Lesson II: The Cell and its Functions

Question 1

is separated from the cytoplasm
by a nuclear membrane

Answer 1

nucleus

Question 2

is separated from the surrounding fluids by a cell membrane, also
called the PLASMA MEMBRANE

Answer 2

cytoplasm

Question 3

The different substances that make up the cell are
collectively called

Answer 3

protoplasm

Question 4

Protoplasm is composed mainly of five basic substances:

Answer 4

✓ water
✓ electrolytes
✓ proteins
✓ lipids
✓ carbohydrates

Question 5

The principal fluid medium of the cell, which is present in most cells, except for fat cells, in a concentration of 70 to 85 percent.

Answer 5

water

Question 6

Important ions in the cell include

Answer 6

✓ potassium
✓ magnesium
✓ phosphate
✓ sulfate
✓ bicarbonate
✓ and smaller quantities of sodium, chloride and calcium

Question 7

provide inorganic chemicals for cellular reactions

Answer 7

ions

Question 8

they are necessary for operation of some of
the cellular control mechanisms.

Answer 8

ions

Question 9

acting at the cell membrane are required for transmission of
electrochemical impulses in nerve and muscle fibers.

Answer 9

ions

Question 10

the most abundant substances
in most cells

Answer 10

proteins

Question 11

proteins, which normally constitute ___ to ___ percent of the cell mass.

Answer 11

10-20 percent

Question 12

proteins can be divided into two
types:

Answer 12

structural and functional proteins

Question 13

present in the cell mainly in the
form of long filaments that are polymers of many individual protein molecules.

Answer 13

structural proteins

Question 14

a prominent use of such intracellular filaments is to form _________ that provide the __________ of such cellular organelles as ______, _________, the
________, and a tangled mass of thin
__________ that hold the parts of the cytoplasm and
nucleoplasm together in their respective compartments

Answer 14

microtubules
cytoskeleton

cilia, nerve axons, mitotic of mitosing cells, filamentous tubules

Question 15

are found especially in the
collagen and elastin fibers of connective tissue and in blood
vessel walls, tendons, ligaments, and so forth

Answer 15

fibrillar proteins

Question 16

are an entirely different type
of protein, usually composed of combinations of a few
molecules in tubular-globular form.

Answer 16

functional proteins

Question 17

are several types of substances that are grouped together because of their common property of
being soluble in fat solvents.

Answer 17

lipids

Question 18

important lipids
are ____________ and ___________ which together constitute only about 2 percent of the total cell mass

Answer 18

phospholipids and cholesterol

Question 19

some cells
contain large quantities of triglycerides, also called

Answer 19

neutral fat

Question 20

triglycerides often account for as much
as how many percent of the cell mass.

Answer 20

95%

Question 21

have little structural
function in the cell except as parts of glycoprotein molecules, but they play a major role in nutrition of the cell.

Answer 21

carbohydrates

Question 22

small amount
of carbohydrate is stored in the cells in the form of

Answer 22

glycogen

Question 23

which is an insoluble polymer of glucose that can
be depolymerized and used rapidly to supply the cells’
energy needs.

Answer 23

glycogen

Question 24

The cell is not merely a bag of fluid, enzymes, and chemicals; it also contains highly organized physical structures,
called

Answer 24

intracellular organelles

Question 25

more than 95 percent of the cell’s energy release from nutrients would cease immediately.

Answer 25

mitochondria

Question 26

membranes include;

Answer 26

✓ cell membrane ✓ nuclear membrane, ✓membrane of the endoplasmic reticulum ✓ membranes of the mitochondria, ✓ lysosomes ✓ Golgi apparatus

Question 27

for passage of specific substances through the membrane

Answer 27

actual pores

Question 28

(also called the plasma membrane), which envelops the cell, is a thin, pliable, elastic structure only 7.5 to 10 nanometers thick. It is composed almost entirely of proteins and lipids.

Answer 28

cell membrane

Question 29

The approximate composition is;

Answer 29

proteins, 55 percent phospholipids, 25 percent cholesterol, 13 percent other lipids, 4 percent carbohydrates, 3 percent.

Question 30

is composed of phospholipid molecules.

Answer 30

basic lipid bilayer

Question 31

One end of each phospholipid molecule is soluble in water; that is, it is

Answer 31

hydrophilic

Question 32

The other end is soluble only in fats; that is, it is

Answer 32

hydrophobic

Question 33

The phosphate end of the phospholipid

Answer 33

hydrophilic

Question 34

the fatty acid portion

Answer 34

hydrophobic

Question 35

The lipid layer in the middle of the membrane is impermeable to the usual water-soluble substances, such as;

Answer 35

ions, glucose, urea

Question 36

fat-soluble substances such as; can penetrate this portion of the membrane with ease.

