Anatomy and Physiology Chapter 3: The Cellular Level of Organization

What are cells?
Living structural and functional units enclosed by a membrane.

What is cell division?
Process by which all cells arise from existing cells and one cell divides into two identical cells.

What is cell biology?
The study of cellular structure and function.

1. Name and describe the three main parts of a cell.

What are the three main parts of a cell?
1. Cell membrane
2. Cytoplasm
3. Nucleus

What is the plasma membrane and function?
The plasma membrane forms the cell’s flexible outer surface, separating the cell’s internal environment (inside the cell_ from the external environment (outside the cell).

The cytoplasm consists of what two components?
1. Cytosol: The fluid portion of the cytoplasm containing water, dissolved solutes, and suspended particles.
2. Organells: Surrounded by cytosol each type of organelle(little organ) has a characteristic shape and specific functions. Examples include the cytoskeleton, ribosomes, endoplasmic reticulum, golgi complex, lysosomes, peroxisomes, and mitochondria.

What is the nucleus?
A large organelle that houses most of a cells DNA.

1. Describe the structure and functions of the plasma membrane.
2. Explain the concept of selective permeability.
3. Define the electrochemical gradient and describe its component.

What is the plasma membrane?
A flexible yet sturdy barrier that surrounds and contains the cytoplasm of a cell.

What is the lipid bilayer of a cell?
The basic structural framework of the plasma membrane. Back to back layers made up of three types of lipid molecules. phospholipids, cholesterol, and glycolipids.

What is the percentage makeup of the membrane?
75% are membrane phospholipids, 20% is cholesterol, and 5% are glycolipids.

What does amphipathic mean?
Both polar and nonpolar parts. The polar part is the head of the phospholipid which is hydrophilic (water loving), and the tail is nonpolar hydrophobic.

What does hydrophillic mean?
Water loving

What does hyrdophobic mean?
Water hating

Where are cholesterol molecules in the cell membrane?
They are intersdespersed among the other lipids in both layers of the membrane. The tinny-OH group is the only polar region of cholesterol. They fit among the fatty acid tails of the phospholipds and glycolipids.

Where are the glycolipid molecules in the cell membrane?
Glycolipids appear only in the membrane layer that faces the extracellular fluid.

Where are integral proteins located?
They extend into or through the lipid bilayer among the fatty acid tails are firmly embedded in it.

Where are the transmembrane proteins located?
Most integral proteins are transmembrane.They span the entire lipid bilayer and protrude into both the cytosol and extracellular fluid.

Where are peripheral proteins located?
As the name implies they are not as firmly planted in the membrane. The associate more loosely with the polar heads of the membrane lipids or with integral proteins at the inner or outer surface of a membrane.

What are glycoproteins?
Proteins with carbohydrte groups attached to the ends that protrude into extracellular fluid.

What is glycocalyx?
Portion of glycolipids and glycoproteins form an extensive sugary coat called glycolayx. Act like a molecular signal that enables cells to recognize on another.

What are ion channels?
Pores or holes through whih specific ions, such as potassium ions (K+) can flow to get into or out of the cell. Most ion channels are selective, they only allow a certain type of ion to pass through.

What are receptors?
Serve as cellular recognition sites.

What are ligands?
A specific molecule that binds to a receptor is called a ligand.

What are linkers?
Integral proteins that anchor proteins in the plasma membranes of neighboring cells. Peripheral proteins also serve as enzymes and linkers.

What are cell identity markers?
They enable a cell to recognize other cells of the same kind during tissue formation or to recognize and respond to potential dangerous foreign cells.

What is selective permeability?
The property of a membrane by which it permits the passage of certain substances but restricts the passage of others.

What is a concentration gradient?
Difference in the concentration of a chemical from one place to another, such as from the inside to the outside of the plasma membrane.

What is an electrical gradient?
The difference in the electrical charges between the inner surface and outer surface of the membrane. Typically, the inner surface of the plasma membrane is more negatively charged and the outer surface is more positively charged.

What is a membrane potential?
When there is an electrical gradient this is typically referred to as the electrochemical gradient.

1. Describe the processes that transport substances across the plasma membrane

What is the passive process in terms of cellular membranes?
A substance moves down its concentration or electrical gradient to cross the membrane using only its “OWN kinetic energy”. There is no input of energy from the cell.

