2.1.6 - Cell Division, Cell Diversity and Cellular Organisation Flashcards
1
Q
What’s in interphase
A
G1
S
G2
2
Q
G0
A
Cell has left cell cycle:
To differentiate
Apoptosis
Senescence
3
Q
Senescence
A
Cells no longer divide
4
Q
Checkpoints in cell cycle
A
At G1
At G2
5
Q
Why are there checkpoints
A
To prevent uncontrolled division that would lead to tumours
To detect and repair damage to DNA
6
Q
M phase
A
Checkpoint chemical triggers condensation of chromatin
Cell growth stops
4 stages of mitosis
Cytokinesis then occurs
7
Q
G1
A
Cells grow
Transcription of genes to make RNA occurs
Synthesis of biological molecules occur e.g. protein synthesis
8
Q
S phase
A
DNA replicates (doubles)
Each chromosome has two sister chromatids
Once the cell has entered this phase, it is committed to completing the cell cycle
9
Q
Why does S phase happen very rapidly
A
Exposed DNA base pairs are more susceptible to mutagens so this phase happens quickly to reduce the chances of mutations
10
Q
G2
A
Cells grow
Chemicals stimulate histones and formation of the spindle
Organelles duplicate
11
Q
Prophase
A
Chromosomes condense Centrioles duplicate and move to opposite poles Mitotic spindle begins to form Nuclear envelope breaks down Nucleolus no longer visible
12
Q
Metaphase
A
Chromosomes align at equator and attach by their centromeres
Two sister chromatids of each chromosome are attached to spindle fibres
13
Q
Anaphase
A
Centromere splits
Sister chromatids separate from each other and are pulled towards opposite poles of the cell due to spindle fibres shortening (now chromosomes)
14
Q
Telophase
A
Chromosomes decondense
Spindle disappears
Nuclear envelope reforms and a nucleolus reappears
15
Q
Cytokinesis in an animal cell
A
An actin ring around the middle of the cell pinches inwards, creating an indentation called the cleavage furrow
16
Q
Cytokinesis in a plant cell
A
The cell plate forms down the middle of the cell, creating a new wall that partitions it in two
17
Q
Where does mitosis occur in plants
A
Roots
Shoots
18
Q
Prophase I
A
Starting cell is diploid
Homologous chromosomes pair up and exchange fragments (crossing over of non-sister chromatids)
19
Q
Metaphase I
A
Homologue pairs line up at the metaphase plate
The orientation of pairs is random
20
Q
Anaphase I
A
Homologues separate to the opposite ends of the cell
Sister chromatids stay together
21
Q
Telophase I
A
Newly forming cells at haploid
Each chromosome has 2 non-identical sister chromatids
22
Q
Prophase II
A
Chromosomes condense
Spindle fibres begin to capture chromosomes
23
Q
Metaphase II
A
Chromosomes line up individually along the equator
24
Q
Anaphase II
A
Independent segregation of sister chromatids to opposite ends of the cell
25
Telophase II
New forming gametes are haploid
| Each chromosome has just one chromatid
26
Reasons we get many genetically different gametes
Crossing over
| Random orientation of homologue pairs
27
How does crossing over ensure genetically different gametes
The points where homologues cross over and exchange genetic material are chosen more or less at random
They will be different in each cell and humans undergo meiosis a lot
28
How does random orientation of homologue pairs ensure genetically different gametes
The random orientation in metaphase I allows for the production of gametes with many different assortments of homologous chromosomes
29
Why do we need mitosis
Growth
Repair
Asexual reproduction
30
Genetic variation in meiosis
Crossing over genetic material (allele reshuffling) in prophase I
Independent assortment of homologous chromosomes in metaphase I
Independent assortment of sister chromatids in metaphase II
Independent segregation of sister chromatids in anaphase II
31
How does sexual reproduction increase genetic variation
It involves the combining of genetic material from 2 individuals
Variation increases species chance of survival due to adaptations
32
Tissues
A group of specialised cells working together to perform a specific function
33
Organs
A group of tissues working together to perform a specific function
34
Animal tissues
Epithelial
Connective
Muscle
Nervous
35
Plant tissues
Epidermal
Vascular
Meristematic
36
Epithelial tissue
This tissue lines free surfaces in the body such as the skin, cavities of the digestive and respiratory system, blood vessels, heart chambers and walls of organs
37
Characteristics of epithelial tissue
Made up almost entirely of cells
Cells are very close to each other
No blood vessels
Squamous epithelium is made of specialised squamous
Ciliated epithelium is made up of ciliated epithelial cells
38
Squamous epithelium
Very flat cells
Only one cell thick
Form lining of lungs and of blood vessels
39
Ciliated epithelium
Cells that have cilia on the surface that move in a rhythmic manner
Lines the trachea
40
How do epithelium cells recive nutrients
Diffusion from tissue fluid in the underlying connective tissue
41
What does connective tissue consist of
A non-living extracellular matrix
42
What does a non-living extracellular matrix contain
Proteins e.g. collagen and elastin
| Polysaccharides (hyaluronic acid, which traps water)
43
What does a non-living extracellular matrix do
Separates the living cells within the tissue
| Strengthens it
44
Examples of connective tissues
```
Blood
Bone
Cartilage
Tendons
Skin
Ligaments
```
45
Where is cartilage found
In the outer ear, nose and at the edge of and in between bones
46
What is cartilage composed of
Chondrocyte cells embedded in an extracellular matrix that secrete collagen
47
Muscle tissue is well ...
