Chapter 2 The Living Cell Part 1

Front 1

The cells components

Back 1

Plasma membrane
cytoplasm and organelles
Nucleus
Human body has 50-100 trillion

Front 2

Cell Theory

Back 2

-The cell is the basic structural and functional unit of living organisms.
-the activity of an organism depends on both the individual and the collective activities of its cells.

Front 3

Interstitial Fluid

Back 3

-Cell bathed in this it is one of the two compartments of the extracellular fluid space.
-Rich, nutritious "soup"
-Made of: amino acids, sugars, fatty acids.
--Water is the main solvent

Front 4

Fluid Mosaic model

Back 4

The molecular arrangement of the plasma membrane resembles a sea of fluid lipids that contains a variety of different proteins.
-Has a selective barrier (lipid bilayer).
-Plays a role in cell to cell communication.

Front 5

Phospholipids

Back 5

-consist of 1 glycerol, 2 fatty acid chains, and a phosphate group.
-Phosphate group:
--polar head
--hydrophilic (interact with water)
--face the extracellular fluid and the cytoplasm
-the two fatty acid chains are hydrophobic (do not interact with water.
---They are amphipathic
*have various shapes
*are self-orienting in biological membranes.
*Orient themselves so that polar heads face the extracellular and cytosolic fluids and fatty acid chains are sandwiched in the middle away from the fluid.

Front 6

Amphipathic

Back 6

Molecules that have both polar and nonpolar parts.

Front 7

Surfaces of the plasma membrane differ in kinds and amounts of lipids they contain.

Back 7

-Extracellular surface (outside)
-Cytostolic surface (interior)
--Majority of the lipids are the phospholipids.
*Unsturated
*Kinked tails which increases the distance between them
--Promotes membrane fluidity

Front 8

Membrane Fluidity

Back 8

-Fluidity depends on the number of double bonds in the fatty acid tails with "kinks" increasing fluidity as the chains are more separated.
-Fluidity also related to the concentration of cholesterol.

Front 9

Cholesterol

Back 9

-20% of plasma lipids
-Acts as a fluidity buffer in the plasma membrane
-tends to keep the fluidity of the fatty acid chain of the phospholipid bilayer in an intermediate range
-due to the way cholesterol forms hydrogen bonds with the heads of phospholipids and glycolipids and is spaced between the bent tails of the phospholipids, the membrane is stronger but less fluid at normal body temp.
-It can thought of as an anchoring structure.

Front 10

Cholesterol molecules are aligned with the phospholipid molecules on both sides of the bilayer

Back 10

-The hydroxyl group is positioned where it can interact with the lower oxygen molecules on the phospholipids.
-The ringed portion of cholesterol, which is rigid and flat, lies next to the first portions of the fatty acid chains. The cholesterol's linear tail, which is quite flexible, lies among the lower portions of the fatty acid chains.

Front 11

Positioned between the phospholipids, the cholesterol prevents their interaction and possible crystallization.

Back 11

The rigid, planar portion of the molecule tends to block many of the motions of the first portions of the fatty acid chains. this makes the intermediate portion of the bilayer more rigid and less permeable to small, polar molecules.
Lower down, near the center of the bilayer, the flexible tail of the cholesterol molecule allows more movement, making the central part of the bilayer the most fluid.

Front 12

Glycolipids

Back 12

-Phospholipids with attached sugar groups.
-Make up 5% of the plasma membrane.
-Carbohydrate groups form polar head and this section protrudes into the extracellular space.
-Fatty acid tail nonpolar.
-Only found in the portion of the plasma membrane that faces the extracellular fluid space (not the cytoplasm).
-Function--the carbohydrate portion function as receptors or antigens.

Front 13

Lipid rafts

Back 13

-on 20% of the plasma membrane outer layer (extracellular side)
-Less fluid than rest of plasma membrane.
-Dynamic assemblies of saturated phospholipids (packed tightly) and sphingolipids, lots of cholesterol, and specific proteins
-Though to be platforms for molecules involved in cell signaling

Front 14

Sphingolipids

Back 14

Have slightly different structure from phospholipids in that the linkage from the hydrophilic portion of the milecule to the fatty acyl chains is carried out through an amide and an alkyl linkage rather than an ether linkage and the end carbon not involved in the phosphate linkage.
-Are common in neural and muscular tissues and they are present on the surface of eukaryotic cells, where they play roles in cellular recognition and communication.

