Chapter 3- Cells
Cell Theory: - 1. basic structure and functioning units of living organism
2. organismal functions depend on the individual and collective
functions
3. biochemical activities of the cells are dictated by specific subcellular
structures
4. continuity of life has cellular basis
200 different types of cells –
Parts: 1. Plasma membrane ( Cell Membrane ) – flexible outer boundary
2. Cytoplasm – intercellular fluid ( called cytosol ) containing organelles
3. Nucleus – control center
I. Plasma Membrane – separates the intracellular fluid from extracellular fluid
- bilipid layer with dispersed proteins ( not rigid )in constantly
changing fluid mosaic ( like cooking oil ).
- Membrane lipids :
1. phospholipids ( 75%) – this is the basic bilayer lipid
- phosphate head - hydrophilic
- polar
- fatty acid tail – hydrophobic
- non-polar
2. glycolipids (5%)– lipids with polar sugar group on the outer
membrane surface
3. cholesterol ( 20%) – stabilize the membrane but decrease
the ,mobility of the phospholipids and
fluidity of the membrane
- Membrane proteins – allow communication with environment (ECF)
- ½ mass of the plasma membrane
- some tethered to the intracellular membrane
while some are freely floating
- have specialized membrane functions
2 types:
1. Integral protein – transmembrane protein (thru and thru)
remove by disrupting the cell membrane
has hydrophobic and hydrophilic regions
just like the lipid layer
- function as transport protein – carrier
- channels
- enzymes
- receptors
, 2. Peripheral protein – loosely attached to integral protein
- glycoproteins (extracellular)
- filaments (intracellular) for membrane
support
- functions as – enzymes
- motor protein
- cell links
- Functions of the Membrane protein combined
- transport – channels, carriers
- receptors for signal transduction
- attachment for cytoskeleton and extracellular matrix
- enzymes
- cell junctions
- cell to cell recognition (MHC)
Other membrane structures:
Lipid rafts - 20% of outer membrane surface, serve as platforms
for some receptors
Glycocalyx – lipids, proteins with attached carbohydrates which
are specific for every cell types.
- biological markers for cell recognition
(sperm recognizing the egg to fertilize)
- cancer cells continuously change preventing the
immune cells to recognize them
Membrane junctions: -
1. tight junction – integral proteins of adjacent cells fused
- impermeable, prevent liquid and some
molecules to move in between cells
ex:
2. desmosomes – are anchoring junctions
- like rivets or spot welds that anchor adjacent
cells together at plaques
- cahedrin
- keratin
- skin cells and cardiac cells
3. gap junction – transmembrane proteins (connexon) forms
pores that allow small molecules to
pass through
ex: cardiac muscle, smooth muscles
Membrane transport: - Plasma membrane is selectively permeable
2 ways substances cross the plasma membrane: active and passive processes
Cell Theory: - 1. basic structure and functioning units of living organism
2. organismal functions depend on the individual and collective
functions
3. biochemical activities of the cells are dictated by specific subcellular
structures
4. continuity of life has cellular basis
200 different types of cells –
Parts: 1. Plasma membrane ( Cell Membrane ) – flexible outer boundary
2. Cytoplasm – intercellular fluid ( called cytosol ) containing organelles
3. Nucleus – control center
I. Plasma Membrane – separates the intracellular fluid from extracellular fluid
- bilipid layer with dispersed proteins ( not rigid )in constantly
changing fluid mosaic ( like cooking oil ).
- Membrane lipids :
1. phospholipids ( 75%) – this is the basic bilayer lipid
- phosphate head - hydrophilic
- polar
- fatty acid tail – hydrophobic
- non-polar
2. glycolipids (5%)– lipids with polar sugar group on the outer
membrane surface
3. cholesterol ( 20%) – stabilize the membrane but decrease
the ,mobility of the phospholipids and
fluidity of the membrane
- Membrane proteins – allow communication with environment (ECF)
- ½ mass of the plasma membrane
- some tethered to the intracellular membrane
while some are freely floating
- have specialized membrane functions
2 types:
1. Integral protein – transmembrane protein (thru and thru)
remove by disrupting the cell membrane
has hydrophobic and hydrophilic regions
just like the lipid layer
- function as transport protein – carrier
- channels
- enzymes
- receptors
, 2. Peripheral protein – loosely attached to integral protein
- glycoproteins (extracellular)
- filaments (intracellular) for membrane
support
- functions as – enzymes
- motor protein
- cell links
- Functions of the Membrane protein combined
- transport – channels, carriers
- receptors for signal transduction
- attachment for cytoskeleton and extracellular matrix
- enzymes
- cell junctions
- cell to cell recognition (MHC)
Other membrane structures:
Lipid rafts - 20% of outer membrane surface, serve as platforms
for some receptors
Glycocalyx – lipids, proteins with attached carbohydrates which
are specific for every cell types.
- biological markers for cell recognition
(sperm recognizing the egg to fertilize)
- cancer cells continuously change preventing the
immune cells to recognize them
Membrane junctions: -
1. tight junction – integral proteins of adjacent cells fused
- impermeable, prevent liquid and some
molecules to move in between cells
ex:
2. desmosomes – are anchoring junctions
- like rivets or spot welds that anchor adjacent
cells together at plaques
- cahedrin
- keratin
- skin cells and cardiac cells
3. gap junction – transmembrane proteins (connexon) forms
pores that allow small molecules to
pass through
ex: cardiac muscle, smooth muscles
Membrane transport: - Plasma membrane is selectively permeable
2 ways substances cross the plasma membrane: active and passive processes
