Chapter 7Cell Structure and Function

The discovery of cells was

dependent on the invention of the

microscope

The Cell Theory1. All organisms (bacteria, protists, fungi, plants,

animals) are made of cells.

2. Cells are the basic unit of structure and function of living things.

3. All cells come from preexisting cells.

Important Scientists

• Hooke discovered and named cells

Early Microscopes = Light Microscopes, where light reflects off an object. Usually cannot see

most organelles with these.

Van Leeuwenhoek’s Microscope

Original Copy

An old German Microscope

Stains add contrast. Some can identify chemical types

Acid-secreting cells of Rattlesnake Venom

Glands

From:Zoologischer Anzeiger - A Journal of Comparative ZoologyVolume 245, Issues 3–4, 24 November 2006, Pages 147–159

Bioweapons synthesis and storage: The venom gland of front-fanged snakes ☆

Stephen P. Mackessy, , Louise M. BaxterSchool of Biological Sciences, University of Northern Colorado, 501 20th St., CB 92, Greeley, CO 80639-0017, USA

Fluorescent Stains

Microscopes are almost always needed to see a cell.

Size: 1-100 micrometers (= µm)

Old terminology: micron

1 m

0.1 m

1 cm

1 mm

100 µm

10 µm

1 µm

100 nm

10 nm

1 nm

Atoms

Small molecules

Lipids

Proteins

Ribosomes

Viruses

Smallest bacteria

Mitochondrion

Nucleus

Most bacteria

Most plant and animal cells

Frog egg

Chicken egg

Length of some nerve and muscle cells

Human height

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Electron Microscopes Today(Note Problem: Cells are not alive)

SEM = Scanning TEM = Transmission

See surface Thin Section; see through

See 3-D See 2-D

Important Scientists

• Schleiden determined that all plants are made of cells.

• Schwann determined that all animals are made of cells.

Important Scientists Van Leeuwenhoek

discovered that microorganisms live in a huge variety of sources (pond water, rivers, his mouth).

Virchow claimed that all cells come from preexisting cells.

The Two Cell Types

Prokaryotes and Eukaryotes

Prokaryotes = Bacteria and Blue-Green Algae

CHARACTERISTICS• Simple• Coffee bean size• No membrane-bound

organelles but do have ribosomes (rRNA)

• Have DNA, but not in a nucleus

Organelle = “little organ”

Bacteria Types

Cocci (round) Bacillus (rod) Spirillum (spiral)

What good are bacteria?

• Autotrophs– Produce oxygen

• Fix nitrogen– So plants can take it in. We need nitrogen to make

DNA & proteins

• Recycle nutrients• Form antibiotics• Help in digestions and formation of vitamins• Production of cheese and yogurt

Eukaryotes

Characteristics

– More complex

– Larger compared to prokaryotes

– Cell membrane; plants and fungi ALSO have cell walls

– Membrane bound organelles

– DNA in nucleus

Eukaryotes

Organelles are important in keeping non-compatible reactions apart, yet allowing them to happen at the same time = DIVISION OF LABOR

The Basic Animal Cell =

Nucleus + Cytoplasm (Cytoplasm =

organelles + cytosol)

Controls what goes in and out.

A phospholipid bilayer.

Embedded proteins involved in transport.

Carbohydrate side chains involved in cell-to-cell recognition.

Plasma Membrane

Endocytosis and ExocytosisHow larger particles get into and out of a cell

Is this green particle inside the cell?

NUCLEUS

Nuclear envelopeNucleolus

Chromatin

Rough endoplasmic reticulum

Smooth endoplasmic reticulum

Ribosomes

Central vacuole

Microfilaments

Intermediate filaments

Microtubules

CYTO-SKELETON

Chloroplast

PlasmodesmataWall of adjacent cell

Cell wall

Plasma membrane

Peroxisome

Mitochondrion

Golgiapparatus

Basic Plant and fungi cells also have cell walls forsupport andprotection Walls are typically made of cellulose (plants) or chitin (fungi).

TYPICALPLANT CELL

NucleusContains chromosomes which are

DNA wrapped around protein spools. • Recall that DNA has the code that tells the cell

what proteins (enzymes) to make.• Uncoiled chromosomes are called chromatin

Also contains nucleoli = areas where rRNA and tRNA are made.

Surrounded by a nuclear envelope that has pores in it.

VacuolesFound in plant cells; store water,

digestive enzymes, salts, pigments, etc.

For support.

VesiclesFound in all cells. Store digestive

enzymes or

other chemicals,

transport chemicals,

LysosomesContain enzymes to break

down food brought in by endocytosis; can also break down own molecules and organelles for recycling.

CytoskeletonA network of

protein fibers that help the cell keep its shape and helps things move around (like a freeway). Some help the cell move.

CiliaShort flagella, often arranged

in rows, that help the cell

move. Typically hundreds.

Primary CiliaSome are chemosensitive, some pressure sensitive. Function in cell signaling, cellular development, and responsible for many diseases.

RibosomesThe site of protein synthesis

Endoplasmic ReticulumA system of tubes

Rough ER:

Lipid components of the cell membrane are made here.

Proteins destined for export, or to become part of the cell membrane, or digestive enzymes are modified here.

Smooth ER:

Lipid components of the cell membrane are also made here.

Involved in the detoxification of drugs.

Golgi ApparatusWhere proteins

from the ER are further refined and packaged for either storage in the cell or final transport out of the cell.

MitochondriaBreak down food to produce

ATP. This process is called cellular respiration

Chloroplasts“Solar Power Plants.” They capture light energy and convert it to chemical energy (sugar). This process is called photosynthesis.

NOTE: Both have their own DNA