Chapter 3- The cell

Question 1

Spontaneous generation

Answer 1

The idea that life can arise from nonliving matter. Aristotle stated that living organisms could come from nonliving material if the material contained “vital heat” (pneuma). He used the fact that animals could appear in new environments that they hadn’t been before, like fish in a puddle of water. The theory persisted until the 17th century

Question 2

Redi’s research on spontaneous generation

Answer 2

Refuted that idea that maggots spontaneously generate on meat left in the open air. He left meat in open jars and left more meat in covered jars. Maggots only appeared in the uncovered jars that were exposed to air and could be accessed by flies

Question 3

Spallanzani’s research on spontaneous generation

Answer 3

Preformed hundreds of experiments using heated broth. Contrary to Needham’s results, heated but sealed flasks were clear, and did develop microorganisms unless they were exposed to air. This suggests that microbes could be introduced from the air. Needham argued that spontaneous generation came from a life force that had been destroyed by the boiling in the experiment.

Question 4

How did Pasteur’s research disprove spontaneous generation?

Answer 4

He created swan neck flasks, which had long and twisted necks. He boiled broth in the flasks. The design of these flasks allowed air to be exchanged between the inside and outside of the flasks, but prevented any microorganisms from entering through the air, as they would be trapped in the neck of the flask. The broth in the flasks remained sterile unless the necks were broken- if the necks were broken, the broth would become cloudy. This disproved spontaneous generation, because any “life source” other than microorganisms would still have access to the broth. This was also the basis of germ theory, because Pasteur suggested that if microbes could cause food spoilage, they could also cause disease

Question 5

Matthias Schleiden

Answer 5

A German botanist who observed plant tissues under a microscope and observed that the tissues were composed of cells. Plant cells are easier to visualize because they are separated by thick cell walls.

Question 6

Theodor Schwann

Answer 6

German physiologist who realized the similarities between plant and animal tissues. He had the idea that cells were the fundamental components of both plant and animal tissues

Question 7

How was modern cell theory discovered?

Answer 7

Two Polish scientists Remak and Virchow published research stating that cells derived from other cells as a result of cell division, and that all cells arise from other cells. These are the 2 main tenets of cell theory.

Question 8

Endosymbiotic theory

Answer 8

The idea that mitochondria and chloroplasts arose as a result of prokaryotic cells establishing a symbiotic relationship within a eukaryotic host. Mitochondria and chloroplasts have their own DNA which is closely related bacteria in DNA sequence and chromosome structure. Mitochondrial and chloroplast ribosomes are also similar to bacterial ribosomes in structure rather than being similar to the eukaryotic ribosomes of the host cells. These organelles also reproduce through binary fission, like bacteria, rather than through mitosis, which is how eukaryotic cells reproduce.

Question 9

How did eukaryotes evolve from prokaryotes (3 steps)

Answer 9

1. Infoldings of the plasma membrane of an early cell brought about membrane bound components like the nucleus and the endoplasmic reticulum
2. The ancestral eukaryote consumed aerobic bacteria that evolved into mitochondria
3. The early eukaryote consumed photosynthetic bacteria that evolved into chloroplasts

Question 10

Germ theory of disease

Answer 10

States that diseases may result from microbial infection. Fracastoro was a proponent of this in the 16th century, but it was not widely accepted until the 19th century

Question 11

Semmelweis’s research and the germ theory

Answer 11

An obstetrician observed that pregnant women were more likely to die when examined by doctors and medical students, who frequently performed autopsies and then examined patients without washing their hands. He proposed that physicians were somehow transferring the causative agent of disease. When physicians washed their hands, the mortality rate dropped drastically.

Question 12

Snow’s research and the germ theory

Answer 12

John Snow’s research represented the first epidemiological study. He conducted a study to determine the source of cholera outbreaks and traced it to two water sources that had been contaminated by sewage. Therefore, he determined that cholera bacteria were transmitted via drinking water and that disease could be transmitted through contaminated items.

