Chapter 4: THE CELLULAR LEVEL

Cell Membrane

Is an elegantly flexible structure composed of phospholipids, cholesterol, and proteins

Hydrophilic

The phosphate group is negatively charged, making the head polar and hydrophilic (water-loving); thus, the phospholipid heads are drawn toward the watery environments inside and outside of the cell.

Hydrophobic

The lipid tails, on the other hand, are uncharged, nonpolar, and are hydrophobic (repels and is repelled by water).

Amphipathic

-Because cell membranes have both hydrophilic and hydrophobic regions, phospholipids are described as
-When ________ molecules are mixed into water-based solutions, they organize themselves so that their hydrophilic regions are exposed to the water, but their hydrophobic regions are huddled together and protected from the watery environment

Aqueous

Human tissues are ________ (Watery) Invironment.

Intracellular fluid

-is the fluid interior of the cell

Extracellular Fluid

-Is the fluid environment outside of the cell membrane

-The term extracellular fluid always refers to the fluid

Interstitial fluid (IF)

is the term given to extracellular fluid not contained within blood vessels; plasma is extracellular fluid within blood vessels.

Transmembrane protein

is a protein that spans the membrane from its intracellular to its extracellular side.

Channel Proteins

are examples of transmembrane proteins that allow select materials, such as certain ions, to pass into or out of the cell

Receptors

are transmembrane proteins found on the extracellular side of the membrane that can selectively bind a specific molecule outside the cell and translate this binding into a chemical reaction inside the cell. (Has ligand)

Ligand

the specific molecule that binds to and engages that receptor

Glycoprotein

is a protein that has carbohydrate molecules attached.

Glycocalyx

Some cells carry so many glycoproteins that these form a coat called a

Peripheral proteins

can be anchored to the interior or exterior membranes of the cell but do not span the membrane

Selectively permeable

The membrane is often referred to as ________ because it allows only substances that are relatively small and nonpolar to cross through the lipid bilayer free.Some examples are:lipids, oxygen, carbon dioxide, and alcohol.

Passive Transport

is the movement of substances across the membrane without the expenditure of cellular energy.

Active Trasport

is the movement of substances across the membrane using energy from adenosine triphosphate (ATP).

Concentration gradient

is the difference in concentration of a substance across a space.

Diffusion

is the term for the movement of molecules in this direction (from an area of higher concentration to an area of lower concentration).

Equilibrium

the state at which there is no net movement in any direction. Take particular note of the word net in this definition of

Facilitated diffusion

Is the diffusion of molecules down their concentration gradients using the assistance of transmembrane proteins.Some molecules cannot cross the membrane on their own (Figure 4.7) due to their molecular properties, but proteins can enable their crossing.

Osmosis

is the diffusion of water through a semipermeable membrane.

Isosmotic

Two solutions that have the same concentra-

tion of solutes are said to be

When comparing two solutions with different solute concentrations, the solution with more solute is called hyperosmotic and the solution with less is hypoosmotic.

Tonicity

To describe the osmolarity of

the extracellular fluid compared to the inside of the cell, we use the term

Isotonic

When cells and their extracellular environments are______,the concentration of water molecules is the same outside and inside the cells, and the cells maintain their normal function

Hypertonic

When the ECF has a higher concentraction of solutes than the ICF, the cell is said to be in a _____ solution.

Hypotonic

solution that has a lower concentration of solutes than the cell it surrounds is said to be hypotonic, and water molecules tend to diffuse into the cell from the ECF. Cells in a _______ solution will take on too much water and swell, with the risk of eventually bursting

Sodium potassium pump

In physiology, the most common example of a molecular pump is the ____________ , which transports sodium out of a cell while moving potassium into the cell.

Electrical gradient

an __________, which is a difference in electrical charge across the membrane, becomes more and more established

Secondary Active Transport

Another common use of a gradient is to fuel ____________ . In this transport mechanism, which is used by many cells the action of an active (ATP-driven) transport pump (the sodium-potassium pump) establishes a contration gradient that is used in the transport of a second molecule such as glucose.

