BI236: Cell and Molecular Biology
Cells and Organelles
• Cell walls of bacteria, archaea, and eukaryotes
• Plasma membrane and cytoplasm
o Movement of solutes across plasma membrane
Receptor –mediated endocytosis
• Cell organelles
• Cell Types
o Aprokaryotic cell
Plasmids: have extra chromosomal DNA, circular, common in bacteria,
antibiotic resistance(not necessary for the survival of the cell, but there are
Certain bacteria that fix atmospheric nitrogen-symbiotic relationship-
risobium ((bacteria)(legumes: beans, pea’s)), it can absorb the nitrogen in
the environment then.
o An eukaryotic cell
Lacks cell wall
Rough ER: ribosomes
Smooth ER: no ribosomes
Mitochondria: respiration takes place
Golgi vesicles Microtubules
Pinocytotic vesicles: wants to get rid of wastes, it secretes materials from
Lysosomes: digestive sites, unwanted material;
• Lysosomes and vacuoles have similar function
• Cell wall
o Found in plants, bacteria, fungi, algae, and some archaea
o Animals and protozoa do not have cell walls
o It surrounds the plasma membrane
o Plant cell walls—contain mostly cellulose
o Fungi-contain chitin
• Bacterial cell wall
o Around the outside of the cell membrane is the bacterial cell wall. Bacterial cell
walls are made of peptidoglycan(also called murin(is only found in bacteria))
o 2 different types of cell wall in bacteria
• Thick cell wall containing many layers of peptidoglycan and
teichoic acid (bacterial polysaccharide)
• Relatively thin cell wall consisting of few layers of peptidoglycan
surrounding by second lipid membrane containing
lipopolysaccharides and lipoproteins
Most bacteria are gram-negative.
The cell wall is essential to the survival of many bacteria
• Cell wall of archaea
o Lacks peptidoglycan, with the exception of one group methanogen
o In that group, the pepidoglycan is a modified form, very different from the kind
found in bacteria Example: Methanococcus janaschii, Methanosarcina barkeri,
• 4 types of cell wall currently known among theArchaea
o 1) composed of pseudopeptidoglycan (also called pseudomurein)
o 2) composed entirely of thick layer polysaccharides
o 3) consists of glycoprotein
o 4) composed only of surface-layer proteins, known as the s-Layer.
• Cell membrane
o Composed of a mixture of protein and lipids.
o Within the cell, it’s a watery environment.
o Exterior of the cell is also watery environment.
o Hydrophillic head, hydrophobic tail
o Glycoprotein and glycolipid- communication
o Protein: across the membrane, for transportation
• Movement across the plasma membrane
o Molecules which move freely
Water, carbon dioxide, ammonia, oxygen
o Carrier proteins transport some molecules
Proteins embedded in lipid bilayer
Fluid mosaic model by Singer and Nicholson(1972)
• Molecule movement and cells
o Passive transport-no energy required, move due to gradient, move to equalize
o Active transport
o Endocytosis-taken inside the cell
o Exocytosis-excrete materials outside the cells
• Types of Passive Transport o Diffusion- molecules move to equalize concentration
o Osmosis-fluid flows lower solute concentration, often involves movement of
water. Into cell, out of cell.
o Facilitated diffusion- Differentially permeable membrane is involved. Channels
(or transport proteins) help molecule or ions to aid ions, water or other solutes
enter or leave the cell.
• Passive Transport
o Movement of molecules DOWN the concentration gradient. It goes from high to
low concentration, in order to maintain equilibrium in the cells. Does not require
o Types of Transport: Diffusion, facilitated diffusion, and osmosis.
o Types of Particles transported:Anything soluble(meaning able to dissolve) in
lipids, small monosaccharide, water, oxygen, carbon dioxide, etc
o Importance of Passive Transport: It maintains equilibrium in the cell. Wastes
(carbon dioxide, water, etc.) diffuse out and are excreted; nutrients and oxygen
diffuse in to be used by the cell.
o Functions: Maintains dynami