Answer 36

oxygen, carbon dioxide and alcohol

Question 37

are attached to the protein molecules on the out side of the membrane and to additional protein molecules on the inside.

Answer 37

carbohydrate moieties

Question 38

controls much of the fluidity of the membrane as well

Answer 38

cholesterol

Question 39

These are membrane proteins, most of which are

Answer 39

glycoproteins

Question 40

There are two types of cell membrane proteins:

Answer 40

integral proteins and peripheral proteins

Question 41

that protrude all the way through the membrane

Answer 41

Integral proteins

Question 42

that are attached only to one surface of the membrane and do not penetrate all the way through.

Answer 42

peripheral proteins

Question 43

through which water molecules and water-soluble substances, especially ions, can diffuse between the extracellular and intracellular fluids.

Answer 43

structural channels or pores

Question 44

Other integral proteins act as ________for transporting substances that otherwise could not penetrate the lipid bilayer

Answer 44

carrier proteins

Question 45

Sometimes these even transport substances in the direction opposite to their electrochemical gradients for diffusion, which is called?

Answer 45

active transport

Question 46

can also serve as receptors for water-soluble chemicals, such as peptide hormones,that do not easily penetrate the cell membrane.

Answer 46

integral membrane proteins

Question 47

Interaction of cell membrane receptors with specific _________ that bind to the receptor causes conformational changes in the receptor protein

Answer 47

ligands

Question 48

enzymatically activates the intracellular part of the protein or induces interactions between the receptor and proteins in the cytoplasm that act as

Answer 48

second messenger

Question 49

thereby relaying the signal from the extracellular part of the receptor to the interior of the cell.

Answer 49

second messengers

Question 50

spanning the cell membrane provide a means of conveying information about the environment to the cell interior.

Answer 50

Integral proteins

Question 51

moecules are often attached to the integral proteins.

Answer 51

peripheral proteins

Question 52

enzymes or as controllers of transport of substances through the cell membrane “pores ”

Answer 52

peripheral proteins

Question 53

Membrane carbohydrates occur almost invariably in combination with proteins or lipids in the form of

Answer 53

glycoproteins and glycolipids

Question 54

most of the integral proteins

Answer 54

glycoproteins

Question 55

one tenth of the membrane lipid molecules are

Answer 55

glycolipids

Question 56

which are mainly carbohydrate substances bound to small protein cores—are loosely attached to the outer surface of the cell as well.

Answer 56

proteoglycans

Question 57

loose carbohydrate coat

Answer 57

glycocalyx

Question 58

is filled with both minute and large dispersed particles and organelles.

Answer 58

cytoplasm

Question 59

clear fluid portion of the cytoplasm in which the particles are dispersed

Answer 59

cytosol

Question 60

cytosol contains mainly dissolved;

Answer 60

proteins, electrolytes, and glucose.

Question 61

Dispersed in the cytoplasm are

Answer 61

neutral fat globules, glycogen granules, ribosomes, secretory vesicles

Question 62

five especially important organelles:

Answer 62

✓ Endoplasmic reticulum ✓ Golgi apparatus ✓ Mitochondria ✓ Lysosome ✓ Peroxisomes

Question 63

their walls are constructed of lipid bilayer membranes that contain large amounts of proteins, similar to the cell membrane.

Answer 63

endoplasmic reticulum

Question 64

a watery medium that is different from the fluid in the cytosol outside the endoplasmic reticulum

Answer 64

endoplasmic matrix

Question 65

show that the space inside the endoplasmic reticulum is connected with the space between the two membrane surfaces of the nuclear membrane.

Answer 65

electron micrographs

Question 66

Attached to the outer surfaces of many parts of the endoplasmic reticulum are large numbers of minute granular particles

Answer 66

ribosome

Question 67

when these are present, reticulum is called the?

Answer 67

granular endoplasmic reticulum

Question 68

are composed of a mixture of RNA and proteins, and they function to synthesize new protein molecules in the cel

Answer 68

ribosomes

Question 69

Part of the endoplasmic reticulum has no attached ribosomes. This part is called the

Answer 69

agranular, or smooth, endoplasmic reticulum

Question 70

are similar physically to lysosomes, but they are different in two important ways.

