SBI 3UC

2.2 &2.3 PROKARYOTIC AND EUKARYOTIC CELLS

http://www.studiodaily.com/2006/07/cellular-visions-the-inner-life-of-a-cell/

• They are single-celled organisms, and they lack membrane-bound organelles. (no organized nucleus, vacuoles etc.)

• Examples include bacteria, archaea and blue-green algae

PROKARYOTIC CELLS

CELL STRUCTURE

• 1. Cell surface membrane (plasma membrane): controls which materials enter and leave the cell, either by active or passive. It is selectively permeable.

• 2. Cell wall: Rigid or semi-rigid wall surrounding plasma membrane. Contains pores to allow passage of materials in & out. The cell wall supports cell and provides shape.

STRUCTURES

• Plasmid: Small circular pieces of naked DNA in addition to main chromosome of prokaryote cells.

• Nucleoid: Region of prokaryote cytoplasm where main chromosome and plasmid are found. Naked DNA - DNA is not bound to proteins (like histones) to reduce the amount of space they take up.

STRUCTURES

• Mesosome: Internal membrane connected to the cell surface membrane. It increases the area available to make ATP (cell energy). It may also aid the replication of DNA and cell division.

MESOSOME

• Pili- are thin protein tube, found outside of the plasma membrane.

• Attachment pili (fimbriae) – allow prokaryotes to stick to surfaces• Conjugation pili (sex pili) – few in number, but longer than

attachment pili. They build a bridge between cells and allow an exchange of plasmids.

PILI

• Cytoplasm: Contains enzymes for catalyzing chemical reactions of metabolism. Contains ribosomes and naked DNA.

• Ribosome: Sites of protein synthesis (scattered throughout cytoplasm rather than in rough ER).

• Flagellum: One to many threadlike, motile structures (locomotion).

• Slime capsule: Layer of thick, jellylike polysaccharides surrounding some prokaryote cells to aid in protection.

STRUCTURES

• Prokaryotic cells divide by BINARY FISSION

• They double their chromosome number and then split in half

DIVISION

PROKARYOTIC CELLS

The photo above shows a cross-section through a prokaryotic cell. Can you identify any of the parts?

• 1. Photosynthesis- Blue-green algae convert light energy into chemical energy (food)

• 2. Nitrogen Fixation- Nitrogen-fixing bacteria convert gaseous nitrogen from air into nitrogen compounds. (rhizobium)

• 3. Fermentation- Some bacteria convert sugars to lactic acid or into alcohol in order to obtain energy. The latter 2 chemicals are then released.

METABOLIC ACTIVITY (NICHES) OF PROKARYOTIC CELLS

• Symbiosis: two organisms live closely together

• Endosymbiosis: one organism lives inside another (like bacteria live inside of us)

• https://www.youtube.com/watch?v=-FQmAnmLZtE • https://www.youtube.com/watch?v=bBjD4A7R2xU

EUKARYOTIC CELLS

• It is thought that chloroplasts and mitochondria were originally free-living prokaryotic cells which gradually became able to live and reproduce within a larger cell.

• The larger cell provided protection and in some cases food to the prokaryote, while the smaller prokaryotic cell (which became the chloroplasts & mitochondria) provided an energy supply to the larger cell.

THEORY OF ENDOSYMBIOSIS

• a. mitochondria and chloroplasts surrounded by double membrane

• b. mitochondria and bacteria have similar size

• c. mitochondrial ribosomes resemble bacterial ribosomes

• d. mitochondria and chloroplast DNA is circular like bacteria

• e. mitochondria divides by simple fission like bacteria

EVIDENCE

• Organelles: Any discrete structure within a cell which has a specific function. Organelles

• a) are each surrounded by a plasma membrane.• b) separate and compartmentalize chemical

reactions in time and space (They organize reactions so they can be more efficient.).

• c) are only found in all eukaryotic cells (They do not exist in prokaryotes.).

• Intracellular: found inside the cell (within cytoplasm).

• Extracellular: found on outer surface of cell.

ORGANELLE'S

• 1) Plasma membrane: Outer surface of animal cells. Phospholipid bilayer. Controls entry & exit of molecules.

• Phospholipid bilayer (polar head=hydrophilic; non-polar tails =hydrophobic)

INTRACELLULAR ORGANELLES

• 2) Nucleus: information center of cell.

• Largest organelle, readily visible. Nuclear envelope: double membrane layer, restricts passage of molecules. Chromosomes: contain heredity information (made of DNA & proteins).

