Cell Structure and Function Quiz

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Questions and Answers

What is the primary form in which structural proteins are present within the cell?

As simple amino acids

As mobile enzymes

As glucose molecules

As long filaments (correct)

Which of the following is a major role of functional proteins in the cell?

Catalyzing chemical reactions (correct)

Storing fat

Forming cell membranes

Providing structural support

Which lipids are primarily involved in forming the cell membrane?

Phospholipids and cholesterol (correct)

Fatty acids and phospholipids

Saturated fats and triglycerides

Triglycerides and cholesterol

What percentage of total cell mass do phospholipids and cholesterol constitute?

About 2 percent Signup and view all the answers

In which cellular organelles do microtubules primarily provide structural support?

Cilia and nerve axons Signup and view all the answers

What is the main stored form of energy in fat cells?

Triglycerides Signup and view all the answers

Which of the following components primarily plays a role in cell nutrition rather than structural function?

Carbohydrates Signup and view all the answers

What type of proteins are primarily found as fibrillar proteins in connective tissues?

Structural proteins Signup and view all the answers

What role do integral proteins primarily serve in the cell membrane?

Facilitate selective diffusion and transportation Signup and view all the answers

What is one function of peripheral proteins in the cell membrane?

Function mainly as enzymes or regulators of transport Signup and view all the answers

How do carbohydrate molecules function on the cell membrane?

They often combine with proteins or lipids forming glycoproteins or glycolipids Signup and view all the answers

What is the function of the selective properties of integral protein channels?

To facilitate preferential diffusion of certain substances Signup and view all the answers

What triggers conformational changes in integral membrane receptors?

Binding of specific ligands Signup and view all the answers

What term describes the process of transporting substances against their natural direction of diffusion?

Active transport Signup and view all the answers

What type of protein is most commonly found as a part of the membrane lipids?

Glycoproteins Signup and view all the answers

What are proteoglycans primarily composed of?

Small protein cores and carbohydrates Signup and view all the answers

What form of carbohydrate is predominantly available in the surrounding extracellular fluid for cells?

Dissolved glucose Signup and view all the answers

What is the main structural component of the cell membrane?

Lipid bilayer Signup and view all the answers

Which of the following is NOT a component of the cell membrane?

Triglycerides Signup and view all the answers

What property of phospholipids allows them to form a bilayer in the cell membrane?

Their hydrophilic and hydrophobic parts Signup and view all the answers

Which type of substances can easily penetrate the lipid bilayer of the cell membrane?

Oxygen and carbon dioxide Signup and view all the answers

What role does cholesterol play in the cell membrane?

It determines the membrane's fluidity and permeability Signup and view all the answers

What percentage of the cell membrane is composed of carbohydrates?

3 percent Signup and view all the answers

Membrane proteins that have carbohydrates attached to them are referred to as what?

Glycoproteins Signup and view all the answers

What percentage of the adult human body is primarily made up of fluid?

60 percent Signup and view all the answers

Which of the following components are part of protoplasm?

Proteins Signup and view all the answers

Which type of proteins primarily provide structural support in cells?

Structural proteins Signup and view all the answers

What role do ions play in cellular function?

They provide inorganic chemicals for cellular reactions. Signup and view all the answers

What types of fluids exist outside of cells?

Extracellular fluid Signup and view all the answers

Which of the following substances constitutes the highest percentage of a typical cell's composition?

Water Signup and view all the answers

What is the primary function of the cell membrane?

To separate the cytoplasm from the surrounding fluids Signup and view all the answers

Which of the following ions is least mentioned as important for cellular functions?

Iron Signup and view all the answers

Study Notes

The Cell

The cell is the basic living unit of the body.
Each organ is made up of many different cells held together by intercellular structures.
Individual cells are adapted to perform specific functions.
Although cells vary, they share common characteristics and the ability to reproduce.

Body Fluid Composition

Approximately 60% of the adult human body is fluid, primarily water with dissolved ions and other substances.
Most of this fluid is intracellular fluid (inside cells).
A smaller portion is extracellular fluid (outside cells), containing ions and nutrients necessary for cell function.
Composition of extracellular fluid:
- Intravascular fluid (blood plasma): 7%.
- Interstitial fluid: 26%.
- Cerebrospinal fluid: less than 1%.

Intracellular Fluid

Intracellular fluid is crucial for cell function.
Proper concentrations of oxygen, glucose, ions, amino acids, fatty substances, and other nutrients are needed for cell survival, growth, and function. These are found in the extracellular fluid surrounding cells.

