Cell Biology

Cells

• Cell – Smallest unit of life that can function independently

– Discovered by Robert Hooke – 1660

– Antony van Leeuwenhoek – improved lenses, made observing cells easier

• Cell Theory – Schleiden, Schwann

– All organisms are made of one or two cells

– Cell fundamental unit of all life

Surface Area/Volume

History of Cell Biology

Robert Hooke 1635-1703

History of Cell Biology

Anton von Leeuwenhoek 1673-1723

Leeuwenhoek Microscope(circa late 1600s)

History of Cell Biology

Cell Theory: 1800s

Theodor Schwann Matthias Schleiden

Microscopes

• Microscope uses an energy source (light, electrons, ect.) to view objects under magnification– Can view things that you cannon view with the naked eye– Light Microscopes – uses light to view things in real color,

item must be thin enough to get light thru.• Compound – uses 2 or more lenses to focus visible light through

a specimen, magnify 1600 times• Confocal – focus white or laser light through a lens to the

object.

– Electron Microscopes – MUCH higher magnification• Transmission – Sends beam of electrons through a sample• Scanning – Sends beam of electrons over the surface of object

Microscopy

Why do we need microscopes?

Resolution

Resolution: ability to distinguish two points as distinct

Picture created and printed at a high resolution

Picture created and printed at a low resolution

Microscopy

Light MicroscopyADV: living cells

DISADV: low resolution

Light Microscopy

Phase Contrast

Light Microscopy

Differential Interference Contrast

Electron Microscopy

Uses beams of electrons

Electron Microscopy

Scanning Electron Microscopy (SEM)ADV: shows details of cell surfaces

Electron Microscopy

Transmission Electron Microscopy (TEM)

Cell Structures

• All cells have these structures:

– DNA

– RNA

– Ribosomes – make proteins

– Proteins

– Cytoplasm – fluid filling of the cell

– Cell Membrane – makes a boundary between inside and outside of cell

Types of Cells – Prokaryotic

• Lack a true nucleus and membrane bound organelles

• Domains Bacteria and Archaea

• Structures:– Nucleoid – contains cells DNA, NOT bound by a

membrane

– Cell Wall – rigid, outside of cell membrane, gives cell its shape (rod-shaped, round, spiral)

– Flagella – whip-like tail for movement

Types of Cells - Eukaryotic

• All other cells except for bacteria, archaea

– Plants, animals, protists, fungi

• Domain – Eukarya

• Have MEMBRANE BOUND organelles, larger than prokaryotic

• 2 basic types of eukaryotic cells

– Animal

– Plant

Cell Membrane

• Function: – Separate cell from environment– Transport substances in and out of cell– Receive and respond to stimuli

• Properties– Hydrophobic and hydrophilic– Selectively permeable

• Structure:– Phospholipid bi-layer– Fluid mosaic of phospholipids, sterols, proteins

• Transport Proteins

• Enzymes

• Recognition Proteins

• Adhesion Proteins

• Receptor Proteins

Proteins

Animal cell membrane

• Cell wall

– Maintain structure

– Maintain internal pressure

Nucleus

• Function:– “Brain” of the cell

– Contains DNA, mRNA

• Structure– Nucleolus – assemble ribosomes

– Nuclear envelope – separates nucleus from cytoplasm

– Nuclear pores – holes in envelop with channels for mRNA to leave nucleus

Nucleus

Nuclear envelope

Nucleolus

Nuclear pore

1) Nuclear envelope2) Outer ring3) Spokes4) Plug

Nucleus

Endoplasmic Reticulum and Ribosomes

• Rough Endoplasmic Reticulum (ER)– Function: Help make cell membrane and secretory

proteins for various bodily functions• In pancreas, insulin; leukocytes, antibodies

– Structure: Connected to nuclear envelop and cell membrane with ribosomes on outside

• Smooth ER– Function: Make and store proteins, carbohydrates, lipids

• In liver, enzymes for detox; muscle, proteins for contraction

– Structure: Same as smooth ER – ribosomes

• Ribosomes– Function: Assemble proteins for the cell– Structure: Large and small subunits

The Endomembrane System

Rough Endoplasmic Reticulum: makes secreted and

membrane proteins, and proteins destined for some organelles

The Endomembrane System

Smooth Endoplasmic Reticulum: synthesizes lipids,

steroids, detoxifies

The Endomembrane System: Endoplasmic reticulum

Rough ER

The Endomembrane System: Endoplasmic reticulum

Golgi Apparatus

• Function:

– Process and complete protein production

– Sorts and packages proteins to send to cell membrane and out or as membrane proteins

• Structure:

– Stack of flat membrane enclosed sacs

The Endomembrane System: Golgi

Receives vesicles from RER and packages proteins for export

The Endomembrane System: Golgi

Receives vesicles from RER and packages proteins for export

Lysosomes

• Function: – Digestion

– Enzymes to break down and recycle food, bacteria, old organelles

• Structure:– Made by Golgi Apparatus

– Fuse with vesicles that have things that need to be digested

• Number of lysosomes depends on type of cell– White blood cells, liver cells - lots

