2.1.6 Flashcards
(81 cards)
1
Q
What happens during interphase?
A
- dna replicated, checked for errors
- protein synthesis in cytoplasm
- mitochondria increases (grows and divides)
- chloroplasts grow and divide (in plants)
- normal metabolic processes (cell respiration)
2
Q
What are the three stages of interphase?
A
G1 - first growth phase
S - synthesis phase
G2 - second growth phase
3
Q
What happens during G1?
A
- proteins are produced (synthesise organelles)
- organelles replicate
- cell gets bigger
4
Q
What happens during S?
A
DNA in nucleus is replicated
5
Q
What happens during G2?
A
- cell gets bigger
- energy stores are increased
- duplicated DNA is checked for errors
6
Q
What happens during the mitotic phase?
A
Mitosis : nucleus divides
Cytokinesis: cell divides
7
Q
What is G0?
A
Phase where the cell leaves the cycle (temporarily or permanently)
8
Q
When does G0 happen?
A
- differentiates (can no longer divide)
- cell DNA may be damaged (enters permanent arrest and no longer viable)
- age (leads to senescent cells)
9
Q
What happens to lymphocytes in an immune response?
A
They can be stimulated to go back to cell cycle
10
Q
When does a cell divide?
A
- at right size
- replicated Dna is error free
- chromosomes are in right position during mitosis
11
Q
Why must these three characteristics be matched before a cell divides?
A
To ensure 2 identical daughter cells
12
Q
What are checkpoints used for?
A
To monitor and verify whether phases have been accurately completed before going on to the next phase
13
Q
What are the three checkpoints?
A
G1 checkpoint
G2 checkpoint
Spindle assembly checkpoint ( metaphase checkpoint)
14
Q
What happens at G1 check point?
A
Checks for:
- cell size
- nutrients
- growth factors
- DNA damage
15
Q
What happens if all is good at G1 checkpoint?
A
Triggers DNA replication
If not cell enters G0
16
Q
What happens at G2 checkpoint?
A
Checks for:
- cell size
- DNA replication
- DNA damage
17
Q
If all is good in G2 checkpoint then what happens?
A
It initiated molecular processes that signal the start of mitosis
18
Q
What happens at the spindle assembly (metaphase) checkpoint?
A
It checks for chromosome attachment to spindle
19
Q
What happens if all is good at metaphase checkpoint?
A
Mitosis proceeds
20
Q
What is the order of stages of mitosis?
A
Prophase
Metaphase
Anaphase
Telophase
21
Q
What are the six steps that happen in prophase?
A
- Chromatin fibres coil and condense making chromosomes
- nucleoulus disappears
- nuclear membrane starts to break down
- Chromatin fibres coil and condense making chromosomes
- Protein microtubules form spindle shaped structures
- 2 centrioles migrate to opposite sides of the pole (help with spindle formation)
- Spindle fibres attach to specific areas on centromeres and start moving chromosomes to middle
- By the end nuclear envelope has dissapeared
22
Q
What happens during metaphase?
A
Chromosomes in the centre of cell (metaphase plate, equator)
23
Q
What happens during anaphase?
A
-chromosomes divide and are pulled to opposite poles (through liquid cytosol) because of shortening spindle fibres
24
Q
What happens during telophase?
A
Chromatids that reach each pole are now called chromosomes.
-nuclear envelope forms around each set of chromosomes
(Nucleolus is formed and chromosomes start to uncoil)
25
What else starts in telophase?
Cytokenisis
26
Describe what happens in cytokinesis in animals.
Cleavage furrow forms
| Cell surface membrane is pulled inwards by cytoskeleton until its close enough to fuse in the middle.
27
Describe cytokinesis in plants.
- vesicles from golgi assemble in same place that metaphase plate was
- they fuse together with cell membrane
- dividing cell into two
- new sections of cell wall form along new sections of membrane
28
What are gametes?
Sex cells
29
What is zygote?
Fertilised egg
30
What type of division is meiosis and why?
Reduction division
| Because for daughter cells (haploid) are produced
31
What are alleles?
Different versions of the same gene (gene variants ) they have the same locus
32
What happens during meiosis I?
First division is reduction division
| Homologous pairs are split into two cells
33
What happens in meiosis I I?
Pair of chromatids in each daughter cell are separated making for haploid cells
34
What happens in prophase I?
-Chromosomes condense
-envelope disintegrates
-nucleolus disappears
-spindle formation
As chromosomes are brought together the entangle this can lead to crossing over
35
What happens in metaphase I?
-Homologous pairs of chromosomes assemble along metaphase
-Maternal and paternal chromosomes may end up facing either pole (independent assortment)
This leads to genetic variation
36
What happens during anaphase I?
Chromosomes are pulled to opposite poles
-forming recombinant chromatids
(Genes being exchanged between chromatids)
Lead to genetic variation
37
What is Chiasmata?
Points were chromatids break and rejoin during crossing over
38
What happens during telephone I?
