Unit a Notes 1 Cell Intro 2005

7/31/2019 Unit a Notes 1 Cell Intro 2005

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CELL STRUCTURE : PART ONE

Cell Theory:

- The study of cells had its birth with the invention

of the microscope. Advances in Cytology (study of

cell) took place in the 1900s with the invention of

better scanning microscopes.

- In the late 1830s two German biologists,

Schleiden (a botanist) and Schwann, (a zoologists)

made similar claims. They found that all

organisms they had studied were composed of

cells. Their discoveries were generalized in the

following statement:

1. The cell is the building block of all

organisms.(All organisms consist of one or more cells)

- A few years later, Rudolph Virchow added the

following observation:

2. All cells come from pre-existing cells.


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Virchow:

- These two statements comprise what is now

known as the CELL THEORY.

Cell Types:

A) Prokaryotic Cells (Pro = First, Karyo =

Nucleus) Primitive (simple) cells.- Do not contain a nucleus or many cell

organelles.

- Lack internal membranes.


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- Only Kingdom Monera (bacteria) have

Prokaryotic cells.

- In Prokaryotic cells, the reactions occur all overthe cytoplasm, and reactions are less efficient.

B) Eukaryotic Cells (Eu =True, Karyo = Nucleus)

Complex cells

- Have a nucleus and many organelles.

- Contains internal membranes.

- Each organelle carries out a certain function.- Eukaryotic cells make up Plants, Animals,

Protists, and Fungi.

Cellular Organelles and Other Cellular

Components:


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Nucleus

- Largest organelle.

- Surrounded by a double-layered membrane

(the nuclear envelope).- Membrane has pores through which larger

molecules pass. (Nuclear Pores)

- Control centre for the cells functions. (The

brain).

- Contains a fluid called the nucleoplasm.

- Contains chromatin (DNA strands which form

chromosomes during cell division).

Nucleolus

- Dark region in the Nucleoplasm.

- One or more found in the nucleus.


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- Site where ribosomal RNA (rRNA) is produced

or stored.

- Involved in interactions between the nucleus and

the cytoplasm.

Chromatin:

- The hereditary material of the cell.

- Condenses to form chromosomes during cell

division.

- Composed of Protein (Histones) and DNA

Chromosomes

- Rod-shaped bodies in the nucleus, only visible

during cell division.

- Contains the hereditary information. (genes)

- Condensed (bunched up) chromatin.

PROTEIN

HISTONE


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Cytoplasm = (Cytosol and cytoplasmic organelles)

- A colloidal substance, which can change from a

solid (gel) to a liquid (solution) state with the

addition of heat or change in metabolic activity.

- It contains and supports all the cells organelles.

Cell Membrane or Plasma Membrane- Composed of proteins and phospholipids (fats

containing a phosphate group).

- Acts as skin around the cells contents.

- Acts as a selectively permeable membrane to

allow movement of materials in and out of the cell.

- Located around the outside of the cell.

- Single- layered membranes are located around

the vacuoles, lysosomes, E.R., Golgi Apparatus.

- Double-layered membrane around the nucleus

and mitochondria.

23 pairs of

chromosomes in

a healthy human

= 46


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- Hydrophilic (water-loving) polar phosphate

heads sticking out, with Hydrophobic (water

fearing) fatty acid tails sticking in.

Smooth Endoplasmic Reticulum

- System of interconnected flattened tubes, sacs, or

canals.- Begins at the nuclear envelope and branches

throughout the cytoplasm to the cell membrane.

- Moves molecules from one area to another.

- It is the site of phospholipid (and steroid)

manufacturing.

- Cells that produce steroid hormones, have an

abundant amount of smooth ER.- Section of both types of ER can break free

blebbing to produce small membrane bound

sacs of either proteins or lipids called vesicles.


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- Often these vesicles contain enzymes that

synthesize lipids and related products such as

steroids.

- Some contain enzymes that detoxify drugs.- Amount of E.R. in a cell increases or decreases

depending on the cells activity.


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Rough Endoplasmic Reticulum

- Like Smooth E.R., but with attached ribosomes.

- Abundant in cells that produce large amounts of

protein for export from the cell.

RoughER

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Unit a Notes 1 Cell Intro 2005