... vascularised
48
What do muscle cells contain
Special organelles called myofilaments made of actin and myosin, these allow the muscle tissue to contract
49
Types of muscle tissue
Skeletal
Cardiac
Smooth
50
Skeletal muscle
Joined to bones by tendons, causing bones to move
| Forms multinucleate fibres containing protein filaments that slide pass each other
51
Cardiac muscles
Makes up the walls of the heart, allowing it to pump
| Forms cross-bridges to ensure that the muscle contracts in a squeezing action
52
Smooth muscle
Lines walls of intestines, blood vessels, uterus and urinary tracts
Propels substances along these tracts
53
What does epidermal tissue consist of
Flattened cells that apart from guard cells lack chloroplasts and form a protective covering over leaves, stems and roots
54
What do some epidermal cells have
Walls with a waxy substance (cuticle)
| Important as reduces water loss - plants in dry areas
55
What does meristematic tissue contain
Stem cells
| From this all other plant tissues are derived
56
Where is meristematic tissue found
Meristems:
At root and shoot tips
In the cambium of vascular bundles
57
Features of meristem cells
Have thin walls containing little cellulose
Do not have chloroplasts
Do not have a large vacuole
Divide by mitosis and differentiation into other types of cell
58
What is vascular tissue concerned with
Transport
59
Xylem vessels
Carry water and minerals from roots to all parts of the plant
60
Phloem sieve tubes
Transfer the products of photosynthesis in solution from leaves to parts of the plant that do not photosynthesise, such as roots, flowers and growing shoots
Contains sieve tube elements and companion cells
61
How do xylem derive from cambium
Differentiation
Lignin is deposited in cell wall - reinforcement and waterproofing
Kills the cells - non - living xylem cells
Ends of cells break down so xylem forms continuous columns with wide lumens to carry water and dissolved minerals
Lignification is incomplete in some areas -> bordered pits
62
How do phloem derive from cambium cells
Differentiation:
Sieve tubes lose most of their organelles and sieve plates develop between them from the numerous sieve pores that develop
Companion cells retain their organelles and continue metabolic functions to provide ATP for the active loading of sugars into the sieve tubes
63
Function of roots
Anchorage in soil
Absorption of mineral ions and water
Storage
64
Life processes carried out by the digestive system
Nutrition to provide ATP and materials for growth and repair
65
Life processes carried out by the circulatory system
Transport to and from cells
66
Life processes carried out by the respiratory system
Breathing and gaseous exchange excretion
67
Life processes carried out by the urinary system
Excretion and osmoregulation
68
Life processes carried out by the integumentary system
Waterproofing
Protection
Temp regulation
(Skin, hair and nails)
69
Life processes carried out by the musculoskeletal system
Support
Protection
Movement
70
Life processes carried out by the immune system
Protection against pathogens
71
Life processes carried out by the nervous and endocrine systems
Communication
Coordination
Control
72
Life processes carried out by the lymphatic system
Lymph nodes and vessels transport fluid back to the circulatory system and is also important in resisting infections
73
Why are stem cells able to express all their genes
All genes are switched on
74
Potency
A cell’s ability to differentiate
75
Totipotent
Can differentiate into any type of cell and produce a whole organism (zygote)
76
Pluripotent
Can form all tissue types but not produce an organism
77
Multipotent
Can become any type of cell within a group of cells e.g. any type of blood cell
78
Sources of stem cells in humans
Embryonic stem cells
Umbilical cord blood
Adult stem cells found in bone marrow of flat bones, skin, adipose tissue, brain, blood
iPS (induced pluripotent stem cells)
79
iPS
Developed in lab by reprogramming differentiated cell’s to switch on genes and become pluripotent
80
Current uses of stem cells
Bone marrow transplants (used to treat sickle-cell anaemia and leukaemia)
