Cells: Structure & Function

Microscope Invented!• The first compound

microscope was created around 1650 by Anton van Leeuwenhoek.

Leeuwenhoek

Cells are discovered!

• The first cells seen were of cork.

• Robert Hooke viewed them under a simple microscope developed by Anton van Leeuwenhoek.

• Hooke described what he saw as “cells,” as those occupied by monks in monastaries

Robert Hooke

Cell Theory Proposed by Schleiden, Schwann, & Virchow

• All organisms are composed of cells.

• All cells come from preexisting cells.

• Cells are the basic units of structure & function.

Virchow

Cell Types:

• Prokaryotic: simple cells that do not have a membrane bound nucleus

E. coli

Staphlococcus

Cell Types:

• Eukaryotic: more advanced cells which do have a membrane bound nucleus.

Paramecium

Ameoba

Euglena

Cell Size

• Cells tend to be microscopic because of diffusion.

• If cells become to large, particles cannot efficiently move in or out of the cell.

Diffusion

Typical Animal Cell

Typical Plant Cell

Cell Structures & their Function:

• The following slides contain the name of the cell organelle along with a picture you have glued onto the back of an index card.

• You are to write the name & function on the back of the picture.

Cell Wall

• Plant, Fungi, & some bacterial cells.

• Provides support & protection.

Chloroplast

• Plant cells, some protists & some bacteria.

• Site of photosynthesis (a process used by autotrophs to make sugars)

Centriole

• Animal cells only.• Special microtubules

(thin tubes of protein that can contract) used to separate chromosomes during cell division.

Lysosome

• Animal cells only.• Special vacuole

containing enzymes used to destroy pathogens (bacteria, fungi, viruses – anything considered deadly to the cell).

Golgi Body

• Packages materials to be secreted from the cell.

• Often described visually as a stack of pancakes.

Microfilaments & Microtubules

• Provide internal structural support.

• Involved in cell movements, internally & externally.

• Made of protein.

Mitochondria

• Provides energy from foods in the form of ATP.

• Referred to as the “Powerhouse” of the cell.

Nucleus

• Contains DNA, the molecule that provides instructions to build protein.

• Often referred to as the “control center” of the cell.

Nucleolus

• Located inside the nucleus.

• Site of RNA synthesis• FYI – RNA is a “sister

molecule” to DNA, the molecule responsible for your unique characteristics.

Plasma (Cell) Membrane• Boundary of animal

cells, next to the cell wall in plants.

• Controls the movement of particles in & out of the cell.

• Described as “selectively permeable.”

Ribosomes

• Site of protein synthesis.

• Not a membrane bound organelle.

Rough Endoplasmic Reticulum (ER)

• Transports the proteins made by its ribosomes throughout the cell.

Smooth ER

• Involved with the synthesis of lipids (fats & oils).

Vacuole

• Storage area for foods, water, & wastes.

Compound Light Microscope

Images from a CLM

Elodea

Red Blood Cells

Copepod

Radiolarian

Preparing a Temporary Wet Mount

• Clean the slide then handle slide by edges• Put a drop of water on the slide• Place specimen in drop of water• Cover drop/specimen with glass coverslip

Types of Transport

Plasma Membrane

Controls the movement of materials into or out of the cell.

Plasma Membrane

• It is the chemistry of the membrane that controls the movement of materials in or out.

• Parts of the membrane have a charge which repels ions

• Large molecules must enter through protein channels

• O2, H2O, and CO2 can all easily pass.

Passive Transport

Movement of particles from an area of high concentration to an area of low concentration that does not require energy.

Types of Passive Transport:

• Diffusion

• Facilitated Diffusion

• Osmosis

Diffusion

• As before, movement of particles from high conctration to low.

• Affected by:• 1. Temperature• 2. Concentration• 3. Pressure• The higher 1,2,3, the

faster the rate of diffusion.

Diffusion Animation

Facilitated Diffusion

• The movement of particles through channel proteins in the membrane.

What Osmosis is Not….

Osmosis• The diffusion of water into or out of a cell• Dependent upon the concentration of particles

inside & outside the cell.• 3 different solutions in which cells can be

exposed:

Isotonic

• “Iso” means equal.

• A cell placed into this type of solution will not gain or lose water.

• Example: Contact saline & your eyeball cells.

• This is the type of solution preferred by animal cells.

Hypotonic

• “Hypo-” means less particles.• A cell placed in this type of solution will

gain more water than it loses.• Example: Tap water & eyeball cells.• This type of solution is preferred by plants;

it causes animal cells to lyse (burst).

Hypertonic

• “Hyper-” means more particles.• A cell placed in this type of solution will lose

more water than it gains.• Example: A salt water solution & throat cells. • Plant cells placed in this type of solution

plasmolize (cell membrane rips away from cell wall)

• Animal cells will shrivel up.

When Membranes are Impermeable:

Elodea in a Hypertonic Solution:

Elodea in a Hypotonic Solution:

Active Transport

• The movement of particles against their normal flow (concentration gradient)

• Requires energy• Analogy: rowing upstream.

Types of:

• Endocytosis: bringing in of particles, See p. 103.

a. Pinocytosis - bringing in of liquids

b. Phagocytosis - bringing in of large particles