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Biology a level - ocr a > Chapter 6 > Flashcards

Chapter 6 Flashcards

1
Q

What is the cell cycle

A

Ordered sequence of events
That takes place in a cell
Resulting in division
And formation of two identical daughter cells

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2
Q

What occurs during interphase

A

Cell grows
Organelles and proteins are made
DNA is replicated and checked for errors
Mitochondria and chloroplasts grow and divide in the cytoplasm
Metabolic processes of cells occur

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3
Q

G1

A

Proteins from which organelles are made from are produced

Organelles and replicates

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4
Q

S

A

DNA is replicated

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5
Q

G2

A

Energy stores are increased
DNA replication errors checked
Proteins made for cell division

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6
Q

Cell division involves 2 stages

A

Mitosis - nuclear division

Cytokinesis - cytoplasmic division

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7
Q

What is Go

A

Phase when the cell leaves the cycle permanently or temporarily

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8
Q

Why would the cell need to leave the cell cycle

A

Differentiation
- a cell becomes specialised to carry out a particular function indefinitely, it won’t need to divide

DNA
- dna may be damaged

Cells become senescent and are only able to divide a limited number of times

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9
Q

What is the point of checkpoints

A

They are the control mechanisms of the cell cycle

Moniteur and verify whether each stage has been accurately completed before progressing

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10
Q

What do checkpoints mainly check for

A

Cell only divides when it as grown to the right size

DNA damage

DNA replication error free

Chromosomes are attached to spindle fibres and aligned

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11
Q

Why is mitosis needed

A

For growth
Repairing damaged tissues
Asexual production

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12
Q

What does mitosis produce

A

Two genetically identical daughter cells

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13
Q

Interphase mitosis

A

Each chromosome is converted into two identical dna molecules called chromotids that are joined at the centromere - which keep the chromotids together during mitosis to make sure one of each is in the new daughter cells

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14
Q

Mitosis in root tips of plants

A

Treated with a chemical to allow the cells to be separated

Squash slides to form single layer of cells

Stained

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15
Q

Prophase mitosis

A
  • Chomotin fibres coil and condensé to form chromosomes that will take up stain and become visible
  • protein microtubules (centrioles) move to opposite ends of pole, form a network of protein fibres called spindle
  • the fibres forming the spindle allow movement of chromosomes
  • spindle fibres attach to centromere
  • nuclear envelope breaks down
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16
Q

Metaphase mitosis

A
  • chromosomes are moved by the spindle fibres to form a plane in the centre of the cell
  • called the metaphase plate
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17
Q

Anaphase mitosis

A
  • centromeres divide

- chromatids are separated and pulled to opposite sides due to shortening spindle fibres

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18
Q

Telophase mitosis

A
  • chromatids reach poles
  • they uncoil and become long and thin ( chromosomes)
  • nuclear envelope forms around each set of chromosomes
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19
Q

Cytokinesis mitosis

Animal cells

A

Cleavage furrow forms around the middle of the cell

Cell surface membrane is pulled inwards by the cytoskeleton until it fuses around the middle

Forming 2 cells

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20
Q

Cytokinesis mitosis

Plant cells

A

Vesicles from Golgi apparatus assemble on the metaphase plate and fuse together and with the cell surface membrane

Dividing the cell in two

New plant cell wall is formed
Otherwise osmotic lysis

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21
Q

What is the purpose of meiosis

A

Happens in the reproductive organs to produce gametes

Genetically different

Haploid
Reduction division

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22
Q

What are homologous chromosomes

A

Matching pairs of chromosomes, one chromosome in the 23 pairs is a maternal chromosome and the other is paternal.