The Endomembrane System: Lysosomes

Membranous sac of digestive enzymes

Vacuoles

• Function:– Same as lysosomes

– Replace lysosomes in plant cells

– Growth

– Maintain pressure

– Holds pigments

– Contractile vacuole – protists (pump water, digest)

• Structure:– Contains water solution of enzymes, sugars, salts,

weak acids

The Endomembrane System: Vacuoles

• Various Functions http://www.youtube.com/watch?v=iG6Dd3COug4

Contractile vacuole

Central vacuole

Peroxisomes

• Function:

– Dispose of toxic substances

– Protect cells from toxic byproducts

• Structure:

– DIFFERENT from lysosomes that originate from ER NOT Golgi body

Peroxisomes

Peroxisomes (green)

Cytoskeleton

• Function: – Transportation within the cell– Support– Cell division– Connectivity– Movement – Cilia and flagella

• Structure:– Network of protein tubules and tracks

• Microfilaments• Intermediate filaments• Microtubules – organized by centrosomes

The Cytoskeleton and Cell Surfaces

Microfilaments

Functions

(1) Structure

(2) Cell motility (muscles)

The Cytoskeleton and Cell Surfaces

Intermediate Filaments

Functions:

(1) Cell shape

(2) Anchor organelles

Keratin intermediate filaments (red)

The Cytoskeleton and Cell Surfaces

Microtubules

Functions:

(1) Support

(2) Tracks

(3) Cell division

The Cytoskeleton and Cell Surfaces: Cilia and Flagella

http://www.youtube.com/watch?v=QGAm6hMysTA

http://www.youtube.com/watch?v=7kM_kRPrcrkhttp://www.youtube.com/watch?v=09kLIsNfaO8&NR=1

Cilia

The Cytoskeleton and Cell Surfaces: Cilia and Flagella

Structure:

9+2

Basal body

Dynein

Spokes

Extracellular Matrix

Glycoproteins: proteins + carbohydrates, fibers

Extracellular Matrix

Glycoproteins: proteins + carbohydrates, fibers

C-terminally truncated human glypican-1

Endosymbiotic Theory

Chloroplast

• Function:– Site of photosynthesis

– Only 1 type of plastid – all have different pigments

• Structure– Double membrane

– Stroma – inner fluid

– Thylakoid – stacked disks with grana• Have photosynthetic pigments (chlorophyll)

– Have OWN DNA and ribosomes

Plastid

Chloroplast

Mitochondria

• Function:– Powerhouse of the cell

– Carries out cellular respiration

• Structure:– Double membrane

– Matrix – inner “goo”

– Crtistae – folds in inner membrane w/ enzymes for cellular respiration

– Have OWN DNA

Cell Junctions

Type Function Example Location

plasmodesmata enable direct, regulated, symplastic intercellular transport of substances between cells

plant cell walls

tight junctions hold cells together; help to maintain the polarity of cells; prevent the passage of molecules and ions through the space between plasma membranes of adjacent cells

the kidney and liver

anchoring (adhering) juctions

serve as a bridge connecting the actin cytoskeleton of neighboring cells through direct interaction

epithelial and endothelial tissues

gap junctions connects the cytoplasm of two cells, which allows various molecules, ions, and electrical impluses to directly pass through a regulated gate between cells

nerves

Cell Junctions: Tight Junction

Cell Junctions: Anchoring (Adhering) Junction

Cell Junctions: Gap Junction

Organelles Summary

Organelle Structure FunctionPlantCells?

Animal Cells?

Nucleus contains DNA and RNA provides a segregated site for genetic transcription, allowing levels of gene regulation that are not available to prokaryotes

Yes Yes

Ribosome highly complex; made up of dozens of distinct proteins

serves as the primary site of biological protein synthesis (translation)

Yes Yes

Rough endoplasmic reticulum

membrane studded with ribosomes manufacture of secreted proteins; manufacture of lysosomal enzymes

Yes Yes

Smooth endoplasmic reticulum

membrane (smooth) synthesizes lipids, phospholipids, and steroids Yes Yes

Golgi apparatus large stacks of membrane-bound structures

packages proteins inside the cell before they are sent to their destination

Yes Yes

Lysosome spherical vesicles containing enzymes break down proteins, nucleic acids, carbohydrates, lipids, and cellular debris

Rarely Yes

Central vacuole enclosed compartments filled with water isolates materials that might be harmful or a threat to the cell; contains waste products

Yes No

Peroxisome lipid bilayer membrane; crystalloid core (not always present)

breakdown very long chain fatty acids; detoxify various toxic substances that enter the blood

Yes Yes

Chloroplast outer and inner membrane surrounding thylakoid system

conduct photosynthesis Yes No

Mitochondrion Membrane surrounding cristae and matrix (containing mitochondrial DNA)

generate most of the cell's supply of ATP, used as a source of chemical energy

Yes Yes

Cytoskeleton network of fibers composed of proteins; dynamic

allows cells to migrate; stabilizes tissues Yes Yes

Cell wall tough, flexible layer surrounding cells protection and filtering Yes No