Question 13

Lister’s research and germ theory

Answer 13

Lister was a British surgeon who attempted to determine the cause of postsurgical infections (50% of surgical patients died from postsurgical infections). Lister promoted handwashing and cleanliness during surgery, and began using a carbolic acid spray as a disinfectant and antiseptic during surgery. These techniques later became standard medical practice

Question 14

Koch’s research and the germ theory

Answer 14

He proposed postulates based on the idea that the cause of a specific disease could be attributed to a specific microbe. Using these postulates, Koch identified the causative pathogens of anthrax, tuberculosis, and cholera. The “one microbe, one disease” concept marked a shift from miasma theory to germ theory

Question 15

Basic fundamental components of the cell (4)

Answer 15

1. Cytoplasm
2. Plasma membrane- contains the cytoplasm
3. One or more chromosomes that contain the genetic blueprints of the cell
4. Ribosomes

Question 16

Cytoplasm

Answer 16

A gel like substance composed of water and dissolved chemicals needed for growth. Contained in the plasma membrane

Question 17

Ribosomes

Answer 17

Organelles used for the production of proteins

Question 18

Two main categories of cells

Answer 18

1. Prokaryotic
2. Eukaryotic

Question 19

Prokaryotic cells

Answer 19

Lack a nucleus surrounded by a nuclear membrane. They usually have a single circular chromosome located in a nucleoid. They are classified within the domains as Archaea and Bacteria

Question 20

Eukaryotic cells

Answer 20

Have a nucleus surrounded by a nuclear membrane that contains multiple rod shaped chromosomes. All plant and animal cells are eukaryotic and eukaryotes are classified in the domain Eukarya.

Question 21

Cell morphology

Answer 21

The shape of the cell. In prokaryotes, there are 6 possible cell morphologies.

Question 22

6 prokaryotic cell shapes

Answer 22

Coccus, bacillus, vibrio, coccobacillus, spirillum, and spirochete

Question 23

Prokaryotic cell arrangements (6)

Answer 23

1. Coccus- single coccus
2. Diplococcus- pair of two cocci
3. Tetrad- grouping of 4 cells arranged in a square
4. Streptococcus- chain of cocci
5. Bacillus- single rod
6. Streptobacillus- chain of rods

Question 24

Cell wall

Answer 24

Found in most prokaryotes and some eukaryotes, it maintains the cell morphology in most prokaryotic cells. It also protects the cell from changes in osmotic pressure

Question 25

Osmotic pressure

Answer 25

Occurs because of differences in the concentration of solutes on each side of the plasma membrane. Water can pass through the semipermeable membrane, but solutes like salts and sugars can’t.

Question 26

Osmosis

Answer 26

Diffusion of water that occurs when solute concentration on each side of the membrane is unequal. Water moves from high to low concentration of solutes until the concentration is equal on both sides.

Question 27

Isotonic medium

Answer 27

The solute concentration inside and outside the cell are equal- there’s no net movement of water

Question 28

Hypertonic medium

Answer 28

The solute concentration outside the cell is higher than the concentration inside the cell. Water diffuses out of the cell into the external environment. Cells become dehydrated and crenate.

Question 29

Hypotonic medium

Answer 29

The solute concentration outside the cell is lower than the concentration inside the cell. Water diffuses into the cell. Cells without a cell wall are prone to lysis in this environment.

Question 30

Tonicity

Answer 30

The degree to which a cell is able to withstand changes in osmotic pressure

Question 31

Plasmolysis

Answer 31

Occurs in cells with a cell wall in place of crenation. The plasma membrane contracts and detaches from the cell wall. There is a decrease in interior volume but the cell wall remains intact, so the cell can maintain its shape for a period of time.

Question 32

Prokaryotic chromosomes

Answer 32

They are usually circular, haploid (unpaired), and not bound by a complex nuclear membrane. In prokaryotes, DNA and DNA associated proteins are concentrated in the nucleoid region of the cell

Question 33

Nucleoid associated proteins (NAPs)

Answer 33

Proteins that interact with prokaryotic DNA and assist in the organization and packaging of the chromosome. They are similar in function to histones in eukaryotic cells

Question 34

Plasmids

Answer 34

Contain extrachromosomal DNA, which is not part of the chromosomes. Plasmids are small, circular, double stranded DNA molecules. Plasmids are most commonly found in bacteria, and they benefit the survival of the organism because they contain genes that code for antibiotic resistance

Question 35

How do ribosomes differ between the 3 domains?

