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AP Biology JCH > Chapter 6 A Tour of the Cell > Flashcards

Chapter 6 A Tour of the Cell Flashcards

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1
Q

Why are cell the basic unit of life?

A

The cell is the simplest collection of matter that can live.

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2
Q

Why are cells so small?

A

As a cell decreases in size, its volume grows proportionally greater than its surface area. Thus, a smaller object has a larger surface area to volume ratio. The need for a surface area sufficiently large to accommodate the volume helps explain the microscopic size of most cells. A sufficiently high ratio of surface area to volume is especially important in cells that exchange a lot of material with their surroundings.

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3
Q

Describe in what way many neurons and intestinal cells have increased their surface area.

A

Nerve cells have narrow, elongated shapes. Intestinal cells may have many long, thin projections from their surface called microvilli, which increase surface area without an appreciable increase in volume.

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4
Q

Describe how a light microscope works.

A

In a light microscope (LM), visible light passes through the specimen and then through glass lenses.
The lenses refract light such that the image is magnified into the eye or onto a video screen.

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5
Q

What is magnification?

A

Magnification is the ratio of an object’s image to its real size.

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6
Q

What is resolving power?

A

Resolving power is a measure of image clarity.

It is the minimum distance two points can be separated and still be distinguished as two separate points.

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7
Q

Describe the resolution and magnification of a light microscope.

A

The minimum resolution of a light microscope is about 200 nanometers (nm), the size of a small bacterium.
Light microscopes can magnify effectively to about 1,000 times the size of the actual specimen.

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8
Q

What is an electron microscope?

A

focuses a beam of electrons through the specimen or onto its surface

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9
Q

Describe transmission electron microscopes. What are they used for?

A

Transmission electron microscopes (TEMs) are used mainly to study the internal ultrastructure of cells.

  • A TEM aims an electron beam through a thin section of the specimen.
  • The image is focused and magnified by electromagnets.
  • To enhance contrast, the thin sections are stained with atoms of heavy metals.
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10
Q

Describe scanning electron microscopes. What are they used for?

A

Scanning electron microscopes (SEMs) are useful for studying surface structures.

  • The sample surface is covered with a thin film of gold.
  • The beam excites electrons on the surface of the sample.
  • These secondary electrons are collected and focused on a screen.
  • The result is an image of the topography of the specimen.
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11
Q

What is cytology?

A

the study of cell structures

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12
Q

What is the goal of cell fractionation?

A

The goal of cell fractionation is to separate the major organelles of the cells so their individual functions can be studied.

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13
Q

What is the machine used for cell fractionation?

A

an ultracentrifuge, a machine that can spin at up to 130,000 revolutions per minute and apply forces of more than 1 million times gravity (1,000,000 g)

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14
Q

Describe the process of fractionation.

A
  1. Fractionation begins with homogenization, gently disrupting the cell.
  2. The homogenate is spun in a centrifuge to separate heavier pieces into the pellet while lighter particles remain in the supernatant.
  3. As the process is repeated at higher speeds and for longer durations, smaller and smaller organelles can be collected in subsequent pellets.
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15
Q

Name 4 things that all cells have.

A
  1. All cells are surrounded by a plasma membrane.
  2. The semifluid substance within the membrane is the cytosol, containing the organelles.
  3. All cells contain chromosomes that have genes in the form of DNA.
  4. All cells also have ribosomes, tiny organelles that make proteins using the instructions contained in genes.
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16
Q

What is the region between the nucleus and the plasma membrane?

A

The region between the nucleus and the plasma membrane is the cytoplasm.
All the material within the plasma membrane of a prokaryotic cell is cytoplasm.

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17
Q

What is one difference between prokaryotic and eukaryotic cells?

A

The location of the chromosomes.
Eukaryotic- membrane enclosed nucleus
Prokaryotic- nucleoid

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18
Q

How do internal membranes impact cellular function?

A

The compartments created by membranes provide different local environments that facilitate specific metabolic functions, allowing several incompatible processes to go on simultaneously in a cell.

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19
Q

What is the structure of membranes?

A

The general structure of a biological membrane is a double layer of phospholipids.
Other lipids and diverse proteins are embedded in the lipid bilayer or attached to its surface.
Each type of membrane has a unique combination of lipids and proteins for its specific functions.

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20
Q

List the components of the nucleus.

A
  • Nuclear envelope
  • Pores
  • Pore complex
  • nuclear lamina
  • Nucleolus
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21
Q

How is DNA organized in the nucleus, and what makes up this structure?

A

Within the nucleus, the DNA and associated proteins are organized into discrete units called chromosomes, structures that carry the genetic information.
Each chromosome is made up of fibrous material called chromatin, a complex of proteins and DNA.

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22
Q

What is the nuclear envelope?

