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A Biology A Level > Topic 3 > Flashcards

Topic 3 Flashcards

1
Q

What is a eukaryotic cell?

A
  • A cell containing a nucleus and other membrane bound organelles
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2
Q

What is a prokaryotic cell?

A
  • A cell with circular DNA and no membrane bound organelles
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3
Q

What is the structure and function of the nucleus?

A
  • Structure: Double membrane perforated by pores. body in nucleus.
  • Function: Control centre of cell which retains genetic info and makes proteins
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4
Q

What is the structure and function of the nucleolus?

A
  • Structure: body in nucleus
  • Function: makes rRNA and ribosomes
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5
Q

What is the structure and function of the ribosomes?

A
  • Structure: made of RNA and proteins
  • Function: site of protein synthesis and translates genetic material into proteins
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6
Q

What is the structure and function of the mitochondria?

A
  • Structure: Double membrane with the inner one folded to form cristae.
  • Function: site of aerobic respiration
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7
Q

What is the structure and function of the rough endoplasmic reticulum?

A
  • Structure: system of interconnected flattened sacs with ribosomes attached to outer surface
  • Function: Protein synthesis
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8
Q

What is the structure and function of the smooth endoplasmic reticulum?

A
  • Structure: no ribosomes
  • Function: makes lipids and carbs and transport when required
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9
Q

What is the structure and function of the cell surface membrane?

A
  • Structure: Phospholipid bilayer containing proteins and other molecules
  • Function: Controls movement as partially permeable membrane
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10
Q

What is the structure and function of centrioles?

A
  • Structure: cylinders made of microtubules
  • Function: Forms spindle during nuclear division
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11
Q

What is the structure and function of lysosomes?

A
  • Structure: Spherical sacs of digestive enzymes formed by golgi
  • Function: Involved in phagocytosis and autolysis.
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12
Q

What is the structure and function of the Golgi apparatus?

A
  • Structure:
  • Function: Modifies proteins and packages them into vesicles
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13
Q

What is the structure and function of the prokaryotic cell wall?

A
  • Structure: Made of peptidoglycan
  • Function: Cell support
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14
Q

What is the structure and function of the capsule?

A
  • Structure: Sticky outer layer
  • Function: Prokaryotes stick together and stop from being detected
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15
Q

What is the structure and function of the plasmids?

A
  • Structure: Small loop of circular DNA
  • Function: DNA separate from chromosomal DNA
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16
Q

What is the structure and function of the flagellum?

A
  • Structure: tail-like structure
  • Function: bacterial movement
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17
Q

What is the structure and function of the pili?

A
  • Structure: Hair like structure on cell surface
  • Function: adhere to surfaces
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18
Q

What is the structure and function of mesosomes?

A
  • Structure: Infolding in plasma membrane
  • Function: aerobic respiration and cell formation
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19
Q

How how proteins modified/trafficked?

A
  • DNA to mRNA in transcription and mRNA leaves the nucleus to ribosome on rER.
  • Proteins are made on the RER.
  • Vesicles contain protein which is folded and processed at RER.
  • Transported to Golgi apparatus where vesicles form and proteins are modified
  • Vesicles pinched from Golgi apparatus and fuse with cell membrane releasing protein in exocytosis
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20
Q

What is the equation for magnification?

A

Magnification = image size/actual size

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21
Q

What is the difference between a light and electron microscope?

A
  • Light: uses light to form image and has low resolution and low magnification
  • Electron: uses electrons to form image and has much higher resolution and magnification
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22
Q

What is the difference between resolution and magnification?

A
  • Resolution is the ability to distinguish between 2 points
  • Magnification is how enlarged an image is compared to a specimen
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23
Q

What are tissues?

A
  • Group of cells that work together to form the same function
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24
Q

What are organs?

A
  • Group of tissues which work together to form the same function
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25
Q

What are organ systems?

A
  • Organisation of organs which perform related functions
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26
Q

What are the 3 stages of Interphase?

A
  • G1, cell grows
  • S, synthesis of DNA + replication
  • G2, proteins synthesised + reorganisation
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27
Q

What is mitosis?

A
  • Two identical sister chromatids separate to produce genetically identical cells
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28
Q

What happens in Prophase?

A
  • Nuclear envelope breaks down
  • Chromosomes condense
  • Centrioles form spindle fibres
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29
Q

What happens in Metaphase?

A
  • Chromosomes align at cell equator
  • Spindle fibres attach to chromosome centromeres
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30
Q

What happens in Anaphase?

A
  • Spindle fibres split centromere
  • One chromatid to each end
31
Q

What happens in Telophase?

A
  • Chromosomes de-condense and spindle fibres break
  • Nuclear envelope reforms so two separate nuclei
32
Q

What happens in cytokinesis?

