2.6* Flashcards
(250 cards)
1
Q
What is cytokinesis?
A
Cytoplasmic division following nuclear division, resulting in two new daughter cells.
2
Q
What is interphase?
A
Phase of cell cycle where the cell is not dividing; it is subdivided into growth and synthesis phases.
3
Q
What is mitosis?
A
Type of nuclear division that produces daughter cells genetically identical to each other and to the parent cell
4
Q
What could early researchers see when observing cell division under the microscope?
A
They could easily see the behaviour of chromosomes during mitosis which is nuclear division followed by cytokinesis or cytoplasmic division, resulting in two daughter cells.
5
Q
What could early scientists not see in cell division?
A
Nuclear and cytoplasmic division, called the M-phase, occupy only a small part of the cell cycle. Between each M-phase is an interphase. Interphase when studied under the microscope, appears to be uneventful. However, more sophisticated techniques have enabled scientists to learn that during interphase there are elaborate preparations being made for cell division, in a carefully ordered and controlled sequence, with checkpoints.
6
Q
What are the two man checkpoints?
A
The G1/S checkpoint, also called the restriction point, and the G2/M checkpoint.
7
Q
Name another checkpoint? (not the two main checkpoints) State its purpose.
A
There is one halfway through mitosis and one in early G1.
The purpose of the checkpoint is;
To prevent uncontrolled division that would lead to tumours (cancer).
To detect and repair damage to DNA (for example, damage caused by UV light).
8
Q
Molecular events that control the cell cycle happen in a specific sequence, what does this ensure?
A
The cell cycle cannot be reversed.
The DNA is only duplicated once during each cell cycle.
9
Q
Cells should usually undergo a certain number of divisions or cycles, what is this known as and how many is it?
A
The number is about 50 and known as the Hayflick constant.
10
Q
What happens if the cell division becomes uncontrolled?
A
If cell division becomes uncontrolled, then a tumour can form which may become malignant or cancerous.
11
Q
What helps regulate cell division?
A
There are proto-oncogenes that help regulate cell division by coding for proteins that help regulate cell growth and differentiation.
12
Q
What happens if the proto-oncogenes fail?
A
If these proto-oncogenes mutate, then they may become oncogenes and can cause cells to fail to undergo apoptosis and instead to keep on dividing, leading to a tumour.
13
Q
Describe the divisions of a tumour.
A
Tumours form because cells divide uncontrollably. The division phase, mitosis, of each cancerous cell takes the same length of time as in a non-cancerous cell. Because the cell division is uncontrolled, there is a greater proportion of cells dividing within a tumour than within normal tissue.
14
Q
Why is the gene p53 important?
A
It triggers the two main checkpoints in the regulation of the cell cycle.
15
Q
What is the gene p53 known as?
A
A tumour suppressor gene.
16
Q
What other regulatory chemicals are there apart from p53?
A
Other regulatory chemicals are proteins called cyclins and CDK (cyclin-dependant kinases). Cyclins are synthesised in response to cell-signalling molecules such as growth factors.
17
Q
Describe the prokaryotic cell cycle.
A
This occurs by a process called binary fission, the cell grows to its limit of size and then splits into two. Before the cell divides, its DNA is replicated. The new loops of DNA are pulled to opposite ends of the cell and a wall forms which begins to separate the bacterial cell. Each new cell also contains replicated plasmids and synthesised ribosome’s.
18
Q
Apart from bacterial cells what other cells split by binary fission?
A
Mitochondria and chloroplasts within eukaryotic cells also divide by binary fission.
19
Q
In the M - phase what does the chemical trigger?
A
A checkpoint chemical triggers condensation of chromatin.
20
Q
What phase of the cell cycle if the M-phase in?
A
Halfway through the cell cycle, the metaphase checkpoint ensures the cell is ready to complete mitosis.
21
Q
What events within the cell occur in the M-phase?
A
Cell growth stops.
Nuclear division (mitosis) consisting of stages : prophase, metaphase, anaphase and telophase.
Cytokinesis (cytoplasmic division)
22
Q
What cells do not have a G 0 (gap 0) phase?
A
Epithelial cells lining the gut do not have this phase.
23
Q
When and how is the G 0 (gap 0) chemical triggered?
A
A resting phase triggered during early G 1 at the restriction point (see below), by a checkpoint chemical.
24
Q
What events happen in G 0?
A
In this phase, cells may undergo apoptosis (programmed cell death) differentiation or senescence.
Some types of cell (e.g. neurones) remain in this phase for a very long time or indefinitely..
25
At what phase of the cell cycle and which checkpoints are involved in G1 (gap 1) phase - also called the growth phase.
A G1 checkpoint control mechanism ensures that the cell is ready to enter the S phase and begin DNA synthesis.
26
State all (5) of the events in G1 phase.
Cells grow and increase in size.
Transcription of genes to make RNA occurs.
Organelles duplicate.
Biosynthesis, e.g. protien synthesis, including making the enzymes needed for DNA replication in the S phase.
The p53 (tumour suppressor) gene helps control this phase.
27
Describe the sequence of the S phase of interphase.
Because the chromosomes are unwound and DNA is diffuse, every molecule of DNA is replicated. There is a specific sequence to the replication of genes - those which are active in all types of cells, are duplicated first. Genes that are normally inactive in specific types of cells are replicated last.
