BIOL 101 > Chapter 4 > Flashcards

Chapter 4 Flashcards

Cells (69 cards)

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1
Q

What are the three principles of the cell theory?

A

All organisms are composed of one or more cells; cells are the smallest living things; cells arise only by division of a previously existing cell.

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2
Q

Why are most cells small?

A

Smaller cells function more efficiently — their command center can reach all parts quickly, and they have a greater surface-to-volume ratio allowing more exchange with the environment.

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3
Q

What is the surface-to-volume ratio and why does it matter?

A

The ratio of a cell’s surface area to its interior volume — a higher ratio means more membrane surface is available to service each unit of volume inside the cell.

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4
Q

What are some structural features that increase a cell’s surface area?

A

Long thin extensions (like axons), flat plate-like shapes, and tiny fingerlike projections called microvilli.

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5
Q

What is the difference between a light microscope and an electron microscope?

A

Light microscopes use light and can resolve structures ~200 nm apart; electron microscopes use electron beams and have 1,000 times greater resolving power, resolving objects ~0.2 nm apart.

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6
Q

What are the two types of electron microscopes?

A

Transmission electron microscope (shows internal detail) and scanning electron microscope (produces a 3D surface image).

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7
Q

What are prokaryotic cells?

A

Simple, usually unicellular organisms that lack a nucleus and membrane-bounded organelles — enclosed by a plasma membrane and usually a cell wall.

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8
Q

What is the nucleoid region?

A

The area of cytoplasm in a prokaryotic cell where DNA is located — it is not enclosed by a membrane and is not a true nucleus.

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9
Q

What are ribosomes?

A

Small structures found in all cells where proteins are synthesized — they lack a membrane boundary.

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10
Q

What are flagella (in prokaryotes)?

A

Long, threadlike protein structures that project from the cell surface and rotate like screws to propel the cell.

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11
Q

What are pili?

A

Short flagella-like structures on prokaryotic cells that help attach to surfaces and aid in the exchange of genetic information between cells.

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12
Q

What are eukaryotic cells?

A

Larger, more complex cells with a nucleus and membrane-bounded organelles that subdivide the cell interior into functional compartments.

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13
Q

What is the cytoplasm?

A

The semifluid matrix inside the plasma membrane that contains the nucleus, organelles, and cytoskeleton.

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14
Q

What is an organelle?

A

A specialized structure within a eukaryotic cell in which particular cell processes occur.

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15
Q

What organelles are found in plant cells but NOT in animal cells?

A

Chloroplasts, central vacuole, cell wall, and plasmodesmata.

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16
Q

What structures are found in animal cells but NOT in plant or fungal cells?

A

Centrioles.

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17
Q

What is the plasma membrane?

A

A delicate double layer of phospholipids with embedded proteins that encloses all cells and regulates what passes in and out.

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18
Q

What is the fluid mosaic model?

A

The description of the plasma membrane as a mix of proteins and lipids that are constantly moving while maintaining a barrier between the cell interior and exterior.

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19
Q

What is a phospholipid?

A

A modified fat molecule with a polar (water-soluble) head and two nonpolar (water-insoluble) fatty acid tails — the main component of the lipid bilayer.

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20
Q

Why do phospholipids form a bilayer in water?

A

Their nonpolar tails are repelled by water and are pushed to the interior, while the polar heads face outward toward the watery environments on each side.

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21
Q

What is the role of cholesterol in the plasma membrane?

A

It resides in the nonpolar interior of the bilayer and helps maintain membrane fluidity and integrity.

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22
Q

What are transmembrane proteins?

A

Proteins that span the entire lipid bilayer and provide passageways for ions and polar molecules to cross the membrane.

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23
Q

What are cell surface proteins?

A

Membrane proteins that project from the surface and act as markers to identify cell types or as receptors to bind hormones and other molecules.

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24
Q

What are the two functions of the nucleus?

A

It is the command and control center directing cell activities, and it is the genetic library where hereditary information (DNA) is stored.

