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Cell Structure and Division Flashcards

1
Q

What are the 4 parts to the cell theory?

A

Living organisms are composed of cells
Each cell maintains its vitality independently
Cells only arise from other cells
Viruses are not cells

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2
Q

What are the 2 ways cells obtain energy?

A

Absorbing light from the sun

Degradation of foodstuffs

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3
Q

What are the genes for a cell responsible for?

A

Control the synthesis of all the components of a cell

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4
Q

What is the only way to view viruses?

A

Using an electron microscope

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5
Q

What are the 2 or 3 parts of a virus

A

Genetic instructions (DNA or RNA)
Protein coat that protects the DNA
Sometimes an envelope of lipids that surrounds the protein coat

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6
Q

How do viruses replicate?

A

They take over the machinery of the host cell and direct it to synthesise new virus particles which are then released from the cell

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7
Q

What is the general process of a viral infection?

A

The virus binds to the host cell to gain entry to the cell. It then put its genomes into the host cell’s DNA so that the virus can replicate. The viral particles are then released and most of the time the host cell is destroyed.

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8
Q

Why do many viruses target glycans for entry into the cell?

A

They help the virus bind to the host cell

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9
Q

How does influenza virus infect?

A

It binds to cell-surface sialic acid receptors using its glycoprotein hemagglutinin. It then replicates and neuraminidase on the virus surface cleaves the virus from the host cell.

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10
Q

How dies herpes simplex virus infect?

A

Low-affinity binding to heparan sulphate proteoglycans using its surface glycoproteins gB and gC. gD then binds to a growth factor on the host cell with higher affinity and promotes membrane fusion (virus into the cell)

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11
Q

How does HIV infect?

A

The surface glycoprotein gp120 binds to CD4 receptor on T cells and then to a coreceptor on the host cell which triggers membrane fusion.

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12
Q

What is the life cycle of coronavirus?

A

Spike proteins on the virus bind to ACE2 which promotes the entry of the virus into the cell. Viral RNA is replicated and transcribed to mRNA which is translated into viral proteins in the endoplasmic reticulum. These particles are released through vesicles which causes a massive inflammatory response

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13
Q

How do vaccines work?

A

Vaccines contain either dead virus particles or one of the viral surface proteins. This stimulates an immune response so that in the future the body can destroy similar viruses

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14
Q

How do antiviral drugs work?

A

They inhibit viral proteins which are responsible for virus cell entry or viral replication in the cell

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15
Q

Why should antiviral drug targets not be similar to proteins in humans?

A

To decrease side effects

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16
Q

Give 2 examples of successful antiviral drug targets

A

Receptors that recognise viral glycoproteins in cell entry

Proteases that are involved in assembly of new viral particles

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17
Q

What is the plasma membrane?

A

The membrane that surrounds every cell and contains the cytoplasm

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18
Q

What are the 2 classes of cells

A

Prokaryotic (bacteria) and eukaryotic (plants and animals)

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19
Q

Give 3 differences between prokaryotes and eukaryotes

A

Prokaryotes don’t have a nucleus, they are also smaller in size and lack certain organelles such as mitochondria

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20
Q

What are the 3 major shapes of prokaryotes

A

Coccus (round), bacillus (rods) and spirilla (coils)

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21
Q

What are the 3 parts to the structure of bacteria cells?

A

External, cell envelope and internal organelles

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22
Q

give 2 examples of external structures of a bacteria cell

A

Flagella (for movement)

Pili, fimbriae and glycocalyx for adhesion to surfaces

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23
Q

What are the 2 parts to the cell envelope of bacteria?

A

Cell membrane and cell wall

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24
Q

Describe the structure of the cell wall in bacteria

A

It is made of peptidoglycan which consists of sugar (NAG and NAM) chains cross-linked by peptides. Gram-negative bacteria also contains an outer lipid membrane.

