Chapter 4

Question 1

What do cells contain?

Answer 1

Water and other small and large molecules

Question 2

How many different types of molecules do cells have?

Answer 2

Over 10,000

Question 3

What do cells use their molecules for?

Answer 3

~transforming matter and energy
~responding to their environments
~reproducing

Question 4

cell theory

Answer 4

~cells are the fundamental units of life
~all living organisms are composed of cells
~all cells come from preexisting cells

Question 5

What is the diameter range for most cells?

Answer 5

1 to 100 micrometers

Question 6

surface area-to-volume ratio

Answer 6

decreases as the size increases

as an object increases in volume, its surface area also increases, but not as quickly

Question 7

What does the volume of a cell determine?

Answer 7

the amount of metabolic activity it carries out per unit time

Question 8

What does the surface area of a cell determine?

Answer 8

the amount of substances that can enter it from the outside environment, and the amount of waste products that can exit to the environment

Question 9

What happens as a living cell grows larger?

Answer 9

metabolic activity, and thus its need for resources and its rate of waste production, increases faster than its surface area

Question 10

Substance motion is more easily accomplished in what size cell?

Answer 10

smaller cells

Question 11

How does a multicellular organism make use of the surface area-to-volume ratio?

Answer 11

large surface area-to-volume ratio represented by the many small cells of a multicellular organism enables it to carry out the many different functions required for survival

Question 12

What is another way for cells to attain an adequate exchange of materials with the environment?

Answer 12

increase surface area through folds in the cell membrane or increase the rate of exchange of materials across the cell

Question 13

light microscope

Answer 13

~uses glass lenses and visible light to form images
~size limit is 0.2 micrometers
~visualise living cells and general cell structure

Question 14

electron microscope

Answer 14

~uses an electron beam focused by magnets to illuminate a specimen and produce an image on a TV-like screen
~size limit is 0.1 nanometers
~specimens must be preserved and stained using toxic heavy metals

Question 15

cell membrane

Answer 15

~selectively permeable barrier
~allows cell to maintain a stable internal environment distinct from the surrounding environment
~important in communicating with adjacent cells and receiving signals from the environment
~has proteins responsible for binding and adhering to adjacent cells or surfaces
~important structural role, contributes to shapes

Question 16

What are the three domains?

Answer 16

Archaea, Bacteria, and Eukarya

Question 17

prokaryotes

Answer 17

~Archaea and Bacteria kingdoms
~typically no membrane-enclosed internal compartments
~no nucleus

Question 18

eukaryotes

Answer 18

~contains membrane-enclosed compartments called organelles

~contains a nucleus, where DNA is located and gene expression begins

Question 19

advantages of compartmentalization

Answer 19

provides possibilities for regulation and efficiency that were important in the evolution of complex organisms

Question 20

cell membrane (prokaryotes)

Answer 20

encloses the cell, separating its interior from the external environment, and regulates the traffic of materials into and out of the cell

Question 21

nucleoid

Answer 21

region in the cell where the DNA is located

Question 22

DNA

Answer 22

the hereditary material that controls cell growth, maintenance, and reproduction

Question 23

cytoplasm (prokaryotes)

Answer 23

the rest of the material inside the cell (liquid and other insoluble filaments/particles)

Question 24

cytosol (prokaryotes)

Answer 24

consists mostly of water containing dissolved ions, small molecules, and soluble macromolecules such as proteins

Question 25

ribosomes (prokaryotes)

Answer 25

complexes of RNA and proteins that are the sites of protein synthesis

Question 26

protein synthesis

Answer 26

where the information encoded by nucleic acids directs the sequential linking of amino acids to form proteins

Question 27

cell wall (prokaryotes)

Answer 27

~supports cell and determines shape ~mostly containing peptidoglycan ~some bacteria have cell walls with phospholipid membranes or layers of polysaccharides

Question 28

capsule (prokaryotes)

Answer 28

the polysaccharide layer enclosing the cell in bacteria, which protects the bacteria from attack, keeps the cell from drying out, and sometimes helps them attach to other cells

Question 29

internal membrane

Answer 29

~in some groups of bacteria | ~contains molecules needed for photosynthesis

Question 30

flagella (prokaryotes)

Answer 30

~appendages that help cells swim and move around | ~made of protein called flagellin

Question 31

cytoskeleton (prokaryotes)

Answer 31

filaments made up of polymers of monomer subunits that play roles in cell division or in maintaining the shapes of cells

Question 32

Why is compartmentalisation the key to eukaryotic cell function?

