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IB Bio > Chapters 7, 8, & 9 HL > Flashcards

Chapters 7, 8, & 9 HL Flashcards

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1
Q

What is the epidermis of plant?

A

outer layer that protects leaves & secretes wax to form a waterproof coating to the leaf (waxy cuticle) that prevents excessive transpiration

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2
Q

Function of lignin in plants.

A

found along xylem walls to prevent collapse / resists tension

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3
Q

Function of hyphae of fungus

A

hyphae of mutualistic fungus may enhance movement of selected ions into roots / increase SA

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4
Q

Adaptations of root hairs

A
  • thin, long for efficient absorption + SA
  • have large amounts of mitochondria to conduct cellular respiration & generate ATP for protein pumps
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5
Q

Adaptations of halophytes

A
  • storing excess ions in vacuoles
  • active transport of ions BACK into soil
  • isolating ions in leaves + shedding them
  • increasing uptake of non-harmful ions e.g. K+ to increase osmosis
  • excretion of ions from special glands
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6
Q

Define xylem

A

long tubular structures w/ strong side walls which transport water & minerals

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7
Q

How does sucrose move through phloem?

A
  • moves by apoplastic & symplastic routes
  • moves through plasmodesmata (during unloading of sucrose from companion cells)
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8
Q

Distinguish b/w apoplastic & symplastic pathways

A

APOPLAST: materials pumped across CELL WALL by membrane proteins

SYMPLAST: materials can pass into sieve tube via interconnecting plasmodesmata (through CYTOPLASM)

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9
Q

Define plasmodesmata.

A

narrow cytoplasmic connections w/ adjacent companion cells

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10
Q

Example of source

A

leaves

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11
Q

Example of sink

A

roots, fruits, seeds

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12
Q

Function of companion cell

A
  • lies adjacent to sieve tube cells
  • provides metabolic machinery for sieve tube cell
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13
Q

Sieve plats

A

have wide opening to ease movement of cytoplasm b/w cells

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14
Q

rigid walls of sieve tube cells

A
  • allows for build-up of hydrostatic pressure
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15
Q

cell membrane on inside of sieve tube cell walls

A
  • holds sap inside sieve tubes
  • has pumps to load / unload sucrose
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16
Q

lumen of sieve tube

A

has no organelles that would obstruct the flow of sap

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17
Q

What provides primary growth / lengthening of plant

A

apical meristems

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18
Q

What provides secondary growth / widening of plant

A

lateral meristems

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19
Q

Outline the functions of auxin

A
  • produced by tip of stem / shoot tip
  • responsible for cell elongation
  • changes patterns of gene expression allowing for plant growth
  • involved in phototropism
  • upregulates expression of expansins
  • causes transport of H= ions from cytoplasm to cell wall
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20
Q

Outline functions of auxin in roots vs shoots

A
  • IN ROOTS: inhibits cell elongation
  • IN SHOOTS: triggers cell elongation
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21
Q

Define phytochrome

A

leaf pigments used by plant to detect periods of light and darkness

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22
Q

Define photoperiodism

A
  • response of plant to relative lengths of light & darkness
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23
Q

Discuss the main structures of a flower

A
  • stigma: collects pollen
  • style: long tube that holds up stigma to allow it to come in contact w/ pollen
  • ovary: contains ovule & female gametes - this is where fertilisation occurs
  • filament: long, thin tube that holds up the anther
  • anther: where the male gametes are produced
  • petals: attract pollinators
  • sepal: a defensive organ that encloses & protects the developing reproductive structures
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24
Q

Term for female plant organs

A

PISTIL

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25
Q

Term for male plant organs

A

STAMEN

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26
Q

Structures of seed

A
  • testa: outer seed coat that protects the embryonic plant
  • micropyle: small pore in outer covering of seed that allows for passage of water
  • cotyledon: contains food stores for seed & forms embryonic leaves
  • plumule: embryonic shoot (also called epicotyl)
  • radicle: embryonic root
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27
Q

What causes Pr to convert into Pfr?

A

absorption of red light (~660 nm)

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28
Q

What do short day plants need in order to flower?

A

they require night period to exceed a critical length
- Pfr INHIBITS flowering in short-day plant

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29
Q

What doe long-day plants require in order to flower?

