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BLG 143 Chapter 1 > Chapter 3 > Flashcards

Chapter 3 Flashcards

1
Q

According to morphology, the two broad groupings of life are

A
  1. Prokaryotes, which lack a membrane-bound nucleus
  2. Eukaryotes, which have such a nucleus
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2
Q

According to phylogeny, or evolutionary history,
there are three domains:

A
  1. Bacteria (prokaryotic)
  2. Archaea (prokaryotic)
  3. Eukarya – eukaryotic
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3
Q

Prokaryotes:

A

– Contain a single, circular
chromosome, tightly coiled
to fit inside the cell
 Located in a region called
the nucleoid
– They also may contain
small, circular DNA
molecules called plasmids

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4
Q

Although there is wide variation between bacterial and archaeal cells, all prokaryotes contain

A

Plasma membrane, chromosome, and protein-synthesizing ribosomes

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5
Q

Prokaryotes have ribosomes, which are

A

– Macromolecular machines
– Consist of RNA molecules and protein
– Used for protein synthesis

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6
Q

Many prokaryotes have internal photosynthetic membranes, they are

A
  • Develop from folds of the plasma membrane
  • The green stripes in this photosynthetic bacterium are membranes that contain the pigments and enzymes required for photosynthesis. This photo has been colourized to enhance the membranes
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7
Q

Some bacteria have membrane-bound
compartments called

A

Organnelles

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8
Q

Organnelles perform specialized tasks including

A

– Store calcium ions
– Hold magnetite crystals to serve as a compass
– Organize enzymes for building organic compounds

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9
Q

Bacteria and archaea contain protein fibres that

A

perform a variety of roles including forming the basis of the cytoskeleton

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10
Q

The cytoskeleton

A

– Assists in cell division
– Maintains cell shape
- E.g. FtsZ and MreB – participates in Z-ring formation

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11
Q

The cell wall forms a protective

A

exoskeleton

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12
Q

Most prokaryotes have a cell wall which

A

– Composed of a tough, fibrous layer
– Surrounds the plasma membrane

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13
Q

Many species have an additional layer outside the cell wall composed of

A

glycolipids

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14
Q

Many prokaryotes, such as E.Coli have
structures that grow from
their

A

plasma membrane, such as flagella and fimbriae

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15
Q

What are flagella

A

long filaments that rotate to propel the cell

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16
Q

The needlelike projections that promote attachment to other cells or
surfaces

A

Fimbriae

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17
Q

The close up view of a prokaryotic cell
is created by

A

This painting is David Goodsell’s representation of a cross-section through part of a bacterial cell
It is based on electron micrographs of bacterial cells and is drawn to scale.
David Goodsell is a professor at the Scripps, Research Institute in Canada, but a google images search will also show that he is an amazing artist

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18
Q

Eukaryotes range in size from

A

microscopic algae
to 100-metre-tall redwood trees
– Protists, fungi, plants, and animals are eukaryotes
– May be multicellular or unicellular

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19
Q

Most eukaryotic cells are larger than most

A

prokaryotic cells

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20
Q

Eukaryotic cells have a large

A

surface-to-volume ratio
– Difficult for molecules to diffuse across the entire cell
– The fluid portion, the cytosol, has a small volume

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20
Q

Eukaryotic cells have a large

A

surface-to-volume ratio
– Difficult for molecules to diffuse across the entire cell
– The fluid portion, the cytosol, has a small volume

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21
Q

Organelles break up the large cell volume into smaller membrane-bound organelles
This compartmentalization offers two advantages:

A
  1. Separation of incompatible chemical reactions
  2. Increasing the efficiency of chemical reactions
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22
Q

Three key differences between eukaryotic and prokaryotic cells

A
  1. Eukaryotic cells are generally much larger
  2. Prokaryotic chromosomes are in a nucleoid region;
    eukaryotic chromosomes are enclosed in a nucleus
  3. Eukaryotic cytoplasm is compartmentalized into a
    larger number of distinct organelles
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23
Q

The nucleus stores and transmits

A

Information. The genetic, or hereditary information is encoded in DNA, which is a component of the chromosomes inside the nucleus

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24
Q

The nucleus

A
  • The nucleus is large and highly organized . It is surrounded by a double-membrane nuclear envelope.
  • Studded with pore-like openings
  • The inside surface is linked to the nuclear lamina (Lattice-like sheet of fibrous proteins)
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25
Q