What is the active process in terms of cellular membranes?
Cellular energy is used to drive the substance “uphill” against its concentration gradient.

Another active process in the use of vesicles…describe.
An active process in which tiny, spherical membrane sacs called vesicles are used. i.e. endocytosis and exocytosis.

What is diffusion?
A passive process in which the random mixing of particles in a solution occurs because of the particles kinetic energy. i.e. both the solutes and the solvent undergo diffusion. If the particular solute is high concentration in one area of the solution and in low concentration in another area, solute molecules will diffuse toward the area of lower concentration-they move down their concentration gradient.

What are the factors that influence the diffusion rate of substances across plasma membranes?
1. Steepness of the concentration gradient: Greater the better
2. Temperature: Hotter the better
3. Mass of the diffusing substance: smaller the better
4. Surface area: Greater the better
5. Diffusion distance: Shorter the better.

What is simple diffusion?
In simple diffusion a substance moves across the lipid bylayer of the plasma membrane without the help of membrane transport. “NONPOLAR”, hydrophobic molecules move through the process of simple diffusion.

What is facilitated diffusion?
A substance moves across the lipid bilayer aided by a channel protein or carrier protein. Solutes that are “TOO POLAR” or “HIGHLY CHARGED”.

What is channel mediated facilitated diffusion?
When a solute moves down it concentration gradient across the lipid bilayer through a membrane channel. Most membrance channels are ion channels, integral transmembrane proteins that allow passage of small, inorganic ions are too hydrophilic to penetrate the non polar interior of the lipid bilayer.

What is carrier-mediated facilitated diffusion?
A carrier, also called a transporter, is used to move a solute down its concentration gradient across the plasma membrane. The solute binds to a specific carrier on one side of the membrane and is released on the other side after the carrier undergoes “CHANGE IN SHAPE”. The solute binds more often with a higher concentration of solute. Substances that move across by carrier mediated facilitated diffusion include glucose, fructose, galactose, and some vitamins.

How does glucose enter the body?
1. Glucose binds to a specific carrier protein called the glucose transport (GluT) on the outside surface membrane.
2. As the transporter undergoes a change in shape, glucose passes through the membrane.
3. The transporter releases glucose on the other side of the membrane.

What is osmosis?
Osmosis is a type of diffusion in which there is net movement of a solvent through a selectively permeable membrane. Identified as a passive process.

During osmosis, water molecules pass through the plasma membrane via 2 ways:
1. By moving through the lipid bilayer via simple diffusion.
2. By moving through aquaporins.

What are aquaporins?
Integral membrane proteins that function as water channels.

What is hydrostatic pressure?

What is osmotic pressure?

What is tonicity?
A measure of the solution’s ability to change the volume of cells by altering their water content.

What is an isotonic solution?
Any solution in which a cell maintains its normal shape and volume. Iso=”same”. I.e. .9% of saline solution for IBCs.

What is a hypotonic solution?
A solution that has a lower concentration of solutes than the cytosol inside the RBCs. hypo=”lower”. In this case water molecules enter the cells faster than they leave, causing the RBCs to swell and eventually to burst. Pure water is very hypotonic and has causes rapid hemolysis.

What is hemolysis?
The rupture of RBCs is due to being in a hypotonic solution. lysis=”to loosen or to split apart”

What is a hypertonic solution?
A solution that has a higher concentration of solutes than does the cytosol inside RBCs. One example of a hypertonic solution is 2%. In such a solution, water molecules move out of the cells faster than they enter, causing the cells to shrink Such shrinkage of cells is called “crenation”.

What is active transport?
The movement of substances across cell membranes against a concentration gradient “MOVING UPHILL”, requiring the expenditure of cellular energy. Active transport is considered an active process because energy is required for carrier proteins to move solutes across the membrane against a concentration gradient as opposed to passive transport that doesn’t require intracellular energy.

What are two sources of cellular energy?
1. Energy obtained from hydrolysis of adenosine triphosphate (ATP) is the source in primary active transport.
2. Energy stored in ionic concentration gradient is the source of secondary active transport.

What is primary active transport?
Energy derived from hydrolysis of ATP changes the shape of a carrier protein, which pumps a substance across a plasma membrane against its concentration gradient.

What are pumps?
Carrier proteins that mediate primary active transport.