A

they require the night to be LESS THAN a critical length
- Pfr ACTIVATES flowering in long-day plants

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30
Q

What is the advantage if end-product inhibition?

A
  • intermediates do not build up
  • helps to regulate levels of reactants & products
  • once concentration of products falls, enzyme can return to catalysing the reaction, allowing reaction to begin once again
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31
Q

State example of negative feedback mechanism in metabolic reactions

A

end-product inhibition

32
Q

Outline the key stages of glycolysis

A
  • occurs in cytoplasm of cell & produces small quantity of ATP
  • molecule of glucose becomes phosphorylated by binding of 2 phosphates from ATP
  • forms HEXOSE BIPHOSPHATE
  • causes its bonds to weaken
  • splits into 2 3-C molecules to produce 2 TRIOSE PHOSPHATES
  • 2 atoms of H removed from each triose phosphate –> OXIDATION
  • 2 NADs –> 2 reduced NADs
  • energy released converts 2 ADP –> 2 ATP
  • 2 molecules of pyruvate are formed
33
Q

State the products of glycolysis in mammals & bacteria

A
  • lactate (in the muscles)
  • known as LACTIC FERMENTATION
34
Q

State the products of glycolysis in yeasts & plants

A
  • ethanol & CO2
  • alcoholic fermentation
35
Q

Outline the link reaction

A
  • occurs in matrix of mitochondria
  • pyruvate loses a carbon atom in the form of CO2 (decarboxylation)
  • loses electrons (hydrogen) & thus becomes oxidised
  • NAD is reduced to NADH
  • OXIDATIVE DECARBOXYLATION
  • combines w/ an acetyl group to form acetyl-co-A
36
Q

Outline the key stages in the Krebs Cycle

A
  • 2C acetyl-co-A enters into Krebs cycle in matrix of mitochondria
  • 4-C accepts 2C acetyl fragment from acetyl co-A to form 6C
  • decarboxylation of 6C compounds –> 2x loss of CO2
  • oxidation of 6C releases H atoms
  • reduction of NAD & FADH (4 x oxidation reactions in total)
  • substrate level phosphorylation (1 ATP produced per pyruvate - ADP –> ATP)
37
Q

What is produced per GLUCOSE molecule in the Krebs Cycle (only, not including glycolysis or link reaction)?

A
  • 4CO2
  • 2 ATP
  • 6 NADH + H+
  • 2 FADH2
38
Q

Define chemiosmosis.

A
  • the use of a proton/electrochemical gradient to generate ATP (conversion of ADP into ATP) when protons diffuse back into matrix
39
Q

What is the role of oxygen in cell respiration?

A
  • acts as final electron acceptor
  • is REDUCED
  • removes de-energised electrons to prevent chain from becoming blocked
  • binds free protons in matrix to form water
  • maintains hydrogen gradient
40
Q

What would happen if oxygen was not present in ETC for cell respiration?

A
  • hydrogen carriers cannot transfer energised electrons to chain
  • ATP production is halted
  • reduced NAD NOT converted back into NAD
41
Q

Outline the structure/function relationship of mitochondria.

A
  • cristae: infoldings of plasma membrane - provide large SA for oxidative phosphorylation
  • matrix: jelly-like fluid that contains enzymes for use in Krebs cycle + link reaction
  • outer membrane: isolates the mitochondria from the rest of the cell – creates compartment w/ ideal conditions for aerobic respiration
  • inner membrane: contains ETC & ATP synthase which carry out oxidative phosphorylation
  • intermembrane space: small volume to enable rapid build-up of protons in chemiosmosis
  • 70S ribosomes: used to synthesise proteins involved in aerobic respiration
42
Q

Define photophosphorylation.

A

the conversion of ADP to ATP using the energy of sunlight by activation of PSII

43
Q

Outline the photolysis of water.

A
  • water molecules are in the thylakoid space
  • photon of light causes bonds within water molecules to break
  • leads to splitting of water molecule
  • oxygen is released as waste product
  • hydrogen ions contribute to proton gradient
44
Q

Outline the key stages of the Calvin Cycle

A
  • part of light-independent reactions
  • occurs in stroma
  • RuBP, a 5C compounds is CARBOXYLATED (CO2 added)
  • forms an unstable 6-C compound
  • Rubisco catalyses this reaction
  • splits into 3C compound (glycerate-3-phosphate)
  • glycerate-3-phosphate to triose phosphate by ADDING HYDROGEN
  • using NADPH
  • triose phosphate (3C) converted to form hexose / glucose
  • some of the triose phosphate goes to making more RuBP
  • FOR EVERY 6 MOLECULES OF TRIOSE PHOSPHATE FORMED, 5 ARE CONVERTED INTO RuBP
  • 1 is used is produce 1/2 glucose
45
Q

Outline the structure/function relationship of chloroplasts.

