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A Level Biology (SNAB) > Topic 3 > Flashcards

Topic 3 Flashcards

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1
Q

Eukaryote cell diagram

A

Ngng

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2
Q

Organelles

A

Parts of the cell

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3
Q

Nucleus

A

Nuclear envelope = double membrane
Chromatin = DNA + protein
Nucleolus = makes ribosomes
Nuclear Pore = allows movement between nucleus & cytoplasm

Controls cell activities via controlling DNA transcription

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4
Q

Lysosome

A

Round organelle with membrane
Contains digestive enzymes (seperayed from cytoplasm due to membrane)
- digest invading cells
- break down old cell components

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5
Q

Ribosome

A 
Very small
Floats free or attached to rough endoplasmic reticulum
No membrane
Made of protein + RNA
Comprised of small + large subunit

Site where proteins are made

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6
Q

Rough endoplasmic reticulum (RER)

A

System of membranes

  • fluid filled space
  • covered with ribosomes

Folds + processes proteins made at ribosomes

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7
Q

Smooth endoplasmic reticulum (SER)

A

System of membranes
- fluid filled space

Synthesises and processes lipids

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8
Q

Centriole

A

Small hollow cylinders made IP of microtubules (tiny protein cylinders)

Chromosome separation
- cell division

Somewhat star shaped

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9
Q

Golgi Apparatus

A

System of fluid filled, membrane bound, flattened sacs
- vesicles seen at edges

Processes + packages new lipids & proteins
Makes lysosomes

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10
Q

Mitochodrion

A 
Oval shaped
Double membrane
- inner = folded = cristae
Inside = matrix
- enzymes involved in respiration

Site of aerobic respiration
ATP produced

Found in large numbers in very active cells

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11
Q

Protein production & transport

A
  1. Proteins made at ribosomes
    - ribosomes on RER make proteins that are excreted or attached to the cell membrane
    - free ribosomes in the cytoplasm make proteins that stay in the cytoplasm
  2. New proteins produced at RER are folded + processed in the RER
  3. RER -> golgi apparatus via vesicles
  4. Golgi apparatus: may undergo further processing
  5. Proteins -> vesicles
    - transported around cell
    - or, extracellular enzymes move to cell surface to be excreted (exocytosis)
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12
Q

Prokaryotic cell diagram

A

Ngngn

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13
Q

Prokaryotic cells

A

Cytoplasm = no membrane bound organelles
Ribosomes = smaller than eukaryotic ones
Plasma membrane = protein + lipid bilayer
Cell wall = support (prevents shape change)
- polymer = MUREIN (glycoprotein)
Pili = short hairs
- stick to cells
- transfer genetic material
Capsule = secreted slime (bacteria)
- protects against immune attacks
Mesosome = inwards folds in plasma membrane
- either site of respiration
- or artefacts produced when preparing for microscopic viewing
Plasmids = small loops of DNA
- genes for antibiotic resistance
- pass between pokaryotes
- not always present
Circular DNA = free floating (coiled strand)
- no his tone protein attached
Flagellum = rotating hair like structure (movement)
- not all have

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14
Q

Tissues

A

Group of similar cells especially adapted to work together to carry out a particular function

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15
Q

Squamous epithelium

A

A single layer of cells lining a surface
E.g. aveoli on lungs

Cells are accompanied by a basement membrane to anchor them

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16
Q

Ciliated epithelium

A

Layer of cells covered in cilia
Found where movement is required
E.g. tranchea

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17
Q

Xylem tissue

A

Transports water around plant
Supports plant
- xylem vessel cells (thickened walls perforated by pits)
- parenchyma cells (fills in gaps between vessels)

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18
Q

Cartilidge

A 
Type of connective tissue
Found in joints
Shapes + supports
- ears
- nose
- windpipe

Two cells trapped together
Surrounded by a fibre filled matrix

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19
Q

Mitotic Index

A

Proportion of cells undergoing mitosis

(No. of cells with visible chromosomes)/(total no. of cells observed)

High = lots in mitosis e.g. plant root tip

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20
Q

Organs

A

Group of different tissues that work together to perform a particular function

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21
Q

Leaf

A

Lower epidermis = stoma to let air in/out for gas exchange
Spongy mesophyll = spaces to let gas circulate
Palisade mesophyll = photosynthesis
Xylem = carries water to leaf
Phloem = carries sugar away from leaf
Upper epidermis = covered in waterproof waxy cuticle
- reduced water loss