What percentage of cellular ATP is used for just primary active transport?
40%. Poison cynaide turns off ATP production. That’s why it is lethal!

What is the sodium-potassium pump.
The most prevalent primary active transport mechanism that expels sodium (Na+) from cells and brings postassium in (K+). These sodium-potassium pumps maintain a low concentation of Na+ in the cytosol by pumping them into the extracellular fluid against Na+ concentration gradient. At the same time, the pumps move K+ into cells against the K+ concentration gradient. The sodium-potassium pumps must work nonstop to maintain a low concentration of Na+ and a high concentration of K+. Also known as the Na+/K+ ATPase pump.

Explain secondary active transport.

What is vesicle?
A small spherical sac.

What is endocytosis?
Materials move into a cell in a vesicle formed from the plasma membrane. Active process with energy
supplied by ATP.

What is exocytosis?
Materials move out of cell by fusion with the plasma membrane of vesicles formed in the cell. Active process with energy supplied by ATP.

What are the three types of endocytosis?
1. Receptor-Mediated: A highly selective type of endocytosis by which cells take up specific ligands.
2. Phagocytosis:
3. Bulk Phase Endocytosis

What is the process for receptor mediated endocytosis:
1. Binding
2. Vesicle formation
3. Uncoating
4. Fushion with endosome
5. Recycling
6. Degradation

What is phagocytosis?
A from of endocytosis in which the cell engulfs large solid particles as worn-out cells, whole bacteria, or viruses.

What are phagocytes?
Cells that are able to carry out phagocytosis.

Describe phagocytosis.
Phagocytosis begins when the particle binds to a plasma membrane receptor on the phagocyte, causing to extend pseudopods (projections of its plasma membrane and cytoplasm). Pseudopods surround the particle outside the cell, and the membranes fuse to form a vesicle called a phagosome which enters the cytoplasm. The phagosome fuses with one or more lysosomes, and the lysosomal enzymes break down the ingested material. In most cases, any undigested materials in the phagosome remain indefinitely in a vesicle called a residual body.

Describe bulk-phase endocytosis also known as pinocytosis.

What is exocytosis?
Membrane-enclosed vesicles form inside the cell, fuse with the plasma membrane and release their contents into the extracellular fluid.

What is transcytosis?
Vesicles undergo endocytosis on one side of a cell, move across the cell, and then undergo exocytosis on the opposite side. As the vesicles fuse with the plasma membrane, the vesicular contents are released into the extracellular fluid.

What is cytoplasm?
Cytoplasm consists of all the cellular contents between the plasma membrane and the nucleus.

1. Describe the structure and function of cytoplasm, cytosol, and organelles.

What are the two components of cytoplasm?
1. The cytosol
2. The organelles

What is the cytosol (intracellular fluid)?
The fluid portion of the cytosol that surrounds the organelles. It is 55% of the cell volume. The cytosol is 75-90% water.

What are organelles?
Specialized structures within the cell that have characteristic shapes; they perform specific functions in cellular growth, maintenance, and reproduction

What is the cytoskeleton and its function?
The cytoskeleton is a network of protein filaments that extend throughout the cytosol.

What are the three types of filamentous proteins that contribute to the cytoskeleton’s structure?
Microfilaments, intermediate filaments, and microtubules.

What are microfilaments and what is the function?
The thinnest elements of the cytoskeleton. They help generate movement and provide mechanical support.

What are intermediate filaments and function?
Larger than microfilaments but thinner than microtubles. They help stabilize the position of organelles such as the nucleus, and help attach cells to one another.

What are microtubules and function?
Largest of the cytoskeleton components and are long. They help determine cell shape and function in the movement of organelles.

What is a centrosome and what is its function.
The centrosome is located near the nucleus and is composed of centrioles and pericoentriolar material. The pericentriolar material of the centrosome contains tubulins that build microtubles in nondividing cells and form the mitotic spindle during cell division. These complexes are the organizing centers for growth of the mitotic spindle which plays a key role in cell division and microtubule formation in nondividing cells.

What is the flagella and its function?
Similar to structure to cilia but are typically much longer. Flagella usually move an entire cell. The only example of a cell with flagellum is the sperm cells tail.