The nucleus has a distinct region called the nucleolus, where

A

Ribosomal RNA is synthesized
Ribosome subunits are assembled

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26
Q

Ribosomes are the site of

A

Protein synthesis. Eukaryotic ribosomes are larger than bacterial and archaeal ribosomes but similar in overall structure and function

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27
Q

Ribosomes are complex molecular machines that

A

Manufacture proteins

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28
Q

Ribosomes are not considered organelles because they

A

Lack a membrane

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29
Q

Some ribosomes are free in the cytosol, which

A

Manufacture proteins that remain in the cytosol or are imported to other organelles (e.g., nucleus)

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30
Q

Some ribosomes are attached to the endoplasmic reticulum, which

A

Manufacture proteins with other fates

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31
Q

The Endoplasmic Reticulum Is a
Site of

A

Synthesis, processing, and storage. The ER is continuous with the nuclear envelope and possesses two distinct regions: on the left, the rough ER is a system of membrane-bound sacs and tubules with ribosomes attached; on the right, the smooth ER is a system of membrane-bound sacs and tubules that lacks ribosomes

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32
Q

The endoplasmic reticulum is an organelle that is an extension of the

A

nuclear envelope

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33
Q

Two types of ER are

A

rough and smooth

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34
Q

Rough endoplasmic reticulum (rough ER, RER):

A
  • Is studded with ribosomes
  • Synthesizes proteins that will be:
    shipped to another organelle, inserted into the plasma membrane, secreted to the cell exterior
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35
Q

As proteins are manufactured on the RER, they move to the

A

lumen (inside of any sac-like structure)
In the RER lumen, proteins are folded and processed

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36
Q

Proteins made on the RER may

A
  • Carry messages to other cells
  • Act as membrane transporters or pumps
  • Catalyze reactions
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37
Q

Smooth endoplasmic reticulum (smooth ER,
SER) lacks

A

Ribosomes

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38
Q

Smooth endoplasmic reticulum Contains enzymes that catalyze reactions involving
lipids, that may

A

 Synthesize lipids needed by the organism
 Break down lipids and other molecules that are
poisonous

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39
Q

Which type of ER is a reservoir for Ca2+ ions

A

Smooth ER

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40
Q

The Golgi Apparatus Is a Site of

A

Protein Processing, Sorting, and shipping

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41
Q

The Golgi apparatus is formed by

A

a series of stacked, flat, membranous sacs called cisternae

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42
Q

The golgi apparatus has a distict

A

polarity, or sidedness
 The cis (“on this side”) surface
is closest to the nucleus
 The trans (“across”) surface is
oriented toward the plasma
membrane

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43
Q

The functions of the golgi apparatus are

A

– Processes, sorts, and ships proteins synthesized in the rough ER
– cis side of a Golgi apparatus receives products from the rough ER
– trans side ships them out to other organelles or the cell surface
– Membranous vesicles carry materials to and from the organelle

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44
Q

Lysosomes are

A

Recycling Centres found only in
animal cells

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45
Q

The function of lysosomes is

A

Digest macromolecules and export monomers to the cytosol

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46
Q

Enzymes are

A

acid hydrolases
– Work best at pH 5.0
– Proton pumps in
membrane maintain low
internal pH

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47
Q

Collectively, lysosomes, Golgi apparatus, and ER make up the

A

endomembrane system

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48
Q

The function of the endomembrane system is

A
  • Produces, processes, and transports proteins and lipids
    – For example, acid hydrolases are
     Synthesized in the ER
     Processed in the Golgi apparatus
     Shipped to lysosomes
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49
Q

Vacuoles Are Generally

A

Storage Centres in Plant and Fungal Cells. Vary in size and function. Some contain digestive enzymes and serve as recycling centers; most are large storage containers

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50
Q

Vacuoles are large membrane structures that

A
  • Some specialized for digestion
    – Most used to store water and ions to
    help the cell maintain its normal
    volume
    – In seeds, they are filled with proteins
    – In flower petals or fruits, they contain
    pigments
    – May contain noxious compounds to
    protect leaves and stems from being
    eaten
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51
Q

Peroxisomes buds from

A

ER

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52
Q

Peroxisomes are

A

– Centre of redox reactions
– Liver cell peroxisomes contain
enzymes that oxidize ethanol

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53
Q

Specialized plant peroxisomes oxidize
fats to form an energy-storage
compound, they are

