LSM1401 Notes Summary (2) © Lim Fang Jeng
Cell Biology
Prokaryotes
- Consist of Archae and bacteria
- Single-cell with no nucleus or membrane bound organelles Eukaryotes
- DNA inside nucleus - Larger and more complex Membrane structure
- Phospholipid bilayer - Selective permeability
- Consists of several movement across membranes o Diffusion
o Passive transport o Active transport o Endocytosis o Exocytosis
Diffusion
- Net movement of molecules down the concentration gradient - Osmosis (Special type of diffusion)
o Diffusion of water molecules across semi-permeable membrane down the concentration gradient of water
o Hypotonic (Outside cell)
Higher concentration inside cell
Water flows in the cell, cell will burst o Hypertonic
Lower concentration inside cell
Water flows out from cell, cell shrunk o Isotonic
Same concentration as solute
Passive Transport
- Movement without requirement of energy (such as Glucose across cell membrane)
Active Transport
- Movement which requires energy - Up the concentration gradient
- Can remove unwanted material even if the concentration of it is low and concentration outside the cell is high
Endocytosis & Exocytosis
- Large particle or substances can pass through the membrane by this way - DO NOT occur in prokaryotes
- Endocytosis (move in)
o Engulf large substances from outside the cell by forming vesicles
LSM1401 Notes Summary (2) © Lim Fang Jeng - Exocytosis
o Vesicles fused with plasma membrane and bring substance out from the cell.
Prokaryotic Cells
- No nucleus - DNA
o Single circle of dsDNA o Single chromosome - Bacterial Cell Wall
o Contains peptidoglycan (carbohydrates) - Two types of bacterial cell wall
Gram Positive Gram Negative
2 layers 3 layers
Peptidoglycan-rich Peptidoglycan-poor
Easily absorb stain Resist staining
- Most bacteria which infect us are Gram Negative Bacteria - Movement
o Secrete slime and glime
o By changing operation of flagellum
Cell Organelles
Nucleus
- Separate DNA from the cytoplasm - Major components
o Chromatin – contains DNA o Nuclear Envelope
o Nucleolus - Nuclear envelope
o Consists of two layers of membrane o 4 phospholipid bilayers
- Chromatin
o Contains DNA & Proteins
o They will condense to Chromosome - Nucleolus
o Dense mass of material o Cluster of DNA and proteins o Sythesize ribosomes
Endomembrane System
- Endoplasmic Reticulum
o Rough ER – Main function : Protein making : membrane protein and transport protein
Flattened sacs
Export of proteins o Smooth ER
No ribosome
Lipid synthesis
Inactivate wastes and drugs
LSM1401 Notes Summary (2) © Lim Fang Jeng - Golgi Apparatus – Post office
o Receives material from ER
o Packaging materials for shipment outside the cell or within the cell
For transporting out the cell, exocytosis occurs - Vesicles
o Membranous sacs which move through cytoplasm
Eg, Secretory vesicles, transport vesicles, lysosomes, peroxisomes, etc o Lysosomes
Contain hydrolytic enzymes
Digest organelles and material engulfed by the cell
Act as Garbage collector o Peroxisome
Break down amino acids and fatty acids
Produce H2O2
2H2O2→ 2H2O + O2
Semi-Autonomous Organelles
- It can resemble bacteria, some even think that they are initially prokaryotes but become adapted to the system after being engulfed but NOT digested (Endosymbiotic hypothesis)
- They posses their own DNA, RNA and ribosomes - Mitochondria (animals) and Chloroplast (plants) - Mitochondria
o ATP- Producing o Double membrane
o Inner membrane folds back on itself to form cristae
Matrix – Space in the mitochondria within inner membrane which contains respiratory enzymes
ATP making enzymes are embedded in the inner membrane - Chloroplast
o Inner membrane encloses semi-fluid stroma
Forms thylakoids
The thylakoids stack together to form a grana
LSM1401 Notes Summary (2) © Lim Fang Jeng
Cytoskeleton
- Network of protein fibres
- They can assemble and disassemble as needed - There are 3 types of cytoskeleton
o Microtubules
LARGEST cytoskeletal elements
Composed of tubulin subunits
Polar and dynamic
Maintaining shapes, motility and cell division (during anaphase)
The monomers are put in the way that they have the same direction (towards +ve), so it can have polar properties
Movement along microtubules (motor proteins):
Kinesin (-ve to +ve) and dyelin(+ve to –ve) o Microfilaments
Thinnest of all cytoskeleton
Composed of actin
Involved in movement, formation and maintenance of cell shape o Intermediate filaments
Most stable cytoskeleton
Strengthen and maintain the shape of cells or cell parts
Different cells have different intermediate filaments
o Motor proteins and cross-linking proteins will attach to the tubulin and actin to perform movement
o Mechanisms of movements
Change in length
Shunting of organelles
Sliding of parallel rows … of microtubules
Cilia and Flagella
Hair-like projections with ͞9+2͟ array
- For cell movement in fluids such as sperm,etc
thylakoid
Inner membrane
granum stroma
Outer membrane
kinesin
+ve end -ve end
Microtublues (monomer: tubulin)
