2.6 Cell Division, Cell Diversity and Cellular Organisation Flashcards
Cell Division and Cellular Organisation (75 cards)
1
Q
what is the cell cycle
A
- process that all body cells in multicellular organisms use to grow and divide
- sequence of ordered events which take place in a cell, resulting in cell division
- eukaryotic organisms
2
Q
what are the two phases of the cell cycle
A
- interphase (growth and DNA replication, and normal metabolic processes of cell)
- M phase, mitotic ( mitosis and cytokinesis)
- still a CONTINUOUS process
3
Q
what growth phases is interphase divided into
A
G1
S1
G2
4
Q
how is the cell cycle regulated
A
-by checkpoints
- occur at key points in the cycle to make sure it is OK for the process to continue
- if not, sends cell into G0 = rest phase where cell leaves the cycle (e.g. once differentiated, cell DNA has become damaged
5
Q
what does the G1 checkpoint do
A
- checks that the chemicals needed for DNA replication are present
- checks for any damage to DNA
… AS before entering s phase, at the end of G1 - cell size, nutrients, growth factors too
6
Q
what does the G2 checkpoint do
A
- checks whether all the DNA has been replicated without damage
- checks cell cycle
…AS before cell can enter mitosis, at the end of G2
7
Q
what does the metaphase checkpoint do
A
- cell checks that all the chromosomes are attached to the spindle
…AS before mitosis can continue
8
Q
what is mitosis needed for
A
- growth of multicellular organisms
- repairing damaged tissues
- making genetically identical cells
- asexual reproduction
9
Q
what type of reproduction is mitosis
A
- asexual reproduction
- for some plants, animals and fungi
10
Q
what happens in interphase
A
- cell carries out normal functions (respiration)
- cell’s DNA unravels and replicates (double its genetic content)
- organelles are synthesised so increase in number
- ATP content is increased (provides energy needed for cell division)
-G1 and G2 = cell grows and new organelles and proteins are made
-S = cell replicates its DNA
11
Q
what are the 4 phases of mitosis
A
Prophase
Metaphase
Anaphase
Telophase
12
Q
what do chromosomes look like at the start of mitosis vs the end
A
- double stranded
- because each chromosome has made an identical copy of itself during interphase
- by the end, they end up as single-stranded chromosomes in new daughter cell
13
Q
explain the technical shape of chromosomes at the beginning of mitosis
A
- 2 chromosomes joined in middle by centromere (dot in middle)
- each separate strand is called a chromatid (refer to both as sister chromatids)
14
Q
what happens in prophase
A
- the chromosomes condense, getting shorter and fatter
- centrioles (tiny bundles of protein) start moving to opposite ends of the cell, forming a network of protein fibres across it called the spindle
- the nuclear envelope breaks down
- chromosomes lie free in the cytoplasm
15
Q
what happens during metaphase
A
- the chromosomes (each with two chromatids) line up in middle of the middle of the cell
- become attached to the spindle by the centromere
- at checkpoint, cell checks that all the chromosomes are attached to the spindle
16
Q
what happens during anaphase
A
- the centromeres divide
- separates each pair of sister chromatids
- spindle contracts, pulling chromatids to opposite ends of the cell (centromere first)
17
Q
what happens in telophase
A
- the chromatids reach opposite poles of the spindle
- they uncoil and become long and thin again
-they’re called chromosomes again - a nuclear envelope forms around each group of chromosomes
- now are two nuclei
18
Q
what happens during cytokinesis
A
- the cytoplasm divides
-in animal cells, the cleavage furrow forms to divide the cell membranes - usually begins in anaphase and ends in telophase
- separate process to mitosis
19
Q
what do you end up with at the end of mitosis
A
- two daughter cells genetically identical to the original cell and to another
20
Q
PAG: how would you be able to observe cells dividing in mitosis
A
- stain chromosomes so that you can see them under a microscope
- would be able to watch what happens to them during mitosis
- e.g. use plant root cells under a light microscope
-interphase: chromosomes spread out and not condensed - use a SQUASH microscope slide = squashed under a cover slip = easier to see the chromosomes
21
Q
what happens during sexual reproduction
A
gametes (egg and sperm) join together at fertilisation to form a zygote
- zygote then divides and forms a new organism
22
Q
where does meiosis occur
A
- cell division that occurs in the reproductive organs to form gametes
23
Q
why can meiosis be described as a reduction reaction
A
- cells begin with a full number of chromosomes to start with, but the cells that are formed have half the number of normal chromosomes (called haploids)
24
Q
what type of cells does meiosis form
A
genetically different
- because new cells end up with a different combination of chromosomes
25
what are the two divisions of meiosis, and which is the reduction one?