A

glyoxysomes

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54
Q

Oxidation often produces

A

hydrogen peroxide
– In peroxisomes, the enzyme
catalase “detoxifies

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55
Q

Mitochondria supply

A

ATP to cells

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56
Q

Mitochondria have two membranes

A

 The inner one is folded into a
series of sac-like cristae
 The solution inside the inner
membrane is the mitochondrial matrix

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57
Q

Mitochondria have their own

A

mitochondrial
DNA (mtDNA)

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58
Q

Mitochondria manufacture their own

A

ribosomes

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59
Q

Most plant and algal cells have centres where photosynthesis
takes place called

A

chloroplasts

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60
Q

Chloroplasts Are

A

Sugar- Manufacturing Centres in Plants and Algae

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61
Q

chloroplasts have how many membranes

A

Have three membranes
 Innermost membrane contains
flattened sacs called
thylakoids, arranged in stacks
called grana

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62
Q

Surrounding the thylakoids is the

A

stroma

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63
Q

Chloroplasts contain their own

A

DNA and manufacture their own
ribosomes

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64
Q

Chloroplasts and mitochondria may once have been

A

free-living bacteria

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65
Q

Endosymbiosis theory states

A

Bacteria were engulfed
and a mutually beneficial relationship evolved

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66
Q

Evidence for endosymbiosis is

A

– Mitochondria and chloroplasts contain their own DNA
– Synthesize their own small ribosomes
– Grow and divide independently of cell division

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67
Q

The cytoskeleton is composed of protein fibres and is responsible for

A

– Gives cells shape and structural stability
– Aids cell movement
– Transports materials within the cell
– Organizes the organelles and other cellular structures
into a cohesive whole

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68
Q

Fungi, algae, and plants have a stiff outer

A

Cell wall which gives structural support to the cell. Rods or fibres of a carbohydrate run through a stiff
matrix made of other polysaccharides and proteins

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69
Q

Structure of each cell component
correlates with its

A

function
– Size and number of different types of
organelles
– Correlate with cell’s specialized function

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70
Q

Cells are dynamic living things which

A

– Have interacting parts
– Contain constantly moving molecules

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71
Q

Your body’s cells use, and synthesize,
approximately how many ATP molecules per second

A

10 million

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72
Q

Cellular enzymes can catalyze more than how many reactions per second

A

25,000

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73
Q

Each membrane phospholipid can travel the breadth of its organelle or cell in under a

A

minute

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74
Q

The hundreds of trillions of mitochondria inside you
are replaced about every

A

10 days, for as long as
you live.

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75
Q

The nuclear envelope is perforated with openings called

A

nuclear pore complexes

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76
Q

the function os nuclear envelope is

A

– Connects inside of nucleus with the cytosol
– Consists of about 30 different proteins

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77
Q

RNA and ribosomes are synthesized in the

A

nucleus and exported to the cytoplasm

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78
Q

binds proteins to form ribosomes

A

Ribosomal RNA

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79
Q

carries information to synthesize
proteins

A

Messenger RNA (mRNA)

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80
Q

Proteins needed in the nucleus are made in the

A

cytoplasm and imported into the nucleus (in eukaryotes)
– Proteins for copying DNA or synthesizing RNA
– Proteins for ribosomes

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81
Q

Nucleotides for building DNA and RNA also enter

A

Nuclear envelope

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82
Q

Most of the proteins found inside organelles

A

– Are actively imported from the cytosol
– Contain special signal sequences that target them to
the appropriate organelles

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83
Q

The endomembrane system functions by

A

– Proteins made in the RER
– Move to the Golgi apparatus for processing
– Travel to the correct destination

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84
Q

The secretory pathway hypothesis

A

This hypothesis proposes that proteins intended for secretion from the cell are synthesized and processed in a highly prescribed series of steps
Note that proteins are packaged into vesicles when they move from the rough ER to the Golgi and from the Golgi to the cell surface

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85
Q

A pulse-chase experiment is used to

A

track protein movement within a cell

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86
Q

describe the model of the secret pathway hypothesis

A
  1. Protein enters the ER while being synthesized by the ribosome and is processed; one or more carbohydrate groups are often added (red dots)
  2. Protein exits ER inside a vesicle and travels to the cis face of Golgi apparatus
  3. Protein enters the Golgi apparatus and is processed
  4. Protein exits the Golgi apparatus in a vesicle and moves to the plasma membrane
  5. Protein is secreted from cells
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87
Q

