Molecular and Cellular Bases Pt 2 Quiz

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Questions and Answers

Which type of transport requires energy expenditure by the cell?

Facilitated diffusion

Passive transport

Simple diffusion

Active transport (correct)

What is the primary energy source for active transport?

Oxygen

Glucose

Carbon dioxide

ATP (correct)

What determines the rate of facilitated diffusion?

Quantity of the diffusing substance

Lipid solubility of the substance

Concentration gradient

Quantity of carrier proteins available (correct)

Which of the following most accurately describes "Transcellular (or Epithelial) Transport?"

Step 1 involves active transport. Step 2 involves either simple or facilitated diffusion. Signup and view all the answers

What is the function of carrier proteins in facilitated diffusion?

To bind specifically to the molecule being transported Signup and view all the answers

What is the purpose of channels in facilitated diffusion?

To allow the transport of ions and small hydrophilic molecules Signup and view all the answers

Which type of transport involves the movement of molecules from high to low concentration?

Passive transport Signup and view all the answers

What type of stimulus can open ion channels with a gate?

Voltage change, ligand, or mechanical stimulus Signup and view all the answers

What is the name given to ion channels that are always open?

Leak channels Signup and view all the answers

What is the main function of aquaporins in cells?

To aid water in crossing the cell membrane at a faster rate Signup and view all the answers

In which type of cells are voltage gated channels present?

In all excitable cell types, including muscle, nerve, endocrine, and egg cells Signup and view all the answers

What triggers the opening of ligand gated channels?

Ligand binding Signup and view all the answers

What characteristic of lipid soluble molecules allows them to readily cross the phospholipid bilayer?

Being uncharged and non-polar Signup and view all the answers

What is the minimum membrane potential required to trigger an action potential?

Channel threshold Signup and view all the answers

What determines the rate of water crossing the phospholipid bilayer?

The type of cell Signup and view all the answers

What is a characteristic of channels in membrane proteins?

They have an opening through the internal and external part of the cell membrane Signup and view all the answers

What is the direction of ion movement in passive transport?

From high to low concentration Signup and view all the answers

What is the primary function of membrane proteins in cell transport?

To act as a channel or transport/carrier protein Signup and view all the answers

What is an example of a ligand-gated channel?

Acetylcholine binding to a nicotinic receptor within skeletal muscle cells Signup and view all the answers

What type of molecules have a high permeability in the lipid bilayer?

Small hydrophobic molecules Signup and view all the answers

What type of energy is used in passive transport?

Kinetic energy Signup and view all the answers

What is the amount of pressure required to stop osmosis called?

Osmotic pressure Signup and view all the answers

What is the result of a hypotonic solution on a cell?

The cell will expand and possibly rupture Signup and view all the answers

Approximately how many types of aquaporins are found in mammalian cells?

13 Signup and view all the answers

What is the net movement of water based on the difference in water concentration across a membrane called?

Osmosis Signup and view all the answers

What is the primary difference between exocytosis and endocytosis?

The direction of transport across the cell membrane Signup and view all the answers

What is the name of the process by which cells internalize small particles?

Pinocytosis Signup and view all the answers

What is the mechanism by which potassium is transported from the bloodstream to the interstitial fluid?

Active transport using the sodium-potassium pump Signup and view all the answers

What is a function of receptor-mediated endocytosis?

To mediate the uptake of cholesterol Signup and view all the answers

Which of the following is NOT a type of exocytosis?

Pinocytosis Signup and view all the answers

Co-tranport (AKA: symport) and Counter-Transport (AKA: Antiport) are examples of which of the following?

Secondary active transport Signup and view all the answers

Study Notes

Ligand Gated Channels

Acetylcholine binds to nicotinic receptors in skeletal muscle cells.
Found in skeletal muscle cells and autonomic nervous system neurons.

Molecule Permeability

Small hydrophobic molecules easily dissolve in lipid bilayers, showing high permeability.
Small uncharged hydrophilic molecules diffuse slower than hydrophobic ones.
Ions have low permeability through lipid bilayers regardless of size.

Osmosis

Defined as the net movement of water based on concentration differences.
Water crosses membranes via simple diffusion or aquaporins; humans have around 13 types of aquaporins.
Osmotic pressure measures the pressure needed to halt osmosis.
Isotonic solutions show no osmotic flow, appearing normal.
Hypotonic solutions cause water influx, possibly leading to cell rupture.
Hypertonic solutions result in water exiting cells, often making them shriveled.

Transport Mechanisms

Active transport moves substances against concentration gradients, requiring energy (usually ATP).
Passive transport includes simple diffusion (e.g., osmosis) and facilitated diffusion.

Types of Passive Transport

Simple Diffusion: Movement of molecules through lipid bilayers without protein assistance, influenced by lipid solubility (e.g., oxygen, nitrogen, carbon dioxide).
Facilitated Diffusion: Utilizes carrier proteins; rate depends on available carriers, cannot exceed Vmax.

Carrier Proteins and Channels

Carrier proteins specifically bind and aid in the diffusion of molecules like sugars and nucleotides.
Channels are integral membrane proteins allowing ion and small hydrophilic molecule transport via facilitated diffusion.
Aquaporins enhance the rate of water movement across membranes.
Ion channels facilitate ion flow, some being gated by voltage, ligands, or mechanical stimuli.

Ion Channel Types

Voltage Gated Channels: Found in excitable cells (muscle, nerve, endocrine); essential for signal transmission.
Ligand Gated Channels: Open in response to ligand binding.

Cell Transport

Phospholipid bilayers are semi-permeable; lipid-soluble molecules pass easily while water-soluble molecules struggle.
Membrane proteins facilitate alternative transport forms; they can act as channels or transport proteins.

Active vs Passive Transport

Passive transport occurs down concentration gradients without energy, utilizing kinetic energy.
Example of transcellular transport involves potassium moving via the sodium-potassium pump followed by passive diffusion.

Endocytosis and Exocytosis

Both transport mechanisms use portions of the membrane to move impermeable molecules.
Endocytosis includes:
- Phagocytosis: Ingestion of large particles.
- Pinocytosis: Ingestion of small particles.
- Receptor Mediated Endocytosis: Specific uptake of cholesterol.
Exocytosis: Vesicles fuse with the cell membrane to release contents; can involve consecutive secretion of proteins into the plasma membrane or extracellular matrix.

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Description

Test your understanding of cell transport, the movement of substances across the cellular membrane, and the properties of lipid and water soluble molecules. Learn how the phospholipid bilayer affects the transport of different molecules.