The Cell

Overview: The Importance of CellsAll organisms are made of cells.The cell is the simplest collection of matter that can live (grow, metabolize, reproduce, make adjustments).

Light Microscopes are used to view cells like this one

RELT

50 µm

Differences in Cells1. Size: --smallest @ 0.25μm Mycoplasma hominis

--largest @ 0.75 mm Thiomargarita namibiensis

162,000X

The “sulfur pearl of Namibia”

Chaos chaos (1-5 mm) Siphonous green algae (1m long)

A human egg cell = 100 µm

Vs. human sperm cell

= 5 µm

2. Number--unicellular (Bacteria, Protists like ameba & algae)--multicellular (Plants, Animals, Fungi, & some Protists)

3. Kind/typeA. Prokaryote means

“before kernal”

OR B. Eukaryote means “true kernal”

Which one has a nucleus inside?

4. Plants vs. Animals (lab)

Prokaryote Eukaryote1. No nucleus (do have DNA)

1.True nucleus (enclosed in a membrane)

2. Size: 0.1 to 10 µm 2. Size: 10-100 µm

3. No membrane bound

organelles

3. Have membrane-bound

organelles

4. Single circular chromosome

4. Multiple complex chromosomes

5. Unicellular 5. Unicellular or Multicellular

6. Simple life cycle; usually reproduce asexually

6. Complex life cycle that includes mitosis & meiosis; usu. sex. repro.

7. Kingdoms– include Eubacteria & Archaebacteria

7. Kingdoms– include Protists, Animals, Plants and Fungi

8. Evolved 4 billion yrs. ago

8. Evolved 2 bya

See p. 472

(b) A thin section through the bacterium Bacillus coagulans (TEM)

Pili: used to attach to other cells

Nucleoid: region where thecell’s DNA is located (NOTIn a membrane)

Ribosomes: organelles thatsynthesize proteins

Cell membrane: Encloses the cytoplasm

Cell wall: rigid structure outsidethe plasma membrane

Flagella: used for locomotion

(a) A typical rod-shaped bacterium

0.5 µmOne circular

chromosome

Figure 6.6 A, B

Parts of the Cell3 main locations 1. Cell (plasma) membrane +/- cell wall

2. Nucleus (or nucleoid) 3. Cytoplasm (insides of the cell)

1. The cell membrane (next topic)

Functions as a selective barrier by allowing movement of nutrients & waste in & out

Carbohydrate side chain

Outside of cell

Inside of cell

(b) Structure of the plasma membrane

Phospholipids

ProteinsTEM of a plasmamembrane.

(a)

0.1 µm

2. The Nucleus: Genetic Library of the CellThe nucleus contains most of the genetic info <3.2 billion vs. 5 million (or 0.1%) nucleotide

base pairs (A-T or C-G) in human cells vs. E. coli>

The nuclear envelope w/ pores encloses the nucleus, separating its contents (nucleolus, chromatin) from the cytoplasm

How are these cells different from the previous slide?

Nucleoid region in a ___ karyote

3. CYTOPLASMIC ORGANELLES (“tiny organs”)

A. Ribosomes=not membrane-boundAre particles made of ribosomal RNA & protein.All cells (pro and eukaryote) must have!The smallest and most numerous organelle.

Weighing in at around 150,000 atoms, the ribosome is the engine of life itself, a delightfully intricate cellular gizmo that executes the last piece of the central dogma of biology: information is transferred from DNA to RNA to protein. The ribosome transforms mRNA into the proteins that brick-by-biological-brick build bacteria, birds, & biochemists.from HHMI

Ribosomes: found in all cells because….they act as protein factories (sites of protein synthesis).

