Vanessas Lectures Flashcards
1
Q
What are viruses?
A
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses can infect all types of life forms
2
Q
What is bacteriophage?
A
A virus which parasitizes a bacterium by infecting it and reproducing inside it. Bacteriophages are used in genetic research.
3
Q
What are chromatins made up of?
A
About 50% protein and 50% DNA.
4
Q
Are chromosomes packed randomly within the nucleus?
A
No they occupy discrete fields
5
Q
True or False? The Nuclear envelope is a single membrane.
A
False the nuclear envelope is a double membrane (4 Layers of lipid bilayers)
6
Q
Is the head of a lipid bilayer hydrophilic or hydrophobic?
A
Hydrophilic
7
Q
Is the tail of a lipid bilayer hydrophilic or hydrophobic?
A
Hydrophobic
8
Q
What needs to pass between the nucleus and the cytoplasm
A
RNA and Proteins. DNA never does and Lipids dont need to.
9
Q
What are nuclear pores?
A
Large ring-shaped protein complexes. They go though both membranes of the nuclear envelope.
10
Q
Where are the ribosomes made?
A
In the nucleolus
11
Q
What are ribosomes made of?
A
Protein and RNA
12
Q
What is the main function of the Nucleolus?
A
To make ribosomes
13
Q
What are the functions of the nucleus?
A
Storing DNA and Ribosomal production, transcription, replication of DNA, and the processing the mRNA
14
Q
What are histones?
A
Proteins that help to organise and pack DNA
15
Q
What is the nucleolus?
A
A sub-section of the nucleus. Where ribosomes are made
16
Q
What is the nucleoid?
A
A region within the prokaryotic cytoplasm where DNA is found.
17
Q
What does the endomembrane system include?
A
The nuclear envelope, the endoplasmic reticulum, the Golgi Apparatus, lysosomes, vesicles, endosomes, vacuoles.
18
Q
What does the endomembrane system not include?
A
The mitochondria, plastids
19
Q
Do prokaryotic cells have an endomembrane system?
A
No
20
Q
What does the endomembrane system do? (refer to slides to finish)
A
Trafficking of material
21
Q
What are the two ways of targeting proteins to cellular compartments in the cell?
A
Post-Translational translocation and Co-translational translocation
22
Q
What is cell biology the study of?
A
The structure and function of the cell
23
Q
The term “cells” was coined in 1665 by who?
A
Robert Hooke
24
Q
Cell theory was developed in the 1830s by who?
A
Schleiden and Schwann
25
What are the three premises of cell theory?
1) All organisms are composed of one or more cells.
2) Cells are the smallest living units of all living organisms.
3) Cells arise only by division of a previously existing cell.
26
What is Light microscopy?
A type of microscope that commonly uses visible light and a system of lenses to generate magnified images of small objects. The cells may be living or dead.
27
What is Fluorescence microscopy?
Can be used to study location of
specific proteins in the cell eg. Confocal microscopy eliminates out-of-focus background, giving
a sharper image.
28
How do we study cells?
Instead of focusing visible light on a
sample, electrons are focused on
the sample. Because electrons allow humans to see the smaller parts of cells.
29
What is Electron microscopy?
An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination
30
What are the two forms of electron microscopy?
Scanning electron microscopy (SEM), and Transmission electron microscopy (TEM).
31
What is scanning electron microscopy?
The study of surfaces of objects by measuring the scattered electrons. In this case the samples need to be coated with a conductive material and the samples are dead
32
What is transmission electron microscopy?
Where electrons are passed through a
| sample and the transmitted electrons are detected. Cells are dead in this case.
33
What are the 3 domains of life?
Bacteria, Archaea, and Eukarya
34
What is Archaea?
These microorganisms lack cell nuclei and are therefore prokaryotes. They have distinct molecular characteristics separating them from bacteria
35
What is bacteria?
Bacteria are a type of biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals
36
What is Eukarya?
Eukaryotes are organisms whose cells have a nucleus enclosed within membranes, unlike prokaryotes, which have no membrane-bound organelles.
37
What are the main components of an animal cell?
A nucleus, the mitochondria, the Golgi apparatus, the endoplasmic reticulum, plasma membrane, ribosome, cytoskeleton, and peroxisome.