Contain the same genes at the same loci, but with a variation of those genes called alleles

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23
Q

Meiosis 1

A

Reduction division

Homologous chromosomes are separated into 2 cells

Each intermediate cell will contain a full set of genes instead of 2 = haploid

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24
Q

Meiosis 2

A

Pairs of chromatids in daughter cell are separated

4 haploid daughter cells

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25
Prophase 1 meiosis
Chromosomes condense Nuclear envelope disappears Spindle formation begins - Homologous chromosomes pair up forming bivalents - Chromatids entangle, called crossing over
26
Metaphase 1 meiosis
Homologous pairs assemble on the metaphase plate | Attach to the spindle fibres via their centromeres
27
Independent assortment In meiosis Metaphase 1
Homologous pairs line up randomly along the metaphase plate Maternal or paternal chromosomes can face either pole Is a random process Results in many different combinations of alleles facing the poles which results in genetic varaitaion
28
Anaphase 1 meiosis
Homologous chromosomes are pulled to opposite poles, chromatids stay joined Sections of dna on chromatids that had become entangled during crossing over, break off and rejoin, resulting in a exchange of DNA
29
What is chiasmata
The points which the chromatids break and rejoin
30
What are recombinant chromatids Anaphase 1 meiosis
Sister chromosomes that are now genetically different and no longer copies Creates genetic variation Caused by genes being exchanged
31
Telophase 1 meiosis
Nuclear membrane reforms Chromosomes uncoil Cytokinesis is the same as mitosis
32
Prophase 2 meiosis
Chromatids condense and become visible Envelope breaks down Spindle fibres form
33
Metaphase 2 meiosis
Chromatids align along the metaphase plate This process is random and called independent assortment Creates genetic variation
34
Anaphase 2 meiosis
Centromere divides and separates the chromatids | Pulling the chromatids to opposite sides of the poles, along the spindle fibres
35
Telophase 2 meiosis
Chromosomes uncoil to from chromatin Nuclear envelope and nucleolus reforms Cytokinesis is same
36
What are specialised cells
Cells with a specific structure to serve a specific function
37
Erythrocytes Red blood cells
Flattened biconcave shape - sa:v - transport oxygen Don’t have nuclei - more haemoglobin can be carried Loads of haemoglobin - can bind to and transport more oxygen Flexible - squeeze through capillaries 2 7.5
38
Neutrophils White blood cells
Granular cytoplasm - has lots of lymphocytes ready to attack pathogens Characteristic multi lobed nucleus - easier to squeeze through gaps to get to infections Flexible - can engulf foreign particles Many lysosomes in cytoplasm - digestive proteins 10-14
39
Sperm cells
Flagellum - aids their swimming Many mitochondria - provides energy to swim Acrosome has digestive enzymes - digest protective layers around ovum allow sperm to fertilise
40
Palisade cells
Contains chloroplasts - absorb large amount of light for photosynthesis , can move in cytoplasm Box shaped cells - can pack together closely to form continuous layers Thin cell walls - increases diffusion if co2 Large vacuole - maintain turgor pressure
41
Root hair cells
Long root hairs - increase sa:v Maximises up take of water and minerals from soil Thin cellulose wall
42
Guard cells
If loses water it closes - from osmotic forces Thin outer walls and thicker inner walls - so cell does not change shape symmetrically as volume changes, ensures it opens and closes Tiny pores for gas exchange
43
What are the 4 main categories of tissues in animals
``` Nervous - support transmission of electrical impulses Elipethial - cover body surfaces Muscle tissue - adapted to contract Connective tissue - hold tissues together, a transport medium ```
44
Squamous épithélium tissue
Flat cells Only 1 cell thick Good for rapid diffusion across a surface - lines the lungs Also allows rapid diffusion of oxygen into blood
45
Ciliated epithelium
Hair like structures Rhythmic manner ``` Sweeps mucus (produced by goblet cells) away from lungs Avoids harmful bacteria reaching lungs ```
46
Cartilage Connective tissue
Fibres of proteins elastin and collagen Firm and flexible Formed when Chondroblasts secrete an extracellular matrix that traps proteins fibres Prevents bones from rubbing together and being damaged
47
Muscle
Made of muscle fibres Contain microfibrils and contractile proteins They contract and shorten in length to move bones and body parts
48
What are different tissues in plants
Epidermis tissue - adapted to cover plant surfaces Vascular tissue - adapted for transport of water and minerals
49
Plant epidermis tissue
