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Cell Structureand Function
Chapter 4
The History of Cell Biology
Cell: the smallest unit that can carry on all of the processes of life.
Robert Hooke: 1665
Studied natureUsed “light microscope” pg 69
Viewed a thin slice of cork
Saw many little boxesCELLS
Anton van Leeuwenhoek: 1673
First to observe living cells
Microscope lens was 10x that of Hooke
Was first able to see unseen world of microorganisms
First to view a REAL cell
Matthias Schleiden: 1838
Botanist
First to view plant cells
Concluded: All plants are composed of cells.
Theodor Schwann: 1839
Zoologist
Concluded: All animals were made of cells.
Rudolf Virchow: 1821 - 1902
Physician
All cells come from other cells.
CELL THEORY
1. All living organisms are composed of one or more cells.
2. Cells are the basic units of structure and function in an
organism.
3. Cells come only from the reproduction of existing cells.
Developments:
Discovery of cells and cell theory:
MICROSCOPE
Basic Characteristics of ALL living things:
1. made of organized parts2. obtain energy from their
surroundings3. perform chemical reactions
4. change with time5. respond to the environment
6. reproduce
Section 2: Introduction to Cells
In a body: pg 72 Different cells
Different shapes
Different functions
All in same body
Cell Shape
Shape reflects the different functions
PAGE 72
Cell Size
A few types of cells are large enough to be seen without a microscope
Ex. Giraffe’s nerve cells: 6 ½ ft long Human egg cell: size of a period
MOST cells: 1/500th the size of a period
WHY are cells MICROSCOPIC?
SURFACE AREA-TO-VOLUME RATIO
Nutrients and oxygen go inWaste goes out
BOTH pass through surface
Happens QUICKLY therefore need more surface area to volume page
73Cells MUST be microscopic!!!
BASIC PARTS OF A CELL
3 basic parts to all cells1. Cell Membrane
2. Cytoplasm
3. Nucleus
1. Cell Membrane
Also called the plasma membrane
Covers the surface
Acts as a barrier
All materials enter or exit through this
2. Cytoplasm
Hold all of the organelles
3. Nucleus
Control centerHolds DNAMembrane bound and free floating
DNA
Two Basic type of cells
PROKARYOTES
Lack a membrane-bound nucleus
Lack membrane-bound organelles
May have a nucleoid: concentrated area of DNA
DOMAIN Archaea DOMAIN Bacteria
EUKARYOTES
In organisms made up of one or more cells
Contain organelles Larger in size than
prokaryotes
Cellular Organization
Page 76
Cell Tissue Organ Organ System
1. Cell Membrane
Functions: A. Allows only certain molecules to
enter or leave the cell B. Separates reactions inside the cell
from outside the cell C. Excretes waste D. Interacts with environment
Parts of Cell Membrane
Phospholipids
Proteins Cell surface markers – emerge from
only one side of the membrane
Receptor proteins – recognizes and binds to substances outside the cell
Transfer proteins – helps substances move across the membrane
Enzyme –
2. Nucleus
Houses and protects genetic information Chromosomes: holds DNA
Nuclear Envelope: surrounds nucleus
Nucleolus: denser area in nucleus
3. Cytoplasm
Holds organelles
organelles
MitochondriaRibosomesEndoplasmic reticulumGolgi aparatusVesiclesMicrotubulesMicrofilamentscentrioles
Mitochondria
Mitochondria: tiny organelles that transfer energy into ATP
ATP: Adenosine triphosphate Powers the cell’s chemical reactions
HIGH in # in muscle cells! FEW in # in fat cells.
Ribosomes
Small, roughly spherical organellesResponsible for building proteinNo membraneMade of protein and RNACreated in nucleus, finished in
cytoplasmFound in
Cytoplasm Some endoplasmic reticulum
Endoplasmic Reticulum
Called ERSystem of tubes and sacs
(cisternae)Function as a “highway”: a path
along which molecules move from one part of the cell to another
2 types: Rough Smooth
Rough ER
System of interconnected, flattened sacs covered with RIBOSOMES
Pg 81Produces phospholipids and proteinsRibosomes on ER:
Produce digestive enzymes that contain proteins
Vesicles (sacs) pinch off and store these enzymes until they are released
Smooth ER
Smooth appearanceBuilds In ovaries and testes: produces
hormones
*abundant in liver and kidneys:
Long term alcohol and drug abuse:
Golgi Apparatus
Pg 82Another system of flattened,
membrane sacs
Sacs closest to the nucleus receive vesicles from the ER containing newly made proteins or lipids
Proteins get “address labels”
Types of Vesicles
VESICLE: small sacs that head to the plasma membrane and release contents outside of cell
1. LYSOSOME2. PEROXISOME3. others
Vesicles: Lysosomes
Vesicles from Golgi Apparatus that contain digestive enzymes
Breakdown proteins, carbs, fats, bacteria.
Responsible for breaking down cell when it is time to die!
Vesicles: Peroxisomes
Abundant in liver and kidney
Detoxify alcohol and other drugs
Also breakdown fatty acids
MAJOR FUNCTION OF CELL:protein synthesis pg 83
1. proteins assembled by ribosomes on rough ER
2. Vesicles transport proteins to thegolgi apparatus
3. Golgi modifies the proteins and packages them in new vesicles
4. Vesicles release proteins that have destination outside of cell
5. Vesicles needing to remain inside of cell stay.
Cytoskeleton
Network of thin tubes and filaments Give shape to the cell from the inside
ex. Tent poles
Also acts as a system of internal tracks to allow items to move around in cell
Microtubules, Microfilaments, &Intermediate filaments
Microtubules
Hollow tubes made of protein called “tubulin”
1. Hold organelles in place2. Maintain cell’s shape3. Act as track to guide organelles
Microfilaments
Finer than microtubules2 strands of intertwined protein
1. contribute to cell movement2. muscle contraction3. maintainance and changing of
shape
Intermediate Filaments
Rods that anchor the nucleus and other organelles to their place
Maintain INTERNAL shape of nucleus
How does a cell MOVE?Short, hair-like structures!
CILIA
Extend from surface of cell
Short Large #’s
Inner ear: vibrate and help detect sounds
Protisits: sweep food into mouthlike opening
FLAGELLA
Extend from surface of cellLongless #’s
Section 4: Unique features of plant cells
Plant cells have 3 additional kinds of structures
1. cell wall
2. large central vacuole
3. plastids
Why does a plant need these different structures?
Make their own food: photosynthesis
Must reach up towards the sun
Need to hold water
Cell Wall
Rigid layer outside of plasma membrane
Made of cellulose: a carb that makes the celllike a stiff box
2 layers: Primary wall Secondary wall
(wood)
Large Central Vacuole
Large, fluid-filled organelle
Mainly stores water
90% of the plants volume
Causes plant to stand upright
Chloroplasts
Used in photosynthesis
Use light energy
Contain chlorophyll:
green pigment that absorbs light and captures the light energy
chromoplasts
Colored pigment
Found in carrots: orange
flowers: red, purple, yellow & white