The signal hypothesis

A
  • explains how proteins destined for secretion enter the endomembrane system
  • All proteins start to be synthesized on free ribosomes
  • Proteins bound for the endomembrane system have a zip code
  • It directs the growing polypeptide to the RER
  • This zip code is a 20-amino-acid-long ER signal sequence
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88
Q

According to the signal hypothesis, proteins destined for secretion contain

A

a short stretch of amino acids that interact with a signal recognition particle (SRP) in the cytosol. This interaction directs the synthesis of the remaining proteins into the rough ER lumen

89
Q

describe the process of signal hypothesis

A
  1. ER signal sequence is synthesized by ribosome
  2. ER signal sequence binds to signal recognition particle (SRP) and halts synthesis
  3. SRP binds to receptors in the ER membrane
  4. SRP is released. Protein synthesis continues. Protein enters ER through the trans colon
  5. ER signal sequence is removed. Protein synthesis then proceeds to the completion
    The ER signal sequence binds to a signal recognition particle (SRP)
    They move to the RER membrane and bind to a receptor there
    The SRP is released, and protein synthesis continues through a channel
    The growing proteins is fed into the RER lumen
    The ER signal sequence is removed
90
Q

In the RER lumen, proteins are

A

folded

91
Q

Enzymes add carbohydrate side chains in a process called

A

glycosylation
– Carbohydrates serve as indicator for shipment
– Resulting glycoprotein is ready to be shipped to next
destination

92
Q

Proteins are transported in vesicles that

A

– Bud off from the ER
– Move away
– Fuse with the membrane on the cis face of the Golgi
apparatus
– Dump their cargo inside

93
Q

How do proteins reach their destinations?

A
  • Each protein that comes out of the Golgi apparatus has a molecular tag
    that places it in a particular type of transport vesicle
  • Each type of transport vesicle also has a tag that allows it to be transported to the correct destination
94
Q

Proteins are secreted out of a cell by

A

exocytosis

95
Q

Describe the process of protein sorting and vehicle transport in the golgi apparatus

A
  1. In the endomembrane system, proteins bound for different destinations carry distinct tags that serve as molecular postal codes
  2. Proteins are sorted in the Golgi apparatus when they bind to different receptors
  3. Transport vesicles bud off the trans face of the Golgi apparatus and travel to their destinations
  4. Cytosolic and membrane proteins cause transport vesicles to attach and fuse at destinations
  5. Vesicles deliver content
96
Q

Large molecules must be digested by lysosomes before

A

their monomers can be used by the cell

97
Q

Materials are brought into the cell by

A

pinching off the plasma membrane in a process called endocytosis

98
Q

The two types of endocytosis are:

A
  1. Receptor-mediated endocytosis
  2. Phagocytosis
99
Q

How many pathways exist to recycle material in the lysosome?

A

Three: receptor-mediated endocytosis, phagocytosis, and autophagy

100
Q

Receptor-mediated endocytosis and phagocytosis involve

A

bringing in material from the outside and surrounding it with a lipid bilayer from the plasma membrane

101
Q

Endosomes mature into lysosomes or, like phagosomes, will

A

fuse with existing lysosomes

102
Q

In autophagy, material within the cytoplasm is

A

encapsulated with an internal membrane before fusing with the lysosome

103
Q

what is receptor-mediated endocytosis

A

Receptor-mediated endocytosis uses receptors to bind to macromolecules outside the cell. The plasma membrane pinches in to form a vesicle that delivers cargo to early endosome
The early endosome is acidified and matures into the late endosome, and eventually, a lysosome

104
Q

What is phagocytosis?

A

Phagocytosis brings smaller cells or food particles inside the cell, forming a phagosome
A phagosome is delivered to the lysosome, which fuses with the phagosome and digests its contents

105
Q

What is autophagy

A

Autophagy encloses a damaged organelle within a membrane, forming an autophagosome that is delivered to a lysosome and digested
Lysosome releases small molecules from digested materials in the cytosol

106
Q

The cytoskeleton is

A

– Is a dense and complex network of fibres
– Helps maintain cell shape by providing structural
support
– Is not a static structure like scaffolding used at
construction sites

107
Q

the fibrous proteins of the cytoskeleton move and change to

A

– Alter the cell’s shape
– Shift its contents
– Even move the cell itself

108
Q

The three types of cytoskeletal elements are:

A
  1. Actin filaments (microfilaments)
  2. Intermediate filaments
  3. Microtubules
109
Q

the cytoskeletal filaments are distinguished by

A

their size, structure, and type of protein subunit

110
Q

describe the structure of actin filaments

A
  • Actin filaments, or microfilaments, are the smallest cytoskeletal elements
  • Formed by polymerization of individual actin molecules into long strands
  • Two strands coil around each other
  • Grouped together into long bindles or dense networks
  • Usually found just inside the plasma membrane
111
Q

describe the function of actin filaments

A
  • Maintain cell shape by resisting tension (pull)
  • Move cells via muscle contraction or cell crawling
  • Divide animal cells in two
  • Move organelles and cytoplasm in plants, fungi, and animals
    Help define the cell’s shape
  • Cell crawling is caused by actin filaments growing in one direction, moving the cell
112
Q

Actin and motor protein myosin work together to perform which functions

A
  • Uses ATP to change shape and do work: muscle contraction, cytoknesis and cytoplasmic streaming
113
Q

What is cytoknesis

A

dividing cytoplasm during cell division

114
Q

What is cytoplasmic streaming

A

flow of cytoplasm

115
Q

describe how actin and myosin collaborate

A
  • Actin and myosin interact to cause movement
  • When a myosin “head” attaches to actin and moves, the actin filament slides
  • Actin-myosin interactions draw the membrane in, divide a cell in two
  • Cytoplasmic streaming in plants- actin-myosin interactions move cytoplasm around a cell
  • ATP hydrolysis in the head region of myosin causes the protein to attach to actin and change shape. The movement slides the myosin towards the plus head of actin
  • Actin-myosin interactions can divide cells and move organelles and cytoplasm
116
Q

Describe the structure of intermediate filaments

A
  • Are defined by size rather than composition
  • Many types exist, each consisting of a different protein
  • About 20 types of keratin- found in nails and hair
117
Q

Describe the function of intermediate filaments

A
  • Provide structural support for the cell
  • Are not involved in the movement
  • Maintain cell shape by resisting tension (pull)
  • Acnchor nucleus and some other organelles
118
Q

Describe the structure of microtubules

A
  • Microtubules are the largest cytoskeletal
    elements
    – Large, hollow tubes made of tubulin dimers
    – Have two polypeptides, called α-tubulin and β-tubulin
    – Have polarity
    – Are dynamic
    – Usually grow at their plus ends
119
Q

describe the function of microtubules

A
  • Maintain cell shape by resisting compression (push)
  • Move cells via flagella or cilia
    Move chromosomes during cell division
  • Assist formation of cell plate during plant cell division
  • Provide tracks for intracellular transport
120
Q

microtubules originate from

A

The microtubule organizing center
Plus ends grow outwards
Radiating throughout the cell

121
Q

In animal cells, the microtubule organizing centre is called

A

The centrosome
It contains two bundles of microtubules called centrioles

122
Q

What is the structure and function of centrosome in animal cells

A
  • Centrosomes are a type of microtubule-organizing centre
  • Animal cells typically have a single centrosome at their centres
  • The minus ends of the microtubules are attached to the surface of the centrosome while the plus ends extend outwards and can reach the inner surface of the plasma membrane
123
Q

Vesicle transport requires a motor protein called

A

kinesin

124
Q

What is the function of kinesin

A

– Uses ATP to do mechanical work
– The head region binds to a microtubule
– The tail region binds to a transport vesicle

125
Q

how does kinesin interact with the microtubule

A
  • Kinesin “walks” along a microtubule
    – Through a series of conformational changes
    – As it hydrolyzes ATP
  • The two head segments act like feet that alternately attach, pivot, and release in response to the gain or loss of a phosphate group from ATP
126
Q

How many distinct regions does kinesin have

A

3

127
Q

Which elements of the cell work to move the entire cell

A

Cilia and Flagella

128
Q

long, hair-like projections from the
cell surface that move cells

A

Flagella

129
Q

Prokaryotic flagella

A

– Are helical rods made of a protein called flagellin
– Move the cell by rotating the rod like a ship’s propeller
– Are not surrounded by the plasma membrane

130
Q

Eukaryotic flagella

A

– Consist of several microtubules
– Move the cell by undulating—they whip back and forth
– Are surrounded by the plasma membrane
– Probably evolved independently from prokaryotic
flagella

131
Q

closely related to eukaryotic flagella

A

Cilia
– Short, hair-like projections
– Cells generally have just one or two flagella
– Some cells have many cilia

