MPP lecture 5

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Questions and Answers

Which type of protein spans across the lipid bilayer and is involved in transportation?

Extrinsic Proteins

Transmembrane Proteins

Integral Proteins (correct)

Peripheral Proteins

What primary function do peripheral proteins NOT perform?

Cell Recognition

Osmosis (correct)

Signal Transduction

Structural Support

In terms of cellular transport, what accurately distinguishes osmosis from diffusion?

Diffusion occurs under all conditions while osmosis requires a selective membrane. (correct)

Osmosis creates a volume change, whereas diffusion does not.

Osmosis involves solute movement while diffusion does not.

Diffusion can occur in both water and solute while osmosis occurs only in water.

Which of the following statements about primary active transport is incorrect?

It occurs passively without energy expenditure. Signup and view all the answers

What is the primary role of secondary active transport?

It depends on the gradient of another solute to function. Signup and view all the answers

How does simple diffusion primarily differ from facilitated diffusion?

Simple diffusion is passive and unaffected by saturation, unlike facilitated diffusion. Signup and view all the answers

Which of the following factors influences the rate of simple diffusion?

Gradient intensity Signup and view all the answers

What characteristic is common to both facilitated diffusion and active transport?

Both involve membrane proteins. Signup and view all the answers

Which statement accurately reflects the relationship between osmotic pressure and water movement?

Higher solute concentrations generate greater osmotic pressure, attracting water. Signup and view all the answers

What is the primary function of cholesterol in the plasma membrane?

Regulates the membrane's fluidity at varying temperatures Signup and view all the answers

Which element is most abundant in extracellular fluid (ECF)?

Sodium (Na+) Signup and view all the answers

What structural feature of phospholipids contributes to the formation of the lipid bilayer?

Combination of glycerol backbone and fatty acid tails Signup and view all the answers

In which body fluid compartment do red blood cells reside?

Plasma Signup and view all the answers

What characteristic of the plasma membrane allows for selective permeability?

The lipid bilayer's hydrophobic core Signup and view all the answers

Which of the following statements about intracellular fluid (ICF) is true?

ICF contains high levels of potassium ions Signup and view all the answers

How does the lipid bilayer structure impact membrane fluidity?

The unsaturated fatty acids increase fluidity Signup and view all the answers

What is the primary role of glycolipids in the plasma membrane?

Facilitating cellular communication and signaling Signup and view all the answers

Which of the following ions is primarily found in high concentrations within intracellular fluid (ICF)?

Potassium (K+) Signup and view all the answers

What is the main significance of the plasma membrane's semi-permeable nature?

It maintains the internal environment of the cell Signup and view all the answers

What is the primary function of facilitated diffusion carriers?

Facilitate the passive movement of molecules without energy Signup and view all the answers

Which of the following is NOT a type of active transport carrier?

Glucose transporter (GLUT) Signup and view all the answers

Which process requires energy to transport molecules across a membrane?

Primary active transport Signup and view all the answers

What defines the transport maximum (Tm) in carrier-mediated transport?

The transport rate when saturation of carriers occurs Signup and view all the answers

How do co-transporters function in active transport?

By utilizing energy from the electrochemical gradient to move two molecules in the same direction Signup and view all the answers

What is a characteristic of active transport carriers compared to facilitated diffusion carriers?

They require energy to move molecules against a gradient Signup and view all the answers

Which statement about secondary active transport is correct?

It relies on the electrochemical gradient created by primary active transport Signup and view all the answers

What type of transport involves moving molecules in opposite directions across the membrane?

Counter-transporter (exchanger, antiporter) Signup and view all the answers

Which carrier primarily facilitates the uptake of glucose based on its concentration gradient?

GLUT transporter Signup and view all the answers

Which mechanism results in the passive transport of molecules across the membrane?

Facilitated diffusion carriers Signup and view all the answers

What is the primary role of integral membrane pores in transport?

Allowing the free diffusion of specific small molecules. Signup and view all the answers

Which statement accurately describes the energy requirements for carrier proteins?

Carriers do not require energy for passive transport, but require it for active transport. Signup and view all the answers

How do gated-ion channels operate to facilitate ion transport?

By responding to specific stimuli to open or close their gates. Signup and view all the answers

What distinguishes leak-ion channels from gated-ion channels?

