Cell Biology Membrane Structure Quiz

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Questions and Answers

What is the name of the model that describes the structure of cell membranes?

The fluid mosaic model

What are the two main components of the cell membrane?

carbohydrates and proteins

lipids and carbohydrates

phospholipids and proteins (correct)

nucleic acids and lipids

What are the long chains of carbon and hydrogen that make up phospholipids called?

fatty acids (correct)

sugars

amino acids

nucleotides

What part of the phospholipid is hydrophilic?

both B and C Signup and view all the answers

Which type of membrane protein spans the entire lipid bilayer?

integral membrane proteins Signup and view all the answers

What is the primary function of transporters?

moving molecules across the membrane Signup and view all the answers

What type of membrane protein allows the cell to be selective about what passes through?

Integral membrane proteins Signup and view all the answers

Passive transport requires energy to move molecules across the membrane.

False Signup and view all the answers

What type of passive transport involves the movement of water from high to low concentration?

Osmosis Signup and view all the answers

Which type of passive transport utilizes carrier proteins for moving molecules?

facilitated diffusion Signup and view all the answers

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

facilitated diffusion Signup and view all the answers

What type of carrier protein is involved in secondary transport?

Symporters Signup and view all the answers

What are the two types of bulk transport?

endocytosis and exocytosis Signup and view all the answers

Phagocytosis is the process by which a cell takes in only fluid.

False Signup and view all the answers

What type of endocytosis involves specific molecules binding to receptors?

Receptor-mediated endocytosis Signup and view all the answers

Exocytosis is the process of moving substances from the inside of the cell to the outside.

True Signup and view all the answers

Study Notes

Cell Membranes

Cell membranes are composed of phospholipids arranged in a bilayer.
Globular proteins are embedded within the lipid bilayer.
Phospholipids have a polar hydrophilic head and nonpolar hydrophobic tails. This arrangement creates a barrier in water.

Phospholipids

Phospholipids are composed of glycerol, two fatty acids, and a phosphate group.
Glycerol is a 3-carbon polyalcohol that forms the backbone.
Two fatty acid chains are attached to the glycerol.
The phosphate group is attached to the glycerol, forming a polar head.

Phospholipid Properties

Fatty acids are nonpolar, making them hydrophobic (water-fearing).
The phosphate group is polar, making it hydrophilic (water-loving).

Membrane Structure

The fluid-mosaic model describes the structure of cell membranes.
The arrangement of phospholipids with their hydrophilic heads facing outward and hydrophobic tails facing inward creates a barrier in water.
Proteins are embedded within this phospholipid bilayer, forming a mosaic pattern.

Membrane Proteins

Membrane proteins perform various functions.
- Transporters: move molecules across the membrane.
- Enzymes: catalyze reactions.
- Cell surface receptors: bind to signaling molecules.
- Cell surface identity markers: identify the cell type.
- Cell-to-cell adhesion proteins: connect cells.
- Attachments to the cytoskeleton: provide structural support.

Peripheral Membrane Proteins

Anchored to a phospholipid in one layer of the membrane.
Possess nonpolar regions inserted in the lipid bilayer.
Free to move throughout one layer of the bilayer.

Integral Membrane Proteins

Span the lipid bilayer (transmembrane proteins).
Nonpolar regions are embedded in the interior of the bilayer.
Polar regions protrude from both sides of the bilayer.
Possess at least one transmembrane domain, a region of the protein containing hydrophobic amino acids that spans the lipid bilayer.

Passive Transport

Passive transport is the movement of molecules across the membrane without energy input.
Molecules move down their concentration gradient (from high to low concentration).
- Diffusion: movement of molecules from high to low concentration.
- Facilitated diffusion: diffusion with the assistance of transport proteins.
Osmosis: movement of water across a semipermeable membrane from an area of high water concentration to an area of low water concentration.

Passive Transport Mechanisms

Channel proteins have a polar interior allowing polar molecules to pass through, and specifically ion channels allow the ions (charged atoms) to pass through.
Carrier proteins bind to a specific molecule to facilitate its passage across the membrane.
- Facilitated diffusion is the movement of a molecule from high to low concentration with the help of a carrier protein.
- The molecule's movement can be chemical or electrical.

Passive Transport Types of Channel Proteins

Ion channels allow the passage of ions (charged atoms or molecules), usually associated with water.
Gated channels open and close in response to a stimulus (e.g., chemical, electrical).

Active Transport

Active transport moves substances against their concentration gradient (from low to high concentration).
Requires energy (ATP).

Active Transport Types of Protein Carriers

Uniporters: move one molecule at a time.
Co-transporters: move two molecules in the same direction (symporters).
Counter-transporters: move two molecules in opposite directions (antiporters).

Primary Active Transport: Sodium-Potassium Pump

An active transport mechanism that uses an antiporter to move 3 Na+ ions out of the cell and 2 K+ ions into the cell, requiring ATP energy to change the protein's conformation.

Secondary Active Transport

Uses the energy released when a molecule moves by diffusion to supply energy to active transport of a different molecule.
A symporter is used (which are a type of carrier protein). Example: Glucose-Na+ symporter.

Bulk Transport: Endocytosis

Endocytosis is the movement of substances into the cell by engulfing them.
- Phagocytosis: intake of particulate matter.
- Pinocytosis: intake of fluid.
- Receptor-mediated endocytosis: intake of specific molecules that bind to receptors on the cell surface.

Bulk Transport: Exocytosis

Exocytosis is the movement of substances out of the cell by fusing vesicles with the cell membrane.
Used in animals to secrete hormones, neurotransmitters, and digestive enzymes; and in plants to export cell wall material.

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Description

Test your knowledge on cell membrane structures and functions with this quiz. It covers key concepts such as phospholipids, transport proteins, and types of transport mechanisms. Perfect for students studying cell biology or related disciplines.