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Biology a level - ocr a > Chapter 6 > Flashcards

Chapter 6 Flashcards

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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
Q

Prophase 1 meiosis

A

Chromosomes condense
Nuclear envelope disappears
Spindle formation begins

  • Homologous chromosomes pair up forming bivalents
  • Chromatids entangle, called crossing over
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26
Q

Metaphase 1 meiosis

A

Homologous pairs assemble on the metaphase plate

Attach to the spindle fibres via their centromeres

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27
Q

Independent assortment

In meiosis
Metaphase 1

A

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

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28
Q

Anaphase 1 meiosis

A

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

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29
Q

What is chiasmata

A

The points which the chromatids break and rejoin

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30
Q

What are recombinant chromatids

Anaphase 1 meiosis

A

Sister chromosomes that are now genetically different and no longer copies
Creates genetic variation

Caused by genes being exchanged

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31
Q

Telophase 1 meiosis

A

Nuclear membrane reforms
Chromosomes uncoil

Cytokinesis is the same as mitosis

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32
Q

Prophase 2 meiosis

A

Chromatids condense and become visible
Envelope breaks down
Spindle fibres form

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33
Q

Metaphase 2 meiosis

A

Chromatids align along the metaphase plate
This process is random and called independent assortment
Creates genetic variation

34
Q

Anaphase 2 meiosis

A

Centromere divides and separates the chromatids

Pulling the chromatids to opposite sides of the poles, along the spindle fibres

35
Q

Telophase 2 meiosis

A

Chromosomes uncoil to from chromatin

Nuclear envelope and nucleolus reforms

Cytokinesis is same

36
Q

What are specialised cells

A

Cells with a specific structure to serve a specific function

37
Q

Erythrocytes

Red blood cells

A

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
Q

Neutrophils

White blood cells

A

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
Q

Sperm cells

A

Flagellum - aids their swimming

Many mitochondria - provides energy to swim

Acrosome has digestive enzymes - digest protective layers around ovum allow sperm to fertilise

40
Q

Palisade cells

A

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
Q

Root hair cells

A

Long root hairs - increase sa:v
Maximises up take of water and minerals from soil

Thin cellulose wall

42
Q

Guard cells

A

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
Q

What are the 4 main categories of tissues in animals

A 
Nervous
- support transmission of electrical impulses 
Elipethial
- cover body surfaces 
Muscle tissue 
- adapted to contract 
Connective tissue 
- hold tissues together, a transport medium
44
Q

Squamous épithélium tissue

A

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
Q

Ciliated epithelium

A

Hair like structures
Rhythmic manner

Sweeps mucus (produced by goblet cells) away from lungs 
Avoids harmful bacteria reaching lungs
46
Q

Cartilage

Connective tissue

A

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
Q

Muscle

A

Made of muscle fibres
Contain microfibrils and contractile proteins

They contract and shorten in length to move bones and body parts

48
Q

What are different tissues in plants

A

Epidermis tissue
- adapted to cover plant surfaces

Vascular tissue
- adapted for transport of water and minerals

49
Q

Plant epidermis tissue

A

Single layer of closely packed cells
Covered by waxy cuticle - waterproof - reduces loss of water
Contain stomata - gas exchange

50
Q

Xylem tissue

A

Water and nutrients

Vessel - elongated dead cells

Cell walls are made of strong waterproof lignin - structural support

51
Q

Phloem tissue

A

Transport organic nutrients

Columns of sieve tube cells
Separated by sieve plates

52
Q

What is an organ

A

Collection of tissue adapted to perform a particular function in an organism

53
Q

What does the Digestive system do = organ system

A

Breaks down large insoluble molecules
Absorbs nutrients into blood stream
Retains water needed by the body
Removes undigested material

54
Q

What are undifferentiated cells

A

Cells that aren’t adapted to any particular function

Have the potential to differentiate into any specialised cells

55
Q

Why can Stem cells undergo cell division over and over

A

Because they are the source of new cells necessary for growth development and tissue repair

56
Q

Potency definition

A

A stem cells ability to differentiate into different cells

57
Q

Totipotent

A

Differentiate into any type

Fertilised egg
Zygote

8/16 cells from first few mitotic divisions

58
Q

Pluripotent

A

Can form all tissue types but not full organs

Early embryos

59
Q

Multipotent

A

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
Q

Embryonic stem cells

A

Totipotent until after 7 days when a mass of cells called blastocyst have formed

Pluripotent state until born

61
Q

Tissue

Adult stem cells

A

Multitotent

Bone marrow

62
Q

where are Stem cells located in plants

A

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
Q

Ethics of stem cells

A

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
Q

What is tissue

A

Collection of differentiated cells that are specialised to work together to carry out a particular function

65
Q

What is an organ system

A

A number of organs working together to carry out a major function in the body

66
Q

State 3 features of a stem cell

A

Unspecialised
Can differentiate into any cells
Are self renewing

67
Q

Difference between anaphase 1 and 11

A 
1 = separates homologous chromosomes into sister chromatids 
11 = separates sister chromatids into single chromosomes ( chromatid)
68
Q

How does meiosis create genetic variation

A

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
Q

Stem cells definition

A

Undifferentiated cells with the potential to differentiate into any specialised cell types

70
Q

Functions of stem cells

A

Become tissue and organ specific cells
Repair and replace damaged cells
Growth
Renew themselves

71
Q

How do stem cells renew themselves and what happens when they differentiate

A

Renew themselves by dividing to produce more undifferentiated cells

Once they are specialised they can’t divide and enter Go phase

72
Q

specialised definition

A

Having a particular structure to carry out a specific function

73
Q

Where does the production of erythrocytes and neutrophils take place

A

Adult stem cells divide and differentiate to make blood cells

In bone marrow

74
Q

Where does the production of xylem vessels and phloem sieve tubes take place

A

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
Q

Uses of stem cells in research (Alzheimers)

A

Nerve cells in brain dies
Causes memory loss
Use stem cells to regenerate healthy nerve cells

76
Q

Uses of stem cells in research (Parkinson’s)

A

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
Q

What is an organ

A

A group of different tissues that work together to perform a particular function

78
Q

Different tissues that make up an organ (lungs)

A

Squamous
Ciliated
Vascular
Elastic connective

79
Q

Different tissues that make up an organ (leaves)

A

Palisade
Epidermal
Xylem
Phloem

80
Q

Different organs that make up an organ system (respiratory)

A 
Trachea 
Lungs 
Mouth 
Nose 
Larynx 
Diaphragm
81
Q

Different organs that make up an organ system (circulatory)

A

Heart
Veins
Capillaries
Arteries

Biology a level - ocr a (11 decks)

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