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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

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cells
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.
there is correlation between the structure of cells and their function
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”

slide4

10 m

Human height

1 m

Length of somenerve andmuscle cells

100 mm(10 cm)

Unaided eye

Chicken egg

10 mm(1 cm)

Frog egg

1 mm

100 m

Light microscope

Most plant andanimal cells

10 m

Nucleus

Most bacteria

Mitochondrion

1 m

Mycoplasmas(smallest bacteria)

100 nm

Viruses

Electron microscope

Ribosome

10 nm

Proteins

Lipids

1 nm

Small molecules

Atoms

0.1 nm

How small are cells?

Most cells are microscopic

  • Cells vary in size and shape
history
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

Eyepiece

Ocularlens

Objective lens

Specimen

Condenserlens

Lightsource

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

Figure 4.1A

slide7

TEM 2,800 

SEM 2,000 

Figure 4.1D

Figure 4.1C

  • The electron microscope
    • Allows greater magnification and reveals cellular details
the cell theory mid 1800 s
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
slide9

Prokaryotic cell

Nucleoidregion

Colorized TEM 15,000 

Nucleus

Eukaryotic cell

Organelles

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

Figure 4.3A

slide10

Prokaryoticflagella

Ribosomes

Capsule

Cell wall

Plasmamembrane

Nucleoid region (DNA)

Pili

  • TYPE OF CELLS: Prokaryotic and Eukaryotic
  • Prokaryotic cells are small, relatively simple cells
    • That do not have a membrane-bound nucleus
slide11
Eukaryotic cells have a nucleus and are

partitioned into functional compartments.

  • All other forms of life( plants and animals) are composed of complex eukaryotic cells
  • Membranes form compartments inside eukaryotic cells to facilitate metabolic activities
slide12

10 m

30 m

30 m

10 m

Surface areaof one large cube 5,400m2

Total surface areaof 27 small cubes 16,200m2

  • A small cell has a greater ratio of surface area to volume
    • Than a large cell of the same shape
slide13

Smooth endoplasmicreticulum

Nucleus

Roughendoplasmicreticulum

Flagellum

Not in mostplant cells

Lysosome

Ribosomes

Centriole

Golgiapparatus

Peroxisome

Microtubule

Plasma membrane

Intermediatefilament

Cytoskeleton

Mitochondrion

Microfilament

  • A typical animal cell
    • Contains a variety of membranous organelles
the cytoskeleton and related structures

Tubulin subunit

Actin subunit

Fibrous subunits

25 nm

10 nm

7 nm

Microtubule

Microfilament

Intermediate filament

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.
functions of the cytoskeleton
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
slide17
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 eukaryotic cells
    • Compartmentalizing the interior of the cell and facilitating a variety of metabolic activities
slide18

Nucleus

Chromatin

Two membranesof nuclearenvelope

Nucleolus

Pore

Roughendoplasmicreticulum

Ribosomes

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

Figure 4.5

organelles of the endomembrane system
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
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

slide21

Transport vesiclebuds off

4

Ribosome

Secretory(glyco-) proteininside trans-port vesicle

3

Sugar chain

1

2

Glycoprotein

Polypeptide

Rough ER

  • Ribosomes on the surface of the rough ER
    • Produce proteins that are secreted, inserted into membranes, or transported in vesicles to other organelles
slide22

Smooth ER

Rough ER

Nuclearenvelope

Ribosomes

Rough ER

Smooth ER

TEM 45,000

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
slide23

Smooth endoplasmicreticulum

Nucleus

Roughendoplasmicreticulum

Flagellum

Not in mostplant cells

Lysosome

Ribosomes

Centriole

Golgiapparatus

Peroxisome

Microtubule

Plasma membrane

Intermediatefilament

Cytoskeleton

Mitochondrion

Microfilament

  • A typical animal cell
    • Contains a variety of membranous organelles
slide24

Golgi apparatus

“Receiving” side ofGolgi apparatus

Golgiapparatus

Transportvesiclefrom ER

TEM 130,000

New vesicleforming

Transportvesicle fromthe Golgi

“Shipping” sideof Golgi apparatus

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 surface

Figure 4.9

slide25

Transport vesicle fromGolgi to plasma membrane

Transport vesiclefrom ER to Golgi

Rough ER

Plasmamembrane

Nucleus

Vacuole

Lysosome

Nuclear envelope

Smooth ER

Golgi apparatus

The endomembrane system

  • The various organelles of the endomembrane system
    • Are interconnected structurally and functionally
slide26

Mitochondrion

Outermembrane

Intermembranespace

Innermembrane

TEM 44,880

Cristae

Matrix

Mitochondria gets chemical energy from food

  • Mitochondria carry out cellular respiration

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

slide27

Rough ER

1

Transport vesicle(containing inactivehydrolytic enzymes)

