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Questions and Answers

What is the main function of integral proteins in the cell membrane?

To regulate cell signaling pathways

To provide structural support to the cell membrane

To facilitate the transport of larger molecules across the cell membrane (correct)

To maintain the cell membrane's fluidity

Which type of molecules can pass through the cell membrane easily?

Ions and hydrophilic molecules larger than water

Small molecules and larger hydrophobic molecules (correct)

Large molecules such as proteins

All of the above

What is the driving force behind passive transport?

pH differences

Concentration gradient (correct)

Temperature differences

Energy from the cell

What is the process by which molecules spread from areas of high concentration to areas of low concentration?

Diffusion Signup and view all the answers

What is the term for the movement of materials across the cell membrane without using energy?

Passive transport Signup and view all the answers

What is an example of a type of passive transport?

Diffusion Signup and view all the answers

What is the function of the plasma membrane in a cell?

To control what enters and exits the cell Signup and view all the answers

What is the main component of a phospholipid molecule?

Two fatty acid chains and a polar head Signup and view all the answers

What is the role of cholesterol in the cell membrane?

To regulate the entry and exit of molecules Signup and view all the answers

What is the fluid mosaic model of the cell membrane?

A model that describes the cell membrane as a fluid structure composed of different molecules Signup and view all the answers

What is the function of proteins in the cell membrane?

To regulate the entry and exit of molecules Signup and view all the answers

What is the primary function of the cell membrane?

To protect the cell from its surroundings Signup and view all the answers

What is selectively permeable to ions and organic molecules?

The cell membrane Signup and view all the answers

What is the name of the model that describes the structure and function of the cell membrane?

Fluid mosaic model Signup and view all the answers

What is the primary characteristic of diffusion across a membrane?

It requires no energy and molecules move from high to low concentration. Signup and view all the answers

Which type of transport involves the movement of molecules through a concentration gradient?

Passive transport Signup and view all the answers

What is the purpose of aquaporins in osmosis?

To act as water channels Signup and view all the answers

Which type of solution has a higher concentration of solutes than the cell?

Hypertonic Signup and view all the answers

What is the primary difference between facilitated diffusion and active transport?

The requirement of energy Signup and view all the answers

What is the function of carrier proteins in facilitated diffusion?

To change shape and move material from one side of the membrane to the other Signup and view all the answers

What is the result of a cell being placed in a hypotonic solution?

The cell will swell and gain water Signup and view all the answers

Which type of transport is involved in the movement of ions against a concentration gradient?

Active transport Signup and view all the answers

Study Notes

Cell Membrane and Transport

The cell membrane is a biological membrane that separates the interior of a cell from its outside environment.
All cells have a cell membrane, also known as the plasma membrane or cytoplasmic membrane.

Functions of Cell Membrane

Protects the cell from its surroundings.
Contains the cytoplasm (fluid in the cell).
Selectively permeable to ions and organic molecules.
Controls what enters and exits the cell to maintain an internal balance called homeostasis.
Allows cell recognition and provides a binding site for enzymes.
Plays a role in anchoring the cytoskeleton to provide shape to the cell, and in attaching to other cells to help group cells together to form tissues.
Maintains the cell potential.

Structure of Cell Membrane

Described by the fluid mosaic model, consisting of various molecules distributed across the membrane.
Composed of:
- Phospholipids (contain 2 fatty acid chains that are nonpolar, and a polar head with a PO4 group and glycerol).
- Cholesterol (helpful in regulating molecules entering and exiting the cell).
- Proteins (integral and peripheral proteins, involved in transporting larger molecules and facilitating transport or communication).

Types of Transport Across Cell Membranes

Two main types: Passive Transport and Active Transport.
Passive Transport:
- The movement of materials across the cell membrane without using energy.
- Caused by concentration gradient.
- Works in both directions.
- Three types: Diffusion, Facilitated Diffusion, and Osmosis.

Diffusion

The process by which molecules spread from areas of high concentration to areas of low concentration.
No energy is required.
When the molecules are even throughout a space.

Facilitated Diffusion

Molecules that cannot directly diffuse across the membrane pass through:
- Channel proteins (embedded in the cell membrane with a pore for materials to cross).
- Carrier proteins (can change shape to move material from one side of the membrane to the other).
No energy is needed.
Used for ions and large molecules (e.g., Cl- and glucose).

Osmosis

The diffusion of water through a selectively permeable membrane down its concentration gradient.
From an area of high-water concentration to an area of lower water concentration.
Aquaporins are water channels used during osmosis.

Osmotic Solutions

Hypotonic: lower concentration of solutes.
Isotonic: concentrations of solute and solvent are equal.
Hypertonic: higher concentration of solutes.

Osmotic Pressure

Not specified in the text.

Active Transport

Movement against a concentration gradient.
Requires energy (ATP).
One direction.
Types: Molecular Transport (e.g., Na+-K+ Pump) and Bulk Transport (Endocytosis and Exocytosis).

Endocytosis

The process by which cells absorb material (molecules such as proteins) from outside the cell by engulfing it with their cell membrane.
Two types: Pinocytosis and Phagocytosis.

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