubules is responsible for the beating of flagella and cilia•The protein, dynein, is responsible for the movement

How Dynein “WalkingMoves Cilia and Flagella

A Comparison of the Beating of Flagella and Cilia

The microtubule assembly of a cilium or flagellum is anchored in the cell by a Basal Body, which is structurally identical to a centriole.

Sea Urchin Sperm

Microfilaments and Motility

Microfilaments also aid in •Cell motility (Ex: pseudopodia)•Cell division (cleavage furrowformation)•Cytoplasmic Streaming

A Structural Role of Microfilaments

Microfilaments•Made of the protein actin •Located in the cytoplasm of most eukaryotic cells•Works with myosin to cause muscle cell contractions

Intermediate Filaments

•Anchor nucleus and other organelles•Reinforces cell shape •Make up nuclear lamina that lines the interior of the nuclear envelope

Plant Cell Walls

Intercellular Junctions in Animal Tissues

Extracellular matrix (ECM)

1)What are the two major

types of electron microscopes?

2) All cells are classified as

either _______ or _____.

3) Under the microscope, bacteria are typically measured in ___________ (units).

4) Two similarities between plant and animal cells are. . .. two differences are . . ..

5) The term used to describe the fact that the cell membrane allows some materials in and keeps others out is. . .

6) The lipid bilayer of the cell membrane is made of:

1)The organelle that packages proteins for export from the cell is the . . .

2) Cellular respiration occurs in the ___________ and energy is made in the form of ________.

3) The major difference between a prokaryotic and eukaryotic cell is that a prokaryotic cell lacks a/an:

4) The oldest cells on earth are ______ cells. They evolved . . . . years ago.

What characteristic of the cell membrane allows some molecules into the cell and keeps other out?

The primary purpose of the cellwall is..

The cell membrane is composed primarily of. .

Why is the cell membrane referred to as a “fluid mosaicmodel”?

Since some molecules can passthrough the cell membrane and others cannot it is termed. .

If a molecule is too big to get through the cell membrane, it mustenter through _________ channels.

The centers of protein synthesis in the cell are the _________.

Describe the role of the cytoskeleton in the cell.

Name two different things stored by vacuoles.