Answer 32

each type of organelle has a specific role in the cell

Question 33

ribosomes (eukaryotes)

Answer 33

~translate the nucleotide sequence of a messenger RNA molecule into a polypeptide chain ~consist of one larger and one smaller subunit, each containing one to three ribosomal RNA molecules and smaller protein molecules ~not membrane-enclosed compartments

Question 34

nucleus (eukaryotes)

Answer 34

``` ~contains most of the DNA ~usually the largest organelle ~location of the DNA and the site of DNA replication ~where DNA is transcribed into RNA ~contains a region called the nucleolus ```

Question 35

nucleolus

Answer 35

a region inside the nucleus where ribosomes begin to assemble from RNA and proteins

Question 36

What is the nucleus enclosed by?

Answer 36

two lipid bilayer membranes that together form the nuclear envelope

Question 37

chromosomes

Answer 37

extremely long, thin threads of DNA molecules and proteins

Question 38

chromatin

Answer 38

DNA-protein complexes

Question 39

What is the outer membrane of the nucleus continuous with?

Answer 39

the membrane of the endoplasmic reticulum

Question 40

endomembrane system

Answer 40

~interconnected system of membrane-enclosed compartments | ~includes: nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes

Question 41

vesicles

Answer 41

tiny membrane-surrounded droplets which shuttle substances between the various components of the endomembrane system

Question 42

endoplasmic reticulum

Answer 42

networks of interconnected membranes branching through the cytoplasm, forming tubes and flattened sacs

Question 43

rough endoplasmic reticulum

Answer 43

~has ribosomes attached to the outer surface of the membrane ~protein enters if it contains a specific sequence of amino acids that signals the ribosome to attach to the RER ~inside, proteins are chemically modified to induce 3D functional shape ~transports proteins to other locations in the cell

Question 44

glycoproteins

Answer 44

proteins covalently linked to carbohydrate groups

Question 45

smooth endoplasmic reticulum

Answer 45

~connects to portions of the RER but lacks ribosomes and is more tubular ~chemical modification of small molecules ~glycogen degradation in animal cells ~where lipids and steroids are synthesised ~stores calcium ions, which when released trigger a number of cell responses, including muscle contraction

Question 46

Golgi apparatus

Answer 46

~cisternae and small vesicles ~concentrates, packages, and sorts proteins before they are sent to their cellular or extracellular destinations ~adds some carbohydrates to proteins ~where some polysaccharides for the plant cell wall are synthesised

Question 47

cisternae

Answer 47

~cis region - lies closest to the nucleus or a patch of RER, protein-containing vesicles fuse here ~trans region - lies closest to the cell membrane, vesicles carry their component away from the Golgi apparatus ~medial region - lies in between

Question 48

primary lysosomes

Answer 48

~originate from the Golgi apparatus ~contain hydrolases (digestive enzymes) ~macromolecules (proteins, polysaccharides, nucleic acids, and lipids) are hydrolysed into their monomers

Question 49

phagocytosis

Answer 49

pocket forms in the cell membrane and then deepens and encloses material from outside the cell, becoming a phagosome which breaks free of the cell membrane to move into the cytoplasm

Question 50

phagosome

Answer 50

a small vesicle containing macromolecules, formed by phagocytosis, which can fuse with a primary lysosome to form a secondary lysosome

Question 51

secondary lysosome

Answer 51

where hydrolysis occurs, later fuses with the cell membrane to release undigested contents to the environment

Question 52

phagocytes

Answer 52

specialised cells whose major role is to take in and break down materials

Question 53

autophagy

Answer 53

the programmed destruction of cell components

Question 54

mitochondria

Answer 54

~primary function is to harvest the chemical energy of energy-rich molecules in a form the cell can use, namely ATP ~contains some DNA ~can divide independently of the central nucleus ~outer membrane - large pores which most substances can pass through ~inner membrane - extensively folded into cristae ~contains enzymes for energy metabolism, as well as DNA and ribosomes for the synthesis of some mitochondrial proteins

Question 55

mitochondrial matrix

Answer 55

fluid-filled region inside the inner membrane

Question 56

ATP

Answer 56

adenosine triphosphate, an energy rich nucleotide

Question 57

plastids

Answer 57

present in the cells of plants and algae and can divide autonomously

Question 58

chloroplast

Answer 58

~contains chlorophyll | ~site of photosynthesis

Question 59

thylakoids