A
  • stroma: contains enzymes for Calvin Cycle & large quantities of Rubisco
  • Granum: stack of thylakoids for absorption as many of the available photons of light as possible
  • thylakoid membranes: provide large total SA for light-absorbing photosystems –> also provide a site for electron flow, generation of a proton gradient & chemiosmosis
  • 70S ribosomes: allow synthesis of proteins inside chloroplasts
  • chloroplast envelope: creates compartment in which enzymes & other components of photosynthesis can be concentrated
  • starch grain: for storage of carbohydrates produced by photosynthesis util it is exported from chloroplast
45
Q

Outline the structure/function relationship of chloroplasts.

A
  • stroma: contains enzymes for Calvin Cycle & large quantities of Rubisco
  • Granum: stack of thylakoids for absorption as many of the available photons of light as possible
  • thylakoid membranes: provide large total SA for light-absorbing photosystems –> also provide a site for electron flow, generation of a proton gradient & chemiosmosis
  • 70S ribosomes: allow synthesis of proteins inside chloroplasts
  • chloroplast envelope: creates compartment in which enzymes & other components of photosynthesis can be concentrated
  • starch grain: for storage of carbohydrates produced by photosynthesis util it is exported from chloroplast
46
Q

Examples of non-coding sequences of DNA.

A
  • REGULATING GENE EXPRESSION –> e.g. sites where proteins can bind that are promoters or repressors of transcription
  • INTRONS –> removed during post-transcriptional modification (in eukaryotes)
  • TELOMERES –> repetitive base sequences at ends of chromosomes –> protect genes
  • GENES FOR tRNA & rRNA –> produces tRNA & ribosomal RNA that forms ribosome
47
Q

Explain tRNA activation.

A
  • tRNA-activating enzymes recognize specific tRNA molecules by their SHAPE + CHEMICAL PROPERTIES
  • enzyme-substrate specificity e.g.
  • ATP + appropriate amino acid & tRNA bind to active site of activating enzyme
  • a pair of phosphates is released from ATP & the remaining AMP bonds to amino acid
  • raises its energy level –> allows the amino acid to bond to tRNA
48
Q

Discuss the structure of nucleosomes.

A
  • 8 histones in core have N-terminal tails that extend outward
  • during condensation of chromosomes, the tails of histones in adjacent nucleosomes link up
  • & pull chromosomes together –> supercoiling
  • N terminal tails reversibly modified by adding ACETYL or METHYL groups
  • prevents adjacent nucleosomes from packing together
  • binding of DNA to nucleosome core is loosened when H1 protein is removed
49
Q

Describe the function of nucleosomes.

A
  • control which sections of chromosomes are condensed / decondensed
  • during interphase, changes to nucleosome allow chromosomes to decondense
  • allows access to DNA by polymerase enzymes (Replication/transcription)
50
Q

Discuss transcription & gene expression.

A
  • happens in cytoplasm
  • involves promoter = base sequence close to start of gene
  • repressor proteins can prevent transcription
  • epigenetics = environment can trigger heritable changes
  • methylation
  • total number of proteins an organism can produce may be increased by ALTERNATIVE SPLICING
  • hormones/chemical env. can affect gene expression e.g. auxin
  • nucleosomes limit accessibility of transcription factors to DNA (in eukaryotes)
51
Q

How does transcription differ in prokaryotes & eukaryotes?

A
  • RNA polymerase binds to promoter in prokaryotes
  • in eukaryotes, proteins called transcription factors bind FIRST to promoter which allows RNA polymerase to initiate transcription
52
Q

Define proteome.

A

all the proteins produced by a cell, tissue, or organism –> variable

  • it is unique because of differences in activity + amino acid sequences of proteins
53
Q

Define genome.

A

all of the genes in an organism –> fixed

54
Q

Describe the structure of tRNA.