What is cilia and its function?
The cilia’s function is to move fluid along a cell’s surface. Cilia are numerous, short, hairlike projections that extend from the surface of the cell. Microtubules are dominant components of the cilia and flagella.

What are ribosomes and functon?
Sites of protein synthesis. The function of ribosomes associated with endoplasmic reticulum is to synthesize proteins destined for insertion in the plasma membrane or secretion from the cell. The second function of ribosomes is to synthesize proteins used in the cytosol.

What is the endoplasmic reticulum(ER) and function?
The ER is a network of membrane-enclosed sacs or tubules that extend through-out the cytoplasm and connect to the nuclear envelope.
1. The rough ER synthesizes glcoproteins and phospholipids that are transferred into cellular organelles, inserted into the plasma membrane, or secreted during exocytosis.
2. The Smooth ER synthesizes fatty acids and steroids, such as estrogens and testosterone; inactivates or detoxifies drugs and other potentially harmful substances; removes the phosphate group from glucose-6-phosphate; and stores and releases calcium ions that trigger contraction in muscle cells.

What is the rough ER?
It is continuous with the nuclear membrane and usually is folded into a series of flattened sacs. The outer surfaw of rough ER is studded with ribosomes, the sites of protein synthesis.

What is smooth ER?
It extends from the rough ER to form a network of membrane tubules. Unlike rough ER, smooth ER does not have ribosomes on the outer surfaces of its membrane. However smooth ER contains unique enzymes that make it functionally more diverse than rough ER. As mentioned above one of the functions of smooth ER is to detoxify drugs.

What is the Golgi complex and what its functions?
An organelle in the cytoplasm of cells consisting of four to six flattened sacs (cistern), stacked on one another, with expanded areas at their ends;
Functions include:
1. Modifies, sorts, packages, and transports proteins received from the rough ER.
2. Forms secretory vesicles that discharge processed proteins via exocytosis into extracellular fluid; forms membrane vesicles that ferry new molecules to the plasma membrane; forms transport vesicles that carry molecules to other organelles such as lysosomes.

What are lysosomes and functions?
Lysomes (lyso=dissolving, somes=bodies) are membrane-enclosed vesicles that form from the Golgi complex. There functions include:
1. Digest substances that enter a cell via endocytosis and transport final products of digestion into cytosol.
2. Carry out autophagy (auto=self, phagy=eat, the digestion of worn-out organelles.
3. Carry out autolysis, the digestion of entire cell.
4. Carry out extracellular digestion.

What is autophagy?
The process by which entire worn-out organelles are digested.

What is an autophagosome?
In autophagy, the organelle to be digested is enclosed by a membrane derived from the ER to create a vesicle called an autophagosome.

What is autolysis?
Auto=self, lysis=destruction: Self-destruction of cells by their own lysomal digestive enzymes after death or in a pathological process.

What is a peroxisomes also called microbodies?
Peroxi=peroxide; somes=bodies; Another group of organelles similar in structure to lysosomes but smaller.

What is a proteasome?
some=bodies; Tiny cellular organelles in cytosol and nucleus containing proteases that destroy unneeded, damaged or faulty proteins.

What is mitochondria and its function?
Mito=thread; chondria=granules. Referred to as the powerhouses of the cell. They function to generate ATP through reactions for aerobic cellular respiration. Like peroxisomes, mitochondria self replicate.

1. Describe the structure and function of the nucleus.

What is the nucleus and function?
The nucleus is a spherical or oval-shaped structure that usually is the most prominent feature of a cell. Its function is:
1. Control cellular structure
2. Direct cellular activity
3. Produce ribosomes in nucleoli

What is the nuclear envelope?
A double membrane called the nuclear envelope separates the nucleus from the cytoplasm.

What are nuclear pores?
Many opening called nuclear pores extend through the nuclear envelope. Nuclear pores control the movement of substances between the nucleus and the cytoplasm.

What is the nucleoli?
Inside the nucleus are one or more spherical bodies called nucleoli that function in producing ribosomes.

What are genes?
A biological unit of heredity; a segment of DNA located in a definite position on a particular chromosome; a sequin of DNA that codes from a particular mRNA, rRNA, or tRNA.

What are chromosomes?
Chrom=threadlike, Somes=bodies; One of the small threadlike structures in the nucleus of a cell, normally 46 in a human diploid cell (23 from each parent), that bears the genetic material; composed of DNA an proteins during interphase; becomes packaged into rodlike structures that are visible under th elight microscope during cell division.

