Unit One- Chapter 3 Cell Structure

Unit One- Chapter 3Cell Structure

Mrs. CookBiology

History of the Microscope

• Robert Hooke-• 1665- used an early light microscope to look

at slice of cork from an oak tree. • What he saw looked like little boxes that he

called “cells”• He noticed that the cells of trees, roots and

stems looked similar.

Anton Van Leeuwenhoek•1673- Dutch scientist observed first living cells- “microorganisms”. Invented the microscope.• observed cells from algae called spirogyra and bell-shaped cells on stalks of protists called vorticella.• called these organisms “beasties” and then formally “Animacules” we now call them Protists.

The Cell Theory

• 1838, German Botanist- Matthais Schleiden said that all plants were made of cells.

• 1839, German Zoologist, Theodor Schwann said the same thing for animals.

• The German Physician, Rudolf Virchow (1821-1902), said that all cells come from other cells.

The Cell Theory

• These ideas were combined to form a basic theory about the cellular nature of life called The Cell Theory.

1. All living things are made of one or more cells.

2. Cells are the basic units of structure and function of organisms.

3. All cells arise from existing cells.

Note: somatic cells = body cellsgametes = sex cells (sperm and eggs)

All living things include the following characteristics

• ORGANIZATION• METABOLISM• CHANGE WITH TIME• RESPOND TO STIMULI• REPRODUCTION• MAINTAIN HOMEOSTASIS• GROWTH & DEVELOPMENT

Microscopes• The continuous development of microscopes has helped

scientists to clarify our definition of life.

Compound Microscope Scanning electron Microscope

Microsopes cont. • Light microscope: light passes through one or more

lenses to produce an enlarged image.

• Electron microscope: forms an image using a beam of electrons rather than light.

• Parts of a microscope:• Magnification- is the quality of making an image

appear larger than the objects actual size.

• Resolution- is a measure of the clarity of an image

Compound Light microscope

Cell Features• We have trillions of cells that range from 5 nanometers in size to 20

nanometers.

• So, Why do we have trillions of little cells instead of fewer larger cells?• This has to do with surface area to volume ratio.

• Smaller the cell, the quicker it can get substances into the cell and to the area that needs them. The larger the cell, the longer it would take for the substances to travel through the cell.

http://youtu.be/wuXSEOKNxN8

Cell Features cont. http://youtu.be/o1GQyciJaTA

• All cells share 3 common features:1. Cell Membrane (aka plasma cell membrane)-

- the cells outer boundary -acts as a barrier between the inside and the outside of the cell- All materials must enter or exit through this• castle walls• Gates to Turnpike

Cell Features Cont. • 2nd feature common to all cells:

2. Cytoplasm- - the region inside the cell membrane that

includes all fluids (Cytosol), organelles (tiny organs), and the nucleus.

Cell features cont.

• 3rd feature common to all cells:3. DNA

-all cells have DNA for regulating function and reproduction.

- DNA in some cells floats freely- Other cells have a membrane bound

organelle, that contains the cells DNA, called the Nucleus.

Two Basic Types of Cells

Prokaryotes• Smallest and simplest cells• Single celled organisms (bacteria, amoebas)• Lacks a nucleus, has circular DNA• No organelles• Has a protective cell wall surrounding its cell

membrane. Gives the cell structure, stability, and shape.

• Most have flagella- long threadlike structures that protrude from the cell’s surface for movement.

Second Type of Cell

Eukaryotic Cells• cells that have a nucleus

- Nucleus -internal compartment that holds the cell’s DNA - Control center for the cell

• Has specialized structures called organelles.- Organelles- well defined structures that

carry out specific functions within the cell. - located inside the cell membrane

and outside the nucleus• Cilia- some single celled Eukaryotes contain them

to move around- short hair like flagella.

Cell Structures• Cytosol-(watery part of the cytoplasm).

- fluid surrounding the cytoplasm’s organelles, internal membranes, and cytoskeleton fibers.

• Cytoskeleton--holds the cell together and keeps the cell’s

membranes from collapsing. - made up of thin tubes and filaments- also acts as a system of tracks for things to

move around the cell

Cell Structure Cont.• 3 types of Cytoskeleton:

1. Actin Fibers- form a network just beneath the cell membrane. Contracts and expanding to help keep the cell’s shape.

2. Microtubles- act as a highway system for the transportation of information from the nucleus to organelles in the cell.

3. Intermediate Fibers- provide a framework to keep organelles in a particular region of the cell.

Cell Structure Cont.• Cell Membrane

- primarily made of lipids- makes a barrier that separates the

outside of the cell from the inside of the cell- it allows only certain substances in the

environment to pass through, “selectively permeable”

Lipid Bi-layer-phosolipids are arranged in a double layer-non-polar tails make up the interior of the bi-layer. - “Hydrophobic” -polar heads make up the outside of the bilayer. - “Hydrophilic”

Cell Structure cont. • Phospholipid bi-layer contains several types of

Membrane Proteins1. Marker Proteins- attached to carbohydrate on

cell surface and advertise cell type- heart cell, liver cell, etc.