meiosis I and meiosis II
- meiosis I is the reduction one, where the cells become haploids
26
how many chromosomes are there in humans
46, 23 pairs
- one from mum, one from dad
27
what are homologous pairs
- a pair of chromosomes which are the same size and have the same genes (though could be different versions of the gene (allele - which all have the same locus, position, on a chromosome))
- one from your mum (maternal)
- one from your dad (paternal)
28
what happens during prophase I
- the chromosomes condense, getting fatter and shorter
- THE CHROMOSOMES ARRANGE THEMSELVES IN HOMOLOGOUS PAIRS
- CROSSING OVER OCCURS
- centrioles start to move to opposite ends of the cell, forming spindle fibres
- the nuclear envelope breaks down
29
what is crossing over
- occurs during prophase I, where the homologous pairs come together and pair up ( form bivalents)
- the chromatids twist around each other and bits of the chromatis swap over
- chromatids stoll contain the same gene, but have different combination of alleles
30
what happens during metaphase I
- the HOMOLOGOUS PAIRS line up across the centre of the cell
- attach to the spindle fibres by their centromeres
31
what happens during anaphase I
- the spindle contracts, SEPARATING THE HOMOLOGOUS PAIRS
- one chromosome goes to each end of the cell
32
what happens during telophase I
- a nuclear envelope forms around each group of chromsomes
33
what happens after the first phase of meiosis
- cytokinesis
- two haploid daughter cells are produced
34
what happens during meiosis II
- very similar to mitosis
- in anaphase II:
- the pair of sister chromatids separate
- each new daughter cell inherits one chromatid from each chromosome
35
what does meiosis produce
- 4
- genetically different
- haploid daughter cells
- called gametes
36
which are the 2 main events in meiosis which form genetically different daughter cells
- crossing over
- independent assortment of chromosomes
37
how does crossing over of chromatids form genetically different daughter cells
- each of the 4 daughter cells formed contain chromatids with different alleles
- increases genetic variation across offspring
- 2 will stay same, other two will have bits of eachother mixed together
38
where does the independent assortment of chromosomes occur
- lining up in metaphase I
- separated in anaphase I
- also in metaphase and anaphase 2, as each chromatid is still different from eachother
39
how does independent assortment of chromosomes lead to genetic variation
- when the homologous pairs line up in MI and are separated in AI, is is completely random which chromosomes from each homologous pair ends up with which daughter cell
-so the 4 cells produced have completely different combinations of maternal and paternal chromosomes
- "shuffling" of chromosomes leads to genetic variation
40
what are multicellular organisms made out of
- different types of cells that are specialised for their function
- ALL have some form of stem cells
41
what are stem cells
- unspecialised cells that can develop into different type of cells
42
where are stem cells found in humans
- early embryos (develop into any type of cell)
- few places in adults, e.g. bone marrow (only develop into a limited range of cells)
43
what is differentiation
process by which a cell becomes specialised
(stem cells divide into new cells -> become specialised)
44
what are adult stem cells used for
used to replace damaged cells
45
how do plants use stem cells
- needed to make new roots and shoots throughout their lives, as plants are always growing
- can differentiate into various types of cells, like phloem and xylem
46
what is meant by stem cells being able to renew themselves
- they're able to divide to produce more undifferentiated, stem cells
47
what are bones, and describe structure
- living organs
- contain nerve and blood vessels
- main bones of body have marrow in the centre
48
what happens in the bone marrow
- adult stem cells divide and differentiate to replace worn out blood cells
-(erythrocytes and neutrophils)
- always multipotent
49
where are stem cells found in plants
- in the meristems (parts of the plant where growth takes place)
- always pluripotent
50
where do xylem vessels and phloem sieve tubes get differentiated in a plant
- in the vascular cambium (meristem cells found in between x and p)
- go on to divide and differentiate
51
how would stem cells be used to treat diseases
- they could replace damaged tissues in a range of diseases, as can differentiate into specialised cells
- e.g. neurological disorders like Alzheimer's and Parkinson's
52
what is Alzheimer's and how would stem cells be used to treat it
- nerve cells in the brain die in increasing numbers
- results in severe memory loss
- stem cells could be used to regrow healthy nerve cells in patients
53
what is Parkinson's and how could stem cells be used to treat it
- patients suffer from tremors they can't control
- disease causes a loss of a particular type of nerve cell in the brain
- these cells release a chemical called dopamine, which is needed to control movement
- transplanted stem cells may be used to help regenerate the dopamine-producing nerve cells
