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biology paper 2 & 3 > topic 3 > Flashcards

topic 3 Flashcards

1
Q

advantages and disadvantages of electron microscope

A

+huge power of magnification and resolution
-specimens must be examined in vacuum
-may result in artefacts
-extremely expensive
-must be kept at a constant temperature and pressure

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2
Q

advantages and disadvantages of light microscope

A

+relatively cheap
+light and portable
-limited powers of resolution and magnification
-can produce artefacts

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3
Q

difference between transmission electron microscope and scanning em

A

TEMs examine granules
SEMs examine surfaces

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4
Q

which organelles have a double membrane and which have a single membrane

A

DM- nucleus, chloroplast, mitochondria
SM- rer,ser,golgi and lysosome
no M- ribosome

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5
Q

features and functions of mitochondria

A

DM, matrix, cristae to inrease surface area, contain own genetic material, respiration

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6
Q

features and functions of centrioles

A

-arranged at 90 degrees, hollow cylinders containing rings of microtubules
-has a role in mitosis

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7
Q

features and functions of lysosomes

A

-SM, contain digestive enzymes
-take part in apoptosis, intracellular digestion

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8
Q

features and functions of sER

A

-no ribosomes, stack of membrane(cisternea)
-sytnthesis and storage of lipids and carbohydrates

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9
Q

features and functions of rER

A

-ribosomes present, stack of membrane, flattened sacs
-folds proteins into their tertiary st. in its lumen, package 3D proteins into vesicles

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10
Q

features and role of golgi apparatus

A

-stacks of cisternea, smooth, increase then deacrease in size, flattened membranes, incoming and outgoing vesicles present on each end
-formation of quaternary st., modify proteins by adding nonprotein parts, package molecules into vesicles for exocytosis, make lysosomes

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11
Q

organelles in a prokaryotic cell

A

+pilli-for attachment and formation of cytoplasmic bridge
+flagella-rotate tail to move itself
+capsule-protects from phagocytosis, prevents dehydration
+peptidoglycan cell wall
+nucleoid-circular strand of DNA with no histones
+mesosome- contains enzymes of aerobic resp., separation of DNA, formation of cell wall
+plasmid-contains extra genes, genetic modification
+70s ribosomes

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12
Q

what is a tissue?

A

a group of similar cells working together to perform a particular function

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13
Q

what is an organ?

A

a group of different tissues working together for a specific function

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14
Q

what is an organ system?

A

a group of different organs working together for a specific function

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15
Q

compare and contrast tissue and organ

A

-tissue is made up of 1 type of tissue, an organ is made up of many different tissues
-tissue only has one function, organ has many functions
+both are made up of cells

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16
Q

what are homologous chromosomes?

A

matching pair of chromosomes that have alleles of the same gene at he same loci, one is inherited from mom and one from dad

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17
Q

role of cell cycle

A

growth, repair of worn out tissues, asexual reproduction, cloning

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18
Q

what takes place in interphase?

A

G1: growth phase where cell increases in size, SA:Vol ratio becomes lower
S: DNA is replicated
G2: organelles are replicated, ATP synthesized

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19
Q

prophase

A
  • chromosomes condense and become visible
    -nuclear membrane breaks down and nucleolus disappears
    -centrioles move to opposite poles
    -spindle fibres start to form
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20
Q

metaphase

A

-chromosomes line up at the equator
-spindle fibres connected to centromere of chromatids

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21
Q

anaphase

A

-centrioles contract and spindle fibres shorten

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22
Q

telophase

A

-nuclear membrane reforms and becomes visible
-chromosomes decondense and become invisible
-one cell with two nuclei forms
-spindle fibres break down

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23
Q

importance of mitosis

A

-genetically identical cells produced
-chromosome number stays the same

24
Q

fertilization

A

fusion of sperm nucleus and egg cell nucleus

25
Q

explain how meiosis produces genetic variation

A

-crossing over: exchanging sections of DNA during prophase 1
-independent assortment of chromosomes: creating new combinations of maternal and paternal chromosomes at metaphase 1
-random fusion of gametes

26
Q

features of meiosis

A

2 divisions, genetically different gametes, 4 cells produced, halves the chromosome no.

27
Q

features of the male gamete

A

-acrosome for storing enzymes to digest zona pellucida
-haploid nucleus contains genes from father, allows mixing of genes, restoration of diploid no. at fertilization, creates genetic variation
-mitochondria fro aerobic respiration to release ATP for movement
-flagellum-propels sperm

28
Q

features of an egg cell

A

-haploid nucleus (same function as the sperm cell)
-cortical granules fuse with egg cell membrane to harden zona pellucida to prevent polyspermy
-large size increases chances of fertilization
-follicle cells release chemicals to attract the sperm cell
-lipid droplets to supply energy for first divisions

29
Q

roles of nuclei in the pollen

A

-pollen tube nucleus controls and directs growth of the pollen tube
-contains genes to make hydrolytic enzymes
-generative nucleus fuses with the egg cell nucleus to form a new individual

30
Q

explain the events following pollen tube formation

A

-pollen germinates and forms pollen tube down the style towards ovary due to enzymes released by embryo sac
-pollen secretes enzymes to digest style tissue
-absorbs glucose to release ATP through respiration
-generative nucleus undergoes mitosis to produce two haploid sperm nuclei
-pollen tube enters into embryo sac through micropyle, double fertilization takes place
-one male nucleus fertilizes the egg cell nucleus to form the zygote
-one male nucleus fertilizes the two polar nuclei to form the endosperm

31
Q

what is polygenic inheritance?

