Chapter 3 Flashcards
Cell Theory 3 parts
- Cells are the smallest unit of life
- All organisms are made of one or more cells
- All cells come from preexisting cells
Properties of cells
- Differ in size, shape, and subcellular components (organelles)
- Differences in structure lead to difference in function
Generalized cell (3 main parts)
-Plasma Membrane) separates cell from environment
Cytoplasm) Thick ICF, contains organelles
Nucleus) Contains DNA
Plasma Membrane (structure)
- Made of a double layer of phospholipids (lipid bilayer)
- Called fluid mosaic model because it it made of many pieces
- Is selectively permeable.
Intracellular Fluid
-Fluid inside the cell (cytoplasm)
Extracellular fluid
-Fluid outside cells
ex:
Interstitial Fluid: Submersed cells
Blood Plasma
Cerebrospinal Fluid.
Cellular secretions
Extracellular matrix
Membrane Lipids
Phospholipids) Form lipid bilayer. have hydrophobic tail and a hydrophilic head.
Glycolipids: Lipids with polar sugar groups on membrane surface
Cholesterol) Increases membrane stability
Integral Proteins
- Inserted into the membrane (Most are transmembrane)
- Have Hydrophobic and Hydrophilic areas
a) Hydrophobic region interact with lipid tails
b) Hydrophilic areas interact with water - Function as transport proteins
Peripheral Proteins
- Loosely attached to integral proteins. Include filaments on the intracellular surface for plasma membrane support.
- Function as Enzymes
- Some are motor proteins involved in mechanical functions
- Responsible for cell to cell connections
6 Functions of Membrane Proteins
1) Transport) transport molecules across the membrane.
2) Receptors) Sense signals from hormones and relay information
3) Attachment) to the cytoskeleton or extracellular matrix.
4) Enzymatic Activity)
5) Intercellular Joining
6) Cell Cell recognition
Glycocalyx
- Consists of sugars sticking out of the cell surface.
- Some are attached to lipids (glycolipids) and some are attached to proteins (glycoproteins)
- the coating is different for each cell and it provides specific markers for each cell, Allows recognition for self vs nonself.
Homostatic Imbalance
-Damaged cells are able to continue reproducing because the immune system cannot recognize the glycocalyx as incorrect.
Cell Juntions
-Binds cells into communities
Tight Junctions
- Adjacent integral proteins form an impermeable junction around the cell which prevents fluids from moving between cells
- useful in places like digestive tract.
Demosomes
- Zipper like cell junction formed with liker proteins (cadherins) of neighboring cells.
- Linker protein is anchored in a thickened part of the membrane called plaque
- Allows for flexibility under tension
Gap Junction
-Transmembrane proteins form pores (called Connexons) which allow molecules (such as ions/electrical signals) to move around.
Active Transport
Uses energy (ATP) to move a particle across a selectively permeable membrane - Moves particles across a selectively permeable membrane.
Passive Transport
Does not use energy to transport a particle across a selectively permeable membrane
Filtration
Diffusion across a capillary wall not plasma membrane
Diffusion
- Molecules move from areas of high concentration to low concentration (down concentration gradient).
- The speed of diffusion is influenced by concentration of molecules, size of the molecules, and temperature.
Simple Diffusion
- Unassisted Diffusion of a Non Polar, Lipid Soluble (hydrophobic) molecule. These substances diffuse directly through the lipid bilayer.
ex) O, CO2, Steroids, Fatty acids, and some very small substances.
Facilitated Diffusion
-Transport of hydrophobic molecules
Carrier Method Facilitated Diffusion
- Transmembrane proteins (carriers) carry specific molecules that are too large for membrane channels
- Carrier binds to a molecule which moves it across the membrane
- Binding is limited to the number of carriers (when carriers are full they are saturated).
Channel-Mediated Diffusion
- Transmembrane protein Channels with aqueous-filled cores
- Transport Ions or Water (Osmosis) down the concentration gradient.
- Water channel is called an aquaporin
Osmosis
- Movement of solvent (Water) across a selectively permeable membrane
- Water is moving from higher to lower concentration
- Can diffuse through plasma membranes/lipid bilayer through channels called aquaporins.
Osmolarity
- Measure of concentration of total number of solute particles in a solvent.
- Water will move from areas of low solute (high water) concentration to areas with high solute (low water) concentration.
- Moves through channels called aquaporins.
Hydrostatic Pressure
Outward pressure exerted on a cell due to osmosis
-Referred to as back
Osmotic Pressure
Inward pressure due to the tendency of water to be pulled into a cell with higher osmolarities.
Tonicity
-Ability of a solution to change shape or tone of cells by altering internal water volume.
Isotonic Solution
-Same osmolarity outside the cell as inside which leaves the volume of the cell unchanged.
Hypertonic Solution
-Higher osmolarity outside the cell then inside. Causes water to flow out of the cell which causes shrinking. crenation