Cell+Organelles

=I. Introduction=

What are Organelles?
A direct translation of the word means "little organs". In the context of Biology we are specifically talking about small organs within individual cells that perform some function. Before we look at the organelles we need to distinguish if a cell is prokaryote or a eukaryote. From there we need to be able to distinguish plant cells from animal cells.

II. There are TWO TYPES OF CELLS (2)
All cells fit into either of two categories: Prokaryotes and Eukaryotes

Prokaryotes & Eukaryotes share these characteristics:

 * have a cell membrane (aka plasma membrane)...that acts as a semipermeable barrier
 * have cytoplasm...that organelles are suspended in
 * have ribosomes...which make proteins
 * have DNA....which are cellular instructions

Prokaryotes differ from Eukaryotes in the following ways:

 * they lack a true nucleus....instead their DNA is a dense bundle
 * they also have no membrane bound organelles: (i.e. no nucleus, no mitochondria, etc.)
 * example of a prokaryote: bacteria like //E. coli//
 * To summarize prokaryotic cells and their organelles are much simplier than eukaryotic cells. This is said because they do not have highly specialized organelles.

Eukaryotes differ from Prokaryotes in the following ways:

 * has a true nucleus with DNA contained inside
 * has membrane bound organelles
 * example of a eukaryote: human muscle and brain cells
 * To summarize eukaryotic cells and their organelles are more advanced than prokaryotic cells. This is true because they have highly specialized organelles that perform specific functions.


 * Note that the shape of a cell does not strictly make it a prokaryote or a eukaryote. The text consistently uses similar drawings with prokaryotes having a pill shape and eukaryotes as round. Shape has little to do in distinguishing the two.
 * Note that the presence of an external cillia or flagella does not make it a prokaryote or a eukaryote.**

To know how to distinguish a prokarote from a eukaryote you must look at the cell closely.

III. Comparing and Contrasting Plant & Animal Cells
In terms of identifying wheather a cell is a plant OR an animal cell you need to look at the whole cell.
 * I had asked you to create a Venn Diagram to illustrate this concept.**
 * Check your answers**

__Plant cells__
cell membrane **(aka plasma membrane)** chloroplasts **with** chlorophyll **- these will be green**
 * a** vacuole **(aka central vacuole) - typically as large or larger than most other organelles**

__Animal cells__
DIFFER

__**from plant cells because:**they have a__
centrosome **- make** microtubules **- what are those for**

__Animal and plant cells have the following__
IN COMMON cell membrane **(aka plasma membrane)** cytoplasm lysosomes **with digestive enzymes** rough ER **and** smooth ER mitochondria ribosomes Golgi apparatus **(aka Golgi body)**
 * a** nucleus **with** nuclear pores **(outside),** DNA **(inside) and** a nucleolus **(inside - dense circular bundle)**
 * a** nuclear membrane

Practice with pictures:

A. Introduction
Sections 7.2 & 7.3 do a good job explaining the structure and function of the cell membrane (plasma membrane) and all other cellular structures. It might be helpful to note a few things


 * The term **membrane** **bound organelle and organelle is used synonymously when they really aren't the same.**
 * i.e. a ribosome is an organelle which makes protein but it is not bound by a membrane
 * i.e. nuclear pores are holes in the nuclear envelope which makes the nucleus a membrane bound organelle

1. Function of the plasma membrane…what does it do?
The survival of all cells relies on its ability to maintain homeostasis...maintaining stable environment inside the cell when the outside changes or becomes harsh. We said the cell membrane (in both plants and animals) creates a semi permeable barrier between the inside and outside of the cell. So think of some new examples of homeostasis you can think of in cells as you read below.

**a. So what substances need to be let into and out of the cell through the plasma membrane?**
__**i). In**__…a steady supply of: Water (H2O) Ions (charged particles) Glucose (a specific type of sugar with the formula C6H12O6) Lipids (fats) Amino Acids (the building blocks of protein)

__**ii). Out**__…when levels get too high: Water Ions Byproducts (waste) of glucose, lipids, and amino acids Other waste products

2. Structure of the plasma membrane….what it is made-up of?
The cell membrane is made of a phospholipid bi-layer and other components A phospholipid molecule has two parts: 1) Phosphate group (PO4) – the polar (charged) head 2) Glycerol (the lipid) – the non-polar (neutral) tail

Phosphate group 2 Fatty Acids Tails of Glycerol  The bilayer of phospholipid molecules is arranged · with the polar phosphate groups touching the external environment and inside of the cell (the cytoplasm) · with the two fatty acid tails facing each other  **Note: the plasma membrane is not just a bilayer of pure phospholipds.**

<span style="font-family: Arial,Helvetica,sans-serif;">**Cholesterol** – prevents fatty acid chains from sticking together
 * <span style="font-family: Arial,Helvetica,sans-serif;">So also imbeded inside of the bilayer you also have: **
 * Transmembrane proteins** – act as transport channels to move substances into and out of the cell
 * Carbohydrates** – generic name for different types of sugars



<span style="font-family: Arial,Helvetica,sans-serif;">Altogether this phospholipid bilayer is somewhat flexible and "fluid" <span style="display: block; font-family: Arial,Helvetica,sans-serif;"><span style="font-family: Arial,Helvetica,sans-serif;">The fluid mosaic model points-out that phospholipid molecules move  <span style="display: block; font-family: Arial,Helvetica,sans-serif;"> <span style="display: block; font-family: Arial,Helvetica,sans-serif;">Proteins move along with the phospholipids to create “a mosaic”
 * <span style="font-family: Arial,Helvetica,sans-serif;">spin (clockwise or counterclockwise)
 * <span style="font-family: Arial,Helvetica,sans-serif;">are not in a rigid/fixed location over time

Recap: We have said plants have a cell membrane and a cell wall. The cell wall is rigid unlike the cell membrane. It provides protection and support to plants. <span style="display: block; font-family: Arial,Helvetica,sans-serif;">**The summarized function of the plasma membrane in both plants and animals is....** <span style="display: block; font-family: Arial,Helvetica,sans-serif;">**homeostasis.....to act as a semipermeable barrier regulating the flow of water, ions, glucose, lipids, and** <span style="display: block; font-family: Arial,Helvetica,sans-serif;">**other substances.**

V. Organelles
<span style="display: block; font-family: Arial,Helvetica,sans-serif;">The textbook groups organelles by a common function. I will stick with this format for your notes with one exception. I want to talk about external organelles and then discuss internal organelles grouped by a similar function. Practice without pictures:





Chapter 7 Vocab on [|Quizlet]

__Cilia__ __vs. Flagella__ Cilia are
 * A. External**
 * used for locomotion
 * much shorter in length than flagella
 * typically cover most of the exterior of certain cells and have an oscillating motion about them

Flagella is a long whip-like tail on a cell that are
 * used in locomotion, defense, and consumption (yes eating)
 * are longer than cilia
 * typically only a single organelle that attaches to one part of the organisms' body

__Cell wall__ (in plants, made of cellulose) - the outer most layer of support and protection __Cell membrane__ (in plants and animals, made of a phospholipid bi-layer) - semi-permeable barrier which helps make homeostasis possible.

Cytoplasm Cytoskeleton
 * B. Internal (by this I mean inside the cytoplasm)**

Nuclear Envelope (a.k.a nuclear membrane) Nucleus Chromatin Nucleolus

Ribosomes Rough ER (Endoplasmic Reticulum) Smooth (Endoplasmic Reticulum)

Lysosomes Golgi body (a.k.a Golgi apparatus)

Centrosomes Microtubules

[|This] is a nice slideshow by Massengale which looks better than these notes but also has lots of other information.