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Biology Edexcel > topic 3 > Flashcards

topic 3 Flashcards

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1
Q

what structures are always present in prokaryotic cells (5)

A 
plasmid
circular dna
cell surface membrane
cell wall
cytoplasm
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2
Q

what discrete, membrane bound organelles do eukaryotic cells contain

A
  1. nuclei
  2. mitochondria
  3. chloroplasts (plants only)
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3
Q

differences: eukaryotic and prokaryotic cells

A

eukaryotic bigger

not all eukaryotic cells have a cell wall

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4
Q

lysosome

A

spherical sacks containing digestive enzymes, bound by a single membrane
Breakdown of unwanted structures within a cell and whole cell destruction when old cells replaced/ during development.

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5
Q

Smooth endoplasmic reticulum

A

makes lipids and steroids eg. reproductive hormones

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6
Q

rER

A

system of interconnected membrane bound flattened sacks

Ribosomes attached to outer surface

Proteins made on these ribosomes are transported through the ER to other parts of the cell

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7
Q

Mitochondrion

A

Inner of 2 membranes folded to form cristae.

Site of later stages of aerobic respiration

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8
Q

Golgi apparatus

A

stacks of flattened membrane bound sacs formed by fusion of vesicles from the ER.

Modifies and packages proteins in vesicles for transport

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9
Q

Protein production and route through cell

A
  1. Transcription of DNA to mRNA
  2. mRNA leaves nucleus
  3. Proteins made on ribosomes enter rER
  4. Protein moves through ER, assuming 3D shape en route.
  5. Vesicle pinched off rER contain the protein
  6. Vesicles from rER fuse to form flattened sacs of Golgi apparatus
  7. Proteins modified within Golgi apparatus
  8. Vesicle pinched off Golgi apparatus contain the modified proteins
  9. Vesicle fuses with cell surface membrane, releasing protein such as extracellular enzymes.
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10
Q

2 mammal gametes

A

ovum

sperm

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11
Q

adaptations of ovum (5)

A

large cell
not capable of independent movement
wafted along one of the oviducts from ovary to uterus by ciliated cells lining the tubes and muscular contraction of tubes
cytoplasm of ovum contains protein and lipid food reserves for a developing embryo
‘zona pellucida’: jelly like coating surrounding the cell

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12
Q

sperm adaptations

A

smaller
motile
flagellum powered by mitochondria energy release enables swimming
continually produced once maturity
enter vagina through intercourse + swim through uterus. Passage assisted by muscular contractions of walls
If intercourse during ovulation, sperm meet ovum in oviduct
Sperm attached to ovum by chemicals released by it

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13
Q

Intercourse🍆💦

A
  1. sperm reaches ovum
  2. chemicals released from the cells surrounding the ovum, triggering ACROSOME REACTION
  3. Acrosome swells, fusing with sperm cell surface membrane
  4. Digestive enzymes in acrosome released
  5. enzymes digest through follicle cells
  6. …..and zona pelucidia surrounding ovum
  7. sperm fuses with ovum membrane
  8. Sperm enters ovum
  9. enzymes released from lysosomes in ovum thicken the jelly like layer; preventing entry of other sperm
  10. Nuclei of ovum and sperm fuse
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14
Q

what are gametes

A

HAPLOID
23 chromosomes made up of one of each homologous pair and one sex chromosome

fuse to make a zygote (46 chromosomes)

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15
Q

what is mitosis

A

type of cell division
Produces new body cells as an organism grows and develops
Retains the full (diploid) number of chromosomes

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16
Q

what is meiosis

A 
produces gametes
haploid number of chromosomes
occurs in ovaries//testes
ovaries of flowering plants
creates genetic variation
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17
Q

how does meiosis shuffle existing genetic material

A

crossing over

independent assortment

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18
Q

what is independent assortment

A

a random process which introduces variation

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19
Q

chromosomes in males and females

A

F: XX

M: XY

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20
Q

what is a fertilised ovum

A

a zygote

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21
Q

Interphase: preparation for division

A

individual chromosomes unravelled to allow access to genetic material, enabling new proteins to be synthesised

Cell synthesises additional cytoplasmic proteins, organelles and copies of DNA for 2 new cells.

Vital that DNA identical in structure and quantity. Achieved by DNA replication.

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22
Q

4 stages of mitosis:

A
  1. prophase
  2. metaphase
  3. anaphase
  4. telophase
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23
Q

prophase: (5)

A
  1. chromosomes condense because microtubules in cytoplasm form 3D structure; the spindle.
  2. Chromosomes now thicker and shorter. Each chromosome visible as 2 stands; ‘chromatids’
  3. Centrioles move around nuclear envelope and position themselves at opposite sides of the cell. This forms the 2 poles of the spindle’
  4. Spindle fibres form between poles
  5. Breakdown of nuclear envelope, forming vesicles in the cytoplasm because pores in envelope not large enough for whole molecules of DNA to pass through.

