Cell StructureChapter 6

IB Biology

Prokaryotes vs. Eukaryotes

• Prokaryotes have no nucleus or membrane bound organelles

•Most have a cell wall

•Many have flagella

• Very primitive

•Origin: 3.5 BYA Ex- Bacteria

Prokaryotes:

Eukaryotic Cells

• “Eu” = true “Karyo” = kernal (nucleus)

• “YOU are a Eukaryote”

• Have a nucleus

• Have membrane-bound organelles.

• First appeared in fossil records 1.5 bya

• All members of the following kingdoms have this type of cell: Protocista, Fungi, Plantae, Animalia.

Prokaryotes/Eukaryotes**

Prokaryotes Eukaryotes

No nucleus Nucleus

“Naked” DNA DNA associated with proteins

DNA in cytoplasm DNA in an envelope (nucleus)

No mitochondria Mitochondria

70s ribosomes 80s ribosomes

No organelles organelles

Reproduce by binary fission Reproduce by mitosis

Ex.- Bacteria Ex.- all other cells

Note: s = subunits

Prokaryotic CellBacterium:

Prokaryotic Cells

Escherichia coli

What do all cells have in common?•Cell membrane

•Cytoplasm/cytosol

•Genetic material

•Ribosomes

Cell Membrane

•A selectively permeable phospholipid bilayer that forms a barrier between the cell and its environment

Cytoplasm/cytosol

•Liquid substance that all chemical reactions of life take place in

•Has dissolved ions, macromolecules

Genetic Material- Chromosomes

•DNA is found as either organized chromosomes (eukaryotes) or single, loosely packed chromosome (prokaryotes)

Ribosomes• Two-piece protein-

based organelle that makes proteins in both major types of cell

• Varies structurally in prokaryotes (70S)and eukaryotes (80S).

Generalized Animal Cell

Generalized Plant Cell

Differences between cells

Plants Lack:1. Lysosomes

2. Centrioles

3. Flagella or Cilia

Animals Lack:1. Chloroplasts

2. Vacuoles

3. Cell Walls

4. Plasmodesmata

Eukaryotic Cell Organelles: Nucleus

• Contains cell’s genetic material in form of chromosomes

• Controls most of cell activities

• Site of transcription (1st step in protein synthesis)

• Has a double-membrane

Eukaryotic Cell Organelles: Nucleolus

•Smaller, dark body inside nucleus

•Responsible for ribosome synthesis

Eukaryotic Cell Organelles: ER

• ER =Endoplasmic reticulum

• Part of endomembrane system

• Smooth ER: no ribosomes, synthesizes lipids, detoxifies substances

• Rough ER: studded with ribosomes, transports proteins inside cell

Rough ER makes membrane and proteins

• The rough ER manufactures membranes• Ribosomes on its surface produce proteins

1 2

3

4Transport vesiclebuds off

Ribosome

Sugarchain

Glycoprotein

Secretory(glyco-) proteininside transportvesicle

ROUGH ER

Polypeptide

Eukaryotic Cell Organelles: Golgi Apparatus (not body)

• Part of endomembrane system

• The Golgi apparatus consists of stacks of membranous sacs These receive and modify ER

products, then send them on to other organelles or to the cell membrane

• Packages and exports cell chemicals such as proteins, carbohydrates and lipids

Eukaryotic Cell Organelles: Mitochondria

• Converts glucose into ATP during cell respiration

• Is thought to have been primitive prokaryote because: Has own genome (mtDNA) Directs own division

• Highly folded inner membrane• Found in cells that are motile

and contractible• Has a double membrane, with

inner membrane called the cristae.