54
how are neutrophils adapted
- a type of white blood cell that defends the body against disease
- FLEXIBLE SHAPE allows them to engulf foreign particles and pathogens
- have MANY LYSOSOMES in the cytoplasm, which contain digestive enzymes to break down the engulfed particles
- have a MULTI-LOBED NUCLEUS, which makes it easier for them to squeeze through small gaps and get to site of infection
55
how are erythrocytes adapted
- red blood cell which carry oxygen in the blood
- BICONCAVE DISC SHAPE provides a large surface area for gas exchange
- NO NUCLEUS so have more room for haemoglobin (the protein that carries oxygen)
56
how are epithelial cells adapted
- cover the surface of organs
- joined by interlinking cell membranes and a membrane at their base
- CILIATED= in airways, have CILIA to move particles away
- SQUAMOUS= in the lungs, are VERY THIN to allow for efficient diffusion of gases
57
how are sperm cells adapted
- male sex cells
- have a FLAGELLUM ( tail) so they can swim to the egg
- have lots of MITOCHONDRIA, to provide the energy to swim
- have ACROSOME, containing digestive enzymes to be able to penetrate the surface of the egg
58
how are palisade mesophyll cells adapted
- in leaves, do most of photosynthesis
- contain MANY CHLOROPLASTS, so they can absorb a lot of sunlight
- THIN WALLS, so carbon dioxide can easily diffuse into the cell
- LARGE VACUOLE to maintain turgor pressure
59
how are root hair cells adapted
- absorb water and mineral ions from the soil
- have a LARGE SURFACE AREA, for absorption
- have a THIN, PERMEABLE WALL, for entry of water and ions
- cytoplasm contains EXTRA MITOCHONDRIA, to provide energy needed for active transport
60
how are guard cells adapted
- found in pairs, with a tiny gap in between called the STOMA , which is the TINY PORES on the surface of the leaf used for gas exchange
- in the light, guard cells TAKE UP WATER and become TURGID
- their THIN OUTER WALL and THICKENED INNER WALLS force them to bend outwards, opening the stomata
- allows the leaf to exchange gases for photosynthesis
61
what is a tissue
- a group of cells (plus the extracellular material excreted by them) that are specialised to work together to carry out a particular function
- contains more than one cell type
62
examples of animal tissues
- squamous epithelium
- ciliated epithelium
- muscle tissue
- cartilage
63
what is squamous epithelium
- single layer of flat cells lining a surface ((on a basement membrane))
- found in many places
- found in the alveoli lining the lungs
64
what is ciliated epithelium
- layer of cells covered in cilia
- found on surfaces where things need to be moved
- in the trachea, where cilia waft mucus along
- have goblet cells to trap any unwanted bacteria
65
what is muscle tissue
- made up of bundles of elongated cells called muscle fibres
- 3 different types of muscle tissue:
1) smooth , found in lining of stomach wall
2) cardiac, found in the heart
3) skeletal, which you move
66
what is cartiliage
- a type of connective tissue found in the joints
- shapes and supports the ears, nose and windpipe
- formed when cells called chondroblasts secrete an extracellular matrix ( jelly like substance containing protein fibres) which they become trapped inside
67
what is xylem tissue
- plant tissue which:
1) transports water around the plant
2) supports the plant
- contain hollow, dead xylem vessel strands
- contain living parenchyma cells
- strengthened by lignin
68
what is phloem tissue
- transports sugars around the plant
- arranged in tubes
- made of sieve cells, companion cells, and some ordinary plant cells
- each sieve cell has end walls with holes in them, so that sap can move easily through
- end walls are called sieve plates
69
what is an organ
- a group of different tissues that work together to perform a particular function
70
what are examples of organs, and state what organs tissues they contain
- LUNGS:
-contain squamous epithelial tissue in alveoli,
-ciliated epithelial tissue in the bronchi,
- elastic connective tissue and vascular tissue in the blood vessels
-LEAVES:
- contains palisade tissue for photosynthesis,
- epidermal tissue to prevent water loss from leaf
- xylem and phloem tissues in the veins
71
what is an organ system
- a group of different organs working together to perform a particular function
72
what is the respiratory system and what is it made out of
- involved in breathing
- lungs
- trachea
- larynx
- mouth
- diaphragm
73
what is the circulatory system and what is it made out of
- involved in blood supply
- heart
- arteries
- veins
- capillaries
74
what is meant by the potency of stem cells
a stem cells ability to differentiate into different types of cells
- greater the potency, the more types of cells a stem cell can differentiate into
75
what are the 3 levels of potency
- TOTIPOTENT: stem cells that can differentiate into any type of cell, e.g. first few cells in zygote
- PLURIPOTENT: stem cells that can form all tissue types, not whole organisms, e.g. in early embryos
- MULTIPOTENT: can only form a range of cells within a tissue type, e.g. in bone marrow