A

-many genes at different loci
-for a single characteristic, range of categories
-cumulative effect on phenotype
-continious variation
-normal distribution curve
-ex: eye colour, height, skin colour

32
Q

what is monogenic inheritance?

A

-discreet categories
-discontinious variation
-one gene

33
Q

how are linked genes identified?

A

-located close to each other, recombination rarely occurs, they are more likely to be inherited together
-if loosely located, recombination chances wil be higher, genes on different chromosomes can be inherited independently

34
Q

what is phenotype?

A

-outside appearance of an organism
-is determined by interaction between genotype and environment

35
Q

what is the case with siamese cats?

A

-tyrosinase is defective and the enzyme can only work at cold temperatures
-if tyrosinase was not defective, all gene would be active at both hot and cold environmet, all black cat
-if exposed to hot environment with defective tyrosinase, all white cat
-if exposed to cold env. with defecive tyrosinase, only extremeties are black, core body hot so tyrosinase inactive, core body is white

36
Q

what are transcription factors and how do they work?

A

-proteins that enter into nucleus and bind to DNA and affect gene expression/transcription

37
Q

How can more than one type of protein be synthesized from the RNA produced from one gene?

A

-post transcriptional changes
-introns are removed by enzymes called spliceosomes
-exons are rearranged
-different primary sequence of amino acids produced
-different no of codons on mRNA, different no of amino acids, size and structure of protein changes

38
Q

What is a promoter region?

A

upstream of gene, where RNA polymerase binds

39
Q

What is DNA methylation?

A

-adding methyl group to CpG region on DNA
-this switches off gene and prevents its transcription
-always silences a gene

40
Q

What is histone modification?

A

-histone acetylation may take place which is the addition of acetyl group to lysine amino acid on histone protein (Euchromatin produced)
-histone methylation is the addition of methyl group to lysine in hitone, it may activate or deactivate the enzyme

41
Q

what is a heterochromatin?

A

densely supercoiled and condensed form of chromatin that genes are not available for transcription

42
Q

How does differential gene expression occur?

A

-cell receives correct stimulus such as DNA methylation or histone modification
-results in switching on and off of some genes by DNA methylation and histone modification
-only switched on genes can be transcribed into mRNA
-only these mRNA are translated to produce protein
-protein permanently modifies the cell to make it a specialised cell

43
Q

compare and contrast the structures of pre-mRNA and active mRNA

A

-premRNA also has introns which are not expressed, active mRNA only has exons
-active mRNA may have fewer introns
+both are single-stranded
-both contain A,U,G and C bases
+both have exons

44
Q

totipotent stem cells

A

undifferentiated cells that can differentiate into any type of cell including totipotent cells, no limit for division

45
Q

define induced pluripotent stem cell

A

they are derived from body parts such as the skin that are pluripotent
adult cells which are multipotent are programmed to make pluripotent stem cell

46
Q

define pluripotent stem cells

A

stem cells that can give rise to most specialised cells excluding totipotent s. cells, can keep dividing
ex: blastocyte, umbilical cord, blood

47
Q

state the uses of stem cells

A

-therapeutic cloning
-neurodegenerative disease
-type 1 diabetes

48
Q

state the risks of cell therapy

A

-route o infection
-rejection og organ~stem cell
-can be cancerous

48
Q

state the risks of cell therapy

A

-route of infection
-rejection of organ~stem cell
-can be cancerous

49
Q

what are the ethical issues concerning the use of embryos in stem cell therapy?

A

-parents may object to the use of their spare embryos
-embryo cannot give informed consent
-women are put under financial pressure to supply eggs for embryonic stem cell therapy

50
Q

role of spindle fibres in mitosis

A

-attach to the centromere of chromosomes
-pulls them to opposite poles
-so that each daughter cell has identical genetic material

51
Q

how is a protein secreted

A

-after modification of protein in golgi
-it is packaged in a secretory vesicle which fuses with cell membrane and is secreted out

52
Q

compare and contrast metaphase in mitosis and meiosis

A

-both involve attachment of spindle fibres to their centromeres
-in both chromosomes line up at the equator
-in meiosis independent assortment of chromosomes occurs
-meiosis involves homologous pairs of chromosomes (metaphase I) and sister
chromatids (metaphase II) whereas mitosis involves sister chromatids
-in meiosis there are two stages of metaphase

53
Q

explain how the arrangement of molecules contribute to the physical properties of the cell walls in sclerenchyma fibres

A

-cellulose microfibrils arranged in a mesh like structure
-cellulose for reduced flexibility, pectate in middle lamella to prevent them from sliding over each other
-lignin deposited in helices
-lignin is for lateral movement of water

54
Q

drying seed banks for storage

A

-longer storage
-reduces enzyme activity as water is removed
-germination is prevented

55
Q

explain how the change in frequency of this allele can be determined

A

-use of hardy weinberg equilibrium
-DNA analysis to identify different alleles
-compare allele frequency in previous generations with current generation

biology paper 2 & 3 (4 decks)

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