KN 230/232 for exam 1 chapter 4

What is a cell?

A cell is the structural and functional unit of life.

What are the four basic concepts of cell theory?

• Cells are the building blocks of all plants and animals.

• Cells are the smallest functioning units of life.

• Cells are produced through the division of preexisting cells.

• Each cell maintains homeostasis.

What are the three main structural components of a generalized cell?

• Plasma membrane.

• Nucleus.

• Cytoplasm.

What are cellular inclusions?

• They are molecules (such as pigments, glycogen, or triglycerides) temporarily stored in the cytosol.

• They are continuously added to and removed from the cell and are not considered organelles.

What are the three types of lipids contained in the plasma membrane?

• Phospholipids.

• Cholesterol.

• Glycolipids.

Describe the structure of a phospholipid in the membrane.

It resembles a "balloon with two tails," featuring a polar, hydrophilic "head" and two nonpolar, hydrophobic "tails."

What is the function of cholesterol in the plasma membrane and what is it’s location?

It is scattered within the phospholipid bilayer and serves to strengthen the membrane.

What are the four primary functions of the plasma membrane?

• Acts as a physical barrier.

• a physical barrier that allows certain molecules, ions, or substances to pass through while blocking others

• Establishes and maintains electrochemical gradients.

• Functions in cellular communication.

What is the difference between integral and peripheral membrane proteins?

• Integral proteins are embedded within and extend across the phospholipid bilayer.

• Peripheral proteins are loosely attached to the external or interior surfaces and are not embedded in the lipid bilayer.

What are the six primary functions of membrane proteins?

• (regulating movement of substances).

• (binding ligands).

• (Identity markers).

• (catalyzing reactions).

• (securing the cytoskeleton).

• (cell-to-cell attachments).

What is the function of tight junctions?

They are strands of proteins that link cells together, preventing substances from passing between the cells.

What are gap junctions and what do they provide?

They are tiny, fluid-filled tunnels that provide a direct passageway for substances (such as ions) to travel between cells.

What is interstitial fluid (IF)?

It is the fluid surrounding cells that contains thousands of substances, such as amino acids, sugars, fatty acids, and waste products.

What are the two main characteristics of passive processes in membrane transport?

• They do not require the expenditure of cellular energy meaning the cell does not use its own metabolic energy

• They depend on substances moving naturally from an area of higher concentration to an area of lower concentration.

What are the defining characteristics of active processes in membrane transport?

• They require the expenditure of cellular energy meaning the cell does use its own metabolic energy

• They involve moving a substance up its concentration gradient (active transport) or the formation/loss of a vesicle (vesicular transport).

What is diffusion, and what two factors determine its rate?

• Diffusion is the net movement of a substance from an area of greater concentration to an area of lesser concentration.

• The rate depends on the steepness of the concentration gradient and the temperature.

What is simple diffusion, and what types of solutes use it?

• It is movement dependent on a concentration gradient that is not regulated by the plasma membrane.

• It allows small and nonpolar solutes, such as oxygen and carbon dioxide, to pass between phospholipid molecules.

What is facilitated diffusion?

• It is a transport process for small polar solutes that requires assistance from plasma membrane proteins.

What is channel-mediated diffusion, and what are the two types of channels?

• It is the movement of small ions through water-filled protein channels.

• The two types are leak channels (continuously open) and gated channels (usually closed, opening only in response to a stimulus).

How does carrier-mediated diffusion function?

A small polar molecule binds to a carrier protein, causing the protein to change shape and release the substance on the other side of the membrane.

What is osmosis?

It is the passive movement of water (not solutes) through a selectively permeable membrane, driven by differences in water concentration.

What are the two ways water crosses the plasma membrane during osmosis?

Water either slips between the molecules of the phospholipid bilayer or moves through integral protein water channels called aquaporins.

What is osmotic pressure?

It is the pressure exerted by the movement of water across a semipermeable membrane due to a difference in solution concentration.

What defines active transport?

It is the movement of a solute against its concentration gradient meaning it moves from from an area of lower concentration to an area of higher concentration, which requires an energy source to maintain the gradient between the cell and interstitial fluid.

What is the energy source for primary active transport?

It uses energy directly from the breakdown of ATP, which phosphorylates the transport protein and changes its shape.

What is the specific function of the sodium-potassium (Na^{+}/K^{+}) pump?

It continuously exports Na^{+} out of the cell and moves K^{+} into the cell against their gradients to preserve steep gradient differences.

How does secondary active transport acquire energy?

It uses the kinetic energy provided by the movement of a second substance down its own concentration gradient meaning a substance naturally travels from an area of higher concentration to an area of lower concentration to power the transport of another substance against its gradient.

What is the difference between symport and antiport in secondary active transport?

• Symport moves two substances in the same direction.

• Antiport moves two substances in opposite directions.

What is vesicular transport (bulk transport)?

It is the which process requires energy input to transport large substances across the plasma membrane using a membrane-bounded sac called a vesicle.

What occurs during exocytosis?

Large substances are packed within intracellular transport vesicles, which then fuse with the plasma membrane to release their contents outside the cell.