132
Q

Cilia and Flagella Differ in

A

Length and Number
Cilia range in length from 1 to 10 um, while flagella are typically longer and can exceed 1mm.
Cells with flagella typically possess only 1 to 4 flagella
Cilia tend to occur in larger numbers, and certain ciliated cells have up to 14,000 cilia

133
Q

The amount of chemical energy in a covalent bond is based on

A

– Position of shared electrons
– Distance from positive charges in nuclei

134
Q

The potential energy of a molecule depends on the configuration and position of

A

its shared
electrons

135
Q

Weaker bonds with equally shared electrons have

A

high
potential energy

136
Q

Stronger bonds with unequally shared electrons have

A

low potential energy

137
Q

Equal sharing (nonpolar) have longest, weakest bonds and

A

high potential energy

138
Q

Unequal sharing (polar) have shortest, strongest bonds and

A

lowest potential energy

139
Q

Gibbs free energy (G) determines

A

whether a reaction is spontaneous or requires added energy to proceed

140
Q

Standard free-energy change equation is used to

A

Calculate the change in G (ΔG) during the reaction:
ΔG = ΔH –TΔS
– ΔH = change in enthalpy
– ΔS = change in entropy
– T = temperature in degrees Kelvin

141
Q

Enthalpy (H) includes

A

– The potential energy of the molecule (heat content)
– Effect of the molecule on surrounding pressure and
volume

142
Q

Changes in enthalpy (ΔH) are primarily based on

A

the difference in potential energy

143
Q

Exothermic reactions

A

– Release heat energy
– ΔH < 0
– Products have less potential energy than reactants

144
Q

Endothermic reactions

A

– Heat energy is taken up
– ΔH > 0
– Products have higher potential energy than reactants

145
Q

Entropy (S) is

A

the amount of disorder

146
Q

When the products of a chemical reaction become
less ordered than the reactant molecules

A

– Entropy increases
– ΔS > 0
– Spontaneous reactions

147
Q

Second law of thermodynamics states that

A

total entropy always increases in a system

148
Q

ΔG < 0 =

A

a spontaneous reaction
– These reactions are exergonic

149
Q

ΔG > 0 =

A

a nonspontaneous reaction that requires
energy input to occur
– These reactions are endergonic

150
Q

ΔG = 0

A

a reaction that is at equilibrium

151
Q

For most reactions to proceed

A

– One or more chemical bonds have to break
– Others have to form

152
Q

Substances must collide in a specific orientation that brings the electrons involved

A

near each other

153
Q

Higher concentrations and higher temperature increase the number of

A

Collisions

154
Q

Higher concentrations and higher temperature therefore increase

A

reaction rate

155
Q

Energetic Coupling Allows Endergonic Reactions to Proceed Using the

A

Free Energy Released from Exergonic
Reactions

156
Q

Reduction–oxidation reactions (redox
reactions) are

A

-Are chemical reactions that involve electron transfer
- Always occur together
- Represent energetic coupling of two half-reactions

157
Q

Oxidation is

A

loss of an electron(s)

158
Q

reduction is

A

gain of an electron(s)

159
Q

What type of reaction is oxidation

A

exergonic  decreased potential energy

160
Q

What type of reaction is reduction

A

endergonic  increased potential energy of the reduced molecule

161
Q

Redox Reactions Transfer Energy via

A

Electrons

162
Q

During a redox reaction, electrons may be gained or lost in two different ways

A

– Change in the number of electrons in the valence shell of an atom
– electrons are transferred as new covalent bonds that are formed with other atoms

163
Q

Electrons can be transferred from an

A

electron donor to an electron acceptor

164
Q

Most electron acceptors gain

A

potential energy as
they are reduced

165
Q

Reduction often

A

“adds Hs”

166
Q

Oxidation often

A

“removes Hs”

167
Q

Electrons are usually accompanied by a

A

proton (H+)

168
Q

Flavin adenine dinucleotide
(FAD) forms form FADH2 by

A

Accepts two electrons plus two protons. Will later donate these electrons to other electron acceptors. Acts as an electron shuttle

169
Q

Nicotinamide adenine
dinucleotide (NAD+) forms NADH by

A

Accepts two electrons plus one proton. Will later donate these electrons
to other electron acceptors. Acts
as an electron shuttle