Answer 59

~internal membranes of the chloroplast that look like stacks of flat, hollow disks ~here, light is converted into chemical energy

Question 60

grana

Answer 60

stacks of thylakoids

Question 61

peroxisomes

Answer 61

accumulate toxic peroxides and break them down safely without mixing with other components of the cell

Question 62

glyoxysomes

Answer 62

~found only in plants | ~converts stored lipids into carbohydrates for transport to growing cells

Question 63

vacuoles

Answer 63

~storage for toxic by-products and waste products ~structure, dictates turgor pressure based on osmosis ~contains some pigments which help in attracting animals for pollination and seed dispersal ~contain enzymes for catabolism that hydrolyse stored seed proteins into monomers

Question 64

roles of the cytoskeleton

Answer 64

~supports the cell and maintains its shape ~holds cell organelles in position ~moves organelles and other particles around within the cell ~involved with cytoplasmic streaming ~interacts with extracellular structures

Question 65

cytoplasmic streaming

Answer 65

movements of the cytoplasm

Question 66

What are the components of the eukaryotic cytoskeleton?

Answer 66

~microfilaments (smallest diameter) ~intermediate filaments ~microtubules (largest diameter)

Question 67

microfilaments

Answer 67

~help entire cell or cell parts to move ~determine and stabilise cell shape ~made from actin monomers ~dynamic instability

Question 68

actin

Answer 68

monomers that attach to the filament at one end (plus end) and detach at the other (minus end) to assemble microfilaments

Question 69

motor protein

Answer 69

any protein that causes movement within a cell

Question 70

pseudopodia

Answer 70

cellular extensions formed by microfilaments that enable some cells to move

Question 71

intermediate filaments

Answer 71

~more permanent and do not show dynamic instability ~anchor cell structures in place ~resist tension

Question 72

microtubules

Answer 72

~form a rigid internal skeleton for some cells or cell regions ~act as a framework along which motor proteins can move structures within the cell ~dynamic instability

Question 73

tubulin

Answer 73

the protein which microtubules are assembled from

Question 74

cilia

Answer 74

move stiffly either to propel a cell or to move fluid over a stationary cell

Question 75

flagella

Answer 75

occur either singly or in pairs, and can push or pull the cell through its aqueous environment

Question 76

"9+2" array of microtubules

Answer 76

9 fused pairs of microtubules (doublets) form an outer cylinder, and one pair of unfused microtubules runs up the centre

Question 77

dynein molecules

Answer 77

a motor protein, which can change its three dimensional shape, that binds between two neighbouring microtubule doublets

Question 78

kinesin

Answer 78

carry protein-laden vesicles or other organelles from one part of the cell to another by "walking" it along a microtubule

Question 79

Dynein moves attached organelles towards which end of the microtubules?

Answer 79

minus end

Question 80

Kinesin moves attached organelles towards which end of the microtubules?

Answer 80

plus end

Question 81

What are the "extracellular" molecules made from?

Answer 81

~fibrous macromolecule | ~gel-like medium in which the fibres are embedded

Question 82

What are the roles of the cell wall?

Answer 82

~provides support for the cell and limits the volume of a mature cell by remaining rigid ~acts as a barrier to infection by fungi and other organisms that can cause plant diseases ~contributes to plant form by controlling the direction of cell expansion during growth and development

Question 83

plasmodesmata

Answer 83

cell membrane-lined channels connecting the cytoplasms of adjacent plant cells

Question 84

extracellular matrix

Answer 84

~hold cells together in tissues ~contribute to physical properties of tissues ~filter materials passing between different tissues ~orient cell movements during embryonic development and tissue repair

Question 85

What connects the cell membrane to the extracellular matrix?

Answer 85

proteins (ex: integrin) that bind to the interior of the cell and to collagen in the extracellular matrix

Question 86

cell junction

Answer 86

specialised structures protruding from adjacent cells to "glue" them together

Question 87

tight junctions

Answer 87

prevent substances from moving through spaces between cells

Question 88

desmoosmes

Answer 88

hold adjacent cells together with stable protein connections, but materials can still move around in the extracellular matrix

Question 89

gap junctions

Answer 89

channels that run between membrane pores in adjacent cells, allowing substances to pass between cells