Transcript The Cell

The Cell
Cell Theory/History
Structures
Transport
Differentiation
Levels of Organization
Robert Hooke
• English physicist
• 1665
• Saw a slice of cork
tree tissue
– Tiny chambers
– Termed them
“cells”
(looked like monks’
cells in monastery)
Robert Hooke
• Published his book
Micrographia
– Contained drawings
of cork cells
– Used early
microscope
Anton Van Leeuwenhoek
• Dutch businessman
• 1674
• Perfected
microscope
(about 300x)
• Saw living things in
pond water
– “Animalcules”
– Observed bacteria
(on wood teeth)
and protozoa
Matthias Schleiden
• German botanist
• 1838
• Concludes that all
plants are made up
of cells
Theodor Schwann
• German zoologist
• 1839
• Concluded that all
animals are made
up of cells
Rudolph Virchow
• German
physician/pathologist
• 1855
• Worked with eggs
from various
organisms
• Proposes that all cells
come from existing
cells
Cell Theory
• All living things are composed of
cells.
• Cells are the basic units of
structure and function in living
things.
• New cells are produced from
existing cells.
Janet Plowe
• 1931
• Demonstrates that the cell
membrane is a physical structure,
not an interface between two
liquids.
Lynn Margulis
• 1970
• Proposes a theory
that certain
organelles were
once free-living
cells themselves
Singer - Nicholson
• 1972
• Fluid Mosaic Model
– Membranes are phospholipid bilayers
with globular proteins embedded in
them
– Membrane is always moving
– Made up of smaller pieces (mosaic)
Prokaryote cells

Very simple
(bacteria)
Eukarote cells

Larger, complex
Cell Structures
Barriers…

Cell Wall
 Plants & prok. (not animals)
 Structural (plant support) & protective role
 Cellulose
 Freely permeable
Cell walls of onion skin…
Barriers…

Cell Membrane (plasma membrane)
 In ALL cells
 Support/protection
 Regulates movement in/out of:
○ Water
○ Nutrients
○ Waste products
Cell Membrane...
Barriers…

Nuclear Envelope (nuclear membrane)
 Surrounds nucleus
 Thousands of pores
○ Material move in/out, incl. RNA
Nuclear envelope
Fluids…

Cytoplasm (cytosol)
 Bet. cell mem. and nuclear env.,
site of most chemical activity

Nucleoplasm
 Semi-fluid medium of nucleus

Protoplasm
 Term used for all substances inside cell
The Nucleus
The Nucleus…
Controls most cell processes
 Contains Chromatin

 DNA bound to proteins
 During cell division, condenses to
Chromosomes…

Has a Nucleolus
 Small, dense region
 Assembly of Ribosomes

Nuclear Envelope (or membrane)
Organelles
of the cytoplasm
Cytoskeleton…
Protein filaments
 Maintains cell shape
 Involved in cell movement

Cytoskeleton
Ribosomes…
Small,made of RNA
 Assembly of proteins
 Free in cytoplasm or att. to ER

Endoplasmic Reticulum…
Called “ER”
 Two types:

 Rough ER
○ Ribosomes stud surface
○ Aids in synthesis and modif. of proteins
○ Found wrapped around nucleus
 Smooth ER
○ No ribosomes
○ Special tasks with certain enzymes
(such as making lipids)
Mitochondrion…
Uses energy from food
 Makes high-energy compounds (ATP)
needed for Rx elsewhere.
 The POWERHOUSE of the cell

Golgi Apparatus…
Receives proteins from rough ER
 Enzymes attach carbs and lipids to the
proteins
 Can store proteins until needed
 Proteins then sent to final destination
 PACKAGING and SHIPPING

Golgi Apparatus
Vacuoles…
Saclike structure
 Stores water, salts, proteins, carbs
 Can be large in plant cells

 Helps in plant support by keeping turgor
pressure high
Vacuoles
Vacuoles
Korotnovella, an
amoeba. Inside this
cell we can see a
nucleus near the
center with a rather
angular dark
nucleolus, various
food vacuoles, and a
clear round contractile
vacuole at about 10
o'clock.
Lysosomes…
Filled with enzymes
 Breaks down

 lipids, carbs, and proteins from food
 old organelles
 debris and harmful invaders
Video
Plastid 1: Chloroplasts…
In plants, not animals or fungi
 Uses sunlight to make energy rich food
mol. thru photosynthesis

Chloroplasts…
Chloroplast
Plastid 2: Leucoplast

Sometimes called amyloplast; stores
starch (amylose = starch)
Plastid 3: Chromoplast

Stores pigments in plants
Centrioles
Cylindrical; group of microtubules
 In animal cells, used in cell division
 As “basal bodies,” form cilia and flagella

The Cell Membrane

Is composed of a phospholipid bilayer
A barrier; reg. what passes in/out
 Supports and protects
 Selectively permeable – only certain things pass through.
 About 5 nanometers thick (1 nm = 1 Billionth of a meter)