170
Q

Adenosine triphosphate (ATP) is

A

is the energy currency for cells
– It provides the fuel for most cellular activities

171
Q

ATP forms bonds between

A
  • three negatively charged phosphate
    groups
    – Negative charges repel each other
    – High-energy bonds store a large amount of potential energy
  • stores a large amount of potential energy
172
Q

ATP Hydrolysis Releases

A

Free Energy
- Hydrolysis of the bond between the two outermost phosphate groups results in formation of ADP and Pi (inorganic phosphate,
H2PO4−)
– In a highly exergonic reaction
 Releases 7.3 kilocalories of energy per mole of ATP

173
Q

Energy released during ATP hydrolysis is transferred to a

A

substrate by phosphorylation

174
Q

Phosphorylation is

A
  • adding a phosphate group
    – Usually causes a change in the protein’s shape
175
Q

Exergonic phosphorylation reactions are coupled to

A

endergonic reactions
In cells, many reactions only occur if one reactant is activated by phosphorylation
The phosphorylated reactant molecule has high enough free energy that the subsequent reaction is exergonic
In this graph, the free energy being tracked on the y-axis represents A,B, and the 35.0kJ/mol that is released when ATP is hydrolyzed
For simplicity, the free energy in ADP and Pi is not shown G represents the change in free energy between the reactants and products for each indicated step

176
Q

Most biological chemical reactions occur fast enough only in the presence of an

A

enzyme

177
Q

Enzymes are protein

A

catalysts

178
Q

Enzymes work by

A

– Bring reactants together in precise orientations
– Make reactions more likely
– Are specific for a single type of reaction

179
Q

Before a reaction can take place, reactants need to

A
  1. Collide in a precise orientation
  2. Have enough kinetic energy to overcome repulsion between electrons that come into contact as a bond forms
180
Q

Enzymes bring

A

substrates together

181
Q

Substrates bind to the enzyme’s

A
  • active site
    – Enzymes help them collide in a precise orientation
    – Bonds break and form to generate products
182
Q

Many enzymes undergo a

A

conformational change
– When the substrates are bound to the active site
– This change is called an induced fit

183
Q

Substrates bind via

A

hydrogen bonding or other interactions with amino acid residues in the active
site

184
Q

An unstable intermediate condition called the

A

transition state is formed

185
Q

Activation energy (Ea)

A

is required to strain substrates’ bonds so they can reach the transition
state

186
Q

Interactions between the enzyme and the substrate

A

– Interactions between substrates and amino acid
residues of the enzyme
– Stabilize the transition state
– Lower the activation energy required for the reaction to
proceed

187
Q

are enzymes consumed during the reactions?

A

No, enzyme is unchanged

188
Q

Enzyme catalysis has three steps

A
  1. Initiation—substrates are precisely oriented as they bind to the active site
  2. Transition state facilitation interactions
    between the substrate and active site R-groups
    lower the activation energy
  3. Termination—reaction products are released from the enzyme
189
Q

What Limits the Rate of Catalysis?

A

Saturation of
enzyme active
sites

190
Q

The speed of an enzyme-catalyzed reaction

A
  1. Increases linearly at low substrate concentrations
  2. Slows as substrate concentration increases
  3. Reaches maximum speed at high substrate concentrations
191
Q

Temperature affects

A

– Folding
– Movement of the enzyme
– Kinetic energy of substrates

192
Q

pH affects

A

– Enzyme’s structure and function by affecting:
– The charge on carboxyl and amino groups in residue side chains
– The active site’s ability to participate in reactions that involve the transfer of protons or electrons

193
Q

Enzymes Have an Optima

A

Temperature and pH

194
Q

An Enzyme’s Activity Is Precisely

A

regulated
* Regulation via noncovalent interactions
– Does not permanently affect the enzyme structure
– Is referred to as “reversible”

195
Q

Competitive inhibition occurs when

A

a molecule competes with
the substrate for the active site
When the enzyme is in absence of regulation, the substrates cannot bind when a regulatory molecule binds to the enzyme’s active site

196
Q

Allosteric regulation
occurs

A

when a molecule binds at a location other than the active site
– Causes a change in enzyme shape
– Can activate or deactivate the enzyme

197
Q

Regulation may involve

A

covalent modifications
– Changes the enzyme’s primary structure
– Can be reversible or irreversible

198
Q

Irreversible changes often result from

A

cleavage of
peptide bonds

199
Q

Most common reversible modification of enzymes is

A

the addition of phosphate groups
(phosphorylation)
– Causes a change in shape
– May activate or inactivate the enzyme

200
Q

Enzymes Can Work Together in

A

Metabolic Pathways
– A series of reactions
– Each catalyzed by a different enzyme
– To build biological molecules
– Much like an assembly line in a factory

201
Q

An initial substrate A is sequentially modified by enzymes 1–3 to produce product D. The B and C molecules are referred to as

A

intermediates in the pathway
– they serve as both a product and a reactant.
– molecule B is the product of reaction 1 and the reactant
for reaction 2.

