Cell Structure and Function Quiz

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Questions and Answers

What is the primary component of the plasma membrane?

Carbohydrates

Proteins

Nucleic acids

Phospholipids (correct)

Which type of lipid is responsible for the fluidity of the plasma membrane?

Cholesterol

Unsaturated fatty acids (correct)

Saturated fatty acids

Glycolipids

What is the function of cholesterol in the plasma membrane?

To act as a transport protein

To increase membrane fluidity

To provide structural support (correct)

To decrease membrane fluidity

What is the main function of glycoproteins and glycolipids in the plasma membrane?

To facilitate cell-to-cell communication (C) Signup and view all the answers

Which of the following is NOT a function of the plasma membrane?

Producing ATP for cellular processes (C) Signup and view all the answers

What is the difference between simple diffusion and facilitated diffusion?

Simple diffusion moves small molecules, while facilitated diffusion moves large molecules. (C) Signup and view all the answers

Which type of transport requires energy to move solutes across the membrane?

Active transport (A) Signup and view all the answers

What is secondary active transport?

Transport of solutes indirectly using the energy stored in an electrochemical gradient. (D) Signup and view all the answers

What is the term for the movement of water across a selectively permeable membrane?

Osmosis (D) Signup and view all the answers

What is the role of aquaporins in water movement across the membrane?

They create channels for water movement between phospholipids. (D) Signup and view all the answers

What is the term for the ability of a solution to cause a cell to gain or lose water?

Tonicity (A) Signup and view all the answers

What is the role of SNARES in vesicle transport?

They promote the docking and fusion of vesicles to the correct target membrane. (A) Signup and view all the answers

What is the difference between transport vesicles carrying secreted proteins and transport vesicles carrying embedded proteins?

Secreted proteins are released into the interstitial fluid, while embedded proteins remain within the cell. (D) Signup and view all the answers

Which of the following is a characteristic of the plasma membrane?

It is selectively permeable to certain substances. (B) Signup and view all the answers

What is the main function of the glycocalyx?

To facilitate cell-to-cell communication (D) Signup and view all the answers

What is the term for the difference in concentration of a substance between two areas?

Concentration gradient (C) Signup and view all the answers

Study Notes

Cell Structure and Function

Cells are fundamental units of life, with three primary components: plasma membrane, cytoplasm, and nucleus.
The plasma membrane acts as a barrier between the cell's internal environment and its surroundings.
The cytoplasm is the cellular material outside the nucleus; it includes the cytosol (intracellular fluid), organelles, and inclusions.
The nucleus houses the cell's genetic material (DNA).

Cytoplasm

Cytoplasm is the area between the plasma membrane and the nucleus.
It's composed of cytosol, organelles, and inclusions.
Cytosol is the fluid portion of the cytoplasm, composed largely of water with dissolved solutes (e.g., salts, sugars, proteins)
Organelles are specialized structures with specific functions inside the cell (e.g., mitochondria, ribosomes).
Inclusions are varied chemical substances, often stored, depending on the cell type (e.g., glycogen, lipid droplets, crystals).

Plasma Membrane

The plasma membrane is a phospholipid bilayer that encloses the cell contents and controls what enters and exits.
Lipids (phospholipids and cholesterol) contribute to membrane fluidity and stability.
Proteins embedded in the membrane have diverse functions, including transport, signaling, and structural support.
Glycolipids and glycoproteins are attached carbohydrate-based molecules that project from the exterior surface of the cell; these are involved in cell-to-cell recognition and interaction.
The membrane is selectively permeable, meaning it controls which substances can pass through.

Membrane Fluidity

Membrane fluidity is influenced by temperature and fatty acid composition (saturated vs. unsaturated).
Cholesterol strengthens and stabilizes the membrane.

Membrane Proteins

Membrane proteins perform a diverse range of tasks, including transport, cell signaling, and structural support.
Integral proteins are embedded in the lipid bilayer; peripheral proteins are loosely attached.

Diffusion

Diffusion is the tendency of molecules to spread from areas of high concentration to areas of low concentration.
Factors influencing diffusion rate include concentration gradient, temperature, molecule size, and membrane permeability.
Diffusion across the membrane can be passive (no energy required) or facilitated (aided by membrane proteins).

Active Transport

Active transport moves molecules against their concentration gradient, requiring energy (often ATP).
Primary active transport directly uses ATP for transport.
Secondary active transport uses the electrochemical gradient established by primary active transport to drive the movement of another substance.
Types of active transport include pumps and cotransport systems.

Vesicular Transport

Vesicular transport involves the movement of substances across the membrane within vesicles.
Exocytosis is the process where materials are expelled from the cell using vesicles.
Endocytosis is the process where materials are taken into the cell using vesicles (e.g., phagocytosis, pinocytosis, receptor-mediated endocytosis).

Tonicity and Osmosis

Tonicity describes the ability of a solution to cause a cell to gain or lose water.
Isotonic solutions have equal solute concentrations inside and outside the cell, resulting in no net water movement.
Hypotonic solutions have a lower solute concentration than inside the cell, causing water to move into the cell, potentially causing swelling or lysis.
Hypertonic solutions have a higher solute concentration than inside the cell, causing water to move out of the cell, potentially causing shrinking or crenation.

Membrane Permeability

Selectively permeable means the cell membrane allows some substances to pass through but not others. Molecules have varying degrees of permeability across the membrane (polar/non-polar, small/large).
The membrane is semi-permeable, letting select molecules pass through.
Gases, hydrophobic molecules, small polar molecules, and water can easily pass through the lipid bilayer. Larger polar molecules and ions require assistance.

Specialised transport proteins (gated channels)

Channel proteins form hydrophilic channels in the membrane allowing specific molecules/ions to move through.
Ligand-gated channels only open when a specific signaling molecule (ligand) binds.
Voltage-gated channels have sensitivity to changes in membrane potential.

Osmotic pressure

The opposing pressure needed to completely stop net movement of water by osmosis.
Hydrostatic pressure refers to pressure exerted by water against a membrane.

Cytoskeleton

A network of protein filaments that supports the cell shape and facilitates movement.

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Description

Test your knowledge on the fundamental units of life with this quiz focused on cell structure and function. Explore the roles of the plasma membrane, cytoplasm, and nucleus, and understand the components that make up the cell. Perfect for those studying biology and cellular functions.