2.

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24
Q

metaphase

A

centromeres attach to spindle fibres at the equator

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25
Q

what is the spindle involved in

A

organisation of cell fibres

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26
Q

what is the widest part of the spindle known as

A

the equator

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27
Q

what produces spindles

A

centrioles

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28
Q

anaphase

A

centromeres split and spindle fibres shorten, which pulls the 2 halves of each centromere in opposite directions.

One chromatid of each chromosome is pulled to each of the poles

ends when separated chromatids reach the poles and spindle breaks down

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29
Q

telophase

A

reverse of prophase

chromosomes unravel and nuclear envelope reforms so 2 sets of genetic info are enclose in separate nuclei

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30
Q

cytoplasmic division in animal and plant cells

A

ANIMAL
cell surface membrane constricts around centre of cell

Ring of protein filaments bound to inside of cell surface membrane contracts until cell is divided in 2 new cells (proteins actin and myosin).

PLANT
instead of constriction, they synthesise a cell plate between the 2 new cells and Golgi apparatus carries material for a new cell move along the microtubules and fuse.

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31
Q

Why is mitosis important

A

insures genetic consistency (identical): growth, repair, asexual reproduction

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32
Q

what type of cell doesn’t carry out mitosis or meiosis

A

prokaryotes e.g. bacteria. Do not contain chromosomes. Thus, binary fission: one cell splits into 2 identical cells

33
Q

early embryo cells are known as…..

A

TOTIPOTENT (can develop into complete human)

34
Q

when does a blastocyst form and what is it

A

a hollow ball of cells formed 5 days after conception

outer layer goes on to form placenta

inner cell mass forms tissues of developing embryo known as ‘pluripotent embryonic stem cells’

35
Q

what are adult stem cells

A

multi potent

eg. red and white blood cells

36
Q

in plants can cells de - differentiate

A

yes, and many remain totipotent

37
Q

why can plants be reproduced in tissue culture

A

totipotency. Small pieces of plants (explants) are surface sterilised and placed on solid agar medium with nutrients and growth regulators.

Cells divide to form mass of undifferentiated cells known as a callus.

38
Q

what are human stem cells used for

A 
replacing
regenerating
engineering
tissues
organs
cells
39
Q

how are stem cells used in research

A

embryo allowed to grow to form blastocyst
cultured to see if stem cells grow
isolated from each embryo and rest of embryo discarded
stem cells cultured and used in research

40
Q

2 ways around tissue rejections

A

tissue typing

drugs

41
Q

method of therapeutic cloning

A
  1. Diploid cell removed
  2. nucleus removed
  3. fused with ovum that has haploid nucleus removed
  4. diploid cell
  5. somatic cell nuclear transfer
  6. cell stimulated to divide via mitosis
42
Q

uses of adult stem cells

A

produce cells for transplantation
treat patients with burns

use own stem cells for transplantation, e.g. trachea from donor windpipe is stripped of cells and other patients is grown on surface. Costly, and isolation and culturing of stem cells is difficult.

43
Q

using stem cells to treat burns

A

patients skin stem cells from unburned area cultured
cells multiply
form sheet of cells covering bottom of culture flask
transplanted to burn

however, cells cannot differentiate so do not contain structures such as sweat glands

44
Q

why would we reprogramme somatic cells

A

to make induced pluripotent stem cells

45
Q

how is reprogramming somatic cells beneficial

A
  1. overcome problem of cell rejection
  2. address ethical concerns with use of embryonic stem cells
  3. effective for range of diseases e.g. parkinsons
46
Q

what are embryonic and pluripotent stem cells used for in research

A

human development and diseases
help understand how cancer cells develop
how certain birth defects occur
provide a source of normal human cells in virtually any tissue type for use in screening new drugs.

47
Q

who regulates the laws on stem cell usage

A

parliament - HOC and HOL (+advisory committees).

48
Q

acceptable usage of human embyos: (5)

A

promote advances in infertility treatment
increase knowledge on congenital disease
increase knowledge on miscarriage causes
develop more effective contraceptive methods
develop methods for detecting gene/ chromosome abnormalities in embryos prior to implantation

49
Q

where is development controlled

A

nucleus

50
Q

what is the role of the EPIGENOME

A

influences which genes can be transcribed in a particular cell.

