CELLS All organisms are made up of cells The cell is the unit of structure and function of all living things Life arises from the interaction of all cellular.

CELLS

• All organisms are made up of cells

• The cell is the unit of structure and function of all living things

• Life arises from the interaction of all cellular components.

You must check this web site

• www.cellsalive.com

There is correlation between the structure of cells and their function

Ex: The shapes of muscles cells, sperm cells, red blood cells,, nerve cells are appropriate for their function.

Example: the flat tile like epithelial cells of the skin fit closely together making a barrier to bacterial entrance, water loss etc.

Another way to say this is that

“shape reflects function”

How small are cells?

Most cells are microscopic– Cells vary in size and shape

Human height

Length of somenerve andmuscle cells

Chicken egg

Frog egg

Un

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Lig

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Ele

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10 m

1 m

100 mm(10 cm)

10 mm(1 cm)

1 mm

100 m

10 m

1 m

100 nm

10 nm

1 nm

0.1 nmAtoms

Proteins

Small molecules

Lipids

Viruses

Ribosome

Nucleus

Mycoplasmas(smallest bacteria)

Most plant andanimal cells

Most bacteria

Mitochondrion

History• Robert Hook (1665) named “cells” after observing tiny

compartments in cork .• Anton VanLeeuwenhoek (1600’s) improved the

primitive microscopes and observed one celled organisms, even bacteria. He documented his findings with letters and diagrams to the Royal Society (of Science) in London.

• Robert Brown (1600’s)discovered the nucleus• Electron microscope was developed in the late 1930’s

and allows scientist to see up to 0.5 nanometers. About 1000 times larger than regular microscopes.

How are cells studied?

Microscopes and Biochemistry– The light microscope (LM) magnify cells up to 1000 times

• Enables us to see the overall shape and structure of a cell

Eyepiece

Ocularlens

Objective lens

Specimen

Condenserlens

Lightsource

Figure 4.1A

– The electron microscope• Allows greater magnification and reveals cellular

details

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Figure 4.1C Figure 4.1D

The cell theory (mid-1800’s)

• Mathew Schleiden and Theodor Schwann examined plant and animal tissues and came to the conclusion that they both consist of cells

• Rudolph Virchow came to the conclusion that young cells come from the division of other cells

•  1.    All organisms are made up of cells• 2.    Cells are the units of structure and function of all

living things, that is cells have all the properties of life.• 3.    All cells come from pre-existing cells

• Prokaryotic cells are structurally simpler than • eukar yotic cells

– There are two kinds of cells• Prokaryotic- No nucleus- Bacteria and Archeae• Eukaryotic- have nucleus- plants, animals and fungi

Prokaryotic cell

Nucleoidregion

Nucleus

Eukar yotic cell Organelles

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Figure 4.3A

– TYPE OF CELLS: Prokaryotic and Eukaryotic

– Prokaryotic cells are small, relatively simple cells • That do not have a membrane-bound nucleus

Prokar yoticflagella

Ribosomes

Capsule

Cell wallPlasmamembrane

Nucleoid region (DNA)

Pili

Eukaryotic cells have a nucleus and are

par titioned into functional compar tments.– All other forms of life( plants and animals) are

composed of complex eukaryotic cells– Membranes form compartments inside

eukaryotic cells to facilitate metabolic activities

– A small cell has a greater ratio of sur face area to volume

• Than a large cell of the same shape

30 m 10 m

30 m 10 m

Surface areaof one large cube 5,400 m2

Total surface areaof 27 small cubes 16,200 m2

– A typical animal cell• Contains a variety of membranous organelles

NucleusSmooth endoplasmicreticulum

Roughendoplasmicreticulum

Ribosomes

Golgiapparatus

Plasma membrane

Mitochondrion

Flagellum

Not in mostplant cells Lysosome

Centriole

Microtubule

CytoskeletonIntermediatefilament

Microfilament

Peroxisome

THE CYTOSKELETON AND RELATED STRUCTURES

The cell’s internal skeleton helps organize its structure and activities– A network of protein fibers

• Make up the cytoskeleton.

Actin subunit

Microfilament

7 nm

Fibrous subunits

10 nm

Intermediate filament Microtubule

25 nm

Tubulin subunit

Functions of the cytoskeleton

– Tubules and filaments are made up of protein fibers

– Microfilaments of actin • Enable cells to change shape and move

– Intermediate filaments • Reinforce the cell and anchor organelles

– Microtubules give the cell rigidity• provide anchors for organelles and act as tracks for

organelle movement

Over view: Many cell organelles are connected through the endomembrane system

– All cells on earth are enclosed in membranes that maintain internal conditions different from the surroundings, have DNA as their genetic material and can convert forms of energy from one to another.