What is endocytosis?

It is the cellular uptake of large substances from the external environment, used for digestion, retrieving membrane regions, and regulating membrane proteins.

What is tonicity?

It is the ability of a solution to change the volume or pressure of a cell by osmosis.

How do isotonic, hypotonic, and hypertonic solutions affect a cell's volume?

• Isotonic: No net movement of water occurs.

• Hypotonic: Water enters the cell, which can cause lysis (rupturing).

• Hypertonic: Water leaves the cell, which decreases volume and causes (shrinking).

What is the resting membrane potential (RMP)?

It is the electrochemical gradient, at the plasma membrane, when a cell is at rest.

What two conditions establish the resting membrane potential?

• Unequal distribution of ions across the plasma membrane (more K^{+} inside, more Na^{+} outside).

• Unequal relative amounts of positive and negative charges (the outside of the cell is more positive than the inside).

Which ion is the most important determinant of the specific value of the resting membrane potential?

Potassium (K^{+})

How is the resting membrane potential maintained?

Na^{+}/K^{+} pumps maintain the gradients by continually pumping Na^{+} out of the cell and K^{+} into the cell against their concentration gradients.

What are the three components of the cytoplasm?

Cytosol, organelles, and inclusions.

Which organelles are membranous?

Mitochondria, peroxisomes, lysosomes, endoplasmic reticulum (ER), and Golgi apparatus.

What is the primary function of mitochondria?

it is the "powerhouse" of the cell and it digests fuel molecules to synthesize ATP through aerobic cellular respiration.

How do rough and smooth (ER) differ in function and structure?

• Rough ER: Has ribosomes attached and functions in protein production.

• Smooth ER: Lacks ribosomes and functions in the synthesis, transport, and storage of lipids, carbohydrate metabolism, and detoxification.

What is the polarity of the Golgi apparatus?

It features a cis-face (proximal to the ER) and a trans-face (distal from the ER).

What is the primary function of the Golgi apparatus?

It modifies, packages, and sorts proteins, and forms secretory vesicles.

What is the role of lysosomes?

They are small membranous sacs containing digestive enzymes that participate in the digestion of unneeded substances and the contents of endocytosed vesicles.

What are peroxisomes and what are their metabolic functions?

They are membrane-enclosed sacs pinched off from the rough ER that function in chemical digestion (beta oxidation) and lipid synthesis.

What are the three primary functions of the cytoskeleton?

Structural support and cell organization, cell division, and movement.

What are the three main components of the cytoskeleton?

• Microfilaments: The smallest components, made of actin, that maintain cell shape and aid in cell division.

• Intermediate filaments: Intermediate-sized and more rigid components that provide structural support.

• Microtubules: The largest components, composed of tubulin, that maintain shape and facilitate cell transport.

What is the difference in function between bound and free ribosomes?

• Bound ribosomes synthesize proteins that will be exported, incorporated into the plasma membrane, or housed in lysosomes.

• Free ribosomes synthesize proteins strictly for use within the cell.

What is the primary function of the centrosome?

It organizes microtubules within the cytoskeleton and it divides cells.

What is the nuclear envelope?

It is a double phospholipid membrane that encloses the nucleus, separating the cytoplasm from the nucleoplasm.

What is the function of the nucleolus?

Composed of protein and RNA, it produces both the small and large ribosome subunits.

What are the three components of a DNA deoxyribonucleotide?

• A five-carbon sugar (deoxyribose).

• A phosphate.

• One of four nitrogenous bases (Adenine, Cytosine, Guanine, or Thymine).

What is the difference between chromatin and chromosomes?

When a cell is not dividing, DNA exists as a finely filamented mass called chromatin

when a cell is dividing, DNA condenses into a tightly coiled mass called chromosomes.

What are the functions of cilia, flagella, and microvilli?

• Cilia: Hair-like projections that move substances along the cell surface.

• Flagella: Longer projections that propel the entire cell.

• Microvilli: Extensions of the plasma membrane that increase surface area.

What are the two main steps of protein synthesis?

• Transcription: Forming an RNA copy of a gene from DNA inside the nucleus.

• Translation: Using RNA to synthesize a protein at the ribosomes in the cytosol.

What are the three types of RNA produced during transcription?

Messenger RNA (mRNA), Transfer RNA (tRNA), and Ribosomal RNA (rRNA).

What are the three events of transcription?

Initiation, Elongation, and Termination.

What role does RNA polymerase play during transcription?

It is the enzyme that assists with complementary base pairing of free ribonucleotides to the exposed bases of the DNA template strand.

What occurs during the translation step of protein synthesis?

The mRNA code is translated by ribosomes in the cytoplasm to convert nucleotide sequences into a strand of amino acids, producing a new protein.

What are the two major phases of the cell cycle?

• Interphase: Lasts approximately 23 hours.

• Mitotic (M) phase: Lasts about 1 hour.

What is the difference between mitosis and meiosis?

• Mitosis is cell division occurring in somatic cells, where one cell divides to produce two identical daughter cells.

• Meiosis is cell division occurring only in sex cells (cells that give rise to sperm or oocytes).