CH 4 CELL STRUCTURE AND FUNCTION. Discovery of cells Early scientists had to make their own...
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Transcript of CH 4 CELL STRUCTURE AND FUNCTION. Discovery of cells Early scientists had to make their own...
CH 4 CELL STRUCTURE AND FUNCTION
Discovery of cells
Early scientists had to make their own microscopes
Better microscopes = better knowledge of microscopic life
Robert Hooke Observed cork slides Observed ‘cells’ (like where monks live)
Anton van Leeuwenhoek (10x Hooke’s magnification) Observed algae and ‘animalcules’ (protists)
Other scientists
Mathias Schleiden Plants are made of cells
Theodor Schwann Animals are made of cells
Rudolf Virchow Cells come from other cells
What is the importance of all of these observations?
Cell theory
1. All organisms are made of one or more cells
2. Cells are the basic units of structure and function in an organism
3. Cells come from pre-existing cells
Cell size
Cells come in many shapes and sizes Size of a cell is limited by its surface
area-to-volume ratio As a cell grows, volume increases much
faster than surface area If a cell gets too big, materials entering
and leaving a cell would not be transported fast enough = cell would starve
Cell sizeWorking in pairs, consider two cubes, one with a side
that is 1 cm long and the other with a side that is 6 cm long. For each cube calculate:
1. Surface area (= height × width × number of sides)
2. Volume (= height × width × length)
3. Surface area-to-volume ratio (= surface area:volume)
What pattern do you observe as the size of the cube increases?
What inferences can you make regarding cell size?
Take a few minutes to discuss, and then present your conclusions to the class.
Answers
1. Surface area = 6 cm2 for the first cube and 216 cm2 for the second cube
2. Volume = 1 cm3 for the first cube and 216 cm3 for the second cube
3. Surface area:volume = 6:1 for the first cube and 1:1 for the second cube
As the cube size increases, the surface area to volume ratio decreases.
These calculations show why most cells are small (cells must maintain a large surface area to volume ratio in order to function).
Parts of a cell
PLASMA MEMBRANE aka: Cell membrane Cell’s outer surface Barrier Regulate movement of materials in/out of cell
Cytoplasm: fluid portion of cell Contains all organelles
NUCLEUS Control center Where DNA is located Or floating in cytoplasm
All cells have
these 3 parts.
Two types of cells
Prokaryotes: lack a nucleus and membrane-bound organelles Pro- before Kary- nucleus
Contain a nucleoid: region where DNA is concentrated *not an organelle
Bacteria and Archea
Two types of cells
Eukaryotes: have a nucleus and membrane-bound organelles Eu- true
Organelles: well defined; intracellular bodies that perform specific functions All are enclosed in a
membrane Generally larger than
prokaryotes
Cellular organization
Multicellularity found in more advanced species
Tissue: groups of cells that do a specific job
Organs: tissues that perform a particular job
Organ systems: group of organs that accomplish a related task
Plasma membrane (aka: Cell Membrane)
Location: Surrounds the cell
Functions: Allows only certain molecules to
enter/exit a cell Separates internal metabolism
from external environment Present in ANIMAL & PLANT cells
The “GATE-KEEPER”
Plasma Membrane
Composed of a phospholipid bilayer: double layered membrane of phospholipids
Phospholipids Polar (hydrophillic)
heads – oriented to H2O Nonpolar (hydrophobic)
tails – orient away from H2O
POLAR
NONPOLAR
Membrane components
Many proteins are embedded in plasma membrane
Receptor proteins: recognize and bind to substances outside of cell
Enzymes: assist chem rxns Transport proteins: help substances move
across membrane Fluid mosaic model: phospholipid bilayer
behaves like a fluid more than a solid Lipids and proteins can move around w/in
membrane
Nucleus
Houses and protects genetic information When cell is not dividing, DNA is in
chromatin form Threadlike material
When cell is dividing, DNA is condensed into chromosomes DNA surrounded by proteins
CHROMOSOME
Control Center
Nuclear envelope
Double membrane surrounding nucleus Nucelar pores regulate movement of
materials in/out of nucleus
Nucleolus
Nucleolus: structure inside nucleus Location of ribosomal RNA (rRNA)
synthesis Ribosomes: cell structure responsible
for protein sysnthesis Composed of rRNA
Mitochondria
Double-membraned organelle responsible for energy conversion Organic molecules (glucose + O2) ATP
Inner membrane has many folds cristae More surface area = more ATP
production Have their own DNA Believed to have originated from
prokaryotic cells that were incorporated into ancient eukaryotic cells Symbiotic relationship (both benefit)
Powerhouse
Endoplasmic reticulum (ER)
System of membranous tubes and sacs
2 types Rough (RER):
Attached ribosomes protein synthesis
Smooth (SER): No ribosomes Tubular appearance Lipid and steroids
synthesis
Freeway
Golgi Apparatus
Location: in cytoplasm Function:
package and modify proteins or lipids as they pass them from sac to sac
“address labels” A & P Double membrane
Packaging Center
Lysosomes
Location: in cytoplasm Function:
Contain digestive enzymes to break down macromolecules
WBC’s >> break down bacteria
Autophagy: = digestion of old organelles
Autolysis = Cells broken down by their own lysosomes
A & P Double membrane
Suicide Sacs
Peroxisomes
Location: in cytoplasm (especially in liver and kidney cells)
Function: Similar to lysosomes; contain
different enzymes Neutralize free radicals
(damaging Oxygen ions) Detoxify alcohol and other drugs Produce H2O2 (hydrogen
peroxide) A & P Double membrane
*PROTEIN SYNTHESIS
1. Ribosomes (on Rough ER) make proteins.2. Vesicles transport proteins to Golgi
apparatus.3. Golgi modifies and packages proteins in new
vesicles.4. Vesicles release proteins that are needed
OUTSIDE the cell.5. Vesicles with ENZYMES stay inside the cell as
Lysosomes Peroxisomes Endosomes
CYTOSKELETONMicrotubules
Small hollow tubes anchored near nucleus
Location: cytoplasm Function:
Hold organelles in place Maintain cell shape “tracks” to guide
movement of organelles and molecules within cell
A & P
CYTOSKELETONMicrofilaments
Small threads wrapped around each other
Location: cytoplasm Function:
Cell movement Muscle contraction WBC crawl
A & P
CYTOSKELETONIntermediate Filaments
Location: nucleus & cytoplasm
Function: Anchor nucleus &
some organelles Maintain shape of
nucleus A & P
Cilia & Flagella
Location: surface of cell Function:
Assist in movement CILIA = tiny hairs FLAGELLA = tails
Made of microtubules A & P
Centrioles
Location: cytoplasm Function:
Assist in MITOSIS (cell division)
Made of microtubules A
PLANT CELLSCell Wall
Location: OUTSIDE plasma membrane
Made of CELLULOSE (carbohydrate)
Function: Form rigid wall Helps cells maintain same
shape P Double membrane sometimes
if secondary cell wall forms (i.e. wood)
PLANT CELLSCentral Vacuole
Location: Cytoplasm Function:
Acts as a reservoir for large amounts of water
Also: enzymes, wastes, etc.
When empty, plant wilts.
P Single membrane
PLANT CELLSChloroplasts
Similar to mitochondria Contain own DNA
Location: Cytoplasm Function:
PHOTOSYNTHESIS Light energy converted into
chemical energy (glucose) *Contain green pigment
P Double membrane
PLANT CELLSChromoplasts & other plastids
Location: Cytoplasm Function:
Give color to plants Carrots = orange pigment Daisies = yellow pigment
A & P Double membrane