MITOCHONDRIONOuter membrane

Inner membrane

Cristae

Matrix

Eukaryotic Cell Organelles: Chloroplast

• Found in plant cells and some protists• Contains chlorophyll• Responsible for converting carbon dioxide and

water into glucose during photosynthesis

Eukaryotic Cell Organelles: The Cytoskeleton

-Fibrous proteins (actin & tubulin)-Roles: Support, cell motility, biochemical

regulation, organelle movement-Microtubules:

•thickest (25 nm) •tubulin protein (hollow rods) •maintains shape, support, transport,

chromosome separation-Microfilaments: •thinnest ( 7 nm) •actin protein filaments; •motility, cell division, shape-Intermediate filaments: • middle diameter (8-12 nm)

•keratin; •shape, nucleus anchorage

MICROFILAMENT

Figure 4.17B

INTERMEDIATEFILAMENT

MICROTUBULE

Actin subunit Fibrous subunitsTubulinsubunit

7 nm 10 nm25 nm

The Cytoskeleton

Basic jobs of each

Microtubules Microfilaments Intermediate-give the cell rigidity -made of actin -reinforce the cell

-provide anchors for -enable cells to change -anchor certain organelles

organelles shape and move

-act as tracks for

organelle

movement

Eukaryotic Cell Organelles: Lysosome

• Vesicle that comes off of Golgi body containing hydrolytic digestive enzymes

• Responsible for digestion of old, worn out cell parts and cells

• Also digests nutrients **Found extensively in

Macrophages (WBC’s)

Eukaryotic Cell Organelles: Centriole

• Found only in animal cells

• Composed of microtubules in triplet arrangement

•Organizes microtubules that attach to chromosomes during cell division

Eukaryotic Cell Organelles: Vacuole

• Small ones in animal cells

• Large ones found in plant cells, stores water to maintain turgor pressure

• Can accumulate wastes, pigments in plant cells

Eukaryotic Cell Organelles: Peroxisomes

• Single membrane• Oxidative organelle ***strips e-’s (H’s) from

substances• Produce hydrogen peroxide

(H2O2) in cells• Metabolism of fatty acids;

detoxification of alcohol (liver)

• Hydrogen peroxide then converted to water

Eukaryotic Cell Organelles: Cell Wall

• Found only in plants

•Made of cellulose

• Non-living

• Has small pores called plasmodesmata, which allows materials in and out.

Eukaryotic Cell Organelles: Cilia/Flagella

•Cilia: short hairlike projections used in cellular movement

•Flagella: whiplike projection used in cellular movement Structure in

prokaryotes is slightly different

ECM: Extracellular Matrix**

•Extracellular matrix (ECM) composed of (located on outside of cell):

-Proteins & Carbodydrate

-Specifically:-glycoproteins

-glycolipids

-integrins

-fibronectins

-collagen (50% of all protein in the body)

Extracellular Matrix (ECM) - Pg. 118-120

Animal cells secrete or produce:

Glycoproteins: •proteins covalently bonded to carbohydrate

Collagen

(50% of protein in human body

•embedded in proteoglycan

(another glycoprotein-95% carbohydrate)

Fibronectins

bind to receptor proteins in plasma membrane called integrins

(cell communication?)

Functions: support, adhesion, movement**

ECM’s in Plants**

Cell Walls are an ECM.

-maintain shape

-prevents excessive water uptake, and

-holds the plant up against the force of gravity.

Samples of Various Types of Cells

•Protists may have contractile vacuoles

Figure 4.13B

Nucleus

Contractilevacuoles

– These pump out excess water

•Cell, stained for mitochondria, actin, and nucleus

Figure 4.1x

•Prokaryotic cells, Bacillus polymyxa

Figure 4.4x1

•Prokaryotic cell, E. coli

Figure 4.4x2

•Pili on a prokaryotic cell

Figure 4.4x3

•Prokaryotic flagella

Figure 4.4x4

•Prokaryotic and eukaryotic cells compared

Figure 4.4x5

• Paramecium, an animal cell

Figure 4.5Ax

•Plant cells

Figure 4.5Bx1

•Chloroplasts in plant cells

Figure 4.5Bx2

•Nuclei (yellow) and actin (red)

Figure 4.6x

Red Blood Cells