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25
What is the nuclear envelope?
A double membrane surrounding the nucleus that acts as a barrier between the nucleus and cytoplasm.
26
What are nuclear pores?
Openings in the nuclear envelope lined with proteins that control the passage of proteins and RNA into and out of the nucleus.
27
What are chromosomes?
Segments of DNA wound around proteins and packaged into compact units found in the nucleus of eukaryotic cells.
28
What is chromatin?
The uncoiled, extended form of chromosomes present in a non-dividing cell — available for protein synthesis.
29
What is the nucleolus?
A region within the nucleus where ribosomal RNA (rRNA) is made and ribosome subunits are assembled.
30
What is the endoplasmic reticulum (ER)?
An extensive system of internal membranes that creates channels and vesicles within the cell — involved in protein and lipid synthesis and transport.
31
What is rough ER?
ER studded with ribosomes on its surface — the site where proteins intended for export are synthesized.
32
What is smooth ER?
ER with few or no ribosomes — contains enzymes that aid in the manufacture of carbohydrates and lipids.
33
What is the Golgi complex?
Stacks of flattened membrane sacs that collect, package, and distribute molecules made in the ER — delivering them to other cell compartments or to the cell surface for secretion.
34
What are lysosomes?
Vesicles derived from the Golgi complex that contain powerful digestive enzymes — they break down worn-out organelles and recycle their components.
35
What are vacuoles?
Membrane-bounded storage compartments — plant cells have a large central vacuole that stores water, sugars, ions, and pigments.
36
What is the function of the central vacuole in plant cells?
To store water and other substances and to help maintain the shape and turgor pressure of the plant cell.
37
What are mitochondria?
Sausage-shaped organelles with a double membrane where cellular respiration occurs — they extract energy from food molecules and produce ATP.
38
What are cristae?
Folds of the inner membrane of a mitochondrion that increase surface area for cellular respiration.
39
What are chloroplasts?
Bacteria-like organelles found only in plant and algal cells where photosynthesis takes place — bounded by a double membrane with internal thylakoid membranes.
40
What are thylakoids?
Stacked membrane vesicles inside chloroplasts where the energy-harvesting reactions of photosynthesis occur.
41
What is the stroma?
The semiliquid interior of a chloroplast surrounding the thylakoids.
42
What is the theory of endosymbiosis?
The theory that mitochondria and chloroplasts evolved from ancient bacteria that were engulfed by early eukaryotic cells and formed a mutually beneficial relationship.
43
What evidence supports the endosymbiotic theory?
Mitochondria and chloroplasts have double membranes, circular DNA similar to bacteria, ribosomes similar in size to bacterial ribosomes, and divide by simple fission like bacteria.
44
What is the cytoskeleton?
A lattice of protein fibers inside eukaryotic cells that determines cell shape, anchors organelles, and enables cell movement.
45
What are the three types of cytoskeleton fibers?
Microfilaments (actin filaments), microtubules, and intermediate filaments.
46
What are microfilaments?
Thin actin protein fibers (~7 nm) responsible for cell movements such as contraction, crawling, and pinching during cell division.
47
What are microtubules?
Hollow tubes (~25 nm) made of tubulin protein — they organize metabolism, intracellular transport, and chromosome movement during cell division.
48
What are intermediate filaments?
Ropelike protein bundles that provide mechanical strength and structural reinforcement to the cell — stable and do not readily break down.
49
What is the 9 + 2 arrangement?
The structure of eukaryotic flagella and cilia — nine pairs of microtubules surrounding two central microtubules.
50
What is the difference between flagella and cilia in eukaryotes?
They are identical in structure — cilia are shorter and more numerous; flagella are longer and usually fewer in number.
51
What is diffusion?
The net movement of molecules from an area of higher concentration to an area of lower concentration due to random molecular motion.
52
What is osmosis?
The diffusion of water across a membrane from an area of higher free water concentration to an area of lower free water concentration.
53
What are aquaporins?
Protein channels in the plasma membrane through which water molecules rapidly cross the membrane.
54
What is osmotic concentration?
The total concentration of all dissolved solutes in a solution.
55
What does isotonic mean?
Two solutions have equal osmotic concentrations — no net movement of water between them.
56
What does hypertonic mean?
A solution with a higher solute concentration — water moves out of a cell placed in a hypertonic solution, causing it to shrink.
57
What does hypotonic mean?
A solution with a lower solute concentration — water moves into a cell placed in a hypotonic solution, causing it to swell.
58
What is osmotic pressure?
The pressure created by water moving into a cell by osmosis — can cause a cell to swell and burst if unopposed.
59
What is turgor pressure?
The osmotic pressure in plant cells that pushes against the cell wall — important for maintaining plant cell shape.
60
What is endocytosis?
The process by which a cell engulfs material by folding its plasma membrane around it to form a vesicle.
61
What is phagocytosis?
Endocytosis of solid particles or organisms — "cell eating."
62
What is pinocytosis?
Endocytosis of liquid or dissolved substances — "cell drinking."
63
What is exocytosis?
The reverse of endocytosis — vesicles fuse with the plasma membrane and release their contents to the outside of the cell.
64
What is selective permeability?
The ability of the plasma membrane to control which molecules enter and leave the cell by using specific transport proteins.
65
What is selective diffusion?
Transport through protein channels that act as open doors — molecules move freely in either direction down their concentration gradient.
66
What is facilitated diffusion?
Transport using carrier proteins that bind specific molecules and release them on the other side of the membrane — movement is still down the concentration gradient and requires no energy.
67
What is active transport?
The movement of molecules across a membrane against their concentration gradient using energy (ATP) and carrier proteins.
68
What is the sodium-potassium pump?
An active transport protein that uses ATP to pump sodium ions (Na+) out of the cell and potassium ions (K+) into the cell — responsible for over one-third of cellular energy expenditure.
69
What is coupled transport?
A transport mechanism in which a molecule (such as a sugar or amino acid) can only cross the membrane paired with a sodium ion — the sodium concentration gradient drives both molecules into the cell.
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