L02 L03 The Cell

Learning Objective 1: Identify typical cellular components and organization

What are organisms composed of?

Cells.

What are humans a collection of?

Roughly 30 trillion cells.

What is a defining characteristic of human cells?

They are highly specialized.

What are the two principal categories of cells?

Sex cells and somatic cells.

What are male sex cells called?

Sperm.

What are female sex cells called?

Oocytes.

What are somatic cells?

All other cells in the body that are not sex cells.

How many copies of each chromosome do mature sex cells carry?

One copy.

How many copies of each chromosome do somatic cells carry?

Two copies.

What is the cell membrane also called?

Plasma membrane.

What is the plasma membrane?

The exterior membrane of the cell.

What is the cytoplasm?

Everything contained within the plasma membrane.

What is the cytosol?

The fluid component of the cytoplasm.

What are the major functions of the cell membrane?

Physical isolation, sensitivity, structural support, and regulation of exchange with the environment.

What does physical isolation by the cell membrane provide?

Separation of the cell from its environment.

What does sensitivity of the cell membrane allow?

Detection of environmental conditions.

What does structural support by the cell membrane provide?

Support for the cell.

What process does the cell membrane regulate with the environment?

Exchange of substances.

What property describes regulation of exchange across the cell membrane?

Permeability.

What are the major passive cellular processes listed?

Diffusion, osmosis, and facilitated diffusion.

What are the major active cellular processes listed?

Active transport, endocytosis, and exocytosis.

What is cytosol?

The general term for the material inside the cell.

What is a characteristic of cytosol?

It is very high in protein.

How does the protein concentration of cytosol compare with extracellular fluid?

Cytosol has more proteins.

What percentage of the cell's weight is attributed to proteins?

Approximately 20%.

What is another name for cytosol?

Intracellular fluid.

What does cytosol contain?

Dissolved nutrients, ions, soluble and insoluble proteins, and waste products.

What separates cytosol from surrounding extracellular fluid?

The plasma membrane.

What are organelles?

Intracellular structures that perform specific functions.

What is cytosol principally composed of?

Water.

What role does water play in cytosol?

It acts as the intracellular solvent for other components.

What ion is present at a high concentration in cytosol?

Potassium (K⁺).

What ion has a high concentration in extracellular fluid relative to cytosol?

Sodium (Na⁺).

What dissolved substances are found in cytosol?

Amino acids, lipids, and carbohydrates.

How are organelles distributed among body cells?

Their types and numbers differ among cell types.

What functions are organelles essential for?

Normal cell structure, maintenance, and/or metabolism.

What are the two broad categories of organelles?

Nonmembranous and membranous organelles.

What characterizes nonmembranous organelles?

They are always in contact with the cytosol.

What nonmembranous organelles are listed?

Cytoskeleton, centrioles, cilia, flagella, and ribosomes.

What characterizes membranous organelles?

They are surrounded by a phospholipid bilayer membrane.

What membranous organelles are listed?

Mitochondria, nucleus, endoplasmic reticulum, Golgi apparatus, lysosomes, and peroxisomes.

What is the cytoskeleton?

The internal protein framework that gives the cytoplasm strength and flexibility.

How many major components does the cytoskeleton have?

Four.

What are the four major cytoskeletal components?

Microfilaments, intermediate filaments, thick filaments, and microtubules.

What are microfilaments composed of?

Actin.

What do microfilaments anchor?

The cytoskeleton to integral proteins.

What do microfilaments stabilize?

The position of membrane proteins.

What do microfilaments anchor the plasma membrane to?

The cytoplasm.

What are intermediate filaments composed of?

Keratin.

What is one function of intermediate filaments?

Providing strength.

What is another function of intermediate filaments?

Stabilizing organelle position.

What are microtubules composed of?

Polymerized tubulin.

What is a major role of microtubules in the cytoskeleton?

They are a primary component of the cytoskeleton.

What do microtubules control?

Cell shape.

What cellular processes do microtubules aid?