Answer 35

Prokaryotic cells contain 70s ribosomes (a measure of size) while eukaryotic cells contain ribosomes with a size of 80s. Bacterial and archaeal ribosomes are the same size but have different proteins and rRNA molecules

Question 36

Inclusions

Answer 36

Cytoplasmic structures that store excess nutrients in a polymerized form. This keeps osmotic pressure under control. Some structures store glycogen and starches. Found in prokaryotic cells that live in unstable environments

Question 37

Volutin (metachromatic) granules

Answer 37

Inclusions that store polymerized inorganic phosphate that can be used in metabolism and assist in the formation of biofilms

Question 38

Sulfur granules

Answer 38

An inclusion that are found in sulfur bacteria of the genus Thiobacillus. They store elemental sulfur that is used for metabolism

Question 39

Polyhydroxybutyrate (PHB)

Answer 39

A type of inclusion that is surrounded by a phospholipid monolayer embedded with protein

Question 40

Magnetosomes

Answer 40

Inclusions of magnetic iron oxide or iron sulfide surrounded by a lipid layer. This allows for movement by aligning cells with a magnetic field

Question 41

Carboxysome inclusions

Answer 41

Have outer shells made of thousands of protein subunits. They are filled with the Rubisco enzyme and carbonic anhydrase, which are used for carbon metabolism. Prokaryotic cells use these inclusions to compartmentalize the enzymes used for certain chemical reactions

Question 42

Endospores

Answer 42

Structures that protect the bacterial genome in a dormant state when environmental conditions are unfavorable. They allow bacteria to survive without food and water for a period of time, as well as to survive harsh conditions like extreme temperatures and radiation. The bacteria that causes anthrax is a gram positive bacteria capable of forming endospores, which allows it to survive for decades- endospores are difficult to kill

Question 43

Sporulation

Answer 43

The process by which vegetative cells transform into endospores. It can begin when nutrients are depleted or when the environment becomes unstable

Question 44

Steps of sporulation (6)

Answer 44

1. DNA of the cell replicates
2. Membranes form around the DNA to form a septum that separates the DNA from the host cell
3. Forespore forms additional membranes, separating the chromosomes from the cell by a second membrane. This is the core of the endospore.
4. Protective cortex forms around the spore- composed of calcium and dipicolinic acid
5. Protein coat forms around the cortex while the DNA of the host cell disintegrates
6. Spore is released once the mother cell disintegrates

Question 45

Germination

Answer 45

When endospores enter a vegetative state. This occurs when living conditions of the cell improve. After germination, the cell becomes metabolically active and can carry out all of its normal functions.

Question 46

Cell envelope

Answer 46

Structures that enclose the cytoplasm and internal structures of the cell

Question 47

Plasma membrane

Answer 47

All cells have a plasma membrane. It is selectively permeable and its structure is described using the fluid mosaic model. In eukaryotic cells, the membrane is a phospholipid bilayer that is formed with ester linkages and proteins. Phospholipids and proteins can move laterally in the membrane, and they also move between the two layers

Question 48

Fluid mosaic model

Answer 48

The ability of membrane components to move within the membrane. The components (lipids and proteins) of the membrane have a mosaic-like composition

Question 49

How are archaeal membranes different from bacterial and eukaryotic membranes?

Answer 49

Archaeal membrane phospholipids are formed with ether linkages. Also, the phospholipids have branched chains in contrast to the straight chains in bacterial and eukaryotic membranes. Some archaeal membranes are a bilayer, but others have lipid monolayers.

Question 50

Functions of cell surface proteins

Answer 50

Cell to cell communication, and sensing environmental conditions and pathogenic virulence factors.