What is chromatin?
the threadlike mass of genetic material, consisting of DNA and histone proteins, that is present in the nucleus of a nondividing or interphase cell.

What is a genome?
The complete set of genes of an organism.

What are histones?

What are nucleosomes and their components?
Consists of double stranded DNA wrapped twice around a core of eight proteins called histones.

What is linker DNA?

What are the two types of cell division?
Somatic cell division and reproductive cell division.

What is a somatic cell?
Any cell of the body other than a germ cell(sperm or oocyte) or an any precursor cell destined to become a gamete.

What is a gamete?
A germ cell.

Somatic cells undergo what two types of division?
Mitosis and cytokinesis.

What is reproductive cell division?
The mechanism that produce gametes, the cells needed to form the next generation of sexually reproducing organisms. This process consists of a special two-step division called meiosis by which the number of chromosomes in the nucleus is reduced by half.

What are homologous chromosomes?
Two chromosomes that belong to a pair. Also called homologs. 23 from each parent. The pairs of chromosomes from that pair up are called homologous chromosomes. A to A and B to B for example.

Describe the two major phases of somatic cell cycles?
1. Interphase: When a cell is not dividing
2. Mitiotic phase: When a cell is dividing.

What is interphase?
The period of the cell cycle between cell divisions, consisting of the G1-(gap or growth) phase, when the cell is engaged in growth, metabolism, and production of substances required for division; S-(synthesis)phase, during which chromosomes are replicated; and G2-phase.

Interphase consists of what 3 phases?
G1, S, G2 phases.
G1 phase: Replication of organelles and cytosolic components but not DNA. lasts in general for 8-10 hours.
S phase: Now committed to go thru cell division. DNA replication is now taking place. Lasts about 8 hours.
G2 phase: Cell growth continues, enzymes and other proteins are synthesized in preparation for cell division.
Once a cell completes G1, S, and G2 phases the mitotic phase begins.

What is the mitotic phase of cell division?
The cell cycle consists of nuclear division (mitosis) and a cytoplasmic division (cytokinesis) to form two identical cells.

What are the four phases of mitosis?
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase

The sequence of somatic cell division can be summarized as:
G1 phase, S phase, G2 phase, mitosis, cytokinesis

Describe and summarize the events of somatic cell cycle (table 3.3)

What is meiosis?
A type of cell division that occurs during production of gametes, involving two successive nuclear divisions that result in cells with haploid (n) number of chromosomes.

What are haploid cells?
Contain half the number of chromosomes as normal human cells. Thus gametes contain 23 chromosomes and are referred to as haploid cells.

What is apoptosis?
“PROGRAMMED” cell death; a normal type of cell death that removes unneeded cells during embryological development, regulates the number of cells in tissues, and eliminates many potentially dangerous cells such as cancer cells. During apoptosis, the DNA fragments, the nucleus condenses, mitochondria cease to function, and the cytoplasm shrinks, but the plasma membrane stays intact.

What is necrosis?
A pathological type of cell death that results from disease, injury, or lack of blood supply in while many adjacent cells swell, burst, and spill their contents into the interstitial fluid triggering an inflammatory response.

1. Describe how cells differ is size and shape
I.E. oocyte, red blood cells, nerve cells, smooth muscle cells, epithellial cell, sperm cells, etc.

1. Describe the cellular changes that occur with aging.

What is geriatrics?
Ger=old age, iatrics=medicine: The specialized branch of medicine that deals with the medical problems and care of elderly person.

***Observations suggest that mitosis is a normal, genetically programmed event.

What are telemeters?
Specific DNA sequences found only at the tips of each chromosome. These pieces of DNA protect the tips of the chromosomes. In most normal body cells each cylce of cell division shortens the telomers.

**What are the names of the passive processes?
1. Diffusion: Simple, Channel-mediated facilitated diffusion, and carrier mediated facilitated diffusion.
2. Osmosis

**What are the names of the active processes?
1. Primary active transport: Sodium-potassium pump
2. Secondary active transport:
3. Transport in vesicles: Endocytosis (receptor mediated, phagocytosis, bulk phase endocytosis), exocytosis, and transcytosis).

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