28
State all (4) of the events in S phase.
Once the cell has entered this phase, it is committed to completing the cell cycle.
DNA replicates.
When all chromosomes have been duplicated, each one consists of a pair of identical chromatids.
This phase is rapid, and because the exposed DNA base pairs are more susceptible to mutagenic agents, this reduces the chances of spontaneous mutations happening.
29
What is the purpose of G 2 (gap 2) phase of interphase.
Special chemicals ensure that the cell is ready for mitosis by stimulating proteins that will be involved in making chromosomes condense and in formation of the spindle.
30
State all of the events in G 2 (gap 2) phase of interphase.
Cells grow.
31
What are chromatids?
Replicates of the chromosomes.
32
What is cytokinesis?
Division of the cytoplasm of a cell following mitosis.
33
What is mitosis?
Type of nuclear division that maintains the chromosome number; each new daughter cell contains the same genetic information as the parent cell. They are also genetically identical to each other.
34
Asexual reproduction;
| Give an example of how single-celled protoctists divide.
Single-celled protoctists such as Amoeba and Paramecium divide by mitosis to produce new individuals.
35
Asexual reproduction;
| Give an example of how a plant reproduces asexually.
Some plants e.g. Strawberry, reproduce asexually by forming new plantlets on the end of stolons (runners).
36
How do fungi reproduce?
Fungi such as single celled yeasts, can reproduce asexually by mitosis.
37
Does asexual reproduction happen in animals, if so give example.
Asexual reproduction is rarer in animals but some female sharks kept in captivity without any males have produced female offspring that are genetically identical to themselves. Aphids may sometimes produce eggs, by mitosis, that do not need fertilising.
38
How do all multicellular organisms grow?
By producing more cells that are genetically identical to each other and to the parent cell from which they arose by mitosis.
39
How are animal tissues repaired?
Wounds heal when growth factors, secreted by platelets and macrophages (white blood cells) and damaged cells of the blood-vessels walls, stimulate the proliferation of endothelial and smooth muscle cells to repair damaged blood vessels.
40
What has only use asexual reproduction for millions of years?
Two species of stick insect, of the genus Timema, have used only asexual reproduction for millions of years.
41
What are the main stages of mitosis?
Although mitosis is a continuous process, scientists observing the process have defined four main stages of mitosis, namely prophase, metaphase, anaphase and telophase.
42
What is the first stage of mitosis?
Prophase.
43
What is the second stage of mitosis?
Metaphase.
44
What is the third stage of mitosis?
Anaphase.
45
What is the last stage of mitosis?
Telophase.
46
There are four events in Prophase, what is the first?
The chromosomes that have replicated during the S phase of interphase and consist of two identical sister chromatids, now shorten and thicken as DNA supercoils.
47
There are four events in Prophase, what is the second?
The nuclear envelope breaks down.
48
There are four events in Prophase, what is the third.
The centriole in animal cells (normally found within a region of a cell called a centrosome) divides and the two new daughter centrioles move to opposite poles (ends) of the cell.
49
There are four events in Prophase, what is the final event?
Cytoskeleton protien (tubulin) threads form a spindle between these centrioles. The spindle has a 3D structure and is rather like lines of longitude on a virtual globe. In plant cells, the tubulin threads are formed from the cytoplasm.
50
What events happen in Metaphase?
The pairs of chromatids attach to the spindle threads at the equator region.
They attach by their centromeres.
51
What events happen in Anaphase?
The centromere of each pair of chromatids splits.
Motor proteins, walking along the tubulin, pull each sister chromatid of a pair, in opposite directions, towards opposite poles.
Because their centromere goes first, the chromatids, now called chromosomes, assume a V shape.
52
What events happen in Telophase?
| Diagrams for the stages of mitosis are on page 149.
The separated chromosomes reach the poles.
A new nuclear envelope forms around each set of chromosomes.
The cell now contain two nuclei each genetically identical to each other and to the parent cell from which they arose.
53
What happens once mitosis is complete in plant cells?
Cytokinesis
Once mitosis is complete, the cell splits into two, so that each new cell contains a nucleus.
In plant cells, an end plate forms where the equator of the spindle was, and new plasma membrane and cellulose cell-wall material are laid down on either side along this end plate.
Two new identical daughter cells are now formed. they are genetically identical to each other and to the parent cell.
54
What happens once mitosis is complete in animal cells?
Cytokinesis
Once mitosis is complete, the cell splits into two, so that each new cell contains a nucleus.
In animal cells, the plasma membrane folds inwards and 'nips in' the cytoplasm.
Two new identical daughter cells are now formed. they are genetically identical to each other and to the parent cell.
55
How can you examine mitosis in a plant?
Cells of root tips can be stained with acetic orcein (which stains chromosomes) and observed under a microscope, to see the stages of mitosis.
56
Why can you only examine mitosis in plants in their meristems?
Once plant cells have divided and differentiated and have a vacuole and ridged cellulose cell wall, they cannot divide. There are meristems, such as shoot and root tips and cambium between xylem and phloem tissue, where plant cells are undifferentiated and can divide by mitosis,
57
How can you stain and examine root tip cells?
Cell root tips can be stained with acetic orcein (which stains chromosomes) and observed under a microscope, to see the changes in mitosis.
58
What is a haploid?
Having only one set of chromosomes; represented by the symbol 'n'.
59
What is homologous chromosome?
