Question

explain the function of cytoplasm mitochondria in cell membrane flagellum,fimbriae,and nucleus. Identify any of these features that are specific to a prokaryotic or eukaryotic.

Answer 1

1. Cytoplasm.

• Material outside nucleus enclosed within cell membrane.
• Organelles are suspended in it.
• Many metabolic reactions occur in cytoplasm, like translation, glycolysis.

2.Mitochondria:

• Mitochondria has compartments, which has different functions

Outer membrane:

• Outer membrane allows ions and small molecules.
• It has pore forming proteins called porins.

Inner membrane-

• The mechanism of oxidative phosphorylation occurs in mitochondria of live cells.
• Electrons are transported across various components of electron transport chain (ETC), resulting in series of oxidation-reduction reactions within the inner membrane bound complexes in mitochondria (complex I, II, II, IV).

• The inner membrane is folded to form cristae.
• ATP synthase complex, designated as F₀F₁- ATP synthase, is located within the mitochondrial cristae.

Intramembranous space-

• Space contain ions and other molecules.
• Functions in oxidative phosphorylation by ion movements.

3. Cell membrane:

• Cell membrane or plasma membrane is composed of lipid bilayer, with hydrophobic tails within and hydrophilic heads facing outside.
• The plasma membrane is composed of 50 % of lipids, which are majorly phospholipids and lesser amount of cholesterol.
• The cell membrane is semi permeable, and thus, mediates diffusion of ions and molecules specifically and osmosis.
• The proteins are peripheral or extrinsic proteins and intrinsic proteins or integral protein.

The proteins act as pumps, receptors, channels or have other functions.

4. Flagella:

• Flagella are cytoplasmic protrusion, which act as extracellular appendages in some prokaryotes (bacteria like Salmonella), and eukaryote (like Euglena).
• Prokaryotic flagella is not covered with plasma membrane and composed of flagellin.
• Eukatyotic flagella is covered by plasma membrane and is composed of tubulin in 9+2 orientation.
• Flagella mainly have locomotory function and help in cell movement.
• They also have sensory function and may help in detecting signals and respond to stimulus, like chemotaxis. Example moving towards food or mog away from toxic substances.

5. Fimbriae:

• Short finger like projections present in bacteria (similar structure is also designated in some organs).
• Fimbriae are also referred to as attachment pili.
• Major function of fimbriae is attachment or adherence of bacteria to sucfaces.
• They are important in biofilm formation or attaching to host cell.

6. Nucleus

• Nucleus is with membrane and nucleolus, chromosomes.
• DNA replication occurs in chromosomes within the nucleus. DNA polymerase helps in polymerization of nucleotides to form DNA.
• This helps in growth and reproduction of cells.
• Transcription also occurs in nucleus. Transcription is the process by which DNA sequence is copied to mRNA., by enzyme RNA polymerase.

Features	Prokaryotes	Eukaryotes
Cell	Unicellular, 0.2 to 2 micrometers.	Unicellular and multi-cellular, 10 -100 mm.
Cell wall	If present is chemically complex, like peptidoglycan linkages.	If present is simple, cellulosic composition.
Nucleus	Primitive type, nucleoid material, with no membrane or nucleolus.	True nucleus with nuclear membrane, nucleolus, chromosomes.
Ribosomes	Molecular weight- 27000kD Sedimentation co-efficient-70s Subunits: larger subunit- 50s Smaller subunit- 30s rRNA (in larger subunit)- 23s and 5s	Molecular weight- 42000kD Sedimentation co-efficient-80s Subunits: larger subunit- 60s Smaller subunit- 40s rRNA (in larger subunit)-28s, 5.3s, 5s
DNA arrangement	circular	linear
Mitochondria	absent	present
Chloroplast	absent	Present (in phototrophs)
Cytoplasm	Without ER	ER causes compartmentalization
Lysosome	Mesosome, centrosome absent	Mesosome, centrosome usually present
Reproduction	Binary fission	Mitosis
Flagella	If present simple	If present, 9+2 orientation
Fimbriae/ Pili	Present	Absent
Capsule	Present	Mostly absent
Example	Bacteria and Archaea	Eukarya- plant, animals