Question 51

Glycoproteins/glycolipids

Answer 51

The carbohydrates (sugars) associated with the phospholipids or membrane proteins. Glycoprotein and glycolipid complexes extend out from the surface of the cell so that the cell can interact with the environment. The complexes differ between domains, so they can be used to characterize species. Different types of cells are distinguished by the structure and arrangement of glycolipids and glycoproteins. They can also act as cell surface receptors

Question 52

Simple diffusion

Answer 52

Molecules moving from a higher concentration to a lower concentration across the plasma membrane. Small molecules like carbon dioxide can cross the membrane in this way

Question 53

Facilitated diffusion

Answer 53

Cross the membrane from high to low concentration with the help of membrane channels or carrier molecules. This is how charged or large molecules cross the membrane

Question 54

Active transport

Answer 54

When cells cross the membrane moving from low to high concentrations, against their concentration gradients. Uses structures called pumps that require ATP to work

Question 55

Group translocation

Answer 55

As a molecule moves into a cell against its concentration gradient, it is chemically modified so it doesn’t require assistance to be transported. An example is the bacterial phosphotransferase system, which adds phosphate ions to glucose upon entry to the cell.

Question 56

Photosynthetic membrane structures

Answer 56

Some prokaryotic cells, like cyanobacteria, have membrane structures that can perform photosynthesis. Their membrane fold in, and contain photosynthetic pigments like chlorophylls

Question 57

Main function of the cell wall

Answer 57

To protect the cell from harsh conditions in the outside environment

Question 58

Peptidoglycan

Answer 58

The main component of bacterial cell walls. The structure of peptidoglycan looks like a meshwork. Each layer contains long chains of alternating molecules of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM). Peptide bridges connect NAG and NAM in each layer, which gives the layers two dimensional tensile strength. Peptidoglycan is made inside of the cell and is then exported and assembled in layers, giving the cell its shape.

Question 59

How does peptidoglycan structure differ between gram positive and gram negative bacteria?

Answer 59

In gram negative bacteria, there are tetrapeptide chains extending from each NAM unit that are directly cross linked. In gram positive bacteria, the tetrapeptide chains are linked by pentaglycine cross bridges.

Question 60

How is peptidoglycan targeted when fighting infection?

Answer 60

Peptidoglycan is unique to bacteria. Therefore, some antibiotic drugs interfere with peptidoglycan synthesis, which makes the cell wall weaker and makes bacterial cells more susceptible to osmotic pressure. Some cells in the immune system can recognize bacterial pathogens by detecting peptidoglycan in the cell. The cells then engulf and destroy the bacterial cell.

Question 61

Teichoic acids

Answer 61

Gram positive cell walls contain many layers of peptidoglycan. The peptidoglycan layers are embedded with teichoic acids. TAs extend through the peptidoglycan layer and make peptidoglycan more rigid, enhancing its stability. It also allows pathogenic bacteria to bind to proteins on the surface of host cells, allowing them to cause infection. The family Mycobacteriaceae contain mycolic acids in their cell wall

Question 62

How is the structure of gram negative cells different from the structure of gram positive cells?

Answer 62

Gram negative cells have a thinner layer of peptidoglycan and a more complex cell envelope. In the periplasmic space between the cell wall and the plasma membrane, there is a gel like matrix. There is also a second lipid bilayer (the outer membrane) that is external to the peptidoglycan layer. Murein lipoprotein attaches the outer membrane to the peptidoglycan. There is an outer leaflet of the outer membrane that contains lipopolysaccharide (LPS)

Question 63

Lipopolysaccharide (LPS)

Answer 63

Composes the outer leaflet of the outer membrane in gram negative cells. It is an endotoxin in infections, causing fever, hemorrhage, and septic shock. LPS molecules are made of Lipid 1, a core polysaccharide, and an O side chain of sugar-like molecules. The composition of the O side chain varies between different species and strains of bacteria. Parts of the O side chains act as antigens and can be detected with serological or immunological tests to diagnose infection with a specific type of bacteria.

Question 64

How does the archaeal cell wall differ from that of bacteria?

Answer 64

Archaeal cell walls don’t contain peptidoglycan- they contain pseudopeptidoglycan- NAM is replaced with a different subunit. In some archaea, cell walls contain glycoproteins or polysaccharides. A few archaea don’t have any cell walls.

Question 65

Glycocalyx

Answer 65

A sugar coat. The two types are capsules and slime layers. They allow cells to adhere to surfaces, which allows for biofilms to be formed. Biofilms are advantageous to bacterial survival in multiple ways, and are how bacteria typically exist in nature.

