Do you know that….• The average human being is composed of

around 100 Trillion individual cells!!!• Each cell has about 10,000 times as many

molecules as the Milky Way has stars• Three-hundred-million cells die in the

human body every minute

Discovery of Cells

• 1665- English Scientist, Robert Hooke, discovered cells while looking at a thin slice of cork.

• He described the cells as tiny boxes or a honeycomb

• He thought that cells only existed in plants and fungi

Anton van Leuwenhoek

• 1673- Used a handmade microscope to observe pond scum & discovered single-celled organisms

• He called them “animalcules”• He also observed blood cells from

fish, birds, frogs, dogs, and humans• Therefore, it was known that cells

are found in animals as well as plants

• Father of Microscopy

Development of Cell Theory

• 1838- German Botanist, Matthias Schleiden, concluded that all plant parts are made of cells

• 1839- German physiologist, Theodor Schwann, who was a close friend of Schleiden, stated that all animal tissues are composed of cells.

Development of Cell Theory

• 1858- Rudolf Virchow, German physician, after extensive study of cellular pathology, concluded that cells must arise from preexisting cells.

1. All organisms are composed of one or more cells. (Schleiden & Schwann)(1838-39)

2. The cell is the basic unit of life in all living things. (Schleiden & Schwann)(1838-39)3. All cells are produced by the division of preexisting cells. (Virchow)(1858)

The 3 Basic Components of the Cell Theory

Modern Cell Theory

Modern Cell Theory contains 4 statements, in addition to the original Cell Theory:

1.The cell contains hereditary information(DNA) which is passed on from cell to cell during cell division.

2.All cells are basically the same in chemical composition and metabolic activities.

3. All basic chemical & physiological functions are carried out inside the cells.(movement, digestion,etc)

4. Cell activity depends on the activities of sub-cellular structures within the cell(organelles, nucleus, plasma membrane)

Modern Cell Theory

Modern Microscopes–Types

• Light microscope (400-1000X)• Confocal/Fluorescence microscope (500X)

• Electron microscope (1000-10000X)

MICROSCOPE

The light microscope enables us to see the overall shape and structure of a cell

•combined the laser scanning method with the 3D detection of biological objects labeled with fluorescent markers

•achieves a controlled and highly limited depth of focus

Confocal/Fluorescence microscope

Scanning electron microscope (SEM)

• They use a beam of electrons instead of light– allows greater

magnification – reveals cellular

details-produces an image of the 3D structure of the surface of a specimen

Transmission electron microscope (TEM)

DIVERSITY OF CELLS

Two Fundamentally Different Types of Cells

The PRESENCE OR ABSENCE of a NUCLEUS is

important for Classifying Cells.

Prokaryotes – Domain Bacteria

-> Single cell organisms-> No nucleus, no compartments-> Peptidoglycan cell walls-> Binary fission-> For energy, use organic chemicals, inorganic chemicals, or photosynthesis

-> Lack peptidoglycan-> Live in extreme environments Include:

MethanogensExtreme halophilesExtreme thermophiles

-> Role in disease not well understood—this group has only recently been discovered

Prokaryotes – Domain Archea

Eukaryotes

• Structural Differences– Plants have choloroplasts, a

large central vacuole and a cell wall

– Plant cells do not have centrioles

– Plant cells have plasmodesmata

– Animal cells have gap junctions

• Physiological Differences– Plant cells have

photosynthesis in addition to respiration

– During mitosis a cell plate is formed in plant cells

– Starch is molecule for energy storage while in animal cells it is glycogen

– Large central vacuole stores more water and carbohydrates then animal cell vacuoles

Different Cell Parts

In cells, various specialized functions occur in specific places. These places are called organelles (small organs)

Plasma Membrane

FLUID MOSAIC MODEL

• Cell membrane separates living cell from nonliving surroundings– thin barrier = 8nm thick

• Controls traffic in & out of the cell– selectively permeable– allows some substances to cross more easily

than others• hydrophobic vs hydrophilic

• Made of phospholipids, proteins & other macromolecules

Phospholipid Bilayer• Lipids

– Organic compounds– Fats + Oils– Non-polar– Insoluble in water (Not

attracted to water)Phosphate Head

– Polar– Water-soluble (Attracted to

water)

Phosphate Group

Glycerol Backbone

Water-Soluble

Water-Insoluble

Here is what a phospholipid bi-layer looks like as a sphere

FATTY ACIDS

POLARHEAD

• The internal composition of the cell is maintained because the plasma membrane is selectively permeable to small molecules.

• Only small, relatively hydrophobic molecules are able to diffuse across a phospholipid bilayer at significant rates by using passive diffusion.

Permeability of phospholipid bilayers

Transport Across Membranes

Transport Across Membranes: PASSIVE

DIFFUSIONThe movement of molecules or ions from a region where they are at a high concentration to a region of lower concentration

• Gases (oxygen, carbon dioxide)

• Water molecules (rate slow due to polarity)

• Lipids (steroid hormones)

• Lipid soluble molecules (hydrocarbons, alcohols, some vitamins)

• Small noncharged molecules (NH3)

SIMPLE DIFFUSION

• Ions

(Na+, K+, Cl-)

• Sugars (Glucose)

• Amino Acids

• Small water soluble molecules

• Water (faster rate)

FACILITATED DIFFUSION

How do molecules move through the plasma membrane by facilitated

diffusion?