– Membranes form the boundaries of many eukar yotic cells

• Compartmentalizing the interior of the cell and facilitating a variety of metabolic activities

– The nucleus is the cellular control center• Containing the cell’s DNA, which directs cellular

activities NucleusChromatin

Nucleolus

Pore

Ribosomes

Roughendoplasmicreticulum

Two membranesof nuclearenvelope

Figure 4.5

ORGANELLES OF THE ENDOMEMBRANE SYSTEM

The nucleus is the cell’s genetic control center– The largest organelle is usually the nucleus

• Which is separated from the cytoplasm by the nuclear envelope

Inside the nucleus• Chromatin fibers made up of DNA

These thin fibers coil up during cell division becoming thicker and visible. They are called now a chromosome

Nucleolus makes ribosomes

– Ribosomes on the sur face of the rough ER• Produce proteins that are secreted,

inser ted into membranes, or transpor ted in vesicles to other organelles

Secretory(glyco-) proteininside trans-port vesicle

4Transport vesiclebuds off

Sugar chain

3

Rough ER

Glycoprotein2Polypeptide

Ribosome

1

The endomembrane system is a collection of membranous organelles

• That manufactures and distributes cell products\

Smooth endoplasmic reticulum has a variety of functions – Smooth endoplasmic reticulum, or smooth ER

• Synthesizes lipids

• Processes toxins and drugs in liver cells

• Stores and releases calcium ions in muscle cells

Smooth ER

Rough ER

Nuclearenvelope

Rough ERRibosomes

Smooth ER

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– A typical animal cell• Contains a variety of membranous organelles

NucleusSmooth endoplasmicreticulum

Roughendoplasmicreticulum

Ribosomes

Golgiapparatus

Plasma membrane

Mitochondrion

Flagellum

Not in mostplant cells Lysosome

Centriole

Microtubule

CytoskeletonIntermediatefilament

Microfilament

Peroxisome

The Golgi apparatus finishes, sorts, and ships cell products– Stacks of membranous sacs receive and modify ER

products• Then ship them to other organelles or the cell sur face

Figure 4.9

Golgi apparatus

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Transportvesicle fromthe Golgi“Shipping” side

of Golgi apparatus

Golgiapparatus

“Receiving” side ofGolgi apparatus

Transportvesiclefrom ER

New vesicleforming

The endomembrane system– The various organelles of the endomembrane system

• Are interconnected structurally and functionally

Nucleus

Smooth ER Nuclear envelope Golgi apparatus

Lysosome

Vacuole

Plasmamembrane

Rough ERTransport vesiclefrom ER to Golgi

Transport vesicle fromGolgi to plasma membrane

Mitochondria gets chemical energy from food– Mitochondria carry out cellular respiration

It uses the chemical energy in food to make ATP for cellular work

Mitochondrion

Outermembrane

Intermembranespace

Matrix

Innermembrane

Cristae

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Lysosomes are digestive compar tments within a cell– Lysosomes are sacs of enzymes that function in

digestion within a cell

Golgiapparatus

Plasmamembrane

“Food”

Foodvacuole

Lysosomes

2Lysosomeengulfingdamagedorganelle

5

Digestion4

3

Engulfmentof particle

Transport vesicle(containing inactivehydrolytic enzymes)

1

Rough ER

– Lysosomes in white blood cells• Destroy bacteria that have been ingested

• lysosomes also help to digest worn out , damaged cell parts, recycle materials within the cell and fuse with food vacuoles to digest nutrients.

Figure 4.10B

Lysosome

Nucleus

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Lysosomes in white blood cells destroy bacteria and lysosomes also can digest other parts of the

cell

Abnormal lysosomes can cause fatal diseases– Lysosomal storage diseases. These are rare.

• Inter fere with various cellular functions

• Ex: Tay- Sachs, does not break down lipids in nerve cell membranes. Lipids accumulate

• Pompe’s disease, lysosomes cannot digest glycogen and it accumulates in muscle and liver cells

Peroxisomes• Specialized vesicles that contains enzymes

(catalase) that digest hydrogen peroxide H2O2

• Our cells produce hydrogen peroxide during metabolism and the enzymes in peroxisomes break it down into water and oxygen gas which are harmless to the cell.