2. Receptor Proteins- recognize and bind to substances outside the cell. Ex: hormones

3. Enzyme- assist in chemical reactions inside the cell.

4. Transport Proteins- move substances into and out of the cell.

Figure 12, Pg 61

Cell Organelles• Nucleus-

- Control center of the cell. Houses and protects the cells genetic information, DNA.

- when the cell is not dividing DNA is in the form of Chromatin.

- when the cell is dividing, DNA is in the form

of chromosomes.- Contains its own protective cover called the Nuclear

Envelope.- Contains small channels called nuclear

pores. - RNA, made in the nucleus, moves out of the

nucleus through these pores.

Cell Organelles cont. • Nucleus cont.

- Nucleolus- location of the assembly of Ribsomes.

Nucleus

Cell Organelles cont. • Ribosome

- Organelle made of Protein and RNA, and directs Protein Synthesis in the cytoplasm. (They make proteins).

- round in shape- some are free in the cytosol and some are attached to another organelle called the Rough Endoplasmic Reticulum.

Ribosomes

Cell Organelles cont. • Endoplasmic Reticulum (ER)-

- system of tubes and sacs that function as a intercellular highway to move molecules through the cell.-Two Type of ER-

- Rough ER-- covered in Ribosomes-makes phospholipids and

proteins- little sacs or vesicles can pinch

off from the end of the ends of the rough ER and store products until the are released from the cell.

Cell Organelles cont. • 2nd type of ER

- Smooth ER-- does not have

Ribosomes- most cells contain very

little smooth ER- build lipids such as

Cholesterol- produces estrogen and

testosterone in the ovaries and testes; makes calcium in the skeletal and heart muscles.

Endoplasmic Reticulum

Cell Organelles cont.

• Golgi apparatus-- Set of flattened, membrane bound sacs that serves

as the packaging and distribution center of the cell. - Vesicles, containing proteins, that leave the ER move to

the Golgi apparatus. - Enzymes with in the Golgi apparatus modify the proteins

from the ER.- They repackage the proteins in new vesicles which then

leave the Golgi apparatus. - The vesicles then move to the cell membrane, where

they release their contents outside the cell.

Golgi Apparatus

Cell Organelles cont. • Lysosomes

- bud from the Golgi apparatus and contain digestive enzymes. - break down larger molecules- digest old or worn out organelles- breaks down the cell when it is time to die

Lysosomes

Cell Organelles cont. • Mitochondria

- makes energy for the cell by changing organic molecules to ATP. “Power House” of the cell. - The more active a cell is the more mitochondria it will have (like a muscle or heart cell).- Has two membranes; outer membrane is smooth & the inner membrane is folded. - has its own DNA that it uses to make some proteins.

http://youtu.be/4DWaAIVlW3k

Mitochondria

Tour of the Cell

Cell Organelles and their Functions

Cell Organelles cont.• Cilia

-HAIR-LIKE STRUCTURES THAT EXTEND FROM THE SURFACE OF THE CELL

- ARE USED FOR MOVEMENT-ARE SHORT AND ARE PRESENT IN LARGE

NUMBERS

Cell Organelles cont.

Flagella• HAIR-LIKE STRUCTURES THAT EXTEND FROM

THE SURFACE OF THE CELL• ARE USED FOR MOVEMENT• ARE LONG & FAR LESS NUMEROUS IN CELLS• WORK IN A WHIP-LIKE MOTION PROPELLING

CELLS

Cell Organelles cont.

• Centrioles• CONSIST OF TWO SHORT CYLINDERS OF

MICROTUBULES AT RIGHT ANGLES TO EACH OTHER

• ARE SITUATED IN THE CYTOPLASM NEAR THE NUCLEAR ENVELOPE

• OCCUR IN ANIMAL CELLS WHERE THEY ORGANIZE MICROTUBULES FOR CELL DIVISION

Structures of Plant Cells• ***(Add into Notes) Plants have

every organelle that animals cells do with the exception of Centrioles.

• Plant cells have 3 additional structures than the animal cell structures we discussed. 1. Cell Wall-

- rigid layer found outside the cell membrane

- made of cellulose- helps support and

maintain the shape of the cell, protects it from damage, and connects it with adjacent cells.

Plant cell structure cont.

2. Chloroplast- - organelle that uses light energy to make carbohydrates from carbon dioxide and water. - contains the green pigment, Chlorophyll, that absorbs and captures light energy for the cell. -along with mitochondria, supply energy for the activities of plant cells.

Plant cell structure cont.

3. Central Vacuole- much of the cell’s volume is made up of this- stores water, stores ions and nutrients, and contains wastes.- when it is full it makes the cell rigid and enables the plant to stand upright. (empty and the plant wilts.)

Tour of a Plant Cell