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22
Q

Lungs

A

Squamous epithelium = surrounds the aveoli
Fibrous connective = helps force air back out of the lungs when exhaling
Endothelium = makes up wall of capillaries (surrounds aveoli)
- lines the larger blood vessels

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23
Q

Mitosis

A

Parent cell divides -> two genetically identical daughter cells
Growth, repair & asexual reproduction
Part of cell cycle:
- cell growth & DNA replication = Interphase
- mitosis is after interphase

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24
Q

5 stages of Mitosis

A
  1. Interphase
  2. Prophase
  3. Metaphase
  4. Anaphase
  5. Telophase
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25
Q

Interphase

A

Cell carries out normal function + prepares to divide
Cell’s DNA unravels + replicated
Organelles also replicated -> spare ones
ATP content increased

3 stages: G1, S, G2

Note: chromosomes = two chromatic strands joined in middle via centromere
- two strands as genetic copy made during interphase

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26
Q

Gap phases 1 (G1)

A

Cells grow

New organelles made

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27
Q

Gap phase 2 (G2)

A

Cell keeps growing

Proteins needed for division are made

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28
Q

Synthesis (S)

A

Cell replicates DNA

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29
Q

Prophase

A 
Chromosomes condense -> shorter + fatter
Centrioles move to opposite ends of cell
- network of protein fibres formed across cell = spindle
Nuclear envelope breaks down
- chromosomes lie free in cytoplasm
30
Q

Metaphase

A

Chromosomes (each = two chromatids) line up along the middle of the cell
Attach to spindle via centromere’s

31
Q

Anaphase

A

Centromeres divide
-> separates each pair of sister chromatids
Spindles contract
-> chromatids pulled to opposite poles of the spindle (centromere first)
- chromatids appear v-shaped

32
Q

Telophase

A

Chromatids reach opposite poles on the spindle
-> uncoil -> long + thin = chromosomes
Nuclear envelope forms around each group of chromosomes
-> two nuclei
Cytoplasm divides (cytokinesis) -> two daughter cells

33
Q

Gametes

A

Male & female sex cells

  • join together at fertilisation (exact moment the nuclei fuse)
  • males = sperm
  • female = ova
  • 23 chromosomes (one set)
  • offspring = genetically unique
34
Q

Ova (mammalian gamete)

A
  • much larger than sperm
  • contain huge food reserves to help nourish developing embryo
Follicle cells (protective coating)
Zona pellucida = protective glycoprotein layer sperm need to penetrate
Cell membrane (attached to which is sperm receptors)
Cortical granules (triggers thickening of ZP)
Nucleus
35
Q

Sperm (mammalian gamete)

A
  • respiration takes place in mitochondria (energy = ATP)
  • pointed head with tail shape

Acrosome (in head tip) = digestive enzymes required to break down zona pellucida -> penetration
Nucleus (in head)
Cell membrane (surrounds head)
Mitochondria (in between head and flagellum) = lots required for energy to swim
Flagellum = allows swimming

36
Q

Fertilisation in mammals

A
  1. sperm deposited high in vagina, close to cervix entrance
  2. make their way up the cervix -> uterus -> oviduct
  3. in the oviduct -> fertilisation
  4. swim to egg cell
  5. contact zona pellucida
    - acrosome reaction (digestive enzymes released)
    - digest zona pellucida
  6. one sperm moves to cell membrane
  7. head fuses with membrane
    - triggers cortical reaction
  8. egg cell releases contents of vesicles (cortical granule) into space between membrane and ZP
    - ZP thickens (impenetrable)
    - > only one sperm fertilises
  9. nucleus enters -> tail discarded
  10. gametes fuse (nuclei)
37
Q

Female sex organs diagram

A

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38
Q

Acrosome reaction diagram

A

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39
Q

Meiosis

A

Gametes = genetically different

  1. DNA replicates -> chromatids (x2)
  2. DNA condenses -> double armed chromosomes
    = sister chromatids
    3, chromosomes arrange in homologous pairs
  3. first division = pairs separated -> 1/2 chromosome number
  4. second division = pairs of sister chromatids separated
  5. four new genetically different daughter cells = gametes
40
Q

Meiosis creates genetic variation via:

A
  1. Crossing over chromatids

2. Independent assortment of chromosomes

41
Q

Crossing over chromatids

A
  1. Before meiosis’s 1st division, homologous pairs of chromosomes pair up
  2. Two of the chromatics in each homologous pair twist around each other
  3. Twisted bits break off from original chromatic & rejoin onto the other chromatic -> genetic material recombined
  4. Chromatics = same genes, different allele combos

-> 4 new daughter cells = chromatics with different alleles

42
Q

Independent assortment of chromosomes

A
  1. Daughter cells (4) = different chromosome combos
  2. Half paternal, half maternal = all cells
  3. Different combos of maternal + paternal chromosomes go into each cell
  4. Independent assortment = separation
43
Q

Linked genes

A

Position of gene on chromosome = locus

  • independent assortment
  • > genes with loci on different chromosomes end up randomly distributed in gametes

Genes with loci on same chromosome = linked

  • stay together during IA
  • passed into offspring together (unless crossed over)

Closer together gene’s loci on chromosome:

  • closer link
  • less likely to be split up
44
Q

Locus

A

Position of gene on chromosome

45
Q

Sex-linked charecteristics

A

= Locus of allele on sex chromosome

Female = xx
Male = xy
- y < x (size)
-> fewer genes carried
Most genes only carried on X chromosome
- males > females to show x-linked characteristics for recessive alleles
-> only need one copy
E.g. colour blindness + haemophiliac = x-linked
46
Q

Stem cells -> specialised cells

A
  1. stem cells -> specialised cells = differentiation
  2. stem cells = unspecialised
    - divide by mitosis -> new cells -> specialised
  3. ability of stem cells to differentiate = potency
    - Totipotency
    - Pluripotency
  4. Found in:
    - embryo
    - intestines
    - bone marrow
    - plants = growth areas

note: adult stem cells = less flexible; less differentiation potency

47
Q

Totipotency

A

Ability to produce all cell types (all specialist cells & extraembryonic cells)

48
Q

Pluripotency

A

Ability to produce all specialised cells

- lose extraembryonic ability after first few cell divisions in the embryo

49
Q

Gene expression & differentiation

A 
Stem cell = same genes
- expressed only if active
mRNA only transcribed from active gene
-> translated -> protein
Proteins modify cells:
- determine cell structure
- control cell processes (inc gene activation)
Changes to cell via proteins cause differentiation
- difficult to reverse
- stays specialised
50
Q

Transcription Factors:

A

= proteins that bind to DNA
= activate/deactivate genes (expression) by increasing/decreasing transcription rate

Activatiors = increasing factors (help RNA polymerase bind to DNA)
Repressors = decreasing factors (prevent RNA polymerase bind to DNA)
51
Q

Gene expression & differentiation: Red blood cell exp

A

Red blood cells:

  • lots of haemoglobin
  • no nucleus
  • produced from bone marrow stem cells (type)
  • stem cell :
  • > cell with gene for haemoglobin production activated
  • > nucleus removal gene activated also
  • > red blood cell
52
Q

Transcription Factors: Prokaryotes

A

Prokaryotes -> TF’s binds to Operons
- OPERON = dna section that contains a cluster of structural genes that are transcribed together alongside control element + (usually) regulatory gene
– structural gene = useful protein e.g. enzymes (code for)
– control elements = promoter (DNA sequence before structural gene that RNA polymerase binds to)
= Operator( DNA sequence TF binds to)
– regulatory gene = codes for activator or suppressors

53
Q

Transcription Factors: Eukaryotes

A

Eurkaryotes -> TF bind to specific DNA sites

-> near start of target genes ( genes they control expression of)

54
Q

Transcription Factors: E.coli -> Lac operon

A
  1. E.coli = bacterium -> respires glucose, or lactose if glucose unavailable
  2. genes to respire lactose (e.g. produce enzymes) -> lac operon
  3. Lac operon = 3 x structural genes (LacZ, LacY, LacA)
    - produce proteins to help digest lactose
    - > Beta-galactosidase
    - > lactose permease
55
Q

Transcription Factors: E.coli -> Lac operon

Lactose not present

A

Regulatory gene (lacL) produced Lac repressor (TF)

  • > binds to operator site
  • > blocks transcription (RNA polymerase cannot bind to promoter)
56
Q

