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Biology > Cell Divison, Cell Diversity And Cell Differentiation > Flashcards

Cell Divison, Cell Diversity And Cell Differentiation Flashcards

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1
Q

What is interphase?

A

Phase of cell cycle where the cell is not dividing; it is subdivided into growth and synthesis phases

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2
Q

What is mitosis.

A

Type of nuclear division that produces daughter cells genetically identical to each other and to the parent cell

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3
Q

What is cytokinesis?

A

Cytoplasmic division following nuclear division, resulting in two new daughter cells

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4
Q

What are the two main checkpoints?

A

G1/s checkpoint also called restriction point

G2/M checkpoint

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5
Q

What are the purpose of checkpoints?

A

Prevent uncontrolled division that would lead to tumours

Detect and repair damage to DNA

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6
Q

M phase

A

A checkpoint chemical triggers condensation of chromatin

Halfway through the cycle, metaphase checkpoint ensures cell is ready to complete mitosis

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7
Q

Events during M phase

A

Cell growth stops
Nuclear division consisting of stages: prophase, metaphase, anaphase and telophase
Cytokinesis

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8
Q

G0 phase

A

Resting phase triggered during early g1 at the restriction point, by a checkpoint chemical
Some cells don’t have this

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9
Q

Events during g0 phase

A

Cells undergo apoptosis, differentiation or senescence

Some types of cells remain in this phase for a very long time

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10
Q

G1 phase (also called growth phase)

A

G1 checkpoint control mechanism ensures that the cell is ready to enter the s phase and begin DNA synthesis

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11
Q

Events in G1

A 
Cells grow and increase in size 
Transcription 
Organelles duplicate 
Biosynthesis 
P53 gene helps control this phase
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12
Q

S phase of interphase

A

Because chromosomes are unwound and DNA is diffused, every molecule of DNA is replicated
Housekeeping genes which are active in all cells are duplicated first
Normally inactive genes are duplicated last

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13
Q

Events in s phase

A

Once entering this phase, cell is commited to completing cell cycle
DNA replicates
When all chromosomes are duplicated, each one consists of a pair of identical sister chromatids
Phase is rapid and exposed DNA are more susceptible to mutagenic agents. Reduces the chance of spontaneous mutation

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14
Q

G2 phase of interphase

A

Chemicals ensure the cell is ready for mitosis by stimulating proteins that will be involved in making chromosomes condense and in formation of spindles

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15
Q

G2 events

A

Cells grow

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16
Q

What are chromatids?

A

Replicates of chromosomes

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17
Q

What is cytokinesis?

A

Division of the cytoplasm of a cell following mitosis

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18
Q

What is mitosis?

A

Type of nuclear division that maintains the chromosome number; each new daughter cell contains the same genetic information as the parent cell. Genetically identical

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19
Q

What is asexual reproduction and where does it occur?

A

Single celled protoctists such as amoeba divide by mitosis
Some plants produce new plantlets on the end of stolons
Fungi use mitosis
Some female sharks without male produces offspring that is genetically identical
Aphids may produce eggs that do not need fertilising

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20
Q

How do multicellular organisms grow?

A

All multicellular organisms grow by producing cells that are genetically identical to each other and to the parent cell from which they arose by mitosis

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21
Q

How do tissues repair?

A

Wounds heal when growth factors, secreted by platelets and macrophages and damages cells of the blood vessel walls, stimulate the proliferation of endothelial and smooth muscle cells to repair damaged blood vessels

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22
Q

Events during prophase?

A

Chromosomes shorten and thicken as DNA is supercoiled
Nuclear envelope breaks down
Centriole in animal cell divides and two new daughter centrioles move to opposite poles
Cytoskeleton protein threads form spindles between centrioles
(In plants tubulin threads form from cytoplasm)

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23
Q

Events during metaphase

A

Pairs of chromosomes attach to the spindle threads at the equator region
Attach at their centromeres

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24
Q

Events during anaphase

A

Centromere of each pair of chromatids splits
Motor proteins, walk along tubulin threads, pull each sister chromatid of a pair to opposite poles
Chromosomes assume a v shape