Question 66

Capsule

Answer 66

An organized layer located outside of the cell wall and composed of polysaccharides or proteins. A capsule can make bacteria more pathogenic because it makes it difficult for certain white blood cells to engulf and kill the microbe. Capsules are also difficult to stain for microscopy.

Question 67

Slime layer

Answer 67

A less tightly organized layer that is loosely attached to the cell wall and can be easily washed off. These layers are made of polysaccharides, glycoproteins, or glycolipids.

Question 68

How are biofilms advantageous to bacterial survival?

Answer 68

Biofilms hold water like a sponge, preventing them from drying out. They protect the cells from predation and also prevent antibiotics and disinfectants from working.

Question 69

S-layer

Answer 69

A type of cell envelope structure that is composed of structural proteins and glycoproteins. The S-layer is found outside the cell wall in bacteria. In archaea, it acts as a cell wall. In prokaryotic cells, the S-layer seems to help the cell withstand osmotic pressure and interact with the host immune system.

Question 70

Fimbriae

Answer 70

Short, bristle like protein appendages that project from the cell surface. There are hundreds of fimbriae on one cell. They allow cells to attach to surfaces and to other cells, which is important for infection and virulence in pathogens, as well as biofilm formation

Question 71

Pili

Answer 71

Long protein appendages that are less numerous than fimbriae. The F pilus helps bacterial cells to transfer DNA, like when bacteria share genes to gain other traits. Pili can also help the cell to attach to surfaces

Question 72

Flagella

Answer 72

Stiff spiral filaments composed of flagellin protein subunits that extend outward from the cell and spin. They act as propellers in bacteria and help cells to move in aqueous environments. It’s composed of a basal body that is embedded in the membrane and a hook region that connects the basal body to the filaments. Different types of bacteria have different flagella arrangements

Question 73

Monotrichous

Answer 73

A bacteria with one flagellum that is typically located at one end of the cell

Question 74

Amphitrichous

Answer 74

Cells that have a flagellum or tufts of flagella at each end

Question 75

Lophotrichous

Answer 75

Cells that have a tuft of flagella at one end of the cell

Question 76

Peterichous

Answer 76

Flagella that cover the entire surface of a bacterial cell

Question 77

What environmental signals do bacteria respond to?

Answer 77

Light (phototaxis), magnetic fields (magnetotaxis), and chemical gradients (chemotaxis) most commonly

Question 78

How do bacteria purposefully move toward/away from something?

Answer 78

The lengths of runs (rotating in a counterclockwise direction to move forward) is increased and the length of tumbles are decreased. Tumbling helps with orienting the bacteria toward an attractant, but it means that flagella are splayed out while rotating clockwise, which prevents significant forward movement. When no chemical gradient exists, overall movement is more random and the lengths of runs and tumbles are more equal

Question 79

Cytoskeleton

Answer 79

In eukaryotic cells, an internal network that supports transport of intracellular components and helps maintain cell shape. It is made of microfilaments, intermediate filaments, and microtubules. It holds organelles in place, provides a network over which materials can be transported, and provides structural support. Transport vesicle move throughout the cell via the cytoskeletal network

Question 80

Cell morphologies in eukaryotic cells

Answer 80

There are many possible shapes- spherical, oval, cube, cylinder, flat, lenticular, fusiform, crescent, ring, polygonal. Some cells are irregular in shape and some can change shape. The shape is influenced by many factors, including the physical pressure exerted by the environment, the organization of the cytoplasm, and its primary function

Question 81

Nucleus

Answer 81

Having a nucleus is a unique characteristic of eukaryotic cells. The nucleus is bound by a membrane and contains the cell’s genome, which is usually organized in linear chromosomes. This means that the nucleus controls the cell and plays a role in reproduction and heredity. The DNA is highly organized and condensed using histones to fit inside the nucleus

Question 82

Coenocytes

Answer 82

Cells whose nuclei divide, but whose cytoplasm do not

Question 83

Nuclear envelope

Answer 83

Another name for the nuclear membrane. It consists of two lipid bilayers that come into contact with each other. Each membrane has unique proteins on its inner and outer surfaces. The nuclear envelope has protein complexes called nuclear pores, which control the movement of materials into and out of the nucleus

