Essentials of Anatomy and Physiology - Chapter 3: Cells

Flashcards covering cellular structure, membrane transport mechanisms, organelles, protein synthesis, and the stages of mitosis and the cell cycle from Saladin & McFarland Essentials of Anatomy and Physiology Chapter 3.

What is cytology?

The study of cellular structure and function.

How many different kinds of cells are contained in the human body?

There are 200 kinds of cells in the human body.

What are the three major components of a generalized cell?

The plasma membrane, cytoplasm, and nucleus.

What is the cytosol?

The clear gel embedding the organelles, cytoskeleton, and inclusions within the cytoplasm; also termed intracellular fluid (ICF).

What proportion of plasma membrane lipids are phospholipids, and how are they arranged?

Phospholipids make up 75% of membrane lipids; their hydrophilic phosphate heads face water on the inside and outside of the cell, while two hydrophobic fatty acid tails form the middle of the bilayer.

What role does cholesterol play in the plasma membrane?

Cholesterol makes up 20% of membrane lipids and affects membrane fluidity; too much inhibits membrane proteins and enzymes, while too little makes the membrane fragile.

What percentage of plasma membrane lipids are glycolipids?

5%

How do integral proteins and peripheral proteins differ in location within the plasma membrane?

Integral proteins penetrate the cell membrane (most are glycoproteins), whereas peripheral proteins do not protrude into the phospholipid bilayer and are usually located on the intracellular face.

What is the function of receptor proteins in the plasma membrane?

They receive and bind chemical signals from other cells.

What is the function of channel proteins in the plasma membrane?

They possess tunnels that allow water and hydrophilic solutes to enter or leave the cell.

What is the glycocalyx and what are its main functions?

A fuzzy carbohydrate coat covering cells made of short sugar chains of glycolipids and glycoproteins; it functions in cell adhesion, protects the plasma membrane, determines blood types, and helps distinguish healthy cells from foreign or diseased cells.

What are microvilli and what is their primary function?

Finger-shaped projections of the plasma membrane that serve primarily to increase surface area for absorption.

Where are motile cilia abundant in the human body and what do they do?

They are abundant in the mucous membranes of the respiratory tract (moving mucus up to the throat) and in the uterine tubes (moving an egg or embryo toward the uterus).

What is a primary cilium?

A solitary, nonmotile cilium found on most cells that may serve a sensory function.

What cell surface extensions do macrophages use to move and engulf bacteria?

Pseudopods

What is the function of tight junctions?

They encircle epithelial cells near their upper end and join them tightly, making it difficult for substances to leak between cells.

What is the function of desmosomes?

They hold cells together at specific points to keep them from pulling apart, enabling tissues to resist mechanical stress.

How do gap junctions facilitate communication between cells?

They are formed by a ring of proteins surrounding a channel, allowing direct diffusion of ions, glucose, and other solutes from the cytoplasm of one cell into another.

What is filtration in the context of cellular transport?

A process in which pressure forces fluid through a selectively permeable barrier, holding back large particles while allowing water and small particles to pass.

How does simple diffusion move particles across a membrane?

It moves particles down a concentration gradient from high to low concentration using random molecular motion without requiring cellular energy.

What happens to a cell placed in a hypertonic extracellular fluid?

Water is drawn out of the cell by osmosis, causing the cell to shrink.

What happens to a cell placed in a hypotonic extracellular fluid?

Water enters the cell by osmosis, causing it to swell and possibly rupture.

How does active transport differ from facilitated diffusion?

Active transport requires cellular energy (ATP) to move solutes up their concentration gradient, whereas facilitated diffusion moves solutes down their concentration gradient without consuming cellular energy.

What ions and quantities does the sodium-potassium pump transport across the plasma membrane?

It binds and pumps three sodium ions out of the cell and binds and pumps two potassium ions into the cell at the same time.

What are the three forms of endocytosis?

Phagocytosis ('cell eating'), pinocytosis ('cell drinking'), and receptor-mediated endocytosis.

What are the three components of the cytoskeleton and their diameters?

Microfilaments ($6\,nm$ thick), intermediate filaments ($8$ to $10\,nm$ in diameter), and microtubules ($25\,nm$ in diameter).

Which structural protein composes microfilaments and forms the terminal web?

Actin

Which organelle is the largest inside the cell?

The nucleus

What is the difference between chromosomes and chromatin?

Chromosomes are threadlike bodies of DNA and protein found in dividing cells, whereas chromatin is the fine-filament form DNA takes in nondividing cells.

What occurs inside the nucleoli?

Subunits of ribosomes are produced.

What are the primary functional differences between rough ER and smooth ER?

Rough ER is covered with ribosomes and synthesizes proteins and cell membranes; smooth ER lacks ribosomes and synthesizes steroids/lipids while specializing in drug detoxification.

What is the function of ribosomes?

They read genetic messages from the nucleus and assemble amino acids into proteins as specified by DNA.

What is the function of the Golgi complex?

It synthesizes carbohydrates, completes protein and glycoprotein synthesis, and packages finished products into Golgi vesicles.

What functions do peroxisomes perform?

They break down fatty acids into two-carbon molecules for ATP synthesis, neutralize free radicals, detoxify alcohol and drugs, kill bacteria, and produce hydrogen peroxide.

Which mitochondrial structure contains the enzymes responsible for producing most cellular ATP?

The cristae (folds of the inner membrane).

What happens during the transcription stage of protein synthesis?

An enzyme uncoils the DNA double helix at a gene site, and a second enzyme reads the coding strand bases to construct a complementary messenger RNA (mRNA) molecule in the nucleus.

If a DNA base sequence is TACCGTCCA, what is the complementary mRNA sequence?

AUGGCAGGU

What is a codon?

A three-base segment of mRNA that codes for a specific amino acid.

What are the four phases of the cell cycle?

First gap phase ($G_1$), Synthesis phase ($S$), Second gap phase ($G_2$), and Mitotic phase ($M$).

What occurs during the Synthesis ($S$) phase of the cell cycle?

DNA molecules replicate through the activity of DNA polymerase.

Which phases of the cell cycle make up interphase?

The $G_1$, $S$, and $G_2$ phases.

What events occur during Prophase of mitosis?

Chromosomes condense into short rods with sister chromatids joined at centromeres, the nuclear envelope disintegrates, and sprouting spindle fibers push centrioles toward opposite poles.

What occurs during Metaphase of mitosis?

Chromosomes align along the midline (equator) of the cell attached to the mitotic spindle.

What occurs during Anaphase of mitosis?

Centromeres split, and spindle fibers pull the separated sister chromatids (now daughter chromosomes) to opposite poles of the cell.

What occurs during Telophase and Cytokinesis?

In telophase, chromatids gather at each pole, new nuclear envelopes form, and chromatin decondenses; in cytokinesis, a cleavage furrow pinches the cell into two identical daughter cells.