38
What are the main components of a plant cell?
Cell wall, nucleus, mitochondria, Golgi and ribosomes, vacuole, and chloroplasts.
39
How are Eukaryotes generally distinct from prokaryotes?
They contain a nucleus, have organelles and can be multicellular.
40
What is the function of the chromosome?
The compactness of chromosomes plays an important role in helping to organize genetic material.
41
How does the 2m of DNA get packed into each and every cell?
Due to the physical basis of chromosomal packing of successive rounds of coiling and looping. "Super coiling"
42
Which proteins are involved in packing of DNA?
Histone proteins. Histones proteins are also involved in opening of DNA
43
Chromatin is 50% what?
50% protein and 50% DNA.
44
True or False? Chromosomes are not packed randomly within the nucleus, but occupy discrete fields.
True
45
What is the Nuclear Envelope?
The nucleus is surrounded by a lipid membrane called the nuclear envelope. The nuclear envelope is a
double membrane. The pores regulate the passage of macromolecules like proteins and RNA, but permit free passage of water, ions, ATP and other small molecules.
46
What is a double membrane?
A membrane is a lipid bilayer, the plasma membrane (cell
membrane) is single membrane but a double membrane has two lipid bilayers. The nuclear envelope is a
double membrane
47
What needs to pass between
| the nucleus and the cytoplasm?
Proteins and RNA
48
What are nuclear pores?
The nuclear pore is a protein-lined channel in the nuclear envelope that regulates the transportation of molecules between the nucleus and the cytoplasm. Nuclear pores are large ring-shaped protein complexes, nuclear pores go through both membranes of the nuclear envelope.
49
True or False? Nuclear pores are complex
True, they are made from > 456 individual
| proteins
50
What is the Nucleolus?
A dark staining region of the nucleus
that contains very little DNA. The nucleolus makes ribosomal subunits from proteins and ribosomal RNA, also known as rRNA. It then sends the subunits out to the rest of the cell where they combine into complete ribosomes.
51
Functions of the nucleus?
1. Storage of DNA
2. Ribosomal production
3. Transcription of DNA into
mRNA
4. Replication of DNA
5. Processing of mRNA
52
What is the central dogma?
The 'Central Dogma' is the process by which the instructions in DNA are converted into a functional product.
53
Where does transcription take place in the cell?
The nucleus
54
Where does translation take place in the cell?
In the cytoplasm
55
True or False? Bacteria chromosomes are usually circular
True
56
Where is the DNA located in the bacterial cell?
The nucleoid
57
True or False? In bacterial cells translation and transcription occur at the different ends of the cell
False
58
What is the endomembrane system?
The system of membranes within a cell that exchange material either directly or via vesicular transport (works together to modify, package, and transport lipids and proteins)
59
What does the endomembrane system include?
```
Nuclear envelope
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Vesicles, endosomes,
vacuoles
Plasma membrane
```
60
What does the endomembrane system not include?
mitochondria and
| plastids (e.g. chrloroplasts)
61
True or False? Both eukaryotic and prokaryotic cells have an endomembrane system.
False, only eukaryotic cells have an endomembrane system.
62
What are some of the things an endomembrane system does?
The Trafficking of material, Production of proteins, Modification of proteins, Production of lipids, Specific chemical reactions, and Storage of molecules.
63
How are proteins trafficked around the cell?
Carrier proteins are used to transport proteins across cellular membranes such as the plasma membrane, endoplasmic reticulum and nuclear envelope.
64
What are signal peptides or signal sequence?
They are located on the N-terminus of some proteins and enable those proteins to find their correct location outside the cell membrane. The signal sequence tags the protein for transport through the cell membrane and out of the cell. "Codes them"
65
True or False? Different Signal Sequences Send Proteins to Different Locations
True
66
What s a signal sequence/peptide?
A string of amino acids that is apart of a protein sequence dedicated for localizing the protein to its correct cell compartment
67
What are the two types of targeting that occur to membrane-bound systems?
Post-translational translocation and Co-Translational translocation
68
What is Post-translational translocation?
The protein is translated entirely in the cytoplasm by a free ribosome, the signal sequence directs the protein to the appropriate compartment
69
What is Co-Translational translocation ?
The protein is initially translated by a free ribosome, The entire ribosome goes to the membrane, becoming a bound ribosome. The Protein translocates across the
membrane while being translated.
70
What is the endoplasmic reticulum?
A continuous membrane system that forms a series of flattened sacs within the cytoplasm of eukaryotic cells and serves multiple functions, being important particularly in the synthesis, folding, modification, and transport of proteins .
71
What is the endoplasmic reticulum made up of?
Smooth er, rough er, the nuclear envelope, ribosomes, ER lumen, and cristae.
72
What is the difference between smooth and rough ER?
Both the smooth and rough endoplasmic reticulum help in the production and storage of proteins The main difference is that one contains ribosomes on it and the other does not. The rough endoplasmic reticulum (RER) has ribosomes on its surface. ... The smooth endoplasmic reticulum (SER) does not contain ribosomes.
73
What are the functions of smooth ER?
Synthesis of lipids (including steroids) eg. Reproductive tissues, Metabolism of carbohydrates, Detoxification of drugs and poisons, and the Storage of calcium ions.
74
What are the functions of rough ER?
Serves as a site for translation of proteins that are
destined to be secreted or for the plasma membrane, it adds carbohydrates to proteins (glycoproteins), Produces lipids and new membranes, and sends proteins on to the Golgi apparatus via vesicles.
75
What are glycoproteins?
Glycoproteins are proteins that have sugars attached to them. They do many important jobs for the body, such as helping the immune, digestive, and reproductive systems.
76
What are vesicles in the cell?
Vesicles are a small, membrane-bound organelles that shuttle between other organelles, or between an organelle and the plasma membrane.
77
What is Vesicular transport?
Vesicles or other bodies in the cytoplasm move macromolecules or large particles across the plasma membrane. There are two types of vesicle transport, endocytosis and exocytosis. Both processes are active transport processes, requiring energy
78
What is the function of the Golgi Apparatus?
The Golgi apparatus follows the ER in processing proteins and other molecules. The Golgi apparatus is the “shipping and receiving centre” of the cell
79
What are the two models to explain movement of material through the Golgi apparatus?
The vesicular transport model and the Cisternal maturation model
80
What is the vesicular transport model?
Proteins move through the Golgi. Separate vesicles transport materials in both the forward
and reverse directions. The Cisterna remain static.
Return vesicles are required to ensure retention of enzymes
81
What is the Cisternal maturation model?
Individual cisternae of the Golgi mature, transporting
material in the forward direction, taking proteins with
them. Return vesicles are required to
ensure retention of enzymes
82
What does the Golgi apparatus do?
Sends material (proteins, lipids) to various places, Protein processing, and Carbohydrate manufacturing.
83
What is exocytosis?
Vesicle fusion with the plasma membrane
84
What is endocytosis?
Vesicle recovery from the plasma membrane
85
Exocytosis delivers what?
* the protein and carbohydrate contents to the outside of the cell
* lipids to the plasma membrane
* membrane proteins to the plasma membrane
86
Endocytosis retrieves what?
* the contents of the vesicle, including solutes and nutrients
* lipids from the plasma membrane
* membrane proteins
87
What are lysosomes?
Compartments where digestion (lysis) takes place, Contain proteases, nucleases, glycosidases, lipases etc
88
What is phagocytosis?
Phagocytosis is the process by which a cell uses its plasma membrane to engulf a large particle, giving rise to an internal compartment called the phagosome
89
What is Pinocytosis?
A process by which liquid droplets are ingested by living cells.
90
What is the receptor-mediated endocytosis?
A process by which cells absorb metabolites, hormones, proteins – and in some cases viruses – by the inward budding of the plasma membrane
91
What is cisternae?
Sacs that make up the ER or Golgi apparatus
92
What is ER lumen?
The liquidy bit inside the ER
93
What are glycoproteins?
Proteins with sugars added to them
94
What are vesicles?
A small bubble of membrane used for shipping components around the cell
95
Proteins are moved through the cell via what?
Signal sequences
96
Proteins are translated in the cytosol via what?
Post-translational translocation
97
Proteins translated into a membrane enter via what?
Co-translational translocation
98
Material leaves the cell via what?
Exocytosis
99
Material enters the cell via what?
Endocytosis
100
What does the mitochondria do (simple)?
Turn fuel into ATP
101
What do chloroplasts do (simple)?
Turn light into fuel
102
True or False, both the mitochondria and chloroplasts have a similar evolutionary origins.
True
103
Is the membrane of the mitochondria a single or double membrane?
Double membrane
104
What are the two internal compartments of the mitochondra?
The inter-membrane space and the matrix
105
In terms of respiration where does glycolysis occur?
In the cytoplasm
106
In terms of respiration where does the citric acid cycle occur?
In the mitochondrial matrix
107
In terms of respiration where does oxidative phosphorylation occur?
Across the inner mitochondria membrane
108
What happens in the inter-membrane space?
The H+ Gradient forms
109
What happens in the inner membrane?
This is where the electron transport chain is
110
What happens inside the mitochondria?
The citric acid cycle
111
True or False? Eukaryotic cells have between one and thousands of mitochondria.
True
112
How is the mitochondria dynamic?
It changes shape, fuses, and divides
113
What are plastids?
They are found in plants and algae, they are the site of manufacture and storage of important chemical compounds used by the plant cell.
114
True or False? Plastids do not contain DNA
False, plastids do contain DNA
115
What do chromoplasts contain?
The pigments, beta carotenes and xanthophyll
116
What do chloroplasts contain?
The chlorophyll pigment
117
What are the uncoloured plastids, leucoplasts involved int?
Storage and biosynthesis
118
What is amyloplasts involved in?
Storing starch
119
What proteinoplasts involved in?
Storing proteins in seeds
120
What is elaioplasts involved in?
Storing and metabolising lipids
121
Where are chloroplasts found?
In leaves
122
Where are chromoplasts found?
In fruits and flowers
123
What are chloroplasts?
Specialized plastids that carry out photosynthesis. Contains chlorophyll pigments that are responsible for plants green colour
124
What are thylakoids?
Thylakoids are membrane-bound compartments inside chloroplasts and cyanobacteria. They are the site of the light-dependent reactions of photosynthesis
125
Where does light harvesting and ATP synthesis occur in plants?
The thylakoids
126
How did the mitochondria and plastids evolve?
It is widely accepted that mitochondria and plastids evolved from bacteria that were engulfed by nucleated ancestral cells
127
How did the nucleus evolve?
Through infolding of the plasma membrane evidence for this is that the nuclear envelope has a double membrane
128
What is the endosymbiotic theory?
that some of the organelles in eukaryotic cells were once prokaryotic microbes. Mitochondria and chloroplasts are the same size as prokaryotic cells and divide by binary fission. Mitochondria and chloroplasts have their own DNA which is circular, not linear.
129
What is the evidence that mitochondria and plastids were once free-living organsisms?
They have double membranes, their biochemistry resembles bacterial biochemistry, they divide like bacteria and cannot be synthesised, and their ribosomes are more similar to bacterial than eukaryotic.
130
True or False? The mitochondria and chloroplasts have their own DNA
True
131
Is the DNA of the mitochondria linear or circular?
Circular
132
How many proteins does the mitochondria encode?
13
133
How many TRNAs does the mitochondria encode?
22
134
Which is bigger? The genome of the mitochondria or plastids?
The plastid genome
135
Can you use mitochondrial DNA to study populations?
Yes, Because mtDNA does not change as rapidly as nuclear DNA, and because it is not mixed with the father's (paternal) DNA, it leaves a clearer record of distant ancestry – although only through the mothers' (maternal ancestry). (No recombination)
136
What are Haplogroups?
A haplogroup is a group of similar haplotypes that share a common ancestor
137
Why does the mitochondria have a reduced genome?
As genes have moved to the nucleus
138
Why do plastids have a reduced genome?
As genes have moved to the nucleus
139
What is the shuffling of DNA?
DNA shuffling is a way to rapidly propagate beneficial mutations in a directed evolution experiment. It is used to rapidly increase DNA library size
140
What is the extracellular matrix in animals? (ECM)
A 3D network of extracellular macromolecules such as collagen, enzymes, and glycoproteins, that provide structural support to surrounding cells, it is made of proteins and carbohydrates.
141
What is a cell wall?
A layer outside of the plasma membrane providing structural support and protection
142
Who has a cell wall?
Plants, Fungi, Bacteria, and Archea
143
Who doesn't have a cell wall?
Animals and protists (although some protists do)
144
What are composite materials?
Structurally strong materials that contain long, rigid fibres embedded in a matrix.
145
True or False? The extracellular matrix is a composite material
True
146
What is collagen?
An insoluble glycoprotein that forms fibres of high tensile strength. Collagen is the main structural protein in the extracellular matrix in the various connective tissues in the body. As the main component of connective tissue, it is the most abundant protein in mammals,
147
What are the long rigid fibres in the extracellular matrix in animals?
Glycoproteins such as collagen and elastin
148
What is the embedding material of the extracellular matrix in animals?
Proteoglycans
149
Where does the strength of collagen come from?
The triple-helical quaternary structure
150
True or False? The three braids of the collagen molecule are found only in this molecule.
True
151
What percentage of your body is collagen?
40%
152
How many genes for collagen are there in humans?
About 46
153
What are proteoglycans?
A very hydrophilic molecule made up of polysaccharide chains covalently linked to proteins thats main carbohydrate (GAG) makes a gel like substance in collagen.
154
What is a fibroblast?
A fibroblast is a type of biological cell that synthesizes the extracellular matrix and collagen, produces the structural framework (stroma) for animal tissues, and plays a critical role in wound healing
155
Why is it good that the extracellular matrix is strong and elastic?
Because animals require flexibility for movement.
156
What ensures the extracellular matrix is elastic?
Elastin
157
What is elastin?
Elastin is a key protein of the extracellular matrix. It is highly elastic and present in connective tissue allowing many tissues in the body to resume their shape after stretching or contracting.
158
What are the long rigid fibres in the extracellular matrix of plants?
Cellulose (polysaccharide)
159
What is the embedding material of the extracellular matrix of plants?
Pectin, hemicellulose, and proteins
160
Can we renew our matrix?
Yes
161
What is the difference between starch and cellulose?
Their orientation which means that starch gives energy but cellulose does not.
162
What is pectin?
A complex set of polysaccharides that help bind cells together, it is apart of the cell wall matrix. You can also use it in cooking to make jam
163
In plants what is the extracellular matrix like?
It is rigid and stationary which is consistent with the non-motile lifestyle of plants.
164
What is microfibril?
A microfibril is a very fine fibril, or fiber-like strand, consisting of glycoproteins and cellulose. It gives the cell wall strength
165
Why can we digest starch but not cellulose?
Because we have enzymes that can break down starch but not cellulose. We don't have these enzymes because the breaking down of cellulose is just to hard to complete efficiently due to its complex structure. We would also need multiple different specific enzymes because we would not just be breaking down cellulose.
166
What are the stages of the synthesis of the cell wall?
1. The middle lamella (pectins) are laid down first (they act as glue)
2. The primary wall is secreted by young plant cell
3. The wall is strengthend by the addition of a secondary wall after cell growth is complete
167
Where is cellulose synthesised?
Directly at the plasma membrane
168
True or False? Plant cell walls are porous and dynamic
True
169
Why do animals require Vitamin C?
To make hydroxyproline
170
What do animals need hydroxyproline from Vitamin C?
Because it is an amino acid that makes up Collogen which is essential for the extracellular matrix
171
What is the role of the extra cellular matrix in cell walls?
To protect the cells, provide support and rigidity, provide elasticity to tissues, and glue cells together.
172
What is the cytoskeleton?
A complex system of protein filaments that function in shape/mechanical support and motility (moving things within the cells)
173
What is a fun way to think about the cytoskeleton?
That it is like the frame work of a building and the people are the 'motor proteins' that carry the essential tools 'organelles' around the framework to get to the required places.
174
What are the components of the eukaryotic cytoskeleton?
Microtubules, Actin microfilaments, and intermediate filaments
175
Why do microtubules have their name?
Because their shape is similar to a tube hence the tubules in their name
176
What are microtubules made up of?
a-tubulin and b-tubulin which form heterodimers
177
True or False? Microtubules have a plus and a minus end
True
178
Elongation is far more rapid at what end of the microtubules?
The plus end
179
True or False? microtubules grow from an organising centre
True, this is called the centrosome located near the nucleus
180
True or False? Microtubules are not very dynamic
False microtubules are very dynamic
181
What are the motor proteins for the microtubules?
Dynein and Kinesin
182
How do dynein and Kinesin walk along microtubules?
By using ATP
183
What do the cargoes of the microtubule motorproteins contain
Vesicles and organelles and cytoskeleton components
184
Which direction does dynein go in?
Towards the minus end
185
Which direction does kinesin go in?
Towards the plus end
186
Microtubules function how?
In controlling cell shape, motility/migration, and cell division
187
What are the two systems in which microtubules are used to generate cell motility?
1. The mitotic spindle and 2. Cilia and flagella
188
What is the mitotic spindle?
An array of microtubules with associated proteins including the motor proteins kinesin and dynein. It functions to seperate chromosomes during mitosis
189
What are eukaryotic Cilia?
These allow cells to move through solution in multicellular organisms, but in protists function in locomotion and food collection
190
What are monomers?
A single unit
191
What are Dimers?
Two units
192
What are eukaryotic flagella?
They function in locomotion of some unicellular eukaryotes and in sperm cells of animals, algae, and some plants and fungi.
193
Are eukaryotic Cilia, small and numerous or large and have one to a few per cell?
Small and numerous
194
Are eukaryotic flagella, small and numerous or large and have one to a few per cell?
Large and have one to a few per cell.
195
What is the motion of eukaryotic Cilia like?
Whip like alternating power and recovery stroke. Coordinated wave like beating. (Whale e.c.t)
196
What is the motion of eukaryotic flagella like?
Beat in undulating fashion with several waves along length (Snake e.c.t)
197
True or False, eukaryotic cilia and flagella have a common structure
True
198
Which motor protein drives the movement of cilia and flagella?
Dynein. ATP activates Dynein motor activity and causes microtubules to slide past eachother.
199
True or False, Inside the cell microtubules are anchored which force them to bend rather than slide.
True
200
What are actin filaments?
These are thin solid rods composed of a twisting double chain. They form a network that provides mechanical support, determines cell shape, and allows movement of the cell surface, thereby enabling cells to migrate, engulf particles, and divide.
201
Monomers of the actin filaments are typically added at what end and removed from what end?
Added at the plus end and removed from the minus end
202
What is the motor protein for actin filaments?
Myosin which uses ATP to walk along microfilaments towards the plus end
203
What do the cargoes of myosin contain?
Vesicles and organelles and other cytoskeleton components
204
Actin microfilaments function in what?
Cell shape, motility, organelle motility, and muscle motion
205
In muscle cells what do myosin motor proteins do?
They bundle together to form myosin thick filaments
206
In a relaxed muscle how are the thick and thin filaments spaced?
Widely spaced
207
What triggers muscle contraction?
A calcium trigger and ATP
208
What is a sliding filament mechanism?
The sliding filament theory explains the mechanism of muscle contraction based on muscle proteins that slide past each other to generate movement.
209
What is cytoplasmic streaming?
A process used to generate flow in especially large plant cells
210
Half of all prokaryotes are capable of what?
Directional movement which usually uses flagella
211
True or False? Bacterial flagella are structurally and biochemically unrelated to eukaryotic flagella
True
212
What is Prokaryotic Flagella?
A Filament composed of the protein flagellin (which doesn't really do anything). Its movement is driven by the basal apparatus which acts as a motor
213
Bacteria divide by what?
Binary fission
214
True or False? Most eukaryotic cells have a size limit to ensure they can function
True
215
Bacteria use what to move?
Flagella
216
Do bacteria have organelles?
Bacteria are simple cells that do not contain a nucleus or other membrane-bound organelles. However, they do contain other cellular structures that aid with their life processes
217
What does the protein FtsZ do?
Forms a ring around bacterial cells pinching them off in division. It also divides plastids and mitochondria
218
What is the eukaryotic cell cycle?
4 discrete phases M, G1, S, and, G2
219
What is included in the mitotic (M) phase of the eukaryotic cell cycle?
Mitosis and cytokinesis
220
What are the 3 phases of the interphase?
G1, S, and G2
221
What is the G1 phase?
The first growth phase of the eukaryotic cell cycle. Increases cell size and organelles
222
What is the S phase?
The DNA synthesis phase where DNA is copied
223
What is the G2 phase?
The second growth phase.
