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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
explain how meiosis produces genetic variation
-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
features of meiosis
2 divisions, genetically different gametes, 4 cells produced, halves the chromosome no.
27
features of the male gamete
-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
features of an egg cell
-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
roles of nuclei in the pollen
-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
explain the events following pollen tube formation
-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
what is polygenic inheritance?
-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
what is monogenic inheritance?
-discreet categories -discontinious variation -one gene
33
how are linked genes identified?
-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
what is phenotype?
-outside appearance of an organism -is determined by interaction between genotype and environment
35
what is the case with siamese cats?
-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
what are transcription factors and how do they work?
-proteins that enter into nucleus and bind to DNA and affect gene expression/transcription
37
How can more than one type of protein be synthesized from the RNA produced from one gene?
-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
What is a promoter region?
upstream of gene, where RNA polymerase binds
39
What is DNA methylation?
-adding methyl group to CpG region on DNA -this switches off gene and prevents its transcription -always silences a gene
40
What is histone modification?
-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
what is a heterochromatin?
densely supercoiled and condensed form of chromatin that genes are not available for transcription
42
How does differential gene expression occur?
-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
compare and contrast the structures of pre-mRNA and active mRNA
-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
totipotent stem cells
undifferentiated cells that can differentiate into any type of cell including totipotent cells, no limit for division
45
define induced pluripotent stem cell
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
define pluripotent stem cells
stem cells that can give rise to most specialised cells excluding totipotent s. cells, can keep dividing ex: blastocyte, umbilical cord, blood
47
state the uses of stem cells
-therapeutic cloning -neurodegenerative disease -type 1 diabetes
48
state the risks of cell therapy
-route o infection -rejection og organ~stem cell -can be cancerous
48
state the risks of cell therapy
-route of infection -rejection of organ~stem cell -can be cancerous
49
what are the ethical issues concerning the use of embryos in stem cell therapy?
-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
role of spindle fibres in mitosis
-attach to the centromere of chromosomes -pulls them to opposite poles -so that each daughter cell has identical genetic material
51
how is a protein secreted
-after modification of protein in golgi -it is packaged in a secretory vesicle which fuses with cell membrane and is secreted out
52
compare and contrast metaphase in mitosis and meiosis
-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
explain how the arrangement of molecules contribute to the physical properties of the cell walls in sclerenchyma fibres
-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
drying seed banks for storage
-longer storage -reduces enzyme activity as water is removed -germination is prevented
55
explain how the change in frequency of this allele can be determined
-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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