A
  • Whole cell divides
  • Two identical diploid daughter cells
33
Q

What is the importance of mitosis?

A
  • Asexual reproduction
  • Genetically identical
  • Growth
  • Repair
34
Q

What happens in Meiosis I?

A
  • Chromosomes are replicated in interphase.
  • Homologous pairs of chromosomes are separated to produce 2 haploid nuclei.
35
Q

What happens in meiosis II?

A
  • Sister chromatids are separated
  • 4 haploid nuclei produced
36
Q

What is crossing over?

A
  • Sections of DNA are exchanged between homologous chromosomes
  • Same genes, different alleles
37
Q

What is independent assortment?

A
  • Chromosomes are randomly assorted when they line up on the cell equator.
38
Q

How does meiosis produce genetic variation?

A
  • Through non identical gametes
  • Independent assortment of chromosomes
  • Crossing over of alleles in chromatids
39
Q

What do gamete cells fuse to form?

A
  • One zygote
  • Gametes have haploid cells and fuse to form diploid cells
40
Q

What are homologous chromosomes?

A
  • Chromosomes with same genes but different alleles
41
Q

What are the adaptations of sperm cells?

A
  • Acrosome, contains digestive enzymes to hydrolyse zona pellucida
  • Flagellum, for motility towards egg
  • Mitochondria, ATP for respiration and swimming
42
Q

What are the adaptations of an egg cell?

A
  • Zona pellucida hardens to prevent polyspermy
  • Follicle cells provide protective coating
  • Cytoplasm contains nutrients for the embryo
43
Q

What happens in the acrosome reaction?

A
  • Acrosome of sperm fuses with egg cell membrane and releases digestive enzymes
  • Hydrolyses zona pellucida
  • Release chromosomes
44
Q

What is the locus of a gene?

A
  • The position of a gene on a chromosome
45
Q

What sex chromosomes do males have vs females?

A
  • Males = XY
  • Females = XX
46
Q

When is an allele more likely to be expressed in the phenotypes of males?

A
  • If there is a recessive allele present on the non-homologous portion of the X chromosome.
  • Because they only have one X they show sex linked conditions.
47
Q

What happens in the cortical reaction?

A
  • Cortical granules are released from ovum via exocytosis
  • Released into the zona pellucida which thickens and hardens
  • Prevents polyspermy
48
Q

What are stem cells?

A
  • Unspecialised cells that are able to express all their genes.
  • Become more specialised to their function.
49
Q

What is cell differentiation?

A
  • Where stem cells become more specialised into different cell types.
  • Cells express fewer genes
50
Q

How is gene expression controlled?

A
  • By preventing DNA turning into protein
  • Stopping transcription of mRNA
  • Stopping translation of mRNA into protein.
51
Q

What happens when a cell is totipotent?

A
  • Cells have the ability to differentiate into any type of cell
  • eg. embryonic stem cells
52
Q

What happens when a cell is pluripotent?

A
  • Cells can turn into most types of cells
  • eg. blood cells
53
Q

What happens when a cell us unipotent?

A
  • Cells can only turn into one single cell
  • eg. heart cell
54
Q

What are epigenetic changes?

A
  • When gene expression is regulated by chemical modification to chromosomes
55
Q

What makes up the epigenome?

A
  • All the chemical tags attached to the DNA and histones
56
Q

How can chromatin be chemically modified to alter gene expression?

A
  • Signals from the environment cause chemical tags to be added to the histones or DNA.
  • Changes how tightly packed the chromatin is.
  • Methylation of DNA or histone modification via acetylation
57
Q

What happens if the chromatin is too tightly packed?

A
  • RNA polymerase cannot bind to the DNA
  • No transcription
  • No gene expressed
58
Q

What is DNA methylation?

A
  • Methyl group is added to the DNA
  • Transcription factors are unable to bind to DNA as chromatin is tightly packed
  • Switches genes off
59
Q

What is demethylation?

A
  • Switches genes back on
  • Methyl group is removed and transcription can happen as chromatin isn’t packed
60
Q

What is histone acetylation?

A
  • Addition of acetyl group to histone protein
  • Chromatin less condensed so genes are able to be transcribed
  • Switches genes on
61
Q

What is deacetylation?

A
  • Removal of histone proteins
  • Chromatin is more compact so inhibits transcription
  • Switches genes off
62
Q

How do transcription factors (activators + repressors) control gene transcription?

A
  • Activate the genes are called activators, they bind to the start of the gene and help RNA polymerase to bind and transcribe the gene.
  • Deactivate the genes are called repressors, prevent RNA polymerase from binding.
63
Q

What is an operon?

A
  • It is a section of DNA that contains a cluster of genes which are controlled by a single promoter
64
Q

What happens to Lac Operon when no lactose is present?

A
  • Regulatory gene is transcribed and translated to produce repressor protein