2A: Assemblies of molecules, cells and groups of cells within single cellular and multicellular organisms Flashcards
Plasma Membrane
Functions to contain the cell structures and protects them from the environment
Plasma Membrane
Functions to contain the cell structures and protects them from the environment
Composition of Plasma Membrane
Phospholipid Bilayer that can reseal and repair itself if a small portion is removed;
Interior = hydrophobic, nonpolar molecules like CO2 or O2 or Steroid Hormones can easily cross
Exterior = hydrophilic
How does water cross the plasma membrane?
Water passes through aquaporins in order to get through the membrane since its polar
How do ions, carbohydrates and amino acids get through the membrane?
They utilize special channels or transport proteins
Channel Proteins
Selective to certain ions/molecules that need to cross the membrane
How do ions, carbohydrates and amino acids get through the membrane?
They utilize special channels or transport proteins
Fluid Mosaic Model
Accounts for the presence of lipids, proteins and carbohydrates in a dynamic, semisolid plasma membrane that surrounds cells
Phospholipid Bilayer
Contains proteins embedded within the plasma membrane
Phospholipid Bilayer
Contains proteins embedded within the plasma membrane
Membrane Dynamics
The free movement of lipids forming lipid rafts, Flippases that maintain bidirectional transport of lipids between the two layers of the phospholipid bilayer
Movement of Protein & Carbohydrates
Move within the membrane but are slowed by their relatively large size
Movement of Protein & Carbohydrates
Move within the membrane but are slowed by their relatively large size
Movement of Protein & Carbohydrates
Move within the membrane but are slowed by their relatively large size
Membrane Components [Lipids]
Triacylglycerols & Free Fatty Acids
Glycerophospholipids
Cholesterol
Waxes
TAG & FFA
Act as phospholipid precursors and are found in low levels in the membrane
Cholesterol
Present in large amounts and contributes to membrane fluidity and stability
Waxes
They function in waterproofing and defense
Waxes
They function in waterproofing and defense
Function of Proteins in the Cell Membrane
Transports, Cell Adhesion Molecules and Enzymes
Transmembrane Proteins
Can have one or more hydrophobic domains and are most likely to function as receptors or channels
Embedded Proteins
Usually part of a catalytic complex or involved in cellular communication
Embedded Proteins
Usually part of a catalytic complex or involved in cellular communication
Membrane-Associated Proteins
Act as recognition molecules or enzymes
Glycoprotein Coat
Carbohydrates that form a protective coat and functions in cell recognition
Glycoprotein Coat
Carbohydrates that form a protective coat and functions in cell recognition
Cell-Cell Junctions
Regulate transport intracellularly and intercellularly;
Types of Cell-Cell Junctions
Gap Junctions, Tight Junctions, Desmosomes and Hemidesmosomes
Types of Cell-Cell Junctions
Gap Junctions, Tight Junctions, Desmosomes and Hemidesmosomes
Dominance of Biomolecules in the Lipid Membrane
Lipids > Proteins > Carbohydrates > Nucleic Acids
Examples of Phospholipids
Lecithin, Phosphatidylinositol
Examples of Sphingolipids
Ceramides, Sphingomyelins, Cerebrosides, Gangliosides
Cholesterol
Present in large amounts and contributes to membrane fluidity and stability; necessary for steroid synthesis
Embedded (Integral) Proteins
Usually part of a catalytic complex or involved in cellular communication
Membrane-Associated (Peripheral) Proteins
Act as recognition molecules or enzymes
Examples of Sphingolipids
Ceramides, Sphingomyelins, Cerebrosides, Gangliosides
Gap Junctions (Connexons)
Allow for cell-cell communication; groups of connexin form these; permit movement of water and some solutes directly between cells
Gap Junctions (Connexons)
Allow for cell-cell communication; groups of connexin form these; permit movement of water and some solutes directly between cells
Tight Junctions
Prevent solutes from leaking into the space between cells via a paracellular route
Tight Junctions
Prevent water and solutes from leaking into the space between cells via a paracellular route
Tight Junctions
Prevent water and solutes from leaking into the space between cells via a paracellular route
Desmosomes
Bind adjacent cells by anchoring to their cytoskeleton; they are associated with intermediate filaments; primarily found between two layers of epithelial tissue
Hemidesmosomes
Attach epithelial cells to basement membranes
How do concentration gradients aid in solute transport across membranes?
