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Cytology &

The Endomembrane System

What are the benefits & problems of the 2 different kinds of microscopy?

Why organelles?

  • By enclosing parts of the cell in membrane, eukaryotic cells are able to SPECIALIZE!
  • Membranes isolate different areas of the cell, which allows the cell to have varied conditions in different regions (different pH, concentrations of different molecules, etc.)
  • Membranes also provide surface for various reactions (Respiration and Photosynthesis, for instance).
  • The specialization of cellular regions is what makes eukaryotic cells so much more complex than prokaryotic cells.
  • Specialization is also a prerequisite for multicellular life (why?)

All cells must do the following things to stay alive:

  • Process matter: Molecules need to be acquired, synthesized and digested
  • Process energy: In order to process matter, energy must be provided. This energy usually comes from one of two places (where?)
  • Process information: The instructions that enable the cell to process matter and energy must be interpreted by the cellular system. Signals from the environment must also be interpreted.

Many cells will also do the following :

  • Reproduce: The information that runs the cell must be passed on to new generations of cells.
  • Communicate: Cells respond to/direct other cells.

Proteins are the molecules that a cell uses to do most of its work.

Here is a brief list of things that proteins do:

  • Build molecules
  • Digest molecules
  • Carry out chemical reactions
  • Provide structure
  • Copy DNA & RNA
  • Receive and send messages to the environment/other cells
  • Receive and send messages to other cells

We have previously discussed protein structure.

The instructions to build proteins are stored in DNA (we can call them "genes")

Any Questions?

Make Sure You Can:

Big Questions:

Why does life require cells?

How are cells organized?

What is the advantage to having organelles?

How do the interactions of cellular components allow for life processes?

Explain the cell theory

Compare different types of microscopy.

Explain why there are no giant cells around.

Refine your contrast of prokaryotic and eukaryotic cells.

Relate the structure and function of the organelles in this presentation.

Explain the interactions of the organelles in this presentation.

Explain how the organelles in this presentation provide for essential life processes.

Introduction

The Wide World of Cells:

Cytology Techniques

Discovery of Cells (1600's)

Cell Types:

Microscopy

Cell Size:

Cell Fractionation

Dead White Men Who Discovered (and were made of) Cells:

Prokaryotic

Light Microscopy:

  • Maximum Magnification- 1000X
  • Maximum Resolution- 10 micrometers (um)

Remember Me?

You Need To!

A way to isolate different components of cells for detailed study

Cells exist in the 10 um - 1 mm size range.

  • "simpler" (no membrane bound organelles)
  • smaller (typically 10-100 um)
  • Much more abundant

Robert Hooke

Anton van Leeuwenhoek

Types of light microscopy:

Cell Theory:

  • All living things are made of cells
  • The cell is the basic unit of life
  • All cells come from pre-existing cells

Eukaryotic

  • lots of membrane bound organelles.
  • larger (100 um - 1mm)
  • 2 major types

There are physical constraints on cell size:

  • Too small: Can't fit all the stuff inside
  • Too big: Can't exchange matter with the environment efficiently.

Electron Microscopy:

  • Maximum Magnification- 10,000,000X
  • Maximum Resolution- 20 nanometers (nm)

"Plant-like"

"Animal-like"

Types of electron microscopy:

(photoautotrophic)

(chemoheterotrophic)

First person to look at biological material under a high powered (~100X) microscope

Coined the term "cells" to describe the appearance of cork under a microscope

...These are not the only 2 contributions

Cytology: The study of cells

2 Major Points

The Utility of Membrane-Bound Organelles

The Life of the Cell

So many compartments = So many options

Cells have systems to do all of these things!

Proteins

The nucleus

An overview of eukaryotic protein synthesis

Structure: a double membrane, with protein pore channels

flourescence image showing nuclei (yellow)

Function: site of DNA storage and replication, information relay to ribosomes

Ribosomes

Structure: a complex of RNA and protein. 2 subunits ("large" & "small"). Eukaryotic ribosomes are larger than prokaryotic ribosomes.

A Ribosome!

The nucleolus is the region of the nucleus where ribosomal RNA genes are concentrated.

It can be seen under magnification as a dark spot on the nucleus.

Function: site of protein synthesis, using an RNA transcript of a gene

The Endomembrane System

2 Kinds of Ribosomes

How eukaryotic cells send proteins from ribosomes to their particular destinations

"Free":

  • floating in cytoplasm
  • make proteins that stay in the cytoplasm

"Bound":

  • Attached to Endoplasmic Reticulum ("ER")
  • make proteins that go into membranes, or are exported from the cell.

Ribosomes become free/bound based on the protein they are making

Endoplasmic Reticulum

Structure: a network of membrane channels attached to the nuclear membrane.

2 kinds:

  • rough: closest to nucleus, covered in bound ribosomes
  • free: farther from nucleus, no bound ribosomes

Vesicles

Structure: A small compartment surrounded by membrane

Function: Various, depending on the contents.

Golgi Apparatus

Function: Rough ER compartmentalizes the cell, provides structural support, & targeted protein synthesis. Smooth ER synthesizes lipids for the cell (for things like membrane), detoxifies compounds, breaks down glycogen.

Structure: A series of flattened, mebrane-bound sacs

The Endomembrane System

Function: synthesis, modification & packaging of molecules

Plasma Membrane

Structure: a phospholipid bilayer with embedded proteins.

Function: Controls transport of matter into and out of cell.

Receives/Sends messages with environment.

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