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:
The cell contains hereditary information(DNA) which is passed on from cell to cell during cell division.
All cells are basically the same in chemical composition and metabolic activities.
Modern Cell Theory 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)
Light microscope (400-1000X)
Confocal/Fluorescence microscope (500X)
Electron microscope (1000-10000X)
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
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
-> Role in disease not well understood—this group has only recently been discovered
Prokaryotes – Domain Archea
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
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
allows some substances to cross more easily than others
hydrophobic vs hydrophilic
Made of phospholipids , proteins & other macromolecules
Fats + Oils
Insoluble in water (Not attracted to water)
Water-soluble (Attracted to water)
Here is what a phospholipid bi-layer looks like as a sphere FATTY ACIDS POLARHEAD Phosphate Group Glycerol Backbone Water-Soluble Water-Insoluble
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 DIFFUSION The 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 (NH 3 )
(Na + , K + , Cl - )
Small water soluble
Water (faster rate)
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.
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
water net movement of water hypotonic hypertonic
Cells may need to move molecules against concentration gradient
shape change transports solute from one side of membrane to other
“ costs” energy = ATP
“ The Doorman” conformational change ATP low high
Vesicles form as a way to transport molecules into a cell
Large,particulate matter ( Bacteria, viruses, and aged or dead cells).
Liquids and small particles dissolved in liquid
Vesicles form as a way to transport molecules out of a cell
Thick, clear liquid residing between the cell membrane holding organelles
many of the complex chemical reactions/ metabolic pathways take place here such as:
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
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.
Enzymes 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
citric acid cycle or the Krebs Cycle
Chloroplasts chloroplasts in plant cell cross section of leaf leaves chloroplast absorb sunlight & CO 2 make energy & sugar chloroplasts contain chlorophyll CO 2
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
DNA + associated proteins
internal structure of nucleus, site of ribosome assembly
Chromatin vs. Chromosome
The Major Functions of the Nucleus
stores the cell's hereditary material, or DNA
coordinates the cell's activities
-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 ribosomes B) smooth --the 'ER' without any ribosomes
Rough endoplasmic reticulum production and processing of specific proteins at ribosomal sites.
regulation of calcium ions
synthesis of steroids and lipids
metabolism of steroids
Smooth endoplasmic reticulum
Ribosomes Protein 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.
Vacuole " a "space" in a cell that contains water or other materials; usually for storage A) food vacuoles--store food B) contractile vacuoles-- squeeze out excess water
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
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
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
cilia--are typically smaller than flagella, but they cover the outside of the organism
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