Matching chromosomes, containing the same genes at the same places (loci). They may contain different alleles for some of the genes.
60
What is meiosis?
A type of nuclear division that results in the formation of cells containing half the number of chromosomes of the parent cell.
61
Why dies sexual reproduction increase genetic variation?
Because it involves the combining of genetic material from two (usually) unrelated individuals of the same species, by the process of fertilisation.
62
What does genetic variation within a population increase?
Genetic variation within a population increases its chances of survival when the environment changes, as some individuals will have characteristics that enable them to be better adapted to the change.
63
In sexual reproduction why is a diploid zygote produced?
In many organisms, the body cells are diploid. For sexual reproduction to occur they must produce haploid gametes, so that when two gamete nuclei fuse during fertilisation, a diploid zygote is produced and the normal chromosome number is maintained through generations.
64
What does meiosis mean, and when does it occur?
Meiosis means reduction, and it occurs in diploid germ cells to produce haploid gametes.
65
Where are diploid cells that are undergoing mitosis?
The diploid cells undergoing meiosis are in specialised organs called gonads - ovaries and testes (these cells have been in interphase before they enter meiosis).
66
How many chromosomes do you have in your body cells?
46
67
Where did the chromosomes in your body cells come from?
23 came from your mother, in the egg nucleus and 23 came from your gather in the sperm nucleus.
68
What are homologous chromosomes?
The 46 chromosomes in your body cells can form matching pairs - one maternal and one paternal chromosome containing the sane genes at the same place on the chromosome. These matching pairs are called homologous chromosomes.
Homologous chromosomes have the same genes but contain different alleles (variants) for the genes.
69
What is a photomicrograph of chromosomes called?
A karyotype.
70
Describe a Karyotype of a singular male.
One pair of chromosomes is not fully homologous, X,Y but enough homology exists to pair them up. The chromosomes in each of the homologous pairs consist of two chromatids, because these chromosomes were observed using a light microscope abs photographed as the nucleus was dividing.
71
How many divisions are there in meiosis?
There are two divisions in mitosis, and in each divisions there are four stages.
72
What are the stages In the first meiotic division?
The four stages are prophase 1, metaphase 1, anaphase 1, and telophase 1.
73
Sum up the main stages of meiosis.
Before meiosis, during the S phase of interphase, each chromosome was duplicated as its DNA replicated, after which each chromosome consists of two sister chromatids. In meiosis the chromosomes pair up in their homologous pairs.
74
What happens in meiosis after the first meiotic division?
The cell may enter a short interphase before embarking on the second meiotic division that also has four stages. Prophase 2, metaphase 2, anaphase 2 and telophase 2. This takes places at right angles to that of meiosis one.
75
What may the cycle of meiosis end with?
At the end of the second division, cytokinesis.
76
What is the first event in prophase 1 of meiosis?
The chromatin condenses and each chromosome supercoils. In this state, they can take up stains and be seen with a light microscope.
77
In prophase 1 of meiosis? what happens after the chromosome supercoils?
The nuclear envelope breaks down, and spindle threads of tubulin protein form the centriole in animal cells.
78
What are the final stages of prophase in meiosis after the tubulin threads form?
The chromosomes come together in their homologous pairs.
Each member of the pair consists of two chromatids.
Crossing over occurs where non-sister chromatids wrap around each other and may swap sections so that alleles are shuffled.
79
How long does prophase in meiosis last?
Prophase 1 may last for days, mounts or years, depending on the species bs type of gamete (make or female) being formed.
80
What is the crossing over point in meiosis, between two chromatids?
Below the centromere, half way down the middle of the two central chromatids, one from each chromosome.
81
How does metaphase 1 of meiosis begin?
The pairs of homologous chromosomes, still in their crossed over state attach along the equator of the spindle.
Each attaches to a spindle thread by its centromere.
82
What happens in metaphase 1 of meiosis after each chromosome attaches to a spindle threads?
The homologous pairs are arranged randomly, with the members of each pair facing opposite poles of the cell. This arrangement is independent assortment.
The way that they line up in metaphase determines how they will segregate independently when pulled apart during anaphase.
83
What happens in anaphase 1 of meiosis?
The members of each pair of homologous chromosomes ate pulled apart by motor proteins that dead them along the tubulin threads of the spindle.
The centromeres do not divide, and each chromosome consists of two chromatids.
The crossed over area separate from each other, resulting in swapped areas of chromosome and allele shuffling.
84
What is the first event in telophase 1 of meiosis?
In most animal cell, two new nuclear envelopes form around each set of chromosomes, and the cell divides by cytokinesis. There is then a short interphase when the chromosomes uncoil.
85
In telophase 1 of meiosis what happens after chromosomes uncoil?
Each new nucleus contains half the original number of chromosomes, but each chromosome consists of two chromatids.
In most plant cells, the dell goes straight from anaphase 1 into prophase 2.
86
What happens in prophase 2 of meiosis?
If the nuclear envelopes have reformed, then they now break down.
The chromatids coil and condense, each one consisting of two chromatids.
The chromatids of each chromosome are no longer identical, due to crossing over in prophase 1.
Spindles form.
87
In prophase 2 of meiosis where do the new spindles form?
New spindle fibres form at right angles to the previous axis.
88
What happens in metaphase 2 of meiosis?
The chromosomes attach, by their centromere, to the equator of the spindle.