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25
Which enzyme helps with the cross-linking of amino acids and sugars in bacteria cell wall?
DD-transpeptidase
26
Give an example of an antibiotic that interferes with bacterial cell wall synthesis
Penicillin
27
How does Penicillin work?
It binds to transpeptidase and inhibits the cross-linking of peptidoglycan (peptide-sugar) subunits in the cell wall
28
Why does inhibiting the formation of a bacterial cell wall cause the cell to die?
It cannot undergo cell division
29
What is the glycocalyx?
A coating outside of the cell wall which provides protection, adhesion and receptor functions
30
What is the bacterial chromosome/ nucleoid
Condensed DNA molecules that directs genetics and heredity of the cell and codes for proteins
31
What is plasmid
Double stranded DNA circle containing extra genes in bacteria
32
What is the pilus
Elongated, hollow appendages used in transfers of DNA to other cells
33
What are ribosomes
Particles composed of proteins and RNA that are sites of protein synthesis
34
What is the actin cytoskeleton?
Long fibres of proteins that surround the cell inside of the cell membrane and impact the shape of the cell
35
What is the flagellum?
A specialised appendage what holds a long rotating filament and is used to move the cell
36
What is the fimbria?
Hair-like bristles that help with adhesion to other cells
37
What is the inclusion/granule
Stored nutrients such as fat deposited in dense crystals that can be used when needed
38
What is the cell wall?
A semi-rigid casing that provides structural support and the shape of the cell
39
What is the outer membrane on a bacterial cell?
An extra membrane that also contains lipopoly saccharide and controls the flow of materials
40
What is the endospore on bacteria?
A dormant body formed that allows survival of bacteria cells in adverse conditions
41
What is the cytoplasm?
Water-based solution filling the entire cell
42
How do bacteria infect?
The bacteria binds to cell-surface glycoproteins, glycosphingolipids or glycosaminoglycans using adhesins or bacterial fimbriae. Bacteria can also attach by binding matrix glycoproteins or mucin to the mucosal surface
43
What are adhesins on bacteria?
Complex carbohydrate molecules
44
What are the 2 types of bacteria?
Gram-positive and Gram-negative
45
What is Gram-positive and Gram-negative based on
How the cell-wall stains with crystal violet dye (Gram stain)
46
Describe Gram-positive bacteria
The cell wall is a thick layer of peptidoglycan which is porous and contain teichoic acid which gives the cell surface an acidic negative charge. It is stained purple with Gram stain
47
Describe Gram-negative bacteria
The cell wall is a thin layer of peptidoglycan and stains pink with Gram stain. There is an extra layer of protection called the outer membrane which is a phospholipid membrane with porins
48
What are porins?
They are found in the outer membrane of Gram-negative bacteria and are tiny holes/openings
49
How do porins make bacteria antibiotic resistant
They block the entrance of harmful chemicals and drugs. They are also connected to drug pumps which pump out any drugs that enter through them
50
What is LPS on Gram-negative bacteria?
A highly-branched fatty sugar called lipopolysaccharide attached to the outer membrane
51
What does LPS do on Gram-negative bacteria?
It acts as an endotoxin as it induces fever and shock in human cells
52
What is an endotoxin?
A pyrogen found on the outside of a Gram-negative cell wall
53
What are ribosomes
They contain RNA which catalyse protein synthesis and are attached to the endoplasmic reticulum
54
What is the endoplasmic reticulum
Part of the outer membrane of the nucleus. Ribosomes are attached on the outside when involved with protein synthesis and on the inside when involved in lipid metabolism. The network of membranes has a very large surface area
55
What is a lysosome
A vesicle containing hydrolytic enzymes that break down proteins, lipids and nucleic acids
56
What do peroxisomes do?
Vesicles that produce and destroy hydrogen peroxide within membrane so that the rest of the cell is not damaged
57
What are centrioles?
2 centrioles make up a centrosome which is attached to the cell's cytoskeleton. They help organise microtubules
58
What is the cytoskeleton?
A network of protein filaments and tubules in the cytoplasm which help give the cell shape
59
What is the nucleus
The genetic material in the form of DNA and is held in chromatin fibres
60
What does the nucleus do?
Assembles the cell's ribosomes and communicates with the cell's cytoplasm through pores in the double-layered nuclear envelope
61
What is mitochondria (briefly)
The powerhouse of the cell. It contains enzymes that break C-C bonds of food molecules and transfer this energy to ATP at the inner mitochondrial membrane
62
What is the Golgi apparatus?
Flattened sacs that receive vesicles from the endoplasmic reticulum which secretes the contents into the relevant organelles. For example, carbohydrates are added to proteins to form glycoproteins.
63
What is the plasma membrane?
A double layer of phospholipid that acts as a semi-permeable barrier where proteins are embedded and act as pumps and channels
64
What are the 3 main differences between animal cells and plant cells
Plant cells have large fluid filled vacuoles, they also have cell walls and contain chloroplasts
65
What is the role of chloroplasts in plant cells
To carry out photosynthesis by trapping sunlight energy