A

The nucleus is separated from the cytoplasm by a double membrane called the nuclear envelope.

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23
Q

What perforates the nuclear envelope?

A
  • The nuclear envelope is perforated by pores where the inner and outer membranes are fused to form a continuous membrane
  • A protein structure called a pore complex lines each pore, regulating the passage of certain large macromolecules and particles.
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24
Q

What supports the nuclear envelope?

A

The nuclear side of the envelope is lined by the nuclear lamina, a network of protein filaments that maintains the shape of the nucleus.

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25
Q

Describe the structure and function of nucleolus.

A

In the nucleus is a region of densely stained fibers and granules adjoining chromatin, the nucleolus.
In the nucleolus, ribosomal RNA (rRNA) is synthesized and assembled with proteins from the cytoplasm to form ribosomal subunits.

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26
Q

What are ribosomes?

A

Ribosomes, containing rRNA and protein, are the organelles that carry out protein synthesis.

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27
Q

How do ribosome numbers vary?

A

Cell types that synthesize large quantities of proteins (e.g., pancreas cells) have large numbers of ribosomes and prominent nucleoli.

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28
Q

Contrast the two types of ribosomes.

A
  • Free ribosomes, are suspended in the cytosol and synthesize proteins that function within the cytosol.
  • Bound ribosomes, are attached to the outside of the endoplasmic reticulum or nuclear envelope. These synthesize proteins that are either included in membranes or exported from the cell.
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29
Q

Can ribosomes shift between free and bound?

A

Ribosomes can shift between roles depending on the polypeptides they are synthesizing.

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30
Q

What does the endomembrane system do?

A

The endomembrane system regulates protein traffic and performs metabolic functions in the cell

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31
Q

What are the components of the endomembrane system?

A

The endomembrane system includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and the plasma membrane.

32
Q

Describe the structure and location of the ER.

A

The endoplasmic reticulum (ER) accounts for half the membranes in a eukaryotic cell.
The ER includes membranous tubules and internal, fluid-filled spaces called cisternae.
The ER membrane is continuous with the nuclear envelope, and the cisternal space of the ER is continuous with the space between the two membranes of the nuclear envelope.

33
Q

What are the two different regions of the ER?

A

Smooth ER looks smooth because it lacks ribosomes.
Rough ER looks rough because ribosomes (bound ribosomes) are attached to the outside, including the outside of the nuclear envelope.

34
Q

What are the functions the smooth ER?

A
  • The smooth ER is rich in enzymes
  • Enzymes of smooth ER synthesize lipids, including oils, phospholipids, and steroids.
  • In the smooth ER of the liver, enzymes help detoxify poisons and drugs such as alcohol and barbiturates.
  • Frequent use of these drugs leads to the proliferation of smooth ER in liver cells, increasing the rate of detoxification, and in turn leads to tolerance.
  • Smooth ER stores calcium ions.
  • Metabolism of carbohydrates
35
Q

What are the functions the rough ER?

A

-As a polypeptide is synthesized on a ribosome attached to rough ER, it is threaded into the cisternal space through a pore formed by a protein complex in the ER membrane. In the cisternal space the new protein folds into its native conformation. Secretory proteins are packaged in transport vesicles that carry them to their next stage.
-Rough ER is also a membrane factory.
Membrane-bound proteins are synthesized directly into the membrane.
As the ER membrane expands, membrane can be transferred as transport vesicles to other components of the endomembrane system.

36
Q

Describe the function of the smooth ER in muscle cells.

A

Muscle cells have a specialized smooth ER that pumps calcium ions from the cytosol and stores them in its cisternal space.
When a nerve impulse stimulates a muscle cell, calcium ions rush from the ER into the cytosol, triggering contraction.
Enzymes then pump the calcium back, readying the cell for the next stimulation.

37
Q

What are secretory proteins made up of?

A

Mostly glycoproteins/ proteins with a carbohydrate attached

38
Q

What two organelle are abundant in cells that secrete proteins?

A

-Rough ER and golgi apparatus are especially abundant in cells that secrete proteins.

39
Q

Where do transport vesicles from the ER travel to?

A

Many transport vesicles from the ER travel to the Golgi apparatus for modification of their contents.

40
Q

What is the general function of the golgi apparatus?

A

The Golgi is a center of manufacturing, warehousing, sorting, and shipping.

41
Q

Describe the structure of the golgi apparatus.

A

The Golgi apparatus consists of flattened membranous sacs—cisternae—looking like a stack of pita bread.
The membrane of each cisterna separates its internal space from the cytosol.

42
Q

Describe the cis and trans side of the golgi apparatus.

A

One side of the Golgi, the cis side, is located near the ER. The cis face receives material by fusing with transport vesicles from the ER.
The other side, the trans side, buds off vesicles that travel to other sites.