Golgiapparatus

Plasmamembrane

Lysosomeengulfingdamagedorganelle

2

Engulfmentof particle

Lysosomes

3

5

4

Foodvacuole

Digestion

Lysosomes are digestive compartments within a cell

  • Lysosomes are sacs of enzymes that function in digestion within a cell

“Food”

slide28

Lysosome

Nucleus

TEM 8,500

  • 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

slide29
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.
    • Interfere 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
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
Plant Cells
  • Three organelles animals do not have

Chloroplasts

Cell wall

Central vacuole

slide32

Roughendoplasmicreticulum

Nucleus

Ribosomes

Smoothendoplasmicreticulum

Golgiapparatus

Microtubule

Centralvacuole

Intermediatefilament

Cytoskeleton

Not inanimalcells

Microfilament

Chloroplast

Cell wall

Mitochondrion

Peroxisome

Plasma membrane

  • A typical plant cell has some structures that an animal cell lacks
    • Such as chloroplasts and a rigid cell wall
energy converting organelles

Chloroplast

Stroma

Inner and outermembranes

TEM 9,750

Granum

Intermembranespace

ENERGY-CONVERTING ORGANELLES

Chloroplasts convert solar energy to chemical energy. This is where PHOTOSYNTHESIStakes place

  • Chloroplasts, found in plants and some protists

Convert solar energy to chemical energy in sugars

slide34

Nucleus

Chloroplast

Centralvacuole

Colorized TEM 8,700

Vacuoles function in the general maintenance of the cell

  • Plant cells contain a large central vacuole,
    • Which has lysosomal and storage functions
central vacuoles in plants
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
slide36

Nucleus

Contractilevacuoles

LM 650

  • Some protists have contractile vacuoles
    • That pump out excess water
organelles
Organelles
  • NAME LOCATION FUNCTION
  • CytoskeletoncytoplasmMaintains cell shape

facilitates movement and move

materials within the cell

  • Cytosol cytoplasmProtein rich fluid in which

organelles and cytoskeleton

are immersed

  • NucleusInside nuclear envelopeSite of most of cell’s DNA

and nucleolus

  • Nucleolus Inside the nucleus Synthesis of ribosomal RNA
organelles38
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

  • Vesiclesmove through cytoplasmTransport
  • Golgi BodiescytoplasmProcessing, sorting,

shipping of proteins and lipids

  • Mitochondria cytoplasm Gets energy from food (makes ATP

during aerobic respiration)

organelles39
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.

organelles40
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
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 cells42
Plant cells

Plants 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
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
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
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
Desmosomes or Anchoring juctions:

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

slide47

Tight junctions

Anchoring junction

Gap junctions

Extracellular matrix

Space between cells

Plasma membranes of adjacent cells

  • 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

Figure 4.18B

cilia and flagella

Colorized SEM 4,100

LM 600

Figure 4.17A

Figure 4.17B

Cilia and flagella
  • move when microtubules bend
    • Eukaryotic cilia and flagella are locomotor appendages that protrude from some cells
clusters of microtubules drive the whipping action of these organelles

Flagellum

Electron micrographsof cross sections:

Outer microtubuledoublet

Centralmicrotubules

TEM 206,500

Radial spoke

Dynein arms

Flagellum

Plasmamembrane

TEM 206,500

Basal body(structurally identical to centriole)

Basal body

Clusters of microtubules Drive the whipping action of these organelles

.

plasma membrane
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
Membranes
  • http://www.wiley.com/legacy/college/boyer/0470003790/animations/membrane_transport/membrane_transport.htm
slide52

Outside of cell

Cytoplasm

TEM 200,000 

The plasma membrane of the cell is selectively permeableControlling the flow of substances into or out of the cell
plasma membrane53
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

CH3

Hydrophilic head

+

N

CH2

CH3

CH3

CH2

Phosphategroup

O

P

O–

O

O

CH

CH2

CH2

O

O

O

O

C

C

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

Symbol

CH2

CH2

CH

CH2

CH

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH3

CH3

Hydrophobic tails

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
slide55

Water

Hydrophilicheads

Hydrophobictails

Water

Phospholipids form a two-layer sheetCalled a phospholipid bilayer, with the heads facing outward and the tails facing inward
how does it work
How does it work?
  • Membrane is selectively permeable or semi-permeable. Small molecules that are electrically neutraldiffuse 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
slide57
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 lost

Cystic 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
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 membrane59
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.

slide60

Fibers of the extracellular matrix

Carbohydrate(of glycoprotein)

Glycoprotein

Glycolipid

Plasmamembrane

Phospholipid

Proteins

Cholesterol

Microfilamentsof cytoskeleton

Cytoplasm

The membrane is a fluid mosaic of phospholipids with proteins and other molecules embedded in a phospholipid bilayer
other membrane proteins function as receptors for chemical messages from other cells

Messenger molecule

Receptor

Activatedmolecule

Other membrane proteinsFunction as receptors for chemical messages from other cells