Question 84

Nuclear lamina

Answer 84

A meshwork of intermediate filaments that is found outside the nuclear envelope membranes. It is responsible for determining the shape the nucleus

Question 85

Mitosis

Answer 85

The process of clonal reproduction in eukaryotic cells. This is an asexual process because a single parent creates two identical daughter cells. This is different from binary fission because the cell’s chromosomes are replicated and divided among the daughter cells. The two phases are interphase and the mitotic phase

Question 86

Interphase

Answer 86

The cell is undergoing normal growth processes and DNA is replicated to prepare for cell division. The cell is not dividing at this point. The 3 stages are G1, S, and G2

Question 87

Mitotic phase of mitosis

Answer 87

Duplicated chromosomes are aligned, separated, and move to opposite poles of the cell. The chromosomes are then divided into 2 daughter cells. Consists of karyokinesis and cytokinesis

Question 88

Karyokinesis

Answer 88

The nuclear division part of the mitotic phase of mitosis- consists of prophase, prometaphase, metaphase, anaphase, and telophase. These steps result in the division of the cell nucleus

Question 89

Cytokinesis

Answer 89

The second portion of the mitotic phase. It involves the physical separation of the cytoplasmic components into the two daughter cells

Question 90

Meiosis

Answer 90

Sexual reproduction of microorganisms. It involves 2 separate nuclear divisions and creates 4 genetically distinct gametes. Each gamete contains half the number of chromosomes found in the original cell and forms a diploid cell during fertilization

Question 91

Nucleolus

Answer 91

A region of the nucleus where ribosomal RNA (rRNA) biosynthesis occurs. It’s also the site where ribosome assembly begins. rRNA and proteins form preribosomal complexes in the nucleolus and are transported into the cytoplasm, where ribosomal assembly is completed.

Question 92

80s ribosomes

Answer 92

Contain a small 40s subunit and a large 60s subunit. Ribosomes in eukaryotic cells that are not associated with organelles are 80s. Mitochondria and chloroplasts have 70s ribosomes that are the same size as those found in prokaryotic cells.

Question 93

Free ribosomes vs membrane bound ribosomes

Answer 93

Describe the location of eukaryotic ribosomes in the cell. Free ribosomes are found in the cytoplasm and synthesize water soluble proteins. Membrane bound ribosomes are found attached to the rough ER and make proteins for insertion into the cell membrane or proteins destined for export from the cell

Question 94

How are the differences between eukaryotic and prokaryotic ribosomes clinically relevant?

Answer 94

Certain antibiotics target only eukaryotic ribosomes or only prokaryotic ribosomes. Human cells are eukaryotic, so they won’t be harmed by antibiotics that destroy prokaryotic ribosomes. However, negative side effects can occur because mitochondria contain prokaryotic ribosomes.

Question 95

Endomembrane system

Answer 95

A series of membranous tubules, sacs, and flattened disks that synthesize many cell components and move materials around in the cell. It’s composed of some organelles and the connections between them. This is specific to eukaryotic cells, which need a system to transport materials that can’t be dispersed by diffusion. These cells are large and need extra help to transport things

Question 96

Endoplasmic reticulum

Answer 96

An interconnected array of tubules and cisternae (flattened sacs) with a single lipid bilayer. Composed of the rough endoplasmic reticulum and the smooth endoplasmic reticulum- each section synthesizes different molecules

Question 97

Lumen of the ER

Answer 97

Spaces inside of the cisternae (flattened sacs)

Question 98

Rough endoplasmic reticulum

Answer 98

Studded with ribosomes bound on the cytoplasmic side of the membrane. These ribosomes make proteins for the plasma membrane. Once they are synthesized, the proteins are inserted into the membrane of the RER. Newly synthesized proteins are packaged in transport vesicles, which bud off the RER and bring proteins to the small membrane or the Golgi apparatus.

Question 99

Transport vesicles

Answer 99

Single lipid, bilayer, membranous spheres with hollow interiors that are used to carry molecules

Question 100

Smooth endoplasmic reticulum

Answer 100

Appears smooth because it doesn’t have ribosomes. It synthesizes lipids, is responsible for carbohydrate metabolism, and detoxifies toxic compounds within the cell

Question 101

Golgi apparatus

Answer 101

A series of membranous discs (dictyosomes), that each have a single lipid bilayer and are stacked together. Enzymes in the Golgi apparatus modify lipids and proteins transported from the ER to the Golgi and can add carbohydrate components to them. This produces glycolipids, glycoproteins, or proteoglycans. Glycolipids and glycoproteins can be inserted into the plasma membrane and are used for signal recognition by other cells.