Drug research (check toxicity)
Test effectiveness of medicines
Study cell function to find out what can make it fail
Developmental research - studying cells to see how they develop into diff cell types
81
Types of blood cells produced from stem cells
Erythrocytes
| Neutrophils
82
Haploid
Having only one set of chromosomes
83
Homologous
Matching chromosomes, containing the same genes at the same places (loci)
May contain different alleles for some of the genes
84
Diploid
Having two complete sets of chromosomes (found as pairs)
85
Maternal homologues
These chromosomes will have the same genes as the maternal homologue in the chromosome pair
86
Paternal homologues
These chromosomes will have the same genes as the paternal homologue in the chromosome pair
87
Non-sister chromatids
Replicated of chromosomes, originating from different chromosomes
88
How are palisade cells adapted
Long and cylindrical - able to pack several together
Chloroplasts - absorb as much light as possible
Large vacuole - stores nutrients/water, provides structural support, stores waste
Cytoskeleton / motor proteins - moves chloroplasts to reduce CO2 diffusion pathway
89
How are sperm cells adapted
Mitochondria - releases energy for movement
Acrosome - digestive enzymes (egg)
Protein fibres in flagellum - enable rapid movement/ strength
Nucleus - contains genetic info (haploid gamete)
90
How are guard cells adapted
Thicker inner wall - so cell doesn’t change symmetrically when turgid
Large vacuole - to take up water and expand stoma
Active pump - move water in/out to alter water potential of cell
Stomata - O2 and CO2 can diffuse out
91
How are ciliated epithelial cells adapted
Cilia - move mucus
| Goblet cells - produce mucus and trap harmful substances
92
How are squamous epithelial cells adapted
Flat - cover a large area
| Thin - short diffusion pathway
93
How are neutrophils adapted
Membrane bound receptors - recognise materials that needs to be destroyed
Well developed cytoskeleton - enable movement
Many mitochondria - release energy needed
Multi lobed nucleus - easy to squeeze through small gaps
Granular cytoplasm - contains lysosomes w/ digestive enzymes to attack pathogens
94
How are erythrocytes adapted
No nucleus - more space for haemoglobin
Small and flexible - fit through capillaries
Flattened bioconcave shape - increase SA:V - take in more O2
Well developed cytoskeleton - allows it to change shape
95
How are root hair cells adapted
Long extension - increase surface area for diffusion
Active pump - absorb mineral ions and water through active transport
Thin cell wall - short diffusion pathway
Vacuole containing sap - low water potential (sugars and ions) - water can diffuse in
96
How are sieve tube elements and companion cells linked
By numerous plasmodesmata
97
Plasmodesmata
Connections between cells where the cytoplasm is continuous
98
Homologous pair of chromosomes
Chromosomes that contain same alleles
Same length
Centromeres in same position
99
Bivalent
Pair of homologous chromosomes
100
G1 checkpoint
Checks cell is ready for S phase
101
G2 checkpoint
Checks DNA has replicated correctly
102
Do plant cells have centrioles
No
103
Centromere
Where each chromatid touches (usually in the middle)
104
Why is the second division in meiosis different to mitosis
The separating chromatids of a pair aren’t the same
105
Where are erythrocytes and neutrophils produced
Stem cells in bone marrow
106
What are spindle fibres made from
Proteins
107
In what stage of meiosis are chiasmata formed
Prophase I
108
Why is the formation of chiasmata an important feature of meiosis
It provides opportunities for new genotypes to arise
109
Telomere
A region of repetitive nucleotide sequences at the end of a chromatid
110
How are erythrocytes formed from stem cells
Haemoglobin is synthesised
| Organelles associated w/ protein synthesis are digested
111
Examples of pluripotent cells
Embryonic cells in blastocyst
112
Examples of totipotent cells
Stem cells of fertilised eggs
113
Meiosis in plant cells
Skip from Anaphase 1 to Prophase 2
114
Muscle tissue
Group of cells that can contract together