Plant Cells

• Three organelles animals do not have

Chloroplasts

Cell wall

Central vacuole

– A typical plant cell has some structures that an animal cell lacks

• Such as chloroplasts and a rigid cell wall

CentralvacuoleNot in

animalcells

Chloroplast

Cell wall

Golgiapparatus

Nucleus

Microtubule

CytoskeletonIntermediatefilament

Microfilament

Ribosomes

Smoothendoplasmicreticulum

Mitochondrion

Peroxisome

Plasma membrane

Roughendoplasmicreticulum

ENERGY-CONVERTING ORGANELLES

Chloroplasts conver t solar energy to chemical energy. This is where PHOTOSYNTHESIS takes place– Chloroplasts, found in plants and some protists

Conver t solar energy to chemical energy in sugars

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Chloroplast

Stroma

Intermembranespace

Inner and outermembranes

Granum

Vacuoles function in the general maintenance of the cell– Plant cells contain a large central vacuole,

• Which has lysosomal and storage functions

Chloroplast

Centralvacuole

Nucleus

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Central vacuoles in plants

Also help increase the size of cells by absorbing water

Are mostly water, minerals and nutrients

• Store color pigments (that attract insects)

• Store waste products and poisons

– Some protists have contractile vacuoles • That pump out excess water

LM

65

0

Nucleus

Contractilevacuoles

Organelles• NAME LOCATION FUNCTION

• Cytoskeleton cytoplasm Maintains cell shape

facilitates movement and move

materials within the cell

• Cytosol cytoplasm Protein rich fluid in which

organelles and cytoskeleton

are immersed

• Nucleus Inside nuclear envelope Site of most of cell’s DNA

and nucleolus

• Nucleolus Inside the nucleus Synthesis of ribosomal RNA

ORGANELLES

NAME LOCATION FUNCTION

• Rough Endoplasmic Reticulum cytoplasm Protein synthesis,Cell metabolism,

• Smooth Endoplasmic Reticulum cytoplasm Lipid synthesis, storage of calcium, Detoxification of toxic substances

• Ribosomes Rough ER and Protein synthesis free in the cytoplasm

• Vesicles move through cytoplasm Transport

• Golgi Bodies cytoplasm Processing, sorting, shipping of proteins and lipids

• Mitochondria cytoplasm Gets energy from food (makes ATP during aerobic respiration) 

ORGANELLES

NAME LOCATION FUNCTION

• Lysosomes cytoplasm Digestion and breaking down of materials

(only in animal cells) ( including the cell’s own)

• Peroxisomes cytoplasm Sacs of enzymes that break down substances

(alcohol, amino acids) into hydrogen peroxide

and then the hydrogen peroxide into water

and oxygen.

• Plasma Membrane all around the cell Controls substances and signals that go in

and out of cells. Maintains shape and

volume

• Cell wall ( plant cells) cytoplasm Keeps water inside and limits water

uptake, protects from outside influences,

maintains shape.

ORGANELLES

NAME LOCATION FUNCTION

• Central vacuoles center of plant cell water maintenance, stores waste

(plant cells only)

• Plastids cytoplasm plastids provide nutrients and

(plant cells only) pigmentation

• Chloroplast many throughout carry out photosynthesis

(plant cells only) the cytoplasm contain chlorophyll

CELL JUNCTIONS

• What are junctions? Protein or cytoplasmic bridges that serve as physical links between cells.

• The junctions between cells help integrate cells into tissues and higher levels of functioning. Junctions make cells living units greater than each individual part.

• Junctions serve to send and receive signals and materials and to cement itself to other cells and junctions coordinate cell activities.

Plant cellsPlants are covered by cell walls composed of

cellulose fibers.

Cell walls have plasmodesmata, these are channels that pass through adjoining cell walls connecting plant cell to plant cell.

Animal cells:Junctions

• There are different kinds of intracellular junctions between animal cells, integrating each cell into a greater unit.

• Tight junctions

• Desmosomes or Anchoring juctions:

• Gap or Communication junctions:

Tight junctions

They fuse cell to cell to prevent leakage. Ex: cells of the lining of the intestines keeping the fluid inside. All cells of most tissues are joined this way. The skin and the lining of internal cavities (epithelial).

Gap or Communication junctions:

Link the cytoplasm of neighboring cells. They are open channels that allow a flow of materials and signals between cells.

• Very common in embryos and in heart tissue to allow for the passage of ions to cause contraction

Desmosomes or Anchoring juctions:

Joins cells in tissues of the skin, heart and other organs such as the bladder subject to stretching.

– Tight junctions can bind cells together into leakproof sheets

– Anchoring junctions link animal cells into strong tissues

– Gap junctions allow substances to flow from cell to cell

Anchoring junction

Tight junctions

Gap junctions

Extracellular matrix

Space between cells

Plasma membranes of adjacent cellsFigure 4.18B

Cilia and flagella• move when microtubules bend

– Eukaryotic cilia and flagella are locomotor appendages that protrude from some cells

LM

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Figure 4.17A Figure 4.17B

Clusters of microtubules Drive the whipping action of these organelles

. FlagellumElectron micrographsof cross sections:

Flagellum

Basal body

Basal body(structurally identical to centriole)

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Plasmamembrane

Dynein arms

Radial spoke

Centralmicrotubules

Outer microtubuledoublet

PLASMA MEMBRANE• Function:

The cell’s “gate keeper”. Very important.

