2A: Assemblies of molecules, cells and groups of cells within single cellular and multicellular organisms Flashcards Preview

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Flashcards in 2A: Assemblies of molecules, cells and groups of cells within single cellular and multicellular organisms Deck (82):
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Plasma Membrane

Functions to contain the cell structures and protects them from the environment

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Plasma Membrane

Functions to contain the cell structures and protects them from the environment

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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

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How does water cross the plasma membrane?

Water passes through aquaporins in order to get through the membrane since its polar

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How do ions, carbohydrates and amino acids get through the membrane?

They utilize special channels or transport proteins

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Channel Proteins

Selective to certain ions/molecules that need to cross the membrane

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How do ions, carbohydrates and amino acids get through the membrane?

They utilize special channels or transport proteins

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Fluid Mosaic Model

Accounts for the presence of lipids, proteins and carbohydrates in a dynamic, semisolid plasma membrane that surrounds cells

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Phospholipid Bilayer

Contains proteins embedded within the plasma membrane

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Phospholipid Bilayer

Contains proteins embedded within the plasma membrane

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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

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Movement of Protein & Carbohydrates

Move within the membrane but are slowed by their relatively large size

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Movement of Protein & Carbohydrates

Move within the membrane but are slowed by their relatively large size

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Movement of Protein & Carbohydrates

Move within the membrane but are slowed by their relatively large size

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Membrane Components [Lipids]

Triacylglycerols & Free Fatty Acids
Glycerophospholipids
Cholesterol
Waxes

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TAG & FFA

Act as phospholipid precursors and are found in low levels in the membrane

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Cholesterol

Present in large amounts and contributes to membrane fluidity and stability

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Waxes

They function in waterproofing and defense

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Waxes

They function in waterproofing and defense

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Function of Proteins in the Cell Membrane

Transports, Cell Adhesion Molecules and Enzymes

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Transmembrane Proteins

Can have one or more hydrophobic domains and are most likely to function as receptors or channels

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Embedded Proteins

Usually part of a catalytic complex or involved in cellular communication

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Embedded Proteins

Usually part of a catalytic complex or involved in cellular communication

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Membrane-Associated Proteins

Act as recognition molecules or enzymes

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Glycoprotein Coat

Carbohydrates that form a protective coat and functions in cell recognition

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Glycoprotein Coat

Carbohydrates that form a protective coat and functions in cell recognition

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Cell-Cell Junctions

Regulate transport intracellularly and intercellularly;

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Types of Cell-Cell Junctions

Gap Junctions, Tight Junctions, Desmosomes and Hemidesmosomes

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Types of Cell-Cell Junctions

Gap Junctions, Tight Junctions, Desmosomes and Hemidesmosomes

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Dominance of Biomolecules in the Lipid Membrane

Lipids > Proteins > Carbohydrates > Nucleic Acids

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Examples of Phospholipids

Lecithin, Phosphatidylinositol

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Examples of Sphingolipids

Ceramides, Sphingomyelins, Cerebrosides, Gangliosides

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Cholesterol

Present in large amounts and contributes to membrane fluidity and stability; necessary for steroid synthesis

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Embedded (Integral) Proteins

Usually part of a catalytic complex or involved in cellular communication

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Membrane-Associated (Peripheral) Proteins

Act as recognition molecules or enzymes

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Examples of Sphingolipids

Ceramides, Sphingomyelins, Cerebrosides, Gangliosides

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Gap Junctions (Connexons)

Allow for cell-cell communication; groups of connexin form these; permit movement of water and some solutes directly between cells

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Gap Junctions (Connexons)

Allow for cell-cell communication; groups of connexin form these; permit movement of water and some solutes directly between cells

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Tight Junctions

Prevent solutes from leaking into the space between cells via a paracellular route

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Tight Junctions

Prevent water and solutes from leaking into the space between cells via a paracellular route

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Tight Junctions

Prevent water and solutes from leaking into the space between cells via a paracellular route

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Desmosomes

Bind adjacent cells by anchoring to their cytoskeleton; they are associated with intermediate filaments; primarily found between two layers of epithelial tissue

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Hemidesmosomes

Attach epithelial cells to basement membranes

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How do concentration gradients aid in solute transport across membranes?

Help determine appropriate membrane transport mechanisms in cells

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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;

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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

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Types of Passive Transport

Simple Diffusion
Osmosis
Facilitated Diffusion

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Simple Diffusion

Does not require a transporter; small nonpolar molecules utilize simple diffusion until equilibrium is achieved

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Osmosis

Water moves from areas of dilution to areas of concentration

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Osmosis

Water moves from areas of dilution (high water) to areas of concentration (low water); through a selectively permeable membrane

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Osmosis

Water moves from areas of dilution (high water) to areas of concentration (low water); through a selectively permeable membrane

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Hypotonic Solution

Causes a cell to swell as water rushes in; solution is less concentrated than the cell

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Hypertonic Solution

Causes a cell to shrink as water rushes out
solution is more concentrated than the cell

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Isotonic Solution

Causes nothing to happen because the solution and the cell have the same concentration

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Isotonic Solution

Causes nothing to happen because the solution and the cell have the same concentration

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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

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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

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Active Transport

Results in the net movement of a solute against its concentration gradient; requires energy usually in the form of ATP

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Types of Active Transport

Primary Transport
Secondary Transport

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Primary Active Transport

Uses ATP to directly transport molecules across a membrane; involves use of a transmembrane ATPase

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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

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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

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Primary Active Transport in the Body

Occurs in neurons to maintain membrane potential

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Secondary Active Transport in the Body

Occurs in the kidneys to drive reabsorption and secretion of various solutes into and out of the filtrate

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Osmosis
[H2O]

Water moves from areas of dilution (high water) to areas of concentration (low water); through a selectively permeable membrane

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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

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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

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Secondary Active Transport in the Body

Occurs in the kidneys to drive reabsorption and secretion of various solutes into and out of the filtrate

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Sodium/Potassium Pump Solutes
[Na/K ATPase]

3 Na out
2 K in
1 ATP hydrolyzed

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Potassium Leak Channels

K flows down its gradient out of the cell and helps maintain osmotic balance with surroundings

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Where are sodium concentrations higher?

Outside the cell

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Where are potassium concentrations higher?

Inside the cell

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Where are chloride concentrations higher?

Outside the cell

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Where are calcium concentrations higher

Outside the cell

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Where are calcium concentrations higher?

Outside the cell

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Where are calcium concentrations higher?

Outside the cell

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How is membrane potential maintained?

By the action of the sodium potassium pump and leak channels

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How is membrane potential maintained?

By the action of the sodium potassium pump and leak channels

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Endocytosis

Occurs when the cell membrane invaginates and engulfs material to bring it into the cell; consists of Pinocytosis, Phagocytosis

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Pinocytosis

Ingestion of fluids and dissolved particles

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Phagocytosis

Ingestion of large solids such as bacteria

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Exocytosis

Secretory vesicles fuse with the membrane and release material to the extracellular environment