Leak-ion channels are always open, whereas gated-ion channels have a gate. Signup and view all the answers

Which example illustrates the function of pores in membrane transport?

Aquaporins enabling water movement across membranes. Signup and view all the answers

What is the main function of integral membrane channels?

To allow the passive movement of ions based on concentration gradients. Signup and view all the answers

What is the characteristic feature of carriers as integral membrane proteins?

They have at least two gates for transport. Signup and view all the answers

Which type of transport predominantly involves integral membrane proteins with no energy requirement?

Passive movement through channels and pores. Signup and view all the answers

How do ion channels contribute to cellular activity?

By maintaining the resting membrane potential through selective permeability. Signup and view all the answers

What kind of transport is facilitated by integral membrane proteins without the use of ATP?

Facilitated diffusion and passive transport. Signup and view all the answers

Study Notes

Carrier-Mediated Transport

Carriers bind to specific molecules on one side of the membrane, change shape, and release the molecule on the opposite side.
Transport can be categorized as facilitated diffusion or active transport.

Types of Carriers

Facilitated Diffusion Carriers
- Assist in passive movement along concentration gradients without energy.
- Example: Glucose transporter (GLUT) facilitates glucose uptake based on concentration.
Active Transport Carriers
- Move molecules against their concentration gradient using energy (ATP).
- Primary Active Transport: Directly uses ATP to pump molecules.
  - Examples: Na+ K+ ATPase, Ca2+ ATPase, H+ K+ ATPase (proton pump).
- Secondary Active Transport: Utilizes energy from electrochemical gradients established by primary active transport.
  - Co-Transporters (symports): Move two molecules in the same direction.
  - Counter-Transporters (antiporters): Move two molecules in opposite directions.

Body Fluid Compartments

The body comprises approximately 55-60% fluid; the rest is solid tissue.
All cells are surrounded by extracellular fluid (ECF).
ECF Composition: High in Na+, Cl-, Ca2+, HCO3-.
Intracellular Fluid (ICF): High in K+ and free proteins.

Plasma Membrane Structure

Acts as a barrier, gateway for communication, and regulator of homeostasis.
Composed of three key lipids: phospholipids, cholesterol, and glycolipids.

Lipid Bilayer

Formed mainly of phospholipids with a hydrophilic head and hydrophobic tails.
Creates a semi-permeable barrier that ensures selective substance entry and exit.
Fluidity is essential for molecule movement and proper functioning of membrane proteins.

Cholesterol's Role

Found interspersed within the lipid bilayer.
Regulates membrane fluidity:
- High temperatures: Prevents excessive fluidity.
- Low temperatures: Prevents rigidity, maintaining flexibility.

Associated Proteins

Integral Proteins: Span the membrane, involved in transport (e.g., pores, channels, carriers).
Peripheral Proteins: Loosely attached to the membrane, involved in signal transduction and structural support.

Cellular Homeostasis

The selective permeability of the membrane regulates internal environments, ion concentrations, and nutrient/waste transport.

Diffusion vs. Osmosis

Diffusion: Passive movement from high to low concentration using kinetic energy; does not change volume.
Osmosis: Water movement across a semi-permeable membrane towards higher solute concentration, causing volume changes.

Transport Mechanisms and Kinetics

Simple Diffusion: Passive, concentration-driven, without saturation; influenced by permeability, temperature, and surface area.
Facilitated Diffusion: Uses integral proteins for passive transport down the concentration gradient; no energy expenditure.
Primary Active Transport: ATP-dependent, moves solutes against gradients; can reach saturation.
Secondary Active Transport: Gradient-driven; co-transports solutes against gradients, influenced by electrochemical gradients.

Functions of Integral Membrane Proteins

Pores: Provide non-selective passages for small molecules like water or ions; facilitate simple diffusion; no energy required.
Channels:
- Leak-Ion Channels: Always open, allow passive ion movement; energy not required.
- Gated-Ion Channels: Open in response to stimuli (voltage, chemical, mechanical); facilitate passive movement; energy not required.
Carriers (Transporters): Require at least two gates for function, facilitating both facilitated diffusion and active transport.

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Description

Explore the mechanisms of membrane transport, focusing on carriers that facilitate the movement of molecules across cell membranes. Understand the differences between facilitated diffusion carriers and active transport carriers, including their energy requirements and efficiency. Test your knowledge on how these transport processes operate within biological systems.