The chromatids of each chromosome are randomly arranged.
The way that they are arranged will determine how the chromatids separate during anaphase.
89
What happens in anaphase 2 of meiosis?
The centromeres divide.
The chromatids of each chromosome are pulled apart by motor proteins that drag them along the tubulin threads of the spindle, towards opposite poles.
The chromatids are therefore randomly segregated.
90
What events takes place in telophase 2 of meiosis?
Nuclear envelope forms around each of the four haploid nuclei.
In animals, the two cells now divide to give four haploid cells.
In plantsman, a tetrad of four haploid cells is formed.
91
What are the four ways meiosis produces genetic variation?
Crossing over during prophase shuffles alleles.
Independent assortment of chromosomes in anaphase 1 leads to random distribution of maternal and paternal chromosomes of each pair.
Independent assortment of chromatids in anaphase 2 leads to further random distribution of genetic material.
Haploid gametes are produced, which can undergo random fusion with gametes derived from another organism of the same species.
92
What isn't an example of a mutation that may be considers a mutation in meiosis?
Shuffling of alleles during crossing over in meiosis leads to genetic variation, but is not an example of mutation.
93
In the ovaries if human female fetuses when do the cells begin to divide?
Germ cells have already begun meiosis, and these cells remain. Suspended in prophase 1 from birth until puberty, when each mounts completes meiosis 1 and enters meiosis 2. Meiosis 2 is not completed until a sperm has entered the ovum.
94
What is differentiation?
Process by which stem cells become specialised into different types of cell.
95
What are epithelial cells?
Cells that constitute lining tissue.
96
What is a erythrocyte?
A red blood cell.
97
What is a neutrophil?
A type of white blood cell that is phagocytic (can ingest microbes and small particles).
98
What is a stem cell?
A unspecialised cell able to express all of its genes and divide by mitosis.
99
What determines the division of labour in a single celled organism?
Within a single celled organism, such as an amoeba, the division of labour is determined by the organelles, each of which has a specific function.
100
What is an advantage of single celled organisms that helps gasses diffuse across their membrane?
Single-celled organisms are small and have a large surface to volume ratio so that oxygen can diffuse across their plasma membrane, and waste products can diffuse out via the same membrane.
101
What does the lower surface area to volume ratio of a multicellular organism in comparison to a single celled organism mean for gas exchange?
Multicellular organisms are larger and therefore have smaller SA/V ratio, which means that most if their cells are not in direct contact with the external environment. They need specialised cells to carry out particular functions.
102
How do multicellular eukaryotic organisms start life?
As a single undifferentiated cell, called a zygote.
103
How does a zygote result?
When an ovum (egg cell) is fertilised by a spermatozoon and the two haploid nuclei fuse to give a cell with a diploid nucleus.
104
How does a zygote split to form undifferentiated cells?
The zygote is not specialised, and all the genes in its genome are able to be expressed. It is also able to divide by mitosis. It is a stem cell. After several mitotic divisions, an embryo forms, containing many undifferentiated embryonic stem cells.
105
What do genome and gene pool refer to?
Genome refers to the genetic material within an individual. Gene pool refers to all the genetic information within a population. So individuals have a genome, and populations have a gene pool.
106
How do embryonic cells differentiate?
They differentiate as certain genes are switched off and other genes may be expressed more.
107
What may change when cell differentiate?
The proportions of different organelles differs from those of other cells.
The shape of the cell changes.
Some of the contents of the cell change.
Owing to this differentiation, each cell type is specialised for a particular function.
108
What do erythrocytes do in mammals?
Carry oxygen from the lungs to respiring cells.
109
What do neutrophils do in mammals?
Neutrophils ingest invading pathogens.
110
Where are erythrocytes and neutrophils derived from?
These cell are very different from each other, but both derive from stem cells in the bone marrow.
111
Erythrocytes are adapted to carry out their function in several different ways, which adaption involves diffusion.
They are very small, about 7.5 um in diameter, so have a large SA/V ratio. This means that oxygen can diffuse across their membranes and easily reach all regions inside the cell. Their biconcave shape increases their SA/V ratio.
112
What do you find in normal blood?
Erythrocytes ( the highest proportion ), neutrophil, lymphocyte, monocytes and platelets.
See page 153 for a diagram of the proportions within the vesicles.
113
Erythrocytes are adapted to carry out their function in several different ways, which adaption involves the cytoskeleton.
They are flexible. A well developed cytoskeleton allows the erythrocytes to change shape so that they can twist and turn, as they travel through very narrow capillaries.
114
Erythrocytes are adapted to carry out their function in several different ways, which adaption involves organelles.
Most of their organelles are list at differentiation, so they have no nucleus, mitochondrial or endoplasmic reticulum, and very little cytoplasm. This provides more space for the many haemoglobin molecules housed inside them. Haemoglobin is synthesised within immature erythrocytes, whilst they still have their nucleus, ribosomes and rough endoplasmic reticulum.
115
How much of your white blood cells do neutrophils make up?
50%
116
What is the function of neutrophils?
Their function is to ingest bacteria and some fungi by phagocytosis.
117
What are neutrophils attracted to?
They are attracted to and travel towards infection sites by chemotaxis.
118
Briefly compare erythrocytes to neutrophils.
They are about twice the size of erythrocytes, and each neutrophil contains a multilobed nucleus.
