Cell Membrane Structure and Function
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Questions and Answers

What is the primary component of the cell membrane that forms the phospholipid bilayer?

  • Nucleic acids
  • Proteins
  • Phospholipids (correct)
  • Carbohydrates

What characteristic do phosphate heads of phospholipids possess?

  • Non-polar
  • Hydrophobic
  • Amphipathic
  • Hydrophilic (correct)

In diffusion, molecules move from an area of ______ concentration to an area of ______ concentration.

  • High; low (correct)
  • Low; high
  • Equal; equal
  • Low; low

What does a hypertonic solution do to a cell placed in it?

<p>Forces water out of the cell (B)</p> Signup and view all the answers

What is the outcome for a cell when placed in a hypotonic solution?

<p>The cell will burst (C)</p> Signup and view all the answers

What best describes the term 'Isotonic solution'?

<p>Equal solute concentration inside and outside the cell (B)</p> Signup and view all the answers

Which statement about facilitated diffusion is correct?

<p>It helps in the movement of molecules across a membrane. (A)</p> Signup and view all the answers

What characteristic defines the 'Fluid Mosaic Model' of the cell membrane?

<p>Fluidity in membrane movement (A)</p> Signup and view all the answers

What does the term 'semipermeable' refer to in the context of the cell membrane?

<p>Allows some substances to pass but not others (D)</p> Signup and view all the answers

Which of the following correctly describes osmosis?

<p>Movement of water across a semipermeable membrane (C)</p> Signup and view all the answers

What distinguishes the hydrophobic lipid tails from the hydrophilic phosphate heads of phospholipids in the cell membrane?

<p>Lipid tails repel water, while phosphate heads are attracted to it. (C)</p> Signup and view all the answers

In what way does a hypertonic solution affect the movement of water in a cell?

<p>It forces water out of the cell. (A)</p> Signup and view all the answers

Which of the following best describes the concept of facilitated diffusion?

<p>The process that helps molecules move across a membrane with the help of transport proteins. (D)</p> Signup and view all the answers

What does it mean for a cell membrane to be described as 'semipermeable'?

<p>It selectively allows only certain molecules to pass while blocking others. (B)</p> Signup and view all the answers

In which solution is a cell likely to burst due to water influx?

<p>Hypotonic solution (D)</p> Signup and view all the answers

What occurs to a cell when it is placed in an isotonic solution?

<p>There is no net movement of water, maintaining size equilibrium. (C)</p> Signup and view all the answers

How does osmosis differ from diffusion?

<p>Osmosis is the movement of water specifically across a membrane, whereas diffusion includes other substances. (D)</p> Signup and view all the answers

What is a key characteristic of the Fluid Mosaic Model of the cell membrane?

<p>It emphasizes the random arrangement of phospolipids and proteins. (B)</p> Signup and view all the answers

Which term best describes the condition of a cell in a hypertonic solution?

<p>Small and shriveled (C)</p> Signup and view all the answers

What is the primary factor influencing the direction of water movement during osmosis?

<p>The concentration of solutes in the solution (D)</p> Signup and view all the answers

Flashcards

Phospholipid Bilayer

The cell membrane's main component; a double layer of phospholipids, arranged with phosphate heads facing outwards and lipid tails facing inwards.

Phosphate Heads

Water-loving, attracted to water, they form the outer layer of the phospholipid bilayer facing the watery environment.

Lipid Tails

Water-fearing, repelled by water, they form the inner layer of the phospholipid bilayer, avoiding contact with water.

Fluid Mosaic Model

A model that describes the cell membrane's structure as a fluid, constantly moving arrangement of phospholipids and proteins.

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Semipermeable Membrane

Describes the cell membrane's ability to let some substances pass while blocking others, acting as a selective barrier.

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Diffusion

The movement of molecules from an area of high concentration to an area of low concentration. This movement naturally occurs without energy input.

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Osmosis

The movement of water molecules across a semipermeable membrane from an area of high water concentration to an area of low water concentration.