• Channel and Carrier proteins are specific:• Channel Proteins allow ions, small solutes, and

water to pass• Carrier Proteins move glucose and amino acids• Facilitated diffusion is rate limited, by the

number of proteins channels/carriers present in the membrane.

– Osmosis is the diffusion of water across a differentially permeable membrane.

– Osmotic pressure is the pressure that develops in a system due to osmosis.

OSMOSIS

Concentration of water• Direction of osmosis is determined

by comparing total solute concentrations– Hypertonic - more solute, less water

– Hypotonic - less solute, more water

– Isotonic - equal solute, equal water

hypotonic hypertonic

water

net movement of water

Active Transport

“The Doorman”“The Doorman”

conformational change

• Cells may need to move molecules against concentration gradient– shape change transports solute from

one side of membrane to other – protein “pump”– “costs” energy = ATP

ATP

low

high

Endocytosis

Vesicles form as a way to transport molecules into a cell

a. Phagocytosis Large,particulate matter (Bacteria, viruses, and aged or dead cells).

b. PinocytosisLiquids and small particles dissolved in liquid

Exocytosis Vesicles form as a way to

transport molecules out of a cell

Cytoplasm

• Thick, clear liquid residing between the cell membrane holding organelles

•many of the complex chemical reactions/ metabolic pathways take place here such as:

Glycolysisgluconeogenesis biosynthesis of sugars, fatty acids, and amino acids

Mitochondria* site of cellular respiration * POWERHOUSE OF A CELL

Where energy is released from nutrients* there are MANY in a single cell* has two layers, makes up a double membrane

Act similar to electric power plant

Up to 300 to 800 per cell

Come from cytoplasm in EGG

You inherited your mitochondria from your mother

certain organelles originated as free-living bacteria that were taken inside another cell as endosymbionts. Mitochondria developed from proteobacteria

Can replicate itself: BINARY FISSION

ENDOSYMBIOSIS

(1) outer membrane It is fairly smooth. It is composed of

phospholipid bilayer protein.

it has channel protein: hole protein , permit that small molecule substance freely pass.

The ultrastructure of mitochondrion

(2)inner membrane they are more proteins than phospholipids.it has no hole protein , so penetrability is weak.

(3) intermembrane space it contains enzymes. It can

catalyze ATP to create ADP.

(4)MatrixEnzymes are abundant in the matrix . It also contains mitochondrial genetic system including DNA and ribosome.

(5) elementary particle it also call ATP synthase.

it lies in the inner membrane.

The Functions of mitochondrion

•Production of ATP through respiration•cellular metabolism 

citric acid cycle or the Krebs Cycle

Chloroplasts

chloroplastsin plant cell

cross sectionof leafleaves

chloroplast

absorbsunlight & CO2

makeenergy & sugar

chloroplastscontainchlorophyll

CO2

Structure

• Chloroplasts– double membrane– stroma

• fluid-filled interior– thylakoid sacs– grana stacks

• Thylakoid membrane contains– chlorophyll molecules– electron transport chain

outer membraneinner membrane

thylakoidgranum

stroma

Nucleus* surrounded by a nuclear membrane

* only found in EUKARYOTES

* contains genetic material (DNA) in the form of chromosomes that controls the activities of the cell

* serves as the information and administrative center of the cell

•Nucleoplasm•Nuclear envelope•Nuclear pores•Chromatin

DNA + associated proteins

•Nucleolus internal structure of

nucleus, site of ribosome assembly•Chromatin vs. Chromosome

Nucleus: Structure

The Major Functions of the Nucleus

•stores the cell's hereditary material, or DNA•coordinates the cell's activities

-intermediary metabolism-growth-protein synthesis-reproduction (cell

division)

Endoplasmic Reticulum (ER)- a series of interconnecting channels associated

with storage, synthesis, and transport of substances within the cell

two types:A) rough--the 'ER' studded with ribosomesB) smooth--the 'ER' without any ribosomes

Rough endoplasmic reticulumproduction and processing of

specific proteins at ribosomal sites. 

•carbohydrate metabolism•regulation of calcium ions•synthesis of steroids and lipids•drug detoxification•metabolism of steroids

Smooth endoplasmic reticulum

RibosomesProtein Synthesis"translates" the genetic information from ` RNA into proteins

•looks like a stack of flattened pancakes

• All of the proteins and lipids synthesized by the RER and SER are sent to the golgi. 

•sorts, modifies, and packages the products of the RER and SER before sending them to their final destination inside or outside of the cell.

Golgi Apparatus

Vacuole" a "space" in a cell that contains water or other materials; usually for storageA) food vacuoles--store foodB) contractile vacuoles-- squeeze out excess water

Centrioles

•found in animal cells; rare in plants•cylindrical structures (like cans) found in the cytoplasm that appears to function during cell division (reproduction) •involved in the organization of the mitotic spindle and in the completion of cytokinesis

 

Cell Wall•found mostly in plant cells (some monerans, protists, and fungi too)•a non-living structure which surrounds and supports a cell•made of cellulose, a complex carbohydrate

Lysosome “Suicidal bags of the cell”a vacuole that contains digestive

enzymes; helps in the process of nutrition by breaking down nutrients in the cell

Peroxisomes•helps to rid the body of the host organism of toxins•breakdown of very long chain fatty acids through beta-oxidation

Cilia and Flagella•these are hair-like organelles that extend from the surface of many different types of cells

A)cilia--are typically smaller than flagella, but they cover the outside of the organismB)flagella--are much longer than cilia, but there usually are few on a single cell

•these structures usually aid in movement•they can also help sweep materials along the outside of a cell