43
Q

Describe three specific functions of the golgi apparatus.

A

-The Golgi can manufacture its own macromolecules, including pectin and other noncellulose polysaccharides.
-Modifies proteins
-The Golgi sorts and packages materials into transport vesicles.
Molecular identification tags are added to products to aid in sorting.
Products are tagged with identifiers such as phosphate groups.

44
Q

What is the lumen?

A

The lumen is the cisternal space of the ER, which is continuous with the space between the two membranes of the nuclear membrane, as the ER membrane is continuous within the nuclear envelope.

45
Q

What is the lysosome?

A

A lysosome is a membrane-bound sac of hydrolytic enzymes that an animal cell uses to digest macromolecules. Works best at pH 5.

46
Q

Describe 3 functions of a lysosome.

A
  • Lysosomes carry out intracellular digestion of particles engulfed by phagocytosis
  • Recycles cellular components in a process called autophagy.
  • The lysosomes play a critical role in the programmed destruction of cells in multicellular organisms. (webbed hands in humans)
47
Q

Describe autophagy.

A

During autophagy, a damaged organelle or small amount of cytosol becomes surrounded by a double membrane (of unknown origin), and a lysosome fuses with the outer membrane of this vesicle. The lysosomal enzymes dismantle the enclosed material, and the organic monomers are returned to the cytosol for reuse.

48
Q

What is one organism that performs phagocytosis?

A

Amoebas

49
Q

What happens in Tay-Sachs disease?

A

In Tay-Sachs disease, a lipid-digesting enzyme is missing or inactive, and the brain becomes impaired by an accumulation of lipids in the cells.

50
Q

Describe the three types of vacuoles.

A

Food vacuoles, formed by phagocytosis, fuse with lysosomes, whose enzymes digest food.
Contractile vacuoles pump excess water out of the cell, thereby maintaining a suitable concentration of ions and molecules inside the cell.
Mature plant cells generally contain a large central vacuole. There is cell sap solution inside the central vacuole. The functions of the central vacuole include stockpiling proteins or inorganic ions, disposing of metabolic byproducts, holding pigments, and storing defensive compounds that defend the plant against herbivores.The central vacuole plays a major role in the growth of plant cells.

51
Q

What is the membrane of the central vacuole called?

A

The tonoplast

52
Q

What is the function of the mitochondria?

A

Mitochondria are the sites of cellular respiration, generating ATP from the catabolism of sugars, fats, and other fuels in the presence of oxygen.

53
Q

What is the function of the chloroplasts?

A

Chloroplasts, found in plants and algae, are the sites of photosynthesis.
They convert solar energy to chemical energy and synthesize new organic compounds such as sugars from CO2 and H2O.

54
Q

Describe 3 similarities that illustrate the independence of chloroplasts and mitochondria.

A
  • Both organelles have small quantities of DNA that direct the synthesis of the polypeptides produced by these internal ribosomes.
  • Mitochondria and chloroplasts grow and reproduce as semiautonomous organelles.
  • Both have ribosomes
55
Q

Describe the structure of mitochondria.

A

Mitochondria have a smooth outer membrane and a convoluted inner membrane with infoldings called cristae.
The inner membrane divides the mitochondrion into two internal compartments, the intermembrane space, and the mitochondrial matrix, a fluid-filled space with DNA, ribosomes, and enzymes.

56
Q

List three types of plastids

A

Amyloplasts are colorless plastids that store starch in roots and tubers.
Chromoplasts store pigments for fruits and flowers.
Chloroplasts contain the green pigment chlorophyll as well as enzymes and other molecules that function in the photosynthetic production of sugar.

57
Q

Describe the structure of the chloroplasts.

A

Has an envelope consisting of two membranes separated by a narrow intermembrane space. Inside the innermost membrane is a fluid-filled space, the stroma. The stroma contains DNA, ribosomes, and enzymes.
The thylakoids are flattened sacs that play a critical role in converting light to chemical energy. In some regions, thylakoids are stacked like poker chips into grana.

58
Q

Describe the functions of peroxisomes.

A

Peroxisomes contain enzymes that transfer hydrogen from various substrates to oxygen.
The peroxisome contains an enzyme that converts H2O2 to water.Some peroxisomes break fatty acids down to smaller molecules that are transported to mitochondria as fuel for cellular respiration.
Peroxisomes in the liver detoxify alcohol and other harmful compounds.

59
Q

Describe a specialized type of peroxisome.

A

Specialized peroxisomes, glyoxysomes, convert the fatty acids in seeds to sugars, which the seedling can use as a source of energy and carbon until it is capable of photosynthesis.

60
Q

What are the three major functions the cytoskeleton?

A

The cytoskeleton provides support, motility, and regulation.