DNA is wrapped around histone proteins and both the DNA and the histones have chemical markers attached to their surface. These chemical markers make up the epigenome

Helps control change from single celled zygote to fully formed adult. During development, epigenetic changes bring about cell specilisation

51
Q

why (how) are cells specialised

A

only some genes switched on and produce active mRNA that is translated into proteins within the cell

52
Q

what is histone modification

A

the binding of epigenetic markers to histone tails alters how tightly DNA winds around histone proteins

tightly: genes inactive ‘switched off’ as cannot be transcribed to mRNA

53
Q

tissue definition

A

a group of specialised cells working together to carry out one function

54
Q

organ def

A

a group of tissues working together to carry out one function.
eg. muscle, nerve and epithelium working together in heart

55
Q

organ system def

A

a group of organs working together to carry out a particular function e.g. circulatory system

56
Q

what results in changes in epigenome

A

signals from inside and outside the cell

Changes in the epigenome alters the genes transcribed at specific times and locations

57
Q

DNA replication and the epigenome

A

copying of epigenome during DNA replication ensures changes during development are passed onto new cells

58
Q

what are master genes

A

control the development of each segment (arms/legs)

Produce mRNA that is translated into signal proteins

59
Q

what are signal proteins

A

‘switch on’ genes responsible for producing proteins needed for specialisation of cells in that segment

60
Q

what are differences in phenotypes between members of a population caused by

A

genotype

environment in which individual develops

61
Q

what characteristics does genotype control

A

blood group.

Characteristics show ‘discontinuous variation’; they have phenotypes that fall into discrete groups with no overlap

62
Q

characteristics affected by environment and genotype

A

height
‘continuous variation’’

controlled by genes at many loci; known as ‘polygenic inheritance’.
controlled by environment: directly or by influencing gene expression

63
Q

what is monohybrid inheritance and polygenic inheritance

A

MONO= each locus is responsible for a different heritable feature

POLY= more than one gene involved in inheritance of a characteristic

64
Q

what are multifactorial conditions (diseases)

A

several genetic AND environmental factors involved in disease development

65
Q

why has height been increasing over years

A
  1. taller men have more children s gradual change in populations genetic make up
  2. greater movements of people = less interbreeding
  3. better nutrition = greater child growth
  4. improved health + reduction of infectious diseases
  5. end of child labour = more energy into growth
  6. better housing heating + quality clothing = less energy to heat body
66
Q

what is the dark pigment in hair and skin

A

melanin, made in melanocyte cells

67
Q

how is melanin made and what happens when more UV light

A
  1. A stimulating hormone activated melanocyte cells
  2. Receptors for melanocyte stimulating hormone (MSH) receive MSH
  3. Melanocytes place melanin into organelles- ‘melanosomes’
  4. Melanosomes transferred to nearby hair and skin cells- where they collect around the nucleus to protect their DNA from UV light
  5. More receptors = darker skin and hair

UV light increases amount of MSH and MSH receptors - so melanocytes more active + darker skin

Hair lightens because UV light causes chemical and physical changes to melanin and other proteins in hair cells. Melanin destructed by UV light

68
Q

what enzyme makes melanin

A

enzyme tyrosinase changes amino acid tyrosin into melanin

69
Q

what environmental factors can trigger changes in epigenome and affect gene expression

A

medecines
drugs
diet

70
Q

what causes a tumour

A

rate of cell multiplication is faster than cell death

71
Q

cancer causes

A
  1. DNA damage
  2. Carcinogens
  3. Mutations when cells divide - DNA incorrectly copied in gamete formation ‘inherited cancer’
72
Q

2 gene types which have a role in controlling cell cycle in play a part in triggering cancer

A
  1. oncogenes

2. tumour suppressor genes

73
Q

what do oncogenes do

A

code for the proteins which stimulate transition from one stage in cell cycle to next

DNA mutations// epigenetic changes= cell cycle continually active, excessive cell devision + tumour

74
Q

what do tumour suppressor genes do

A

produce proteins which stop the cell cycle.

DNA//Epigenetic changes= inactivated genes- so no brake on cell cycle

75
Q

Chemical environment and cancer

A

smoking: carcinogens in tar

Tar lodges in bronchi and causes damage to surrounding epithelial cells

76
Q

physical environment and cancer

A

UV light

cancer cells spread to other parts of body in blood and lymphatic system if tumour not removed

77
Q

diet and cancer

A

fruit and veg= antioxidants destroy radicals

radicals = ageing + cancer through accumulated damage

78
Q

can a virus infection trigger cancer

A

yes.

Virus RNA may contain an oncogene picked up from one of its hosts and transfer it onto the cell it infects

Biology Edexcel (8 decks)

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