Cell division and movement.

What are ribosomes?

Nonmembranous organelles approximately 20 nm in diameter.

Where are free ribosomes located?

In the cytoplasm.

Where are fixed ribosomes located?

Attached to the endoplasmic reticulum.

What cytoskeletal component dictates plasma membrane integral protein position?

Microfilaments.

What are membranous organelles surrounded by?

A phospholipid bilayer membrane.

What is the mitochondrion?

A membranous organelle involved in cellular energy production.

What are the two membranes of mitochondria?

An outer membrane and an inner membrane.

What does the inner mitochondrial membrane form?

Folds called cristae.

What is the mitochondrial matrix?

The inner network of enzymes and source for cellular energy production.

What is the nucleus?

The storage site of genetic material.

What surrounds the nucleus?

The nuclear envelope.

What is the nuclear envelope?

A double membrane surrounding the nucleus.

What do nuclear pores allow?

Passage of relatively large proteins and nucleic acids into and out of the nucleus.

What is the endoplasmic reticulum?

A network of intracellular membranes.

What structures does the endoplasmic reticulum form?

Hollow tubes, flattened sheets, and rounded chambers called cisternae.

What is the rough endoplasmic reticulum associated with?

Ribosomes.

What does the rough endoplasmic reticulum synthesize?

Proteins.

What does the smooth endoplasmic reticulum synthesize?

Carbohydrates, steroids, and lipids.

What does the endoplasmic reticulum do with translated polypeptides?

It assembles and modifies them.

What does the endoplasmic reticulum store?

Absorbed substances from the cytosol.

What does the endoplasmic reticulum transport?

Key molecules inside its cisternae within the cell.

How does the endoplasmic reticulum affect cellular toxins?

It can inactivate cellular toxins through intracellular enzymes.

What is the Golgi apparatus composed of?

Flattened membrane discs called cisternae.

What is one major function of the Golgi apparatus?

Synthesis and packaging of secretions such as mucins or enzymes.

What is another function of the Golgi apparatus?

Packaging special enzymes for use in the cytosol.

What does the Golgi apparatus do with mature proteins from the endoplasmic reticulum?

It may direct them for deposition to the plasma membrane or elsewhere.

What does the Golgi apparatus supply to the cytosol?

Vesicles.

What organelles originate from the Golgi apparatus?

Lysosomes.

How does the Golgi apparatus coordinate lysosome formation?

It coordinates enzymes formed in the endoplasmic reticulum and packages them.

What are lysosomes?

Small membranous organelles containing digestive enzymes.

How do lysosomes differ from peroxisomes?

Lysosomes contain digestive enzymes, whereas peroxisomes contain enzymes involved in oxidation and fatty-acid breakdown.

What are peroxisomes?

Membranous organelles containing a different group of enzymes.

Where are peroxisomal enzymes formed?

From free ribosomes within the cytoplasm.

What is one function of peroxisomes?

Breaking down organic compounds into hydrogen peroxide.

What is another function of peroxisomes?

Absorbing and breaking down fatty acids.

Learning Objective 2: Relate the structure of cellular components to their function

What structure forms the cell's external boundary?

The plasma membrane.

What is the plasma membrane structurally composed of?

A phospholipid bilayer.

How does the plasma membrane's structure support physical isolation?

Its bilayer separates the cell from the surrounding environment.

How does the plasma membrane regulate exchange?

Through its permeability.

What is the relationship between cytoplasm and plasma membrane?

The plasma membrane contains everything considered cytoplasm.

What is the relationship between cytosol and cytoplasm?

Cytosol is the fluid component within the cytoplasm.

Why is cytosol suitable for cellular reactions?

It is principally composed of water that acts as an intracellular solvent.

Why does cytosol contain many proteins?

Cytosol has a very high protein concentration.

Why are organelles important to cell function?

Each performs specific functions essential to cell structure, maintenance, and/or metabolism.

How does organelle composition relate to cell specialization?

Organelle types and numbers differ among cell types.