Symporters

are secondary active transporters that move two substances in the same direction.

Antiporters

work similarly to symporters, in that they accomplish secondary active transport by utilizing the concentration gradient of one molecule to move a second molecule against its concentration gradient

Endocytosis

is the process of a cell taking material in by enveloping it in a portion of its cell membrane, and then pinching off that membranous envelope

Vesicle

is a sac inside the cell, made of the same lipid bilayer as the cellular membrane

Phagocytosis

is the endocytosis of large particles Many immune cells engage in phagocytosis of invading pathogens.pathogens. Like little Pac-men, their job is to patrol body tissues for unwanted matter (such as invading bacterial cells), phagocytize it, and digest i

Pinocytosis

(“cell drinking”) brings fluid containing dissolved substances into a cell through membrane-bound vesicles

Receptor mediated endocytosis

A more selective form of endocytosis is _______[[[[ , endocytosis that is triggered when membrane-bound receptors bind their ligand (the substance they are selective

for).

Exocytosis

is the process of a cell exporting material by wrapping that material in a vesicle, and then fusing the vesicle with the plasma

Cytoplasm

The watery inside of the cell along with all its compartments and organelles is called the.

Organelle

which are membrane-enclosed bodies within the cell, each of which performs a unique function

Cytosol

the jellylike substance within the cell that provides the fluid medium necessary for biochemical reactions and functions of the cell.

Nucleus

The largest of the cell’s organelles is its ________ which contains the cell’s DNA inside of a membrane

Endoplasmic reticulum (ER)

is a system of channels that is continuous with the membrane of the nucleus.

Rough ER (RER)

is so called because of its relationship with ribosomes. Ribosomes are nonmembranous organelles that function to synthesize proteins

Smooth ER (SER)

lacks these ribosomes, and therefore lacks protein synthesis capacity or a rough appearance.

Golgi apparatus

is responsible for sorting, modifying, and shipping off the products that come from the rough ER, much like a post office.

Lysosomes

are organelles that digest unneeded cellular components, such as a damaged organelle

This “self-destruct” mechanism is called autolysis, and is one form of apoptosis (purposeful cellular death).

Peroxisome

is a membrane-bound cellular organelle that contains mostly enzymes.

Mitochondria

(plural = mitochondria) is a membranous organelle that is the “energy transformer” of the cell. Mitochondria consist of two lipid bilayers, one outer and one inner.

Cristae

The inner membrane is highly folded with a great deal of surface area; the folds of the inner membrane are called

Cyposkeleton

is made up of fibrous proteins that provide structural support for cell

Microtubule

The thickest of the three is the _____[[[ structural filament composed of subunits of a protein called tubulin.

Centriole

can serve as the cellular origination point for microtubules extending outward as cilia or flagella or can assist with the separation of DNA during cell division

Microfilaments

are the thinner of cytoskeletal filaments composed primarily of the protein actiN

Intermediate filament

is a filament intermediate in thickness between the microtubules and microfilament

microvilli, cilia, and flagella

There are three types of appendages of note on human

Microvilli

are tiny and numerous projections on the surface of cells that serve a function of expanding surface area

Cilia

are found on many cells of the body, including the epithelial cells that line the airways of the respiratory system

Flagellum

is an appendage larger than a cilium and specialized for cell locomotion. The only flagellated cell in humans is the sperm cell, which must propel itself toward female egg cells

Genome

The full set of genetic instructions of an organism is called its

Nuclear pore

is a tiny passageway for the passage of proteins, RNA, and solutes between the nucleus and the cytoplasm.

Nucleolus

this is a region of the nucleus that is responsible for manufacturing the RNA necessary for construction of ribosomes.details the types of nucleic acids in healthy human cell

Histone

When not in the process of replicating, cells store their DNA wrapped around a set of proteins like thread wrapped around a spool.