```
Chromosomes
assemble at each point
-nuclear membrane reforms
-chromosomes uncoil
Cell undergoes cytokinesis making haploid
```
39
What are three things that can cause genetic variation?
- Crossing over
- Independent assortment
- genes been exchanged between chromatids
40
What happens during prophase 2?
- chromosomes condensed becoming visible
- nuclear envelope breaks down
- spindle formation starts
41
What happens in metaphase 2?
Line up along metaphase plate but due to IA and CO there’s more genetic variation
42
What happens in anaphase 2?
Chromatids are pulled after centromere division
| Similar to mitosis
43
What happens in telophase 2?
- chromosomes uncoil and form chromatin
- nuclear envelope reforms
- nucleolus becomes visible
44
What’s the product of meiosis?
4 haploid daughter cells that are genetically different due to CO and IA
45
What are specialised cells?
Differentiated cells that have very special functions
46
Describe erythrocytes.
- biconcave (increase SA:V)
- no nuclei (more space for haemoglobin)
- flexible (squeeze through narrow capillaries)
47
Describe neutrophils.
- multi-lobed nucleus to squeeze through small gaps to get to infection sites
- granular cytoplasm has many lysosomes (have enzymes used to attack pathogens)
48
Describe sperm cells.
- tail/flagellum
- mitochondria
- acrosome (head) has digestive enzymes that penetrate ovum's protective layers to penetrate
49
Describe palisade cells
- in mesophyll
- have chloroplasts that can move in cytoplasm to absorb more light
- large vacuole to maintain turgor pressure
- thin cell walls increase co2 diffusion
50
Describe root hair cells.
-long extensions called root hairs (maximise uptake of water and minerals)
51
Describe guard cells.
- have stomata
| - guard cell cell wall is thicker on one side so cell doesn’t change shape symmetrically as volume changes
52
What are tissues?
A collection of differentiated calls with specialised functions/a function
53
What are the 4 main animal tissue catergories?
- nervous: transmission of electrical impulses
- epithelial: covers internal and external body surfaces
- muscle: contracts
- connective: hold tissues together (transport medium)
54
What is squamous epithelium?
- made of squamous epithelial cells
- 1 cell thick (rapid diffusion)
- forms lining of lungs
55
What is ciliated epithelium?
-hair like structures (cilia) move in rhythmic manner
-they are in trachea and move/sweep mucus away from lungs
-goblet cells release mucus to trap unwanted particles
Both these features are used to stop particles (like bacteria) from entering the lungs
56
What is cartilage?
-connective tissue that has: collagen and elastin
-made of chondrocyte cells embedded in extra cellular matrix
Used to stop bones from rubbing
57
What is muscle?
- contracts to move bones
| - skeletal muscle fibres have myofibrils that have contractile proteins
58
What are the two main plant tissues?
- epidermis: covers plant surfaces
| - vascular: transports water and minerals
59
What is epidermis?
- closely packed cells usually covered by waxy cuticle
| - stomata is here
60
What is xylem tissue?
-made of elongated dead cells
-strengthened with waterproof material (lignin)- provides structural support
Transports water and minerals
61
What is phloem tissue?
-made of columns of sieve tube cells that are separated by perforated walls called sieve plates
Transport organic nutrients from where they are made (stem and leaves)
62
What is an organ?
Collection of tissues adapted to perform a particular function
63
Give an example of a human organ.
Heart - pumps blood
| -muscle and connective tissue
64
Give an example of a plant organ.
Leaf - photosynthesis
| Epidermis and vascular tissue
65
What is an organ system?
Number of organs
66
Give 3 examples of organ systems
- digestive
- cardiovascular
- gaseous exchange system
67
What are stem cells?
Undifferentiated cells that originate from mitosis/meiosis
68
When do stem cells stop dividing?
When they become specialised (enter G0 phase)
69
What does uncontrolled division lead to?
Formation of masses making tumours
| May be cancerous
70
What is potency?
Ability to differentiate
71
What does totipotent mean?
-into any type of cell
e.g. a zygote from its first few divisions is totipotent
Eventually makes an organism
72
What does pluripotent mean?
-can form all tissue types not whole organisms
| In early embryos
73
What does multipotent mean?
- can form only a range of cells within a certain tissue
e. g. haematopoetic stem cells (bone marrow)
- > can differentiate into various types of blood cells
74
What is the life span of erythrocytes?
120 days
75
What is the life span of neutrophils?
6 hours
76
What are the two types of stem cell sources in animals?
- embryonic
| - tissue (adult) stem cells
77
What is the potency of embryonic stem cells?
-totipotent at early stages
| After around 7 days a blastocyst is formed during pluripotent state
78
What is a blastocyst?
A mass of cells
79
What is the potency of adult stem cells?
(From birth onwards)
| - are multipotent but can be artificially triggered to be pluripotent
80
Where is the plant stem cell source?
In meristematic tissues (meristems)
—> wherever there is growth (shoots and tips)
—> sandwiched between xylem and phloem tissues = vascular cambium, these cells can differentiate into cells in xylem or phloem
81
What is the potency of plant stem cells?
They are pluripotent