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Hypertonic Solution

A solution with a higher concentration of solutes compared to another solution.

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Hypotonic Solution

A solution with a lower concentration of solutes compared to another solution.

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Isotonic Solution

A solution where the concentration of solutes is equal inside and outside the cell. There is no net movement of water.

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What is the phospholipid bilayer?

The cell membrane is a double layer of phospholipids, with the hydrophilic phosphate heads facing outwards and the hydrophobic lipid tails facing inwards.

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What is the fluid mosaic model?

This model describes the cell membrane as a flexible structure where phospholipids and proteins can move around.

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Why is the cell membrane called semipermeable?

The cell membrane allows some substances to pass through while blocking others, acting like a selective filter.

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What is diffusion?

The movement of molecules from an area of high concentration to an area of low concentration, driven by random motion and the tendency to spread out.

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What is osmosis?

The diffusion of water molecules across a selectively permeable membrane, from a region of higher water concentration to a region of lower water concentration.

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What is a hypertonic solution?

A solution with a higher concentration of dissolved substances (solutes) compared to another solution.

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What is a hypotonic solution?

A solution with a lower concentration of dissolved substances (solutes) compared to another solution.

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What is an isotonic solution?

A solution where the concentration of dissolved substances (solutes) is equal inside and outside the cell.

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What is facilitated diffusion?

Facilitated diffusion is the process of moving molecules across a membrane with the help of transport proteins.

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What is active transport?

Active transport is the movement of molecules across a membrane against their concentration gradient, requiring energy.

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Study Notes

Cell Membrane Structure

  • Cell membranes are composed of lipids and proteins, separating the cell contents from the outside world.
  • The bilayer structure is formed by two layers of phospholipids.
  • Phospholipid heads are hydrophilic (water-loving).
  • Phospholipid tails are hydrophobic (water-fearing).
  • Heads orient towards the water, tails away from water.

Fluid Mosaic Model

  • A more accurate model of the cell membrane structure.
  • Called "fluid" because the components are not static but can move.
  • Called "mosaic" because of the various components embedded in the membrane, such as proteins, cholesterol, and glycoproteins.
  • Includes glycoproteins and glycolipids on the cell surface.

Membrane Permeability

  • Cell membranes are semipermeable, allowing some substances to pass through but not others.

Movement Across Membranes

  • Diffusion: Movement of liquid or gas molecules from high concentration to low concentration.
  • Osmosis: Diffusion of water across a semipermeable membrane.
  • Hypertonic Solution: A solution with a higher solute concentration outside the cell than inside. Water moves out of the cell, causing it to shrink (plasmolyze).
  • Hypotonic Solution: A solution with a lower solute concentration outside the cell than inside. Water moves into the cell, causing it to swell or burst (lyse).
  • Isotonic Solution: A solution with equal solute concentration inside and outside the cell. Water movement is balanced.

Facilitated Diffusion

  • Passive transport using carrier proteins to move molecules across the membrane.
  • Does not require energy.
  • Carrier proteins change shape to move molecules.

Active Transport

  • Requires energy (ATP).
  • Moves molecules against the concentration gradient (low to high).
  • The Sodium-Potassium (Na+/K+) pump is an example.

Bulk Transport

  • Endocytosis: Taking large molecules into the cell.
    • Vesicles engulf the substance.
  • Exocytosis: Removing large molecules from the cell by fusing vesicles with the membrane.
  • Bulk transport is an important aspect of transporting materials in and out of the cell.

Receptor-Mediated Endocytosis

  • Process that uses specific receptors on the cell surface to take in target molecules, a highly targeted process, which specifically imports substances into cells.
  • Specific to the substance being transported.

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Related Documents

Cell Membrane Notes PDF

Description

Explore the intricate details of cell membrane structure, including the fluid mosaic model and membrane permeability. Learn about the dynamics of movement across membranes, covering key processes such as diffusion and osmosis.

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