Nucleosome

Scientists use the term _______ to describe a single, wrapped DNA-histone complex.

Chromatin

This form of loosely organized DNA is called ______ .When a cell is in the process of division, the chromatin condenses into chromosomes, so that the DNA can be safely transported to the “daughter cells.”

Chromosome

is the condensed form of chromatin. It is estimated that humans have almost 22,000 genes distributed on 46 chromosomes.

Proteome

DNA. Just as the cell’s genome describes its full complement of DNA, a cell’s _________ is its full complement of proteins. The process of making a protein begins with its gene.

Gene

is a segment of DNA that provides the genetic information necessary to build a single protein.

Messenger RNA (mRNA)

Messenger RNA (mRNA) is a single-stranded nucleic acid that carries a copy of the genetic code for a single gene out of the nucleus and into the cytoplasm where it is used to produce proteins.

Transcription

Gene expression—the process of making a molecular product from a gene—begins with the process called ________, in which a messenger RNA strand is made from the gene of interest.

RNA polymerase

an enzyme that is capable of building RNA strands, begins to synthesize a complementary RNA molecule

Splicing

removes these noncoding regions from the pre-mRNA transcript to create the mature mRNA molecule

Translation is the process of synthesizing a chain of amino acids called a polypeptide.

Ribosomal RNA (rRNA)

Ribosomes are nonmembranous organelles that are composed of ribosomal RNA (rRNA) and proteins

RNA (tRNA)

The ribosome simply provides the space for translation, bringing together and aligning the mRNA molecule with another form of RNA

Anticodon

This sequence of three bases on the tRNA molecule is called

Somatic cell

is a general term for a body cell, and all human cells, except for the cells that produce eggs and sperm (which are referred to as germ cells), are somatic cells. Somatic cells contain 46 chromosomes

Diploid

This is the ______ number, meaning that within those 46 chromosomes are two copies of each chromosome (one copy received from each parent).

Homologous

pair of chromosomes is the two copies of a single chromosome found in each somatic cell.

Human somatic cells contain 23 homologous pairs of chromosomes in each of the somatic cells; 23 is the haploid number

interphase, mitosis, and cytokinesis.

One “turn” or cycle of the cell cycle consists of three general phases

Interphase

is the period of the cell cycle during which the cell is not replicating.

Mitosis

is the division of genetic material, during which the cell nucleus breaks down and two new, fully functional, nuclei are formed

Cytokinesis

divides the cytoplasm into two distinctive cells.

Meiosis

is the process in which germ cells, which give rise to the egg and sperm reproductive cells, are made.

G1 phase (gap 1 phase)

was described as a “gap” phase by scientists who were seeking cells in mitosis.

S phase (synthesis phase)

The S phase (synthesis phase) is period during which a cell replicates its DNA.

G2 phase

is a second gap phase, during which the cell continues to grow and makes the necessary preparations for mitosis.

DNA replication

is the copying of DNA that occurs during S phase

DNA polymerase

brings in the correct bases to complementary the template strand, synthesizing a new complementary strand nucleotide by nucleotide

Sister chromatic, centromere

For every chromosome, its replicated copy is called a ________ and is physically bound to the other copy at a structure known as a ______

Mitotic phase

the cell includes both mitosis and cytokinesis. In mitosis, the chromosomes are organized and distributed equitably.

Prophase

the first phase of mitosis, the loosely packed chromatin coils and condenses into chromosomes.

Metaphase

is the second stage of mitosis. During this stage, the sister chromatids,attached to the microtubules of the mitotic spindle, are pulled into a line along the middle of the cell.

Anaphase

is the third stage of mitosis. In anaphase, the pairs of sister chromatids are separated from one another, forming individual chromosomes once again.

Telophase

is the final stage of mitosis. In telophase, many of the events of prophase reverse.

Cleavage furrow

is a contractile band made up of microfilaments (actin fibers) that forms around the midline of the cell during cytokinesis