Front 15

Integral Proteins

Back 15

-Firmly inserted into the lipid bilayer. Some protrude from the extracellular face only
-Cell membrane disrupted if these are removed (will destroy the cell)
-Most are transmembrane or spanning proteins (extend through the fatty acid tails of the phospholipis)
-Are amphipathic
-Functions;
*Transport (channels; pores)
*Carriers
*Receptors (for hormones and neurotransmitters; involved in cell signaling pathways)

Front 16

Peripheral Proteins

Back 16

-Can be removed without disrupting membrane integrity.
-Attached loosely to integral proteins or membrane lipids
-Do not penetrate the hydrophobic portion of the membrane
-Include a network of filaments that support the membrane on the cytosolic side.
Functions:
*Enzymes
*Mechanical function to change cell shape (mitosis; muscle cell contraction; cell junctions).

Front 17

Plasma Membrane Proteins

Back 17

*Dynamic and always in flux
*consistency of olive oil
*Lipid molecules can move from side to side (lateral movement)
*They cannot flip-flop from one side of the membrane to the other.
*Some can float freely in the membrane.

Front 18

Glycoproteins

Back 18

Proteins with carbohydrate groups that extend into the extracellular fluid space

Front 19

Glycocalyx

Back 19

The carbohydrate portions of both glycolipids and the glycoproteins protruding into the extracellular space (the sugary coat). the hydrophilic portion attracts water, thus some call this the slime layer.

Front 20

Glycocalyx functions

Back 20

*Cell surface markers for cell recognition
*Cell to cell adherence in some tissues
*Protection from enzymatic digestion
*Protection from enzymatic digestion
*Makes cells slippery
*Protects against cell dehydration
*Cancer cells have changes in glycocalyx allowing them to evade immune cells

Front 21

Microvilli

Back 21

*Finer like projections of the membrane from the free surface of a cell 9apical surface); core made of actin.
*Increase the surface area.
*Found in absorptive cells (GI tract; Kidney tubules)

Front 22

Membrane Junctions

Back 22

Tight junctions
Adherens belt
Desmosomes
Hemidesmosomes
Gap junctions

Front 23

Lumen

Back 23

Cavity inside a tube, blood vessel, or hollow organ.

Front 24

Tight junctions

Back 24

1. Keep contents inside the cell.
2. Web-like strands of trans membrane proteins that fuse the outer surfaces of the adjacent plasma membranes.
3. Plasma membranes fuse together like a zipper.
4. Prevent molecules from passing through the extracellular space between adjacent epithelial cells.
5. Act as regulators.
Locations:
*Epithelial cells that line the stomach, intestine, and urinary bladder.
*blood-brain barrier formed by endothelial cells lining the blood vessels. (regulate what is let into the brain)

Front 25

Adheren Junctions

Back 25

*Resists cell separation
Components:
*Plaque dense layer of proteins on the inner surface of the plasma membrane
*The plaque attaches to actin microfilaments and transmembrane
glycoproteins called cadherins
*these areas form an adhesion belt
Function: Help epithelial cells resist separation

Front 26

Desmosomes

Back 26

-Prevents cell separation under stress or shearing forces.
**Components:
1. Plaques
2. Transmembrane proteins (glycoproteins)
3. Intermediate filaments
Locations:
1. Outer layer of the epidermis
2. Cardiac muscle cells

Front 27

Hemidesmosomes

Back 27

-Attach cells to basement membranes
Components:
1. Plaque
2. Transmembrane glycoproteins (integrins)
3. Intermediate filaments (keratin(
**Do not attach to adjacent cells; instead they attach to the protein laminin which is part of the basement membrane.

Front 28

Gap Junctions

Back 28

-Looks like an open channel.
*Used for cell to cell communication.
(ions going through)
Components:
1. Membrane proteins called connexins which create a fluid filled tunnel called the connexon between adjacent cells.
Function: Pathway for ions and small molecules to diffuse from one cell to another. Means of intercellular communication.
Locations:
1. Nerve cells
2. Cardiac and smooth muscle cells
3. Embryonic cells