119
How are spermatozoa specialised?
The many mitochondria carry out aerobic respiration. The ATP provides energy for the undulipodium (tail) to move and propel the cell towards the ovum.
Because spermatozoa are small but long an thin, they can move easily.
Once the spermatozoon reaches an ovum, enzymes are released from the acrosome (a specialised lysosome). The enzymes digest the outer protective covering of the ovum, allowing the sperm head to enter the ovum.
The head of the sperm contains the haploid male gamete nucleus and very little cytoplasm.
( diagram of spermatozoon on page 154)
120
What are epithelium cells?
Epithelium is lining tissue. It is found on the outside of your body and on the inside - for example making up the walls of the alveoli and capillaries and lining your intestines.
121
What shape are epithelial cells?
Squamous epithelial cells are flattens in shape.
| Many of the cells in epithelium have cilia.
122
How many cells are there in your body, and what does that number include?
There are about 210 different cell types in your body. They include neurones for carrying information, muscle cells for contraction and movement, bone cells in your skeleton, liver cells, pancreatic that make insulin, and cells in your ovaries or testes that make ova (eggs) or spermatozoa for reproduction, to name but a few.
123
How many cells is your body made of?
Your body is made up of around 40-50 trillion cells, of which about 25 billion are erythrocytes. However, you also house many useful bacteria in your mouth and in your large intestine. These cells are very small as you have about 10 times as many bacteria as your own body cells.
124
How may you examine erythrocytes and neutrophils?
You can examine prepared slides of some animal cells. In a blood smear you will see the features of erythrocytes and neutrophils. You may also measure the diameters of these cells.
125
What is a guard cell?
In leaf epidermis, cells that surround stomata.
126
What is a palisade cells?
Closely-packed photosynthetic cells within leaves.
127
What is a root hair cell?
Epidermal cells of young roots with hair-like projections.
128
Name the layers of a palisade cell.
Cuticle, upper epidermis, palisade mesophyll cells, xylem, phloem, lower epidermis, cuticle, spongy mesophyll cell, guard cell and stoma. (Diagram on page 155)
129
What parts of the leaf are present in a diagram of a stoma surrounded by a pair of guard cells?
Chloroplasts, a thickens inner wall, a stoma and two guard cells.
Diagram on page 155.
130
Palisade cells within leaves are well adapted for photosynthesis, which adaption involves shape?
They are long cylindrical, so that they pack together quite closely but with a little space between them for air to circulate; carbon dioxide in these air spaces diffuses into the cells.
131
Palisade cells within leaves are well adapted for photosynthesis, which adaptions the positioning of organelles?
They have a large vacuole so that the chloroplasts are positioned nearer to the periphery of the cell, reduces the diffusion distance for carbon dioxide.
They contain cytoskeleton threads and motor proteins to move the chloroplasts - nearer to the upper surface of the leaf when the sunlight intensity is low, but further down when it is high.
132
Palisade cells within leaves are well adapted for photosynthesis, which adaption allows photosynthesis to take place.
They contain many chloroplasts - the organelles that carry out photosynthesis.
133
Describe guard cells.
These are pairs of specialized cells, known as guard cell, within the lower epidermis, that do not contain chloroplasts. However, they cannot carry out photosynthesis, as they do not have the enzyme needed for the second stage of the process.
134
What makes guard cells swell?
Light energy is used to produce ATP.
The ATP actively transports potassium ions from surrounding epidermal cells into the guard cells, lowering their water potential.
Water now enters the guard cells from neighboring epidermal cells, by osmosis.
The Guard cells swell.
135
How do stoma open as the guard cells dwell?
The guard cells swell, but at the tips the cellulose cell wall is more flexible, and is more ridged where it is thicker. The tips bulge, and the gap between them, the stoma (from Greek word meaning mouth) enlarges.
136
What does the the opening of the stomata allow?
As the stoma open, air can enter the spaces within the layer if cells beneath the palsied cells. As they use it for photosynthesis, this will the maintain a steep concentration gradient.
Oxygen produced during photosynthesis can diffuse out of the palisade cells. As they use it for photosynthesis, this will then maintain a steep concentration gradient.
Oxygen produced during photosynthesis can diffuse out of photosynthesis into the air spaces and out through the open stomata.
When the stomata open, water vapour also exits from them. (Transpiration)
137
What are root hair cells?
Epidermal cells on the outer layer of young plant roots.
138
What increases the amount of mineral ions absorbed by root hair cell?
The hair-like projections greatly increases the surface area for absorption of water and mineral ions, such as nitrates from the soil into which it projects.
139
How are minerals absorbed into root hair cells?
Mineral ions are actively transported into the root hair cells, lowering the water potential within them and causing water to follow by osmosis, down the water potential gradient.
140
What do root hair cells contain that allow them to actively transport minerals.
The root hair cells have special carrier proteins in the plasma membranes in order to actively transport the mineral ions in.
These cells will also produce ATP, as this is needed for active transport.
141
What does Xylem and Phloem form?
The vascular tissue of plants. Xylem vessels and phloem sieve tubes are present in vascular bundles.
142
How were paliside cells named?
Because they resemble a fence made from a row of posts.
143
How would you examine paliside cells and its components?
You can examine prepared slides of leaf sections to identify and not the features of palisade cells, vascular bundles and guard cells. If you use forceps to strip a piece of lower epidermis from a geranium leaf and mount it in water, on a microscope slide, you can observe guard cells in stomata.