It controls what goes in and out of a cell.

Keeps equilibrium between the inside of cells and the outside and promotes homeostasis.

Web site to check:http://www.wisc-online.com/objects/index_tj.asp?objid=AP1101

• Function:

The cell’s “gate keeper”. Very important.

It controls what goes in and out of a cell.

Keeps equilibrium between the inside of cells and the outside and promotes homeostasis.

Web site to check:http://www.wisc-online.com/objects/index_tj.asp?objid=AP1101

Membranes

• http://www.wiley.com/legacy/college/boyer/0470003790/animations/membrane_transport/membrane_transport.htm

The plasma membrane of the cell is selectively permeable

Controlling the flow of substances into or out of the cell

Cytoplasm

Outside of cell

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PLASMA MEMBRANE

 STRUCTURE:

It is a LIPID BILAYER. Its main component is a PHOSPHOLIPID molecule.

• A phospholipid is made up of a hydrophilic head (water loving) and two hydrophobic fatty acid tails (dislike water). These are arranged in two layers with the fatty acids tails sandwiched between the hydrophilic heads.

• The membrane is “fluid”, it moves about, tails twist and wave

• Embedded in the phospholipid bilayer are the surface proteins.

• The membrane is “a mosaic” of different proteins embedded in the fluid matrix of the lipid bilayer.

What makes up the plasma membrane?

– Phospholipids are the main structural components of membranes

Membrane phospholipids form a bilayer• Have a hydrophilic head

and two hydrophobic tails

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH3

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CHCH

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH3

CH2

CH2

CH3

CH3

CH3N+

OO O–P

OCH2

CHCH2

C O C OO O

Phosphategroup

Symbol

Hydrophilic head

Hydrophobic tails

Phospholipids form a two-layer sheetCalled a phospholipid bilayer, with the heads facing outward and the tails facing

inward

Water

Water

Hydrophilicheads

Hydrophobictails

How does it work?• Membrane is selectively permeable or semi-

permeable. Small molecules that are electrically neutral diffuse easily in and out such as O2, CO2, and alcohols.

• The non-polar phospholipid tails of the bilayer repel charged molecules but allow lipid soluble molecules to pass easily.

• Sugars need to be transported through a channel as well as charged ions such as H+, Na+, K+, Cl

• Large molecules (like proteins) cannot diffuse through and must enter the cell by other mechanisms such as active transport. Active transport uses energy (ATP) to “push” the molecules in and out.

• Serious diseases associated with cell membrane defects:Multiple Sclerosis, there is a myelin cover on axons of nerve

cells. Because it is defective muscle control is lostCystic Fibrosis, The channels for chloride to pass through the

membrane do not work. Chloride ion are not able to leave the cell. Results in thick mucus in respiratory track and other ducts in the body.

Proteins found in the plasma membrane:

• Integral penetrate the hydrophobic core of the lipid bilayer

• Peripheral are loosely bound to the surface of the membrane

• Transport proteins

• Receptor proteins

• Recognition proteins

• Adhesion proteins

Proteins found in the plasma membrane:

• Transport proteins: These are open on both sides making a channel, a passage. Water soluble

substances pass through it. It is very specific for the substance that it moves.

• Receptor proteins: Grab or bind substances to pass them through. Have a binding site with a

specific shape that fits the shape of another molecule. It can bind a chemical messenger such as a hormone which then causes a change in the shape of the protein that relays the message to the inside of the cell.

• Recognition proteins: These are glycoproteins. Have a short chain of sugars attached to it. Are like fingerprints. Serve as identification tags that are recognized by other

cells. Your cells recognize “your own”

• Adhesion proteins: Like “glue”, make cells stick together.

The membrane is a fluid mosaic of phospholipids with proteins and other molecules embedded in a

phospholipid bilayer

Fibers of the extracellular matrix

Carbohydrate(of glycoprotein)

Glycoprotein

Microfilamentsof cytoskeleton

Phospholipid

CholesterolProteins

Plasmamembrane

Glycolipid

Cytoplasm

Membrane proteins also function in transportMoving substances across the membrane

ATP

Other membrane proteinsFunction as receptors for chemical

messages from other cells

Messenger molecule

Receptor

Activatedmolecule

Many membrane proteins Function as enzymes