Question 102

How do transport vesicles move through the Golgi apparatus?

Answer 102

Transport vesicles that leave the ER fuse with the Golgi apparatus on its receiving (cis) face. The proteins are modified in the Golgi apparatus. Transport vesicles containing the modified proteins leave the Golgi apparatus on the outgoing (trans) face. The outgoing vesicles will eventually fuse with the plasma membrane or the membrane of other organelles

Question 103

Exocytosis

Answer 103

The process by which secretory vesicles (membranous sacs) release their contents to the cell’s exterior. All cells have constitutive secretory pathways where secretory vesicles continuously transport soluble proteins out of the cell. Some cells have regulated secretion pathways, where substances are only released in response to certain signals and events

Question 104

Lysosomes

Answer 104

Organelles of the endomembrane system that contain digestive enzymes. They can break down food, cellular debris, microorganisms, or immune complexes. The enzymes are contained in the lysosomes so they won’t harm the rest of the cell

Question 105

Peroxisomes

Answer 105

Membrane bound organelles that are not part of the endomembrane system. They form independently in the cytoplasm from when peroxin proteins are synthesized by free ribosomes, and these proteins are then incorporated into existing peroxisomes. Peroxisomes produce hydrogen peroxide to break down molecules like uric acid, amino acids, and fatty acids. They also contain catalase (an enzyme) which degrades hydrogen peroxide. They also play a role in lipid synthesis. The peroxisomes of certain organisms are specialized to meet their functional needs

Question 106

Microfilaments

Answer 106

Composed of 2 intertwined strands of actin. Each one is composed of actin monomers that form filamentous cables. Actin filaments work together with motor proteins like myosin to allow for muscle contraction. In ameboid organisms, actin can exist in a stiff and polymerized gel form and a fluid unpolymerized soluble form. Actin is used for movement in these organisms

Question 107

Pseudopodia

Answer 107

Temporary extensions of the cytoplasmic membrane. They are produced by the forward flow of soluble actin filaments into the pseudopodia. They are followed by the gel cycling of actin filaments, allowing for cell motility. To form pseudopodia, the cytoplasm extends outward and the remaining cytoplasm moves forward, making the cell move forward

Question 108

Functions of microfilaments

Answer 108

Cellular movement (like with pseudopodia), cytoplasmic streaming (circulation of cytoplasm in the cell), cleavage furrow formation during cell division, and muscle movement in animals. Microfilaments are dynamic and can polymerize and depolymerize in response to cellular signals and interactions with other parts of the cell

Question 109

Components of the internal cytoskeleton (3)

Answer 109

1. Microfilaments
2. Intermediate filaments
3. Microtubules

Question 110

Intermediate filaments

Answer 110

Cytoskeletal filaments that act as cables within the cell. They are composed of strands of polymerized subunits that are made up of a wide variety of monomers. They maintain the position of the nucleus, form the nuclear lamina, and anchor the cells together in animal tissues. Desmin is an intermediate filament found in desmosomes, which joins muscle cells together

Question 111

Nuclear lamina

Answer 111

The lining/layer found just inside the nuclear envelope

Question 112

Microtubules

Answer 112

Cytoskeletal filaments composed of tubulin dimers (alpha and beta tubulin). They form hollow tubes that are the framework of the cytoskeleton. They are dynamic and can assemble and disassemble rapidly. Microtubules work with motor proteins like dynein and kinesin to move organelles and vesicles around inside the cytoplasm. They are also the main components of flagella and cilia in eukaryotic cells

Question 113

Centrosomes

Answer 113

Produce the mitotic spindle that separates chromosomes during mitosis and meiosis. The mitotic spindle organizes microtubules at either end of the cell. Centrosomes are composed of pairs of centrioles

Question 114

Mitochondria

Answer 114

The organelle where aerobic cellular respiration occurs. It has its own (bacterial) genome and 70s ribosomes. The bacterial genome supports the endosymbiotic theory