202
Q

Distant cells can communicate through

A

signalling
molecules

203
Q

Neurotransmitters may

A

open or close channels in
distant cells

204
Q

Hormones are

A

information-carrying molecules
 Secreted from a cell
 Circulates in the body
 Acts on target cells far from the signalling cell

205
Q

Hormones are usually

A

– Small molecules—peptides, steroids, or even gases
– Typically present in minute concentrations
– Have a large impact on the activity of target cells

206
Q

Hormones function by

A

binding to signal receptor molecules
– Change shape and activity after binding to a hormone
– Only cells with appropriate signal receptors will
respond to a particular signalling molecule

207
Q

Hormones may be

A

soluble or insoluble in lipids
– Lipid-soluble hormones diffuse across the plasma membrane
 Receptors are in the target cells’ cytoplasm

208
Q

Lipid-insoluble hormones and large hormones do not cross the

A

plasma membrane
 Receptors are on the cell’s plasma membrane

209
Q

Lipid-soluble steroid hormones

A

– Bind to receptors inside the cell
– Trigger a change in the cell’s activity directly

210
Q

The hormone–receptor complex

A

– Is transported to the nucleus
– Where it alters gene expression

211
Q

Some Cell–Cell Signalling Molecules Enter the Cell and Bind to

A

Receptors in the Cytosol
Because they are lipids, steroid hormones can diffuse across cell membranes and bind to signal receptors located on the cytosol
The hormone-receptor complex may then be transported to the nucleus, where it changes the activity of genes

212
Q

describe the processing of lipid-soluble signals

A
  1. The arrival of signal: protein carries steroid hormone to the cell surface
  2. Signal entry: hormone diffuses across the plasma membrane into cytosol
  3. Signal reception: hormone binds to the receptor, inducing conformational change
  4. Direct-signal response: hormone-receptor complex binds to DNA, inducing a change in gene expression
213
Q

Hormones that cannot diffuse across the plasma membrane bind to

A

membrane receptors

214
Q

When a signal binds at the cell surface, it

A

– Triggers a complex series of events
– Collectively called signal transduction
– Converts the extracellular hormone signal to an intracellular signal

215
Q

Signal Transduction

A

converts an extracellular signal to an intracellular signal
A lipid-insoluble signaling molecule will not pass through the membrane to direct a cellular response. Instead, the molecule activates a surface receptor that directs a multistep process to generate intracellular signals. One or more of these intracellular signalling molecules may then be transported to the nucleus to change the activity of genes
1. Signal reception
2. Signal transduction from extracellular signal to intracellular signal. Signal is amplified (in most cases)
3. Signal response: for example, specific proteins are activated, inducing a change in gene expression

216
Q

During signal transduction two things occur

A
  1. The signal may be amplified. By having many steps between the receptor and the response, there is an opportunity for a signalling molecule
    to activate several downstream molecules.
  2. The signal may be diversified. A cell that receives a signal may undergo several related changes as a result.
217
Q

G proteins are

A

intracellular peripheral membrane
proteins
– Closely associated with transmembrane signal
receptors

218
Q

When G proteins are activated by a signal receptor

A

– They trigger production of a second messenger
– Small, nonprotein signalling molecule or ion
– Links the receipt of an extracellular signal to the
production of an intracellular signal

219
Q

G proteins are regulated by guanine nucleotides

A

– When a G protein binds to guanosine triphosphate
(GTP), its shape is altered and it is activated
– When a phosphate group is removed from the bound GTP to form GDP, the G protein is inactivated

220
Q

G-protein-coupled signalling involves three steps

A
  1. A signalling molecule binds to its membrane receptor
  2. The associated G protein exchanges GDP for GTP
     Splits into two parts
  3. The active G protein subunit activates a nearby membrane enzyme
     Catalyzes the production of a second messenger

BLG 143 Chapter 1 (5 decks)

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