66
Describe a cell membrane
A double layer of phospholipid, each being about 2 nm thick, 3.5 nm apart. Within this there are proteins and other lipids. They are dynamic structures which control the contents of the compartments which they enclose
67
What does the plasma membrane control?
The passage of materials into and out of the cell. It also receives messages that regulate the behaviour of the cell
68
Describe the structure of mitochondria
Small elongated bodies what consist of a double membrane, the inner consisting of folds called cristae
69
What is in the matrix of the mitochondria?
Enzymes and some DNA
70
Why is mitochondria described as the powerhouse of the cell?
It produces most of the cell's ATP
71
Describe the structure of the nucleus
The largest organelle which is surrounded by a double membrane with pores. Inside, nucleic acids and proteins are found. DNA is attached to proteins called histones to form chromatin. Densely packed chromatin is called nucleoli
72
What is nucleoli?
Densely packed chromatin granules in the nucleus where ribosomal RNA is made
73
Describe the structure of chloroplasts
They have a double membrane surrounding the matrix (stroma) where there are stacks of lamellae which contain chlorophyll
74
What is the cell wall in plants made from?
Cellulose, a glucose polymer
75
Describe the basic organisation of cells
Groups of cells are called tissues, tissues are organised into organs which are organised into organ systems
76
What is the largest stage in the cell cycle?
Interphase
77
What are the 3 stages within interphase and what happens in each of them
G1: synthesis of RNA and protein S: replication of DNA is completed and duplication of histone proteins occurs (which are used as spindles in mitosis) G2: Synthesis of organelles such as mitochondria and centrioles
78
What are the products if mitosis?
2 genetically identical daughter cells, each the same as the original cell
79
When does meiosis occur?
For the production of gametes by organisms that reproduce sexually
80
How many chromosomes are in a human body cell?
46, 23 homologous pairs
81
How many chromosomes are in the human gamete cells?
23
82
What are the 4 stages to mitosis?
Prophase, Metaphase, Anaphase, Telophase
83
Describe prophase (mitosis)
Chromosomes become visible as long thin threads which become shorter and thicker. The nucleolus disappears and the centrioles that duplicated in interphase migrate to the opposite ends of the cell. The spindle begins to form
84
What happens in metaphase (mitosis)
The nuclear membrane disappears and each chromosome is seen as 2 chromatids joined at the centromere. The centromeres attach the chromatids to the spindle. The chromosomes line up
85
What is the nucleolus?
The region in a cell where the cell's ribosomes are assembled
86
What happens in anaphase? (mitosis)
The centromere of the chromosomes split causing the chromatids to move to opposite sides of the cell. The spindles shorten dragging the chromatids further from the equator
87
What happens in telophase? (mitosis)
2 chromatids assemble at each pole of the cell and a nuclear membrane forms around each pair. The chromatids become uncoiled and nucleoli reforms. Cytokinesis then occurs
88
What is cytokinesis
The last stage within telophase where the cell division is completed by cytoplasmic cleavage.
89
What is produced in meiosis
4 haploid gametes are produced from a diploid cell
90
What is different and similar between mitosis and meiosis stages
Still prophase, metaphase, anaphase and telophase but in meiosis, this occurs twice: PO, MI, AI, TI and PII, MII, AII TII
91
What happens in PI (meiosis)
Long threads of chromosomes pair up to form bivalents (a pair of homologous chromosomes). The chromosomes shorten and thicken. Crosslinks called chiasmata develop between the chromosomes and their pair leading to recombination. The nucleoli disappears and a spindle begins to form
92
What happens in recombination?
Portions of genetic material are exchanged leading to shuffling of genes within the pair of chromosomes
93
What happens in MI (meiosis)
The bivalents (pair of chromosomes) line up along the spindles. Reassortment occurs
94
What is reassortment of genes?
The idea of bivalents being randomly orientated when they line up in metaphase
95
What happens in anaphase? (meiosis)
The spindle microtubules shorten, dragging the chromosomes of each bivalent apart to opposite poled of the cell
96
What happens in TI? (meiosis)
A new nuclear membrane begins to form, the chromosomes uncoil and cytokinesis occurs followed by a short interphase (without DNA replication) so that the 2nd division can occur.
97
What happens in PII? (meiosis)
The centrioles move to opposite ends of the cell and a new spindle is formed
98
What happens in MII? (meiosis)
The nuclear membranes disappear and the chromosomes become attached by their centromeres to the microtubules at the equator of the spindle. Further reassortment of genetic material occurs
99
What happens in AII? (meiosis)
The centromeres of the chromosomes divide and the chromatids are pulled to the edges of the cell
100
What happens in TII? (meiosis)
Nuclear membranes form around the chromatids, the spindle disappears and cytokinesis follows.
101
What is a zygote?
A fertilised egg cell
102
Why is the organism produced from sexual reproduction genetically different to its parents?
Dur to recombination and reassortment of chromosomes

PHAY0003 (22 decks)

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