Question 115

Structure of the mitochondria

Answer 115

The mitochondria has two lipid membranes. The outer membrane is derived from the eukaryotic host cell’s membrane, while the inner membrane is derived from the bacterial plasma membrane. The electron transport chain for aerobic respiration uses integral proteins embedded in the inner membrane. Invaginations of the inner membrane (cristae) increase surface area for the location of biochemical reactions. Folding patterns of the cristae differ among various types of eukaryotic cells

Question 116

Mitochondrial matrix

Answer 116

Corresponds to the location of the original bacterium’s cytoplasm. It contains metabolic enzymes, mitochondrial DNA, and 70s ribosomes

Question 117

What is the purpose of chloroplasts?

Answer 117

Photosynthesis

Question 118

Structure of chloroplasts

Answer 118

Contains 3 membranes: outer, inner, and thylakoid. The stroma is located inside the outer and inner membranes, It is a gel like fluid that makes up most of the chloroplast. The thylakoid system floats in the stroma. It is a collection of folded membrane sacs where the photosynthetic pigment chlorophyll is found and the light reactions of photosynthesis occur. In plants, the thylakoids are arranged in stacks (grana), while in algae, they are free floating

Question 119

How are eukaryotic plasma membranes different from prokaryotic plasma membranes?

Answer 119

Eukaryotic membranes contain sterols like cholesterol that change membrane fluidity. Also, some eukaryotic cells contain specialized lipids like sphingolipids. They play a role in maintaining membrane stability and are involved in signal transduction pathways and cell to cell communication

Question 120

Endocytosis

Answer 120

The uptake of matter through folding in of the plasma membrane and vesicle formation. This is a unique ability of eukaryotic cells. Includes phagocytosis and pinocytosis

Question 121

Phagocytosis

Answer 121

Particles or other cells are enclosed in a pocket (folding in) within the membrane, which pinches off from the membrane to form a vacuole that surrounds the particle, located inside of the cell

Question 122

Pinocytosis

Answer 122

Small, dissolved materials and liquids and taken into the cell through small vesicles.

Question 123

Receptor mediated endocytosis

Answer 123

A type of endocytosis initiated by specific molecules called ligands, once the ligands bind to receptors on the cell membrane. This is how peptide and amine derived hormones use to enter cells, as well as some viruses and bacteria

Question 124

Exocytosis

Answer 124

Vesicles fuse with the membrane and eject their contents out of the cell. This is how the cell removes waste products and releases chemical signals that are received by other cells

Question 125

In eukaryotic cells, what is the cell wall made of>

Answer 125

Cellulose in fungi and plants, agar, carrageenan and other materials in protists and algae, and chitin in fungi. Cell walls stabilize the structure of the cell and protect it from environmental stress

Question 126

Extracellular matrix

Answer 126

A sticky secretion of carbohydrates and proteins in the space between adjacent cells. It helps to maintain shape and provide stability for cells without cell walls. The mass of the matrix is mostly formed by proteoglycans. Its strength is provided by fibrous proteins like collagen. Proteoglycans and collagen are attached to integrin proteins, which interact with transmembrane proteins in the plasma membrane. Some protein components form a basement membrane that ECM components adhere to.

Question 127

What is the significance of the extracellular matrix?

Answer 127

It allows cells to withstand external stress and transmits signals from the outside of the cell to the inside. There is more ECM in connective tissue, and it gives different tissues distinct properties. Pathogens attach themselves to the host cell’s extracellular matrix to establish infection

Question 128

How are eukaryotic flagella different from prokaryotic flagella?

Answer 128

Eukaryotic flagella are more flexible and whip-like. They are composed of 9 parallel pairs of microtubules that surround a central pair of microtubules. The parallel microtubules use dynein motor proteins to bend the flagellum

Question 129

Cilia

Answer 129

Unique to eukaryotes, shorter than flagella and cover the entire surface of the cell. They are structurally similar to flagella. A structure called a basal body is located at the base, which is composed of an array of triplet microtubules embedded in the plasma membrane. Cilia use a rapid, flexible waving motion, and they can sweep particles past or into cells