61
Q

What are the three main types of fibers in the cytoskeleton?

A

There are three main types of fibers making up the cytoskeleton: microtubules, microfilaments, and intermediate filaments.

62
Q

Describe the structure of microtubules.

A

Structure:
Microtubules, the thickest fibers, are hollow rods about 25 microns in diameter and 200 nm to 25 microns in length.
Microtubule fibers are constructed of the globular protein tubulin.
Each tubulin molecule is a dimer consisting of two subunits and the microtubule changes length by adding or removing subunits.

63
Q

Describe the function of microtubules.

A

Function:

  • shape and support the cell.
  • serve as tracks to guide motor proteins carrying organelles to their destination.
  • separation of chromosomes during cell division.
  • responsible for the beating of cilia and flagella.
64
Q

Describe differences between cilia and flagella.

A

-Flagella are longer, and there are usually only 1-2 per cell
-Cilia occur in large numbers on the cell surface
-Cilia and flagella differ in their beating patterns.
A flagellum has an undulatory movement that generates force in the same direction as the flagellum’s axis.
Cilia move more like oars with alternating power and recovery strokes that generate force perpendicular to the cilium’s axis.

65
Q

Describe the structure of cilia and flagella.

A
  • a core of microtubules sheathed by the plasma membrane.
  • Nine doublets of microtubules are arranged in a ring around a pair at the center. This “9 + 2” pattern is found in nearly all eukaryotic cilia and flagella.
  • Flexible “wheels” of proteins connect outer doublets to each other and to the two central microtubules.
  • The outer doublets are also connected by motor proteins.
  • The cilium or flagellum is anchored in the cell by a basal body, whose structure is identical to a centriole.
  • The bending of cilia and flagella is driven by the arms of a motor protein, dynein.
66
Q

Describe the structure of microfilaments.

A
  • solid rods about 7 nm in diameter.
  • twisted double chain of actin subunits.
  • form structural networks due to their ability to branch.
67
Q

Describe the function of microfilaments.

A
  • important in cell motility, especially as part of the contractile apparatus of muscle cells.
  • Triggered by Myosin molecules which act as motor proteins, walking along the actin filaments to shorten the cell.
  • drives cytoplasmic streaming.
68
Q

What is cytoplasmic streaming?

A

a circular flow of cytoplasm in the cell, speeding the distribution of materials within the cell

69
Q

What is the structure of intermediate filaments?

A

Intermediate filaments range in diameter from 8–12 nanometers, larger than microfilaments but smaller than microtubules.

  • built from a family of proteins called keratins.
  • specialized for bearing tension.
70
Q

What is the function of intermediate filaments?

A

They reinforce cell shape and fix organelle location.

71
Q

Describe the function of the cell wall.

A

In plants, the cell wall protects the cell, maintains its shape, and prevents excessive uptake of water.
It also supports the plant against the force of gravity.

72
Q

Describe the structure of the cell wall.

A

The basic design consists of microfibrils of cellulose embedded in a matrix of proteins and other polysaccharides. This is the basic design of steel-reinforced concrete or fiberglass.
A mature cell wall consists of a primary cell wall, a middle lamella with sticky polysaccharides that holds cells together, and layers of secondary cell wall.
Plant cell walls are perforated by channels between adjacent cells called plasmodesmata.

73
Q

What are the functions of the ECM in animal cells?

A

The extracellular matrix (ECM) of animal cells functions in support, adhesion, movement, and regulation.

74
Q

Describe the structure of the ECM.

A

The primary constituents of the extracellular matrix are glycoproteins, especially collagen fibers, embedded in a network of glycoprotein proteoglycans.
In many cells, fibronectins in the ECM connect to integrins, intrinsic membrane proteins that span the membrane and bind on their cytoplasmic side to proteins attached to microfilaments of the cytoskeleton.
The interconnections from the ECM to the cytoskeleton via the fibronectin-integrin link permit the integration of changes inside and outside the cell.

75
Q

Describe Plasmodesmata.

A

Plant cells are perforated with plasmodesmata, channels allowing cytosol to pass between cells.
Water and small solutes can pass freely from cell to cell.
In certain circumstances, proteins and RNA can be exchanged.

76
Q

Describe the 3 types of intercellular links of animal cells.

A 
In tight junctions, membranes of adjacent cells are fused, forming continuous belts around cells. This prevents leakage of extracellular fluid.
Desmosomes (or anchoring junctions) fasten cells together into strong sheets, much like rivets. Intermediate filaments of keratin reinforce desmosomes.
Gap junctions (or communicating junctions) provide cytoplasmic channels between adjacent cells. Special membrane proteins surround these pores.
Ions, sugars, amino acids, and other small molecules can pass. In embryos, gap junctions facilitate chemical communication during development.

AP Biology JCH (12 decks)

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