Cell Structure

Cells have two main parts: the nucleus and the cytoplasm.
The nucleus is separated from the cytoplasm by a nuclear membrane.
The cytoplasm is separated from the surrounding fluids by a cell membrane (plasma membrane).
Protoplasm is a collective term for the substances that make up the cell.
Protoplasm is primarily composed of water, electrolytes, proteins, lipids, and carbohydrates.

Water in Cells

Water is the primary fluid medium within most cells.
Water content ranges from 70 to 85% for most cells (excluding fat cells).
Many cell chemicals are dissolved in this water.
Other cell chemicals are suspended in the water as solid particulates.

Ions in Cells

Important ions in cells include potassium, magnesium, phosphate, sulfate, bicarbonate, sodium, chloride, and calcium.
These ions are crucial for cellular chemical reactions.
Ions acting on cell membranes are required for transmitting electrochemical impulses in nerves and muscles.

Proteins in Cells

Proteins are the most abundant substances in cells after water, commonly comprising 10-20% of cell mass.
Proteins can be categorized into structural proteins and functional proteins.
Structural proteins provide the framework and support for various cellular structures.
Functional proteins include enzymes, crucial for catalyzing cellular chemical reactions (e.g., glucose breakdown).

Structural Proteins

Structural proteins are predominantly filamentous molecules.
They form microtubules that act as the "cytoskeletons" of various cellular components (e.g., cilia, nerve axons, mitotic spindles).
Extracellularly, they are found in collagen and elastin fibers, connective tissue, blood vessel walls, tendons, ligaments, etc., providing structure, support, and strength.

Functional Proteins (enzymes)

Functional proteins (enzymes) are often mobile within the cell fluid; they catalyze specific cellular chemical reactions
Examples of their activities include breaking down glucose and combining it with oxygen to produce energy-rich molecules for cell function.

Lipids

Lipids are various substances grouped by their solubility in fat solvents.
Key lipids are phospholipids and cholesterol, comprising about 2% of cell mass.
Their primary function is forming cell membranes and intracellular membrane barriers for compartmentalization. They are hydrophobic ("water-fearing").
Some cells contain triglycerides (neutral fat) that store energy.

Carbohydrates

Carbohydrates play a crucial role in cell nutrition, though with limited structural roles in most cells.
Dissolved glucose (a sugar) is available in extracellular fluid for rapid uptake.
Glycogen, another form of carbohydrate, is stored to provide energy when needed.

Cell Membrane

The cell membrane, also called the plasma membrane, encloses the cell and is a thin, elastic structure (7.5-10 nanometers thick).
It primarily consists of lipids (mostly phospholipids) and proteins in a bilayer arrangement.
Phospholipids, cholesterol, proteins, other lipids, and carbohydrates are present in specific proportions in the cell membrane.

Cell Membrane Structure

The cell membrane's basic structure is a lipid bilayer.
One end of each phospholipid molecule is hydrophilic ("water-loving") and soluble in water.
The other end is hydrophobic (“water-fearing”); it's soluble in fat.
The hydrophobic portion of the membrane is impermeable to common water-soluble substances but permeable to fat-soluble substances (e.g., oxygen).
The hydrophilic regions ("heads") face the aqueous environments inside and outside of the cell.

Cell Membrane Proteins

Membrane proteins are globular masses embedded in the phospholipid bilayer.
Many are glycoproteins (proteins with carbohydrate components).
Two main types of membrane proteins are:
- Integral proteins: span the entire membrane, acting as channels or carriers for substance transport.
- Peripheral proteins: are attached to one side of the membrane and do not penetrate the entire structure; mostly enzymes or transport controllers.

Membrane Protein Functions

Many integral proteins form channels for molecules to pass between intracellular and extracellular fluids (e.g., water, ions).
Some transport specific substances across, even against, their concentration gradient (active transport).
Other proteins act as receptors, binding to hormones or other substances, initiating internal signals.

Cell Membrane Carbohydrates

Carbohydrates are often attached to proteins (glycoproteins) or lipids (glycolipids) at the cell surface.
The carbohydrate components are often arranged on the outer surface of the membrane.
The carbohydrate-rich layer on the cell surface is called the glycocalyx, and it performs various roles (e.g., cell-to-cell recognition, cell surface characteristics).

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Description

Test your knowledge on structural and functional proteins, lipids, and their roles within the cell. This quiz covers essential concepts regarding cellular composition and the functions of various organelles and membrane proteins. Perfect for biology students focusing on cell biology!