144
What is tissue?
A group of cells that work together to perform a specific function/set of functions.
145
What are cells?
The basic building blocks of living organisms and how, within multicellular organisms, cells become specialized for different functions. A group of similar cells working together to perform a certain function is called a tissue.
146
What are the our main types of tissue in your body?
Epithelial or lining tissue.
Connective tissues - these hold structures together and provide support, e.g. blood, bone and cartilage.
Muscle tissue - made of cells that are specialized to contract and cause movement.
nervous tissue - made of cells specialized to conduct electrical impulses.
147
What does epithelial tissue cover?
It covers and lines free surfaces in the body such as the skin, cavities of the digestive and respiratory system (gut and airways), blood vessels, heart chambers and walls of organs.
148
What are epithelial tissues made up of?
Almost entirely of cells.
149
How are cells connected?
These cells are very close to each other and form continuous sheets. Adjacent cells are bound together by lateral contracts, such as tight junctions and desmosomes.
150
How do epithelial cells receive nutrients?
There are no blood vessels within epithelial tissue; cells receive nutrients by diffusion from tissue fluid in the underlying connective tissue.
151
Describe the surface of a epithelial cell.
Some epithelial cells have smooth surfaces, but some have projections, either cillia or microvilli.
152
What functions is epithelial tissue specialised to carry out?
Protection, absorption, filtration, excretion and secretion.
153
Describe the cell cycle of epithelial cells?
Epithelial cells have short cell cycles and divide up to two or three times a day to replac e worn or damged tissue.
154
How long does it take for epithelial tissue to fully replace.
Every four days your whole intestinal lining will be replaced with new epithelial cells.
155
What are microvilli?
Extensions on the plasma membrane to increase its surface area.
156
What are cillia?
(Do not confuse with microvilli) Cillia are hair like organelles, some of which beat and propel substances along the epithelial surfaces. In some cases, a single cilium on a cell acts as an antenna. It has receptors on it to receive chemical signals from its surroundings.
157
Where are ciliated cells used to transport other cells?
In the oviduct he cillia beat and move the Ovum along the oviduct, from ovary to uterus.
158
Describe the lining of alveoli.
The walls of alveoli (air sacs) in your lungs are one cell thick, they are made of a single layer of flattened squamous epithelial cells. This provides a short diffusion distance for gaseous exchange.
159
What does connective tissue consist of?
It consists of a non-living extracellular matrix containing protien (collagen and elastin) and polysaccharides (such as hyaluronic acid, which traps water).
160
What is the purpose of connective tissue?
The matrix separates the living cells within the tissue and enables it to withstand forces such as weight.
161
Give some examples of connective tissue.
Connective tissue is widely distributed in the body.
| Blood, bone, cartilage, tendons and ligaments are examples of connective tissue. Skin also contains connective tissue.
162
What are the different types of cartiliage?
There are three types, hyaline, fibrous and elastic.
163
How does cartiliage become mature?
Immature cellsin cartilage are called chondroblasts. They can divide by mitosis and secrete the extracellular matrix. Once the matrix has been synthesized, the chondroblasts become mature, less active chondrocytes, which maintain in the matrix.
164
What is the purpose of hyaline cartilage?
Hyaline cartilage forms the embryonic skeleton, covers the ends of long bones in adults, joins ribs to the sternum, and is found in nose, trachea (forming the C-shaped rings of cartilage that keep the trachea open) and larynx.
165
What is the purpose of fibrous cartilage?
Fibrous cartilage occurs in discs between vertebrae in the backbone (spine) and in the knee joint.
166
What is the purpose of elastic cartilage?
Elastic cartilage makes up the outer ear (pinna) and the epiglottis (flap that closes over the larynx when you swallow)
167
What are muscle cells called?
Fibres.
168
Describe muscle fibres.
They are elongated and contain special organelles called myofilaments made of proteins actin and myosin.
169
What do myofilaments allow?
Allow the muscle tissue to contract.
170
What are the three typers of muscle tissue?
Skeletal muscles, cardiac muscle and smooth muscle.
| There are pictures of each muscle on page 158.
171
Describe skeletal muscle.
Packaged by connective tissue sheets, joined to bones by tendons; these muscles, when they contract, cause bones to move.
172
Describe cardiac muscle.
It makes up the walls of the heart and allows the heart to beat and pump blood.
173
Describe smooth muscle.
It occurs in the walls of the intestine, blood vessels, uterus and urinary tracts, and it propels substances along these tracts.
174
What is a meristem?
An area of un-specialized cells within a plant that can divide and differentiate into other cell types.
175
What is an organ?
A collection of tissues working together to perform a function/related functions.
176
What is phloem?
Tissue that carries products of photosynthesis, in solution, within plants.
177
What is xylem?
Tissue that carries water and mineral ions from the roots to all parts of the plant.
178
What does plants epidermal tissue consist of?
Epidermal tissue is equivalent to epidermal tissue in animals. It consists of flattend cells that, apart from the guard cells, lack chloroplasts and form a protective covering over leaves, stems and roots.
179
What is plant tissue?
In animals groups of similar cells work together to perform a certain function. Plants also contain tissues, made up of specialized cells.
180
What are the main types of plant tissues?
Epidermal tissue, vascular tissue and meristematic tissue.