A
  • double stranded sections with base pairing
  • triplet of bases called an anticodon, in a loop of 7 bases + 2 other loops
  • the base sequence CCA at the 3’ terminal, which forms site for ATTACHING an amino acid
55
Q

Describe the structure of ribosomes.

A
  • proteins & ribosomal RNA molecules (rRNA) both form part of the structure
  • 2 sub-units, 1 small 1 big
  • a binding site for mRNA on SMALL subunit
  • 3 binding sites for tRNA on LARGE subunit
55
Q

Describe the structure of ribosomes.

A
  • proteins & ribosomal RNA molecules (rRNA) both form part of the structure
  • 2 sub-units, 1 small 1 big
  • a binding site for mRNA on SMALL subunit
  • 3 binding sites for tRNA on LARGE subunit
56
Q

What is the A site on the ribosome?

A

for tRNA bringing in an AMINO ACID

57
Q

What is the P site on the ribosome?

A

for tRNA carrying the growing POLYPEPTIDE

58
Q

What is the E site for on the ribosome?

A

for the tRNA about to EXIT the ribosome

59
Q

What is a conjugated protein?

A

a protein with a prosthetic group

60
Q

What are polypeptides?

A

unbranched chains of amino acids

61
Q

Benefits of mRNA splicing (removing introns)

A

Splicing of mRNA increases the number of different proteins an organism can produce.

62
Q

What are polysomes?

A

a cluster of ribosomes at different points along mRNA that produce multiple copies of the polypeptide

63
Q

primary structure

A

number & sequence of amino acids in polypeptide

64
Q

secondary structure

A

formation of alpha helices & beta pleated sheets stabilised by hydrogen bonding
- alpha helices represented by HELICAL RIBBONS
- beta pleated sheets represented by arrows

65
Q

tertiary structure

A

the further folding of the polypeptide stabilised by interactions b/w R groups
- R groups can be polar / hydrophobic
- intramolecular bonds b/w amino acids

66
Q

quaternary structure

A

linking of 2 or more polypeptides to form a single protein
- same types of intramolecular bonds exist as in tertiary structure (e.g. ionic, covalent)
- hydrophobic interactions, disulphide bridges (in both)
- may have prosthetic group –> non-polypeptide structure

67
Q

What is a disulphide bridge?

A

a covalent bond
- a disulfide refers to a functional group with the structure R−S−S−R′
- form b/w pairs of cysteines

68
Q

Outline mechanisms by which transcription is regulated.

A
  • promoters
  • proteins that bind to specific base sequences (promoter or operator)
  • nucleosome supercoiling
  • methylation of DNA
69
Q

What is a ribozyme?

A

RNA enzyme involved in splicing of mRNA

70
Q

Outline processes involved in post-transcriptional modification.

A
  • introns removed
  • exons spliced together
  • addition of a methyl group to the 5’-end of the transcribed RNA
  • polyadenylation describes the addition of a long chain of adenine nucleotides (a poly-A tail) to the 3’-end of the transcript
70
Q

Outline processes involved in post-transcriptional modification.

A
  • introns removed
  • exons spliced together
  • addition of a methyl group to the 5’-end of the transcribed RNA
  • polyadenylation describes the addition of a long chain of adenine nucleotides (a poly-A tail) to the 3’-end of the transcript
71
Q

What is alternative splicing?

A
  • particular exons of a gene may be included within or excluded from the final, processed messenger RNA (mRNA) produced from that gene
  • This means the exons are joined in different combinations, leading to different (alternative) mRNA strands
  • proteins translated from alternatively spliced mRNAs will contain differences in their amino acid sequence and, often, in their biological functions
72
Q

Outline the extension of the stem in plants

A

a. apical meristem (of shoot/stem) produces cells/elongates the stem
OR
cell division/mitosis in tip/apex of shoot/stem;
b. auxin stimulates cell/stem growth/extension/enlargement;
c. elongation of cells causes stem to grow (in length);

73
Q

Explain how some plant species are able to respond to changes in their abiotic environment and flower at a precise time of the year.

A
  • genes for flowering are activated
  • shoot apex changes from producing leaves to flowers
  • daylength / duration of day/night detected
  • short day plants in winter, long day plants in summer

IB Bio (10 decks)

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