What is common with every living thing on earth?

I. Development of the Cell Theory

A. Robert Hooke (1600's)- observed cork (dead box-like structures) called cells

B. Other Scientists (1800's)- proposed conclusion of the cell which led to the Cell Theory

CELL THEORY states:

1. All organisms are made of one or more cells.
2. All cells carry on life activities.
3. New cells arise only from other living cells by the process of cell division.

TWO BASIC CELL TYPES

1. Prokaryotic Cells-(means without a nucleus) are single celled organisms that lack internal membrane-bound structures

example: bacteria

2. Eukaryotic Cells-(means with a nucleus) are all living things except bacteria; these cells have many internal membrane-bound structures

example: nucleus

Both use the same life functions, using the same kind of organic compounds.

CELL SIZE

1. Nutrients must get into the cell and wastes must be removed; what limits this exchange is the cell's surface area-to-volume ratio.
2. Therefore, the smaller the cell the larger the surface area this means more materials can be exchanged with the environment.

Cell Structure

ORGANELLES- (small organs of the cell) specialized internal structures of the cell, examples:

1. Cell Wall- rigid, lies outside cell membrane

-contains cellulose
-function is to shape, protect & support cell
-not found in animals, VIRTUAL CELL

2. Cell Membrane- (plasma membrane)

-composed of lipids, proteins & carbohydrates
-selective permeability which allows only certain substances to pass through
-help maintain homeostasis
-Fluid Mosaic Model currently accepted model of the structure of the cell membrane (although research is ongoing in this area)

3. Nucleus- control center (brain of cell)

-has nuclear membrane that surrounds nucleus
-has nucleolus which are dense granular bodies that are responsible for making ribosomes & RNA
-chromatin (DNA) in nucleus which become chromosomes during cell division

4. Cytoplasm- consists mainly of water which allows life processes of cell to occur

5. Endoplasmic Reticulum (ER)- system of fluid filled canals

-transport materials within the cell
-rough ER has ribosomes on surface
-smooth ER does not have ribosomes

6. Golgi Bodies- stacks of flattened membrane sacs

-process, package & store products released by cells
-aids the ER in making the the cell membrane

7. Lysosomes- small sac-like structures surrounded by single membrane

-suicide sacs
-contain digestive enzymes
-produced by golgi bodies

8. Mitochondria- "power house of cell" MIGHTY MITOCHONDRIA

-double layer membrane; inner layer is highly folded for increase surface area
-site of cellular respiration (energy released from food)
-contain its own DNA

9. Microtubules- long hollow cylindrical structures in cytoplasm

-support structure "skeleton of cell"
-found in centrioles, cilia, flagella

10. Microfilaments- "muscles of cell"

-involved in movement of cytoplasm = CYCLOSIS

11. Centrioles- play role in cell division (mitosis)

-in animal cells only lie at right angles

12. Cilia & Flagella- organelles responsible for cell movement

13. Vacuoles- fluid filled sacs (food or contractile)

-in animals usually small
-in plants usually large

14. Ribosomes- make or synthesize proteins

In 1950's, George Palade discovered ribosomes & the function of the endoplasmic reticulum.

15. Plastids- these organelles are found only in plant cells

2 types of plastids

-leukoplasts = store starch

-chloroplasts = sites for photosynthesis & has green chlorophyll pigment, also has its own DNA

in chloroplasts: 1. Grana- membrane stacks of thylakoids for photosynthesis 2. Stroma- material that fills rest of chloroplasts

MAINTAINING CELLULAR HOMEOSTASIS

1. Passive Transport- NO cell energy is used

a. Diffusion- movement of molecules from area of high concentration to an area of low concentration

Concentration Gradient- difference between areas of high + low concentrations [*diffusion only occurs if there is a gradient*]

Equilibrium- molecules are evenly distributed

b. Facilitated Diffusion- specialized transport proteins speed up diffusion

-unlike enzyme does not cause chemical reaction
ex) glucose from blood transported into cell

c. Osmosis- diffusion of "water" through a selectively permeable membrane

-Osmotic Pressure: increased pressure on cell membrane due to osmosis

 

ISOTONIC SOLUTION: a solution that contains the same concentration of dissolved substances as does a living cell place in it

HYPOTONIC SOLUTION: a solution that contains a lower concentration of dissolved substances than inside the cell
ex) cells gain water and swell; animal cells burst (place a salt water fish in freshwater), plant cells gain tugor

HYPERTONIC SOLUTION: greater concentration of dissolved substances than inside the cell
ex) cells lose water and shrink

2. Active Transport- require cell energy (ATP)
-materials move against the concentrated gradient
a. Endocytosis- process of moving materials into a cell by means of a vesicle
(1) Pinocytosis- liquids are taken into the cell
(2) Phagocytosis- the process in which (solid) particles or small
organisms are ingested into a cell

b. Exocytosis- reverse of endocytosis; movement of materials out of the cell

LEVELS of ORGANIZATION

Take a quiz

Organelle Interactive Quizzes

Cells Interactive Quizzes

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