RER

Free ribosomes

Bound ribosomes

Largesubunit

Smallsubunit

TEM >

Diagram of a ribosome

0.5 µm

B. Endoplasmic Reticulum: Biosynthetic Factory

ER is continuous w/ nuclear envelope

Two kinds:1. Smooth ER (SER) that lacks ribosomes2. Rough ER (RER) w/ ribosomes

Smooth ER

Rough ER

ER lumen

Ribosomes

Transport vesicle

Smooth ER Rough ER 200 µm

Nuclearenvelope

The functions of Smooth ER include

--synthesizing lipids (testes/ovaries)

--detoxifying poisons

(liver cells)

SER in the liver

Functions of Rough ER

The RERHas bound ribosomes so it …Produces proteins, which are then distributed by transport vesicles to other parts of the cell like …

C. The Golgi Apparatus: Receiving, Packaging, Shipping Center

Receives the transport vesicles produced by the RER

Looks like stack of flattened empty pancakes

Function =modifies the products of RER

Transport vesicle carries proteins to cell

membrane for secretion

Nuclear envelope isconnected to RER, which is continuouswith SER

Nucleus

Rough ER

Smooth ERcis Golgi

trans Golgi

Transport vesicles “blip” off of ER carrying

contents to GA

Nuclear envelop

1

2

Plasmamembrane

Relationship betw. organelles of inner membrane system

Lysosome containing enzymes

Golgi modifies molecules

1. Code travels from nucleus to RER 2. Ribosomes use code to make raw

protein which then travels quickly thru ER 3. Goes to Golgi where it is modified 4. Transported to Cell membrane for

secretion

D. Vacuolesmembrane-bound sacks in the

cytoplasm = storage containersIn plant cells (larger), they hold water

& starch.In animal cells, they are like little

ziploc baggies; storage containers for food, H2O & waste.

Central VacuolesAre found in plant cells to hold reserves of starch and water

Central vacuole

Nucleus

Cell wall

Chloroplast

5 µm

Figure 6.15

What organism would have lots of these?

E. Lysosomes: Digestive Compartments

Membrane-bound sacs w/ hydrolytic enzymes + acid used to digest all kinds of macro-molecules.

Ex: amylase, pepsin

1 µm

Lysosome w/hydrolyticenzymes

Food vacuole fuses with lysosome

Hydrolyticenzymes digestfood particles into…

Food vacuole

Cell membrane

Digestiveenzymes

Lysosome

Nucleus

Energy Converting OrganellesF. Mitochondria are enclosed by two membranes

(a smooth outer & an inner folded membrane)

Mitochondrion

Intermembrane space

Outermembrane

Ribosomes

MitochondrialDNA

Innermembrane

100 µm

Figure 6.17

Mitochondria

Function: “burn” glucose to produce energy in the form of ATP

Have their own ribosomes and DNA! What does that mean?

The Mitochondrion Mr. W has many of us guys in his

running muscle

cells!

G. Plastids

Found in plants and algaeContain pigments so they can photosynthesize

2 kinds

Chloroplasts: Capture Light EnergyContain chlorophyll (“more like… borophyll”)

Chloroplast

ChloroplastDNA

Ribosomes

Inner &outermembranes

1 µm

ChloroplastsHave two membranesUse light to convert CO2 & H2O into glucose Possess their own ribosomes & DNA!

Chromoplasts contain other pigments

Autumn leaves anyone?

Non-membrane bound organelles

H. Cytoskeleton=network of fibers extending throughout the cytoplasm that supports + organizes structures and activities in the cell Microtubule

0.25 µmMicrofilaments

10 µm

Figure 6.1

I. CentriolesOnly in animal cellsUsed for dividing the

nucleus (mitosis)

Centrosome

Microtubule

Centrioles

0.25 µm

Microtubules

J. Cilia and FlagellaAre locomotor appendages of some cells (protein extensions from the

cell used for movement)

A Cross-Section of a Cilium

The Cell: A Living Unit Greater Than the Sum of Its PartsCells rely on the

integration of structures & organelles to function. Here a white blood cell needs what cell parts to recognize, ingest, and

5 µm

destroy the bacteria?