181
What are some epidermal cells impregnated with?
Some epidermal cells also have walls impregnated with a waxy substance, forming a cuticle. This is particulay important to plants that live in dry places, as the cuticle reduces water loss.
182
What is vascular tissue?
Vascular tissue is concerned with transport. There are two sorts - xylem and phloem both present in vascular bundles.
183
Describe xylem vessels.
Xylem vessels carry water and minerals form roots to all parts of the plant.
184
Decribe phloem vessels.
Phloem sieve tubes transfer the products of photosynthesis (mainly sucrose sugar), in solution, form leaves to parts of the plant that do not photosynthesise, such as roots, flowers and growing shoots.
185
How did early investiagtors into phloem make use of aphids?
Aphids (greenfly) insert their needle-like mouth parts into the phloem tissue of some plants. Early investigations to analyse the composition of phloem made use of this and decapitated plugged in aphids, leaving their inserted mouthparts intact, through which phloem sap could be collected.
186
What is the purpose of lignin and in what shape does it occur?
Walls of some cells have lignin deposited in them, for strength. Lignin sometimes occurs in rings, sometimes as coils and sometimes a spirals.
A micrograph of the lignin in an xylem vessel is on page 159.
The is also a micrograph of a sieve plate on 159.
187
What is meristematic tissue and where is it found?
Meristematic tissue contains stem cells. It is from this tissue that all other plant tissues are derived by cell differentiation. It is found at root and shoot tips, and in the cambium of vascular bundles. These areas are called meristems.
188
Describe the cells in meristems.
They;
have thin walls containing very little cellulose
do not have chloroplasts
do not have a large vacuole
can divide by mitosis and differentiate into other types of cells.
189
When examining meristems what is a commonly used section of pant material?
The onion root tips that you may have examined when studying mitosis, hence many cells there were dividing.
190
What happens as most plant cells mature, and how does this affect the growing of new cells.
They develop a large vacuole and ridged cellulose cell wall. These prevent the cell from diving. However plants need to grow and produce new cells. New cells arise at the meristems, by mitosis.
191
What type of cells differentiate into xylem vessels or phloem sieve tubes?
Cambium cells.
192
Describe how some cambium cells differentiate into xylem vessels.
Lignin (a woody substance) is deposited in their cell walls to reinforce and waterproof them; however, this also kills the cells.
The ends of the cells break down so that the xylem forms continuous columns with wide lumens to carry water and dissolved minerals.
193
Describe how cambium cells differentiate into phloem sieve tubs or companion cells.
Companion cells retain their organelles and continue metabolic functions to provide ATP for active loading of sugars into the sieve tubes.
194
What is in plant vascular bundles?
Plant vascular bundles contain xylem tissue, cambium tissue and phloem tissue.
195
What is the purpose of xylem?
Xylem carries water and minerals.
196
What is the purpose of phloem?
Phloem carries dissolved products of photosynthesis.
197
What is the purpose of cambium cells?
Cambium cells can divide by mitosis and make new cells that may differentiate into either xylem or phloem.
There is a micrograph on page 160 with all the parts of a vascular bundle.
198
What is parenchyma?
Parenchyma is packing tissue and fills spaces between other tissues. In roots, parenchyma cells may store starch. In leaves, some parenchyma cells (called chlorenchyma) have chloroplasts and can photosynthesise.
In aquatic plants, aerenchyma tissue is parenchyma with air spaces to keep the plant buoyant.
199
What is sclerenchyma?
Sclerenchyma cells have lignified walls, and these cells strengthen stems and leaf midribs.
200
What is collenchyma?
Collenchyma cells have thick cellulose walls, and they strengthen the vascular bundles and outer parts of stems, whilst also allowing some flexibility in these regions.
201
What are the main functions of a leaf?
Photosynthesis
202
What are the main functions of the root?
Anchorage in soil
Absorption of mineral ions and water
Storage, e.g. carrot, parsnip, dahlia and swede roots store carbohydrates
203
What are the main functions of the stem?
Support
Holds leaves up so that they are exposed to more sunlight.
Transportation of water and minerals.
Transportation of products of photosynthesis., e.g. potato tubers store starch; rhubarb stems store sugars and polysaccharides
204
What are the main functions of flowers?
Sexual reproduction
205
Why could flowers be regarded to be an organ system?
They include different organs within them - sepals, petals, ovaries and stamens.
206
What are some examples of animal organs?
The heart, kidney, liver, brain, optic nerve, biceps muscle, lungs and the eye.
207
State the organs and tissues involved in the digestive system.
Oesophagus; stomach, intestines plus associated glands; the liver and pancreas.
208
What are some examples of life processes carried out by the digestive system?
Nutrition to provide ATP and materials for growth and repair.
209
State the organs and tissues involved in the circulatory system.
Heart and blood vessels.
210
What are some examples of life processes carried out by the circulatory system?
Transport to and from cells.
211
State the organs and tissues involved in the respiratory system.
Airways and lungs, plus diaphragm and intercostal muscles.
212
What are some examples of life processes carried out by the respiratory system?
Breathing and gaseous exchange, excretion
213
State the organs and tissues involved in the urinary system.
Kidneys, ureters and bladder
214
What are some examples of life processes carried out by the urinary system?
excretion and osmoregulation.
215
State the organs and tissues involved in the integumentary system.