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25
Events during telophase
Separated chromosomes tech poles Nuclear envelope forms around each set Cell now contains two nuclei genetically identical to parent cell they arose from
26
What's happens in animals and plants during cytokinesis?
Animals- plasma membrane folds inwards and nips in the cytoplasm Plant- an end plate forms where the equator of the spindle was, and new plasma membrane and cellulose cell wall materials are laid down either side along this end plate
27
What's a haploid?
Having only one set of chromosomes presented by the symbol 'n'
28
What are homologous chromosomes?
Matching chromosomes, containing the same genes at the same places. They may contain different alleles for some genes
29
What is meiosis?
Type of nuclear division that results in the formation of cells containing half the number of chromosomes of the parent cell
30
Why does sexual reproduction increase genetic variation?
Involved the combining of genetic material from 2 unrelated individuals of the same species, by the process of fertilisation.
31
Why is genetic variation important?
Increases its chances of survival when the environment changes Some individuals have characteristics that enable them to be better adapted to the change
32
What are most body cells?
Diploid
33
What must be produced for sexual reproduction to occur?
Haploid gametes
34
What are matching pairs of chromosomes called?
Homologous pair
35
How many divisions are there in meiosis?
2
36
Prophase 1
Crossing over. Chromosomes compromise 2 chromatids Centrioles at opposite ends of cell Nuclear envelope disintegrates
37
Events during prophase 1
Chromatin condenses and each chromosome supercoils Envelope breaks down Spindle threads of tubulin protein form from centrioles Chromosomes come together in homologous pairs Each member of pair consists of 2 chromatids Crossing over occurs between non sister chromatids. May swap sections so alleles are shuffled
38
Metaphase 1
Spindles attach to centromere at equator
39
Events during metaphase 1
Crossed over chromosomes attach to spindles at centromere Homologous pairs arranged randomly with members of each pair facing opposite poles of the cell - independent assortment The way they line up determines how they will segregate independently when pulled apart
40
Anaphase 1
Homologous chromosomes r pulled to opposite poles
41
Events during anaphase 1
Each pair of homologous chromosomes are pulled apart by motor proteins that drag them along threads of the spindle Centromere do not divide, each chroma some consists of 2 chromatids Swapped areas of chromosomes and allele shuffling
42
Telophase 1
Nuclear envelope forms
43
Events during telophase 1
Two nuclear envelopes form around each set of chromosomes and cytokinesis occurs. Then short interphase where chromosomes uncoil Each nucleus contains half original number of chromosomes but each chromosome consists of 2 chromatids
44
Prophase 2
Centrioles replicate and move to poles | New spindles form at right angles to previous spindle axis
45
Events during prophase 2
Nuclear envelopes break down again Chromosomes coil and condense Chromatids of each chromosome are not identical Spindles form
46
Metaphase 2
Chromosomes lye on the equator of cell
47
Events during metaphase 2
Chromosomes attach, by the centromere, to the equator of the spindle Chromatids of each chromosome are randomly arranged Arrangement determines how they separate during anaphase 2
48
Anaphase 2
Chromatids mace to poles
49
Events during anaphase 2
Centromere divides Chromatids of each chromosome are pulled apart by motor proteins that drag them along the tubulin threads of the spindle, towards opposite poles Chromatids randomly segregated
50
Telophase 2
4 haploid cells
51
Events during telophase 2
Nuclear envelope forms around haploid nuclei In animals, the 2 cells now divide to give 4 haploid In plants, a tetrad of four haploid cells is formed
52
How does meiosis produce genetic variation?
Crossing over during prophase 1 Independent assortment of chromosomes in anaphase 1 leads to random distribution of maternal and paternal chromosomes of each pair Independent assortment of chromatids during anaphase 2 leads to further random distribution Haploid gametes undergo fusion with gametes derived from another organisms
53
What is differentiation?
Process by which stem cells become specialised into different types of cell
54
What are epithelial cells?
Cells that constitute lining tissue
55
Why are erythrocytes?
Red blood cells
56
What are neutrophils?
Type of white blood cell that is phagocyte (can ingest microbes and small particles)
57
What are stem cells?
Unspecialised cell able to express all of its genes and divide by mitosis
58
Why do multicellular organisms need specialised cells to carry out particular functions?
They have a small surface area to volume ratio which means most of their cells are not in direct contact with the external environment
59
What is a zygote a result of?
When the ovum is fertilised by the spermatozoon and the two haploid nuclei fuse to give a cell with a diploid nucleus
60
Why do embryonic cells differentiate when certain genes are switched off and other genes are expressed more?
Proportion of the different organelles differs from those of other cells The shape of the cell changes Some of the contents of the cell changes
61
Name 2 examples of specialised cells in mammals and their function
Erythrocytes - carry oxygen from the lungs to restoring cells Neutrophils - ingest invading pathogens
62
In what ways are erythrocytes adapted to carry out their function?
Very small 7.5 micrometers in diameter Large surface area/volume ratio Can diffuse across membranes to easily reach all regions inside the cell Biconcave Flexible Well developed cytoskeleton to change shape to fit through narrow capillaries No nucleus mitochondria or endoplasmic reticulum very little cytoplasm More space for haemoglobin molecules