Single layer of closely packed cells Covered by waxy cuticle - waterproof - reduces loss of water Contain stomata - gas exchange
50
Xylem tissue
Water and nutrients Vessel - elongated dead cells Cell walls are made of strong waterproof lignin - structural support
51
Phloem tissue
Transport organic nutrients Columns of sieve tube cells Separated by sieve plates
52
What is an organ
Collection of tissue adapted to perform a particular function in an organism
53
What does the Digestive system do = organ system
Breaks down large insoluble molecules Absorbs nutrients into blood stream Retains water needed by the body Removes undigested material
54
What are undifferentiated cells
Cells that aren’t adapted to any particular function | Have the potential to differentiate into any specialised cells
55
Why can Stem cells undergo cell division over and over
Because they are the source of new cells necessary for growth development and tissue repair
56
Potency definition
A stem cells ability to differentiate into different cells
57
Totipotent
Differentiate into any type Fertilised egg Zygote 8/16 cells from first few mitotic divisions
58
Pluripotent
Can form all tissue types but not full organs Early embryos
59
Multipotent
Can only form a range of cells within a certain type of tissue Haematopoetic stem cells in bone marrow - can form into different blood cells
60
Embryonic stem cells
Totipotent until after 7 days when a mass of cells called blastocyst have formed Pluripotent state until born
61
Tissue | Adult stem cells
Multitotent Bone marrow
62
where are Stem cells located in plants
Present in meristematic tissue - meristems Stem Root tips Vascular cambium Differentiate into cells in xylem and phloem tissues - vascular tissue grows as plant grows
63
Ethics of stem cells
Umbilical stem cells are better than adult because they divide better and are less likely to have mutations They are are both multipotent - less useful
64
What is tissue
Collection of differentiated cells that are specialised to work together to carry out a particular function
65
What is an organ system
A number of organs working together to carry out a major function in the body
66
State 3 features of a stem cell
Unspecialised Can differentiate into any cells Are self renewing
67
Difference between anaphase 1 and 11
``` 1 = separates homologous chromosomes into sister chromatids 11 = separates sister chromatids into single chromosomes ( chromatid) ```
68
How does meiosis create genetic variation
The crossing over of homologous chromosomes in meiosis 1 - sister chromatids join and break at chiasmata, exchanging DNA - causes chromatids in the 4 daughter cells to contain a different combination of alleles Independent assortment in meiosis - line up randomly - causes daughter cells to contain any combination of maternal or paternal chromosomes Mutation - changes the nucleotide base sequences - different protein formed Random fertilisation - produces a large number of allele combinations
69
Stem cells definition
Undifferentiated cells with the potential to differentiate into any specialised cell types
70
Functions of stem cells
Become tissue and organ specific cells Repair and replace damaged cells Growth Renew themselves
71
How do stem cells renew themselves and what happens when they differentiate
Renew themselves by dividing to produce more undifferentiated cells Once they are specialised they can’t divide and enter Go phase
72
specialised definition
Having a particular structure to carry out a specific function
73
Where does the production of erythrocytes and neutrophils take place
Adult stem cells divide and differentiate to make blood cells In bone marrow
74
Where does the production of xylem vessels and phloem sieve tubes take place
Stems cells are present in meristematic tissue located between the xylem and phloem = called the vascular cambium Stem cells of vascular cambium divide and differentiate into xylem and phloem, on either side of meristem
75
Uses of stem cells in research (Alzheimers)
Nerve cells in brain dies Causes memory loss Use stem cells to regenerate healthy nerve cells
76
Uses of stem cells in research (Parkinson’s)
Nerve cells that release chemical dopamine that controls movement is lost Causes loss of control of movement Stem cells used to regenerate dopamine producing cells
77
What is an organ
A group of different tissues that work together to perform a particular function
78
Different tissues that make up an organ (lungs)
Squamous Ciliated Vascular Elastic connective
79
Different tissues that make up an organ (leaves)
Palisade Epidermal Xylem Phloem
80
Different organs that make up an organ system (respiratory)
``` Trachea Lungs Mouth Nose Larynx Diaphragm ```
81
Different organs that make up an organ system (circulatory)
Heart Veins Capillaries Arteries

Biology a level - ocr a (11 decks)

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