Cell Structure & Function

Discovery of Cells A. History Of Microscopes

• The microscopemicroscope was developed in the 1600’s, which helped scientists to discover cells.

– 1. Anton van Leeuwenhoeck • Was the first to try stacking several lenseslenses together to view tiny

objects. He looked at pond waterpond water through his lenses. He became the first scientist to describedescribe living cells as seen through a microscope.

– 2. Robert Hooke – used the microscope to examine thin slices of corkcork. He called the tiny boxes he saw cellscells. He chose the name "cells" because the chambers he saw reminded him of rooms in a monasterymonastery which were called cells..

Cell Theory• The discoveries and observations that scientists

made using microscopes led to the development of the cell theory.cell theory.

• The cell theory states…..1. All living thingsliving things are composed of cellscells

2. Cells are the smallest working unit of lifesmallest working unit of life

3. All cells come from pre-existingpre-existing cells through cell divisioncell division.

• All cells contain a cell boundary and DNA.cell boundary and DNA.• There are 2 Types of cells based on the nucleusnucleus

– ProkaryotesProkaryotes & EukaryotesEukaryotes

Types of Cells

• Prokaryotic = “before nucleus”“before nucleus”

• Prokaryotic cells lack a true nucleusnucleus and other membranemembrane bound organelles (internal structures).

• Prokaryotes do contain DNADNA, usually concentrated in a particular region of the cell. All prokaryotes are microscopicmicroscopic and single celledsingle celled.

Prokaryotes

• Eukaryotic = “true nucleus”“true nucleus”

• Eukaryotic cells contain a truetrue nucleusnucleus and other membrane bound organelles.organelles.

• Eukaryotic organisms may be single celledsingle celled or multicellular.multicellular. In multicellular organisms cells become specializedspecialized.

Eukaryotes

Cell Boundaries

There are 2 types of cell boundaries.1. Cell Membrane

2. Cell Wall

Cell Membrane• Every prokaryoticprokaryotic and eukaryoticeukaryotic cell is surrounded by the

cell membrane. It helps to maintain homeostasishomeostasis in the cell by functioning as a protective barrierprotective barrier between the cell and its environment.

• The cell membrane is selectively permeable which means it allows only certain substances init allows only certain substances in and certain and certain substances outsubstances out..

• A.K.A…… the plasma membraneplasma membrane. • The cell membrane is not a fixed sheet of molecules, but

rather it is a fluidfluid structure composed of three biomolecule groups, carbohydratescarbohydrates, lipidslipids, and proteinsproteins.

Cell wall

Cell membrane

Lipids There are two types of lipids that make up the

cell membrane: phospholipidsphospholipids & cholesterolcholesterol

Phospholipid Bilayer• Phopholipids– Phospholipids contain one non-polarnon-polar

end and one polarpolar end. Each phospholipid contains 2 2 non-polar fatty acid tailsnon-polar fatty acid tails and a polar headpolar head.

– The phospholipid bilayerbilayer consists of twotwo layers of phospholipid molecules that surround the cell. The non-polar "tails""tails" point towardtoward each other and the polar headsheads are on the outside forming a sandwich-like membrane.

• Cholesterol – Found in the cell membranes of animal cellsanimal cells onlyonly to help stabilize them.

• Cholesterol is wedged between the non-polar fatty acid tailsnon-polar fatty acid tails of the phospholipid bilayer.

Cholesterol

Carbs & Proteins

• Carbohydrates serve as they are “ID tags”“ID tags” to help identify cells

• Proteins are embeddedembedded in the phospholipid bilayer. Their function is to act as channelschannels and pumpspumps in order to transport specific molecules or ions across the cell membrane.

• A- Phospholipid Bilayer

• B – Protein• Protein Channel

• C – Glycoprotein

• D – Carbohydrate

• E. Cholesterol

• Cell membrane animation

http://www.susanahalpine.com/anim/Life/memb.htm

Cell Wall

• Cell walls are the outer most boundary plantsplants, fungifungi, and bacteriabacteria. They are not found in animal cells.animal cells.

• The primary function of the cell wall is to provide structure and supportstructure and support. The cell wall does not regulate what comes in and outcomes in and out of the cell.

• Cell walls of ……..1. plants are composed of cellulosecellulose2. fungi are composed of chitinchitin3. bacteria are composed of other polysaccharidespolysaccharides