63
Neutrophils
Twice the size of rbc Multilobed nucleus Attracted to and travel towards infection sites by chemotaxis Ingest bacteria and some fungi by phagocytosis
64
How are spermatozoa?
Many mitochondria to carry out aerobic respiration. ATP provides energy for undulipodia to move Small long and thin therefore move easily Enzymes in acrosome outer protective covering of ovum Head contains haploid male gamete nucleus and little cytoplasm
65
Epithelial cells - a type - location - what many have
Squamous Alveoli and intestines lining Cilia
66
Guard cell definition
In leaf epidermis, cells that surround stomata
67
Palisade cells definition
Closely packed photosynthetic cells within leaves
68
Root hair cells definition
Epidermal cells of your roots with long hair like projections
69
Why are palisade cells well adapted to photosynthesis
Long and cylindrical so pack together tightly and have air spaces for diffusion into cells Large vacuole so chloroplasts are nearer to the periphery of the cell reducing diffusion distance Contain many chloroplasts Cytoskeleton threads and motor proteins to move chloroplasts nearer to surface when light intensity Is high and vice versa
70
What do guard cells do to affect the water potential inside them?
They use light energy to create ATP ATP then actively transports potassium ions from surrounding epidermal cells into guard cells, lowering their water potential allowing water to enter
71
Root hair cells adaptions and functions
Hair like projections increasing surface area for absorption of water and mineral ions Ions actively transported in lower water potential bringing water with them Special carrier proteins in membrane in order to actively transport ions Produce ATP needed for active transport
72
Tissue definition
Group of cells that work together to preform a specific function/set of functions
73
What are the four main tissue types?
Epithelial Connective tissue Muscle tissue Nervous tissue
74
Characteristics of epithelial tissue
Made up almost entirely of cells Very close cells to form continuous sheets Adjacent cells are bound together by lateral contacts eg tight junctions and desmosomes No blood vessels within them, cells receive nutrients by diffusion from tissue fluid in the underlying connective tissue Short cell cycles and divide up to 2 or 3 times a day to replace worn or damaged tissue Specialised to carry out its function eg protection, absorption, filtration, excretion, secretion
75
What does connective tissue consist of?
Non living extra cellular matrix containing proteins eg collagen and elastin and polysaccharides eg hyaluronic acid, which traps water Matrix separates the living cells within the tissue and enables it to withstand forces such as weight
76
Examples of connective tissues
``` Blood Bone Cartilage Tendons Ligaments Skin contains it ```
77
What are immature cells in cartilage called? | What can they do?
Chondroblasts | Divide by mitosis and secrete the extracellular matrix
78
What are the 3 types of cartilage
Hyaline cartilage Fibrous cartilage Elastin
79
What does hyaline cartilage do?
Form embryonic skeleton, covers the ends of long bones in adults, joins ribs to the sternum and is found in the nose
80
What does fibrous cartilage do?
In discs between vertebrae in the backbone and in the knee joint
81
What does elastin cartilage do?
Makes up outer ear and the epiglottis
82
Describe muscle tissue
Well vascularised Muscle cells are called fibres Long elongated and contain special organelles called myofilaments made of the protein actin and myosin. These allow tissues to contract
83
What are the 3 types of muscles?
Skeletal muscles - cause bones to move Cardiac muscles - heart beats Smooth muscle - propels substances along tracts eg in intestine walls, blood vessels, uterus and urinary tracts
84
Driven meristem
Area of unspecialised cells within a plant that can divide and differentiate into other cell types
85
Define organ
Collection of tissues working together to preform a function/ related functions
86
Define phloem
Tissue that carries products of photosynthesis, in solution, within plants
87
Define xylem
Tissue that carries water and mineral ions from the roots to all parts of the plant
88
Describe epidermal tissue
Consists of flattens cells that, apart from guard cells, lack chloroplasts and form a protective covering over leaves, stems and roots Some epidermal cells also have walls impregnated with a waxy substance forming a cuticle
89
What are the two types of vascular tissue?
Xylem vessel | Phloem sieve tubes
90
Where is meristem tissue found?
Tips of roots and shoots | Cambium of vascular bundles
91
Cells in meristem are:
Have thin walls containing very little cellulose Don't hav chloroplasts Don't have a large vacuole Can divide by mitosis and differentiate into other types of cells
92
How do some cambium cells differentiate into xylem vessels?
Lignin is deposited in their cell walls to reinforce and waterproof them however this also kills the cell Ends of cells break so xylem forms continuous columns with wide lumens to carry water and displaced nutrients
93
How do cambium cells differentiate into phloem?
Sieve tubes Lose most their organelles and sieve plates develop between them Companion cells retain their organelles and continue metabolic functions to provide ATP for active loading of sugars into sieve tubes
94
Main function of organ | -leaf
Photosynthesis
95
Organ root
Anchorage Absorption of mineral ions and water Storage
96
Organ stem
``` Support Holds leaves up to expose to more sun light Transportation of water and minerals Transport of products of photosynthesis Storage of products of photosynthesis ```
97
Flower organ
Sexual reproduction

Biology (6 decks)

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