Transcription Factors: E.coli -> Lac operon

Lactose present

A

Lactose binds to repressor
-> changes repressor shape -> no longer can bind to operator
RNA polymerase begins structural gene for transcription

57
Q

Treating disease with stem cells

A
  1. stem cell -> specilaised cells; replace damaged tissues
  2. stem cell therapies:
    - leukemia (kills bone marrow stem cells) -> bone marrow transplants
  3. researching:
    - spinal cord injuries -> nerve tissues
    - heart disease + heart attack damage -> damaged heart tissue
  4. benefits:
    - many people die waiting for organ transplants -> stem cells could grow organs
    - improve quality of life e.g. the blind
58
Q

Adult Stem Cells

A 
Adult body tissues (bone marrow)
Relatively simple operation:
- low risk
- lot of discomfort
Donor anesthetised
Needle inserted into bone center (Hip)
Small bone marrow quantity removed
Adult stem cells aren't as flexible
-> develop into limited range
Own cells can be used
-> less risk of rejection
59
Q

Embryonic Stem Cells

A 
Early embryos
IVF (labatory)
4 to 5 days old
- stem cells removed
- rest of embryo destroyed 
Can develop into all cell types
60
Q

Embryonic Stem Cells: Ehtical Issues

A

Destruction of viable embryo
Many believe fertilisation = genetically unique individual
- right to life
Fewer objections = unfertilised egg cells -> artificially divided
- could not last past a few days anyhow
Society has to consider arguments before use

61
Q

Regulatory Authorities process

A
  1. Research proposals -> deciding if allowed
    - ethical issues (research carried out for a good reason)
    - no research uneccessarily repeated
  2. licensing + monitoring centres involved in research
    - trained staff -> understand implications
    - no resource waste
    - no unregulated work
  3. guidelines + codes of practice
    - work in similar manner (comparision)
    - acceptable source of stem cells (e.g. maximum age of embryos + extraction method)
  4. monitoring developments
    - up to date guidelines
    - changes in field regulate appropriately
  5. info + advice -> Government + professionals
    - promote science involved
    - helps society understand
62
Q

Phenotype variation: Continious

A 
Individuals within population vary within a range
- no distinct categories
E.g.:
- height
-mass
-skin colour
63
Q

Phenotype variation: Discontinuous

A

Two+ distinct categories
E.g.:
- blood groups

64
Q

Variation in Genotype

A

-> variation in phenotype

  1. Controlled by one gene = monogenic
    - usually discontinuous
  2. No. of genes at different loci = polygenic
    - continious
65
Q

Environmental Influence

A
  1. Height = polygenic
    - nutrition
  2. Monoamine Oxidase A (MAOA) = enzyme
    - breaks down monoamines
    - low levels -> mental health issues
    = monogenic
    - reduced by smoking + antidepressants
  3. Cancer = genetic
    - diet
    - location
  4. Animal hair colour = polygenic
    - decreasing temperature triggers change
66
Q

Environmental change -> Changes in gene expression

A

Eukaryotes: epigenetic control determines gene expression -> alters phenotype

  • does not alter base sequence if DNA
  • attaches/removes chemical groups to/from DNA
  • > alters how easy it is for enzymes + proteins needed for transcription to interact with transcribed genes

Epiginetic changes play a role in normal cellular processes
Also occur in response to environmental changes e.g. lack of food, pollution

67
Q

Increased methylation of DNA

A

-> represses a gene = epiginetic control

Methylation of DNA = attachment of methyl group to DNA coding for a gene

  • always attaches at CpG site ( = cytosine + guanine next to one another)
  • increased methylation -> changed DNA structure
  • > proteins + enzymes (transcription) cannot bind to gene -> repressed
68
Q

Histones

A

= proteins that DNA wraps around -> chromatin; makes up chromosomes

Chromatin can be highly or less condensed -> affects DNA accessibility (+ binding sites)

69
Q

Histone modification (Epiginetic)

A
  1. Histone = Acetylated
    - chromatin = less condensed
    - > proteins (transcription) can bind
  2. Acetyl groups removed
    - chromatin = highly condensed
    - no transcription -> genes repressed
70
Q

How can epiginetic changes be passed on after cell devision?

A

Methyl groups usually removed during gamete production

  • some escape & end up in gametes
  • carry on epigenetic changes (repression/activation)
  • equipped to deal with changed environment

A Level Biology (SNAB) (10 decks)

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