• Nucleolus: in center of nucleus- manufactures ribosomes.

NUCLEUS

• 3) Endoplasmic reticulum: Tubules for transport and synthesis of large organic molecules. Often continuous with nuclear envelop. Organizes cell interior.

• a) Rough ER (rER): Manufacture proteins for export

ENDOPLASMIC RETICULUM

• Ribosomes: assist in protein synthesis.

• Can be free floating or on RER• b) Smooth ER (sER): Lack ribosomes so they have a

smooth surface. Synthesize carbohydrates and lipids. Associated with detoxification.

RIBOSOMES

• Lysosomes: vacuole containing digestive enzymes. Functions:

• a. Enzymes catalyze breakdown of macromolecules • b. Alter internal pH • c. Digest worn-out cell components • d. Digest pathogens engulfed by WBC's • e. Participate in selective cell death

LYSOSOMES

• Mitochondria: Provides chemical energy (ATP) for cell

• Double membrane Possesses own DNA: produces own RNA (ribosomes) Capable of replication

MITOCHONDRIA

• Chloroplasts: photosynthesis (trap light energy in plants). Occur in plants and algae. Double membranes. Possess own DNA, produce own RNA (ribosomes).

CHLOROPLAST

• Flagella and Cilia: motility • Flagella: long microtubule strands,

locomotion • Cilia: short microtubule strands.

Locomotion, pass fluids, react to sound waves

FLAGELLA AND CILIA

Golgi Apparatus: • Modification, packaging &

distribution of finished macromolecules (carbohydrates & lipids)

GOLGI APPARATUS

• Membrane bound organelles for storage of macromolecules, water, or cellular wastes.

VACUOLES

• Rigid outer layer of plant cells. Made of cellulose microfibrils.

• Barrier to pathogens, provides support/shape

• Plasmodesmata- narrow passages through the cell wall to allow exchange with neighbouring cytoplasm

CELL WALL

• Cellulose –best known e.c.c found in plants. Provides structure

• Bone, cartilage and connective tissue- provide structure and motility

• Hyaline cartilage- a tissue that has cells within a lot of ECM (extracellular matrix). The ECM is associated with the firmness and resilience of cartilage as it interacts with glycoproteins , water and collagen. (p20)

EXTRACELLULAR COMPONENTS

• TYPICAL PLANT CELL STRUCTURE • Organelles Found only in Plant Cells: • 1. Chloroplasts (not found in plant cells

found in roots, or cells found in the dark interiors of stems or branches)

• 2. Cell Wall• 3. Large Central Vacuole (not commonly

found in animal cells)

TYPICAL PLANT

COMPARISONS…

Animal Cells vs. Plant Cells

Animal Cells Plant Cells

1. No Chloroplasts 1. Chloroplasts present (usually)

2. No Cell Wall 2. Cell Wall 3. Usually no large central vacuole.

3. Most have large central vacuole.

4. Carbohydrates stored as glycogen.

4. Carbohydrates stored as starch.

5. Has lysosomes. 5. Generally lacks lysosomes. 6. Shape- Changeable, usually rounded.

6. Shape- Rigid, often with 'straight' edges.

COMPARISONS

Comparison of Prokaryotic & Eukaryotic Cells (EXAM!)

Prokaryotic Cells Eukaryotic Cells

Membrane bound internal organelles None Present

Nucleic Acids Naked DNA (no histones)

DNA covered with histone proteins

Ribosomes Free in cytoplasm Attached to rER or free in cytoplasm

Nucleus None May be Present Cell & Nuclear Division Binary Fission Mitosis & Cytokinesis

• Cells - Building blocks of all life.• Tissues - Group of similar cells. (nervous tissue,

cardiac tissue, skeletal muscle tissue) • Organs - Several types of tissues grouped together

to help do a certain function. (heart, brain, liver) • Organ Systems - Several different organs working

together to perform the same job. (Ex: esophagus, stomach, small intestine etc. are part of the digestive system)

• Organism - Many different organ systems that work together to make one living thing.

ORGANIZATION OF CELLS IN MULTICELLULAR ORGANISMS

• Draw and label ultrastructure of e.coli• Annotate diagrams for each structure• Identify structures in micrographs of

e.coli• State that prokaryotic cells divide by

binary fission

2.2 GOALS

• Draw and label cells• Annotate diagrams• Identify structures in liver micrograph

(p18)• Compare prokaryotic and eukaryotic• State three difference between plant and

animal cells• Outline two roles of extracellular

components

GOALS2.3