Cell membrane - Structure

A phospholipid contains one head; negatively charged phosphate group that is
hydrophilic (water-loving)
 two tails of fatty acid chains that are
hydrophobic (water fearing)
Cell membrane features

The fluid mosaic model
 it is fluid in nature allowing cell mobility
 Scattered in the membrane are various
proteins which perform various functions:
○ enzyme activity,
○ cell attachment,
○ communicating with other cells,
○ Trans. of substances in and out
Passive transport
 Diffusion: net movement of sub. (liquid or gas) from an area
of higher conc. to area of lower conc. Example: perfume
Passive transport
 Osmosis: diffusion of water across a
semi-permeable or selectively perm.
membrane.
○ Hypertonic: Solution having a high conc. of solute.
○ Hypotonic: Solution having a low conc. of solute.
○ Isotonic: Both solutions have equal solute conc.
○ This difference (Δ) of conc. of molecules across a
space is called a Concentration Gradient
Equilibrium
Plasmolysis
Animal
Lysis
Plant
Turgid
Flaccid
Plasmolysis
Passive transport
 Facilitated diffusion
=
trans. of materials across membranes
by transport proteins
Active transport
 Active
transport - Trans. of molecules
against a concentration gradient (from
regions of low conc. to regions of high
conc.) with the aid of proteins in the cell
mem. and energy from ATP
Other types of active transport
Endocytosis – import of materials into cell by
infoldings of the cell membrane.
A. phagocytosis – “cell eating”; extensions of the
cell membrane surround the food and make a
vacuole. Lysosomes then secrete enzymes into
vacuole to digest food.
B. pinocytosis – “cell drinking”; smaller
infoldings allowing droplets of liquid to enter
cell.
Endocytosis in general
Exocytosis – reverse of endocytosis
Dumping of excretions or wastes outside by
discharging them from waste vacuoles.
Also can result in secretion of substances
(ex: gland cells secreting hormones into the
bloodstream)
Cell Differentiation
And hierarchy of organisms’ tissues
Cell differentiation
The process by which unspecialized
cells develop into their mature forms and
functions
 Embryonic Stem Cells

 Undifferentiated (unspecialized)
○ Totipotent – can develop into ANY type tissue

Adult Stem Cells
○ Pluripotent or multipotent – can develop into
certain types of tissues.
Levels of organization

Level one = cells -basic unit of life; examples are
 blood cells
○ Red (RBC, or erythrocytes)
○ White (leukocytes)
 nerve cells (neurons),
 bone cells (osteoblasts)
Levels of organization
Level two -tissues= Made up of cells that are similar in
structure and function and which work together to perform
a specific activity
 -Humans have 4 basic tissues: connective, epithelial,
muscle, and nerve.

 Connective tissue
○ include bones, ligaments, cartilage, blood, tendons
 Epithelial tissue-
○ skin, the mucosa, and the serosa (lines body cavities
and internal organs)
 Muscle tissue-
○ skeletal muscle, smooth muscle, and cardiac muscle
 Nerve tissue-
○ brain, spinal cord, and nerves
Levels of organization

LEVEL 3 – Organs -Made up of tissues that work
together to perform a specific activity
 heart, brain, skin, etc.

LEVEL4 - Organ Systems -Groups of two or more
organs that work together to perform a specific
function for the organism.
 The Human body has 11 organ systems - circulatory,
digestive, endocrine (hormonal), excretory (urinary),
lymphatic (immune), integumentary (skin), muscular,
nervous, reproductive, respiratory, and skeletal.
Levels of organization

LEVEL 5 - Organisms -Entire living things
that can carry out all basic life processes.
 Meaning they can take in materials, release
energy from food, release wastes, grow, respond
to the environment, and reproduce.

Usually made up of organ systems, but an
organism may be made up of only one cell such
as bacteria or protist.

Examples - bacteria, amoeba, mushroom,
sunflower, human
Cell Regulation

What makes a cell divide?
 Internal signal: Enzymes produced by cell
 Ext. signal: like growth factor produced
elsewhere
 When cells packed close, NO division
 Not packed, division starts

Checkpoints: where stop/go signals reg.
division
Uncontrolled division

Too many cells
form a tumor
 Disrupts normal
cell activity
 Takes nutrients
 If one area only:
benign
 If spreading:
malignant
The staging of a carcinoma has to do with
the size of the tumor, and the degree to
which it has penetrated. When the tumor is
small and has not penetrated the mucosal
layer, it is said to be stage I cancer. Stage II
tumors are into the muscle wall, and stage
III involves nearby lymph nodes. The rare
stage IV cancer has spread (metastasized)
to remote organs.
http://www.nytimes.com/imagepages/2007/08/01/health/adam/19222Stagesofcancer.html