Answer 70

peroxisome

Question 71

another oxidase enzyme present in large quantities in peroxisomes, to oxidize many substances that might otherwise be poisonous to the cell

Answer 71

catalase

Question 72

small “transport vesicles” (lalso called

Answer 72

endoplasmic reticulum vesicles

Question 73

are vesicular organelles that form by breaking off from the Golgi apparatus and then dispersing throughout the cytoplasm

Answer 73

lysosomes

Question 74

The lysosomes provide an ____________ that allows the cell to digest (1) damaged cellular structures, (2) food particles that have been ingested by the cell, and (3) unwanted matter such as bacteria

Answer 74

intracellular digestive system

Question 75

is capable of splitting an organic compound into two or more parts by combining hydrogen from a water molecule with one part of the compound and combining the hydroxyl portion of the water molecule with the other part of the compound.

Answer 75

hydrolytic enzymes

Question 76

protein is hydrolyzed to form

Answer 76

amino acids

Question 77

glycogen is hydrolyzed to form

Answer 77

glucose

Question 78

lipids are hydrolyzed to form

Answer 78

fatty acids and glycerol

Question 79

Almost all such secretory substances are formed by the endoplasmic reticulum Golgi apparatus system and are then released from the Golgi apparatus into the cytoplasm in the form of stor- age vesicles called

Answer 79

secretory vesicles or secretory granules

Question 80

secreted later through the outer cell membrane into the pancreatic duct and thence into the duodenum, where they become activated and perform digestive functions on the food in the intestinal tract.

Answer 80

proenzymes

Question 81

called the “powerhouses” of the cell.

Answer 81

mitochondria

Question 82

are concentrated in those portions of the cell that are responsible for the major share of its energy metabolism.

Answer 82

mitochondria

Question 83

composed mainly of two lipid bilayer– protein membranes

Answer 83

outer and inner membrane

Question 84

The liberated energy is used to synthesize a “high-energy” substance called

Answer 84

adenosine triphosphate (ATP)

Question 85

are self-replicative, which means that one mitochondrion can form a second one, a third one, and soon, whenever there is a need in the cell for increased amounts of ATP.

Answer 85

mitochondria

Question 86

is the basic chemical of the nucleus that controls replication of the cell.

Answer 86

DNA

Question 87

The precursor molecules then polymerize to form

Answer 87

filaments

Question 88

large numbers of actin filaments frequently occur in the outer zone of the cytoplasm, called the

Answer 88

ectoplasm

Question 89

A special type of stiff filament composed of polymerized tubulin molecules is used in all cells to construct strong tubular structures

Answer 89

microtubules

Question 90

both the centrioles and the mitotic spindle of the mitosing cell are composed

Answer 90

stiff microtubules

Question 91

primary function of microtubules is to act as a

Answer 91

cytoskeleton

Question 92

providing rigid physical structures for certain parts of cells.

Answer 92

cytoskeleton

Question 93

the control center of the cell

Answer 93

nucleus

Question 94

nucleus contains large quantities of DNA

Answer 94

genes

Question 95

determine the characteristics of the cell’s proteins, including the structural proteins, as well as the intracellular enzymes that control cytoplasmic and nuclear activities.

Answer 95

genes

Question 96

nuclear membrane, also called

Answer 96

nuclear envelope

Question 97

The nuclear membrane is penetrated by several thousand

Answer 97

nuclear pores

Question 98

The nuclei of most cells contain one or more highly staining structures called

Answer 98

nucleoli

Question 99

(1) the smallest known virus, (2) a large virus, (3) a rickettsia, (4) a bacterium, and (5) a nucleated cell,

Question 100

The essential life-giving constituent of the small virus is a

Answer 100

nucleic acid

Question 101

is composed of the same basic nucleic acid constituents (DNA or RNA) found in mammalian cells, and it is capable of reproducing itself under appropriate conditions

Answer 101

nucleic acid

Question 102

Most substances pass through the cell membrane by

Answer 102

diffusion and active transport

Question 103

involves simple movement through the membrane caused by the random motion of the molecules of the substance; substances move either through cell membrane pores or, in the case of lipid-soluble substances, through the lipid matrix of the membrane.

Answer 103

diffusion

Question 104

involves the actual carrying of a substance through the membrane by a physical protein.structure that penetrates all the way through the membrane.

Answer 104

active transport

Question 105

Very large particles enter the cell by a specialized function of the cell membrane called

Answer 105

endocytosis

Question 106

The principal forms of endocytosis are

Answer 106

pinocytosis and phagocytosis

Question 107

means ingestion of large particles, such as bacteria, whole cells, or portions of degenerating tissue.

Answer 107

phagocytosis

Question 108

means ingestion of minute particles that form vesicles of extracellular fluid and particulate constituents inside the cell cytoplasm

Answer 108

pinocytosis