Skin, hair and nails
216
What are some examples of life processes carried out by the integumentary system?
Water-proofing, protection, temperature regulation
217
What organ system involves the skeleton and skeletal muscles?
The musculo-skeletal system
218
What are some examples of life processes carried out by the musculo-skeletal system?
Support, protection and movement
219
State the organs and tissues involved in the immune system.
bone marrow, thymus gland, skin, stomach acid, blood
220
What are some examples of life processes carried out by the immune system?
protection against pathogens
221
State the organs and tissues involved in the endocrine system.
glands that make hormones, e.g. thyroid, ovaries, testes, adrenals
222
What are some examples of life processes carried out by the endocrine system?
communication, control and coordination
223
State the organs and tissues involved in the reproductive system?
testes. penis, ovaries, uterus, vagina
224
What are some examples of life processes carried out by the reproductive system?
reproduction
225
State the organs and tissues involved in the lymph system.
lymph nodes and vessels
226
What are some examples of life processes carried out by the lymph system?
transport of fluid back to the circulatory system and is also important in resisting infections
227
What is an organ system?
A number of organs working together to carry out an overall life function.
228
What is your largest organ?
The skin is your largest organ. Within it are other smaller organs, such as hair follicles.
229
What is the definition of a stem cell?
They are unspecialised cells able to express all of its genes and divide by mitosis.
230
What are stem cells able to do?
Stem cells are undifferentiated cells capable of becoming any type of cell in the organism.
They are able to express all of their genes.
They can divide by mitosis and provide more cells that can then differentiate into specialised cells, for growth and tissue repair.
231
What are stem cells described as?
pluripotent
232
What have the characteristics of stem cells made them useful for?
They are potentially very important in research for medical use.
233
What are the different sources of stem cells?
embryonic stem cells
stem cells in umbilical-cord blood
adult stem cells
induced pluripotent stem cells
234
Describe where embryonic stem cells are present.
These are present in an early embryo formed when a zygote begins to divide.
235
Describe where adult stem cells are present.
(also found in infants and children) Adult stem cells are found in developed tissues, such as blood, brain, muscle, bone, adipose (fat storage) tissue and skin, amongst the differentiated cells; they act like a repair system because they are a renewing scource of undifferentiated cells.
236
Describe where induced pluripotent stem cells are present.
Induced pluripotent stem cells (ipS cells) developed in laboratories by reprogramming differentiated cells to switch on certain key genes and become undifferentiated.
237
What are the different potential uses of stem cells from bone marrow in medicine?
Stem cells from bone marrow are already extensively used in bone-marrow transplants to treat diseases of blood and immune system. They are also used to restore the patients blood system after treatment for specific types of cancer, where the patients's bone-marrow cells can be obtained before treatment, stored, and then put back inside the patient after treatment.
238
State some diseases of the blood stem cells from bone marrow can be used to treat?
Sickle-cell anaemia and leukaemia
239
State some diseases of the immune system stem cells from bone marrow can be used to treat?
Severe combined immunodeficiency or SCID.
240
How may stem cells aid drug research?
If stem cells can be made to develop into particular types of human tissue, then new drugs can be tested first on these tissues, rather than on animal tissue.
241
Developmental biology;
Scientists can make use of stem cells, in many ways, to research developmental biology and enable a better understanding of how multicellular organisms develop, grow and mature. Give two example of things they can study.
They can study how these cells develop to make particular cell types (e.g. blood, bone, muscle and skin) and can learn how each cell type functions and see what goes wrong when they are diseased.
They are trying to find out if they extend the capacity that embryo's have for growth and tissue repair, into later life.
242
Why is research into stem cell repair or replacement still ongoing.
It is quite difficult to culture stem cells in a lab. Also it is necessary to find out which cytokines cell-signalling molecules are needed to direct the differentiation of stem cells into particular cell types.
243
Describe the advances towards treating diabetes with stem cells.
Stem cells have been used to treat mice with type 1 diabetes by reprogramming iPS cels to become pancreatic beta cells. Research is underway to develop such treatment for type 1 diabetes in humans.
244
Are stem cells being used to treat liver disease?
Bone-marrow stem cells can be made to develop into liver cells (hepatocytes) and could be used to treat liver disease.
245
What would stem cells being directed at nerve tissues be being used to treat?
Stem cells directed to become nerve tissue could be used treat Alzheimer and Parkinson diseases or to repair spinal-cord injuries.
246
Describe regenerative medicine using stem cells.
Stem cells may be used to populate a bioscaffold of an organ, and then directed to develop and grow into specific organs for transplanting. This is called regenerative medicine. If the patients cells are obtained, reprogrammed to become iPS cells, and then used to make to make such an organ, there will be no need for immunosuppressant drugs.
247
State some conditions may stem cells eventually be able to treat, but the treatments are not currently being used.
Stem cells may eventually be used to treat many conditions, including arthritis, stroke, burns, vision and hearing loss, Duchenne muscular dystrophy and heart disease.
248
What is the meaning of pluripotent mean?
Pluripotent literally means able to make many cell types - in the case of iPS cells very very many.
249
What is the special word for a cell which can make not only all the cells of the body, but placental cells too?
Totipotent.
250
On page 163 there is an example of a bioscaffold of a human ear and a person who received a trachea bioscaffold, which was populated with stem cells.
The end of 2.6 :)