Help determine appropriate membrane transport mechanisms in cells
How does osmotic pressure aid in solute transport across membranes?
It is pressure applied to a pure solvent to prevent osmosis and is used to express the concentration of the solution;
Passive Transport [-dG]
It’s a spontaneous process because the molecule is moving down its concentration gradient from an area of higher concentration to an area of lower concentration
Types of Passive Transport
Simple Diffusion
Osmosis
Facilitated Diffusion
Simple Diffusion
Does not require a transporter; small nonpolar molecules utilize simple diffusion until equilibrium is achieved
Osmosis
Water moves from areas of dilution to areas of concentration
Osmosis
Water moves from areas of dilution (high water) to areas of concentration (low water); through a selectively permeable membrane
Osmosis
Water moves from areas of dilution (high water) to areas of concentration (low water); through a selectively permeable membrane
Hypotonic Solution
Causes a cell to swell as water rushes in; solution is less concentrated than the cell
Hypertonic Solution
Causes a cell to shrink as water rushes out
solution is more concentrated than the cell
Isotonic Solution
Causes nothing to happen because the solution and the cell have the same concentration
Isotonic Solution
Causes nothing to happen because the solution and the cell have the same concentration
Facilitated Diffusion
Uses transport proteins to move impermeable solutes across the cell membrane; energy barrier is too high for these molecules to cross freely; ion channels, ligand gated and voltage gated channels
Facilitated Diffusion
Uses transport proteins to move impermeable solutes across the cell membrane; energy barrier is too high for these molecules to cross freely; ion channels, ligand gated and voltage gated channels
Active Transport
Results in the net movement of a solute against its concentration gradient; requires energy usually in the form of ATP
Types of Active Transport
Primary Transport
Secondary Transport
Primary Active Transport
Uses ATP to directly transport molecules across a membrane; involves use of a transmembrane ATPase
Secondary Active Transport [Coupled Transport]
It harnesses energy released by one particle going down its electrochemical gradient to drive a particle up its electrochemical gradient
Symport = both particles move in the same direction across the membrane
Antiport = particles move in opposite directions
Secondary Active Transport [Coupled Transport]
It harnesses energy released by one particle going down its electrochemical gradient to drive a particle up its electrochemical gradient
Symport = both particles move in the same direction across the membrane
Antiport = particles move in opposite directions
Primary Active Transport in the Body
Occurs in neurons to maintain membrane potential
Secondary Active Transport in the Body
Occurs in the kidneys to drive reabsorption and secretion of various solutes into and out of the filtrate
Osmosis
[H2O]
Water moves from areas of dilution (high water) to areas of concentration (low water); through a selectively permeable membrane
Facilitated Diffusion
[Polar molecules, Ions]
Uses transport proteins to move impermeable solutes across the cell membrane; energy barrier is too high for these molecules to cross freely; ion channels, ligand gated and voltage gated channels
Active Transport
[Polar molecules or Ions]
Results in the net movement of a solute against its concentration gradient; requires energy usually in the form of ATP
Secondary Active Transport in the Body
Occurs in the kidneys to drive reabsorption and secretion of various solutes into and out of the filtrate
Sodium/Potassium Pump Solutes
[Na/K ATPase]
3 Na out
2 K in
1 ATP hydrolyzed
Potassium Leak Channels
K flows down its gradient out of the cell and helps maintain osmotic balance with surroundings
Where are sodium concentrations higher?
Outside the cell
Where are potassium concentrations higher?
Inside the cell
Where are chloride concentrations higher?
Outside the cell
Where are calcium concentrations higher
Outside the cell
Where are calcium concentrations higher?
Outside the cell
Where are calcium concentrations higher?
Outside the cell
How is membrane potential maintained?
By the action of the sodium potassium pump and leak channels
How is membrane potential maintained?
By the action of the sodium potassium pump and leak channels
Endocytosis
Occurs when the cell membrane invaginates and engulfs material to bring it into the cell; consists of Pinocytosis, Phagocytosis
Pinocytosis
Ingestion of fluids and dissolved particles
Phagocytosis
Ingestion of large solids such as bacteria
Exocytosis
Secretory vesicles fuse with the membrane and release material to the extracellular environment