224
What are the checkpoints in the eukaryotic cell cycle?
They ensure that if the correct 'go ahead' signal is missing the cycle does not proceed. There are G1, G2, and M checkpoints
225
What are the checkpoints checking for in the eukaryotic cell cycle?
That DNA is fine and without mutation
226
Why is it important that the eukaryotic cell cycle has checkpoints?
Because if the DNA has mutations cell division may not be able to occur and the cell will have issues and the incorrect compartments. This is whee weird uncontrolled growth can occur which is cancer.
227
During the S phase why is it important that the sister chromatids are kept together?
So that they can seperate at the right time and not float off
228
What is a chromatid?
A chromatid is one half of a replicated chromosome (One of the sister chromatids after DNA replication)
229
What is chromatin?
"Substance" that makes up chromosomes and is involved in DNA packing.
230
What is the centromere?
The region of a chromosome to which the microtubules of the spindle attach during cell division.
231
What is the centrosome?
The microtubule organising centre in the cell.
232
What is the difference between a chromatid and chromatin?
Chromatin is the substance that makes up chromosomes and a chromatid is one half of a replicated chromosome
233
What is the difference between the centromere and the centrosome?
The centromere is the microtubule organising centre in the cell and the centrosome is the region of a chromosome where the microtubules of the spindle attach during cell division
234
What is mitosis?
A nuclear division where two daughter cells gain identical genetic information. This is asexual reproduction. This process as common to all eukaryotes
235
What are the phases of mitosis?
Interphase, Prophase, Metaphase, Anaphase, Telophase
236
What is the interphase?
The pre-mitotic phase where the chromosomes have replicated, the nuclear envelope is still complete and there is no mitotic spindle.
237
What is the Prophase?
Cytoplasm changes: Mitotic spindle begins to form at centrosomes and centrosomes begin to seperate to opposite polls of the cell.
Nucleus changes: Chromatin condenses into discrete chromosomes and the nuclear envelope breaks down.
(start phase)
238
What is the Metaphase?
The chromosomes align on the metaphase plate and kinetochores are attached to microtubules.
239
What is the Anaphase?
Chromatids move to opposite poles moved by microtubules and microtubule motors (dynein and kinesins)
240
What is the Telophase?
The chromatin decondences, the nuclei reform, and the spindle disassembles. (end phase)
241
What is the mitotic spindle?
An assemblage of microtubules and associated proteins that is involved in the movements of chromosomes during mitosis.
242
What is cytokinesis?
The cytoplasmic division of a cell at the end of mitosis or meiosis, bringing about the separation into two daughter cells.
243
Where does Animal cytokinesis occur?
At the site of the metaphase plate
244
How does the cell divide in animal cytokinesis?
Outside inwards using actin microfilaments and myosin
245
What is the issue with mitosis in plant cells?
They have very strong cell walls
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How is cell division aka mitosis achieved in plant cells?
Vesicles sent from the Golgi Apparatus fuse to form a cell plate in the centre of the cell and then the complete cell divided inside outwards into 2 cells using microtubules and kinesin
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True or False? Cytokinesis works differently in plant and animal cells.
True
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What is asexual reproduction?
Where there is only one parent requires and the offspring produced is genetically identical. This type of reproduction involves mitosis
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What is sexual reproduction?
Where there are 2 parents requires and the offspring is genetically different. This type of reproduction involves meiosis
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What is the difference between mitosis and meiosis?
Mitosis results in genetically identical cells and meiosis results in genetically different cells
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What are homologous chromosomes?
A set of one maternal and one paternal chromosome that pair up with each other inside a cell during fertilization
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Typically homologous chromosomes carry the same genes, which chromosome is the exception?
The sex chromosomes
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Are homologous chromosomes identical?
No but they are similar. They contain the same set of genes but they may have different versions of the genes (alleles) for example both may have the genes for eye colour but one expresses the eye colour of blue and the other expresses brown.
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Which is bigger the Y chromosome or the X chromosome?
The X Chromosome
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What is a haploid cell? (n)
A cell that contains one set of chromosomes
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What is a Diploid cell? (2n)
A cell that contains two sets of chromosomes.
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In animals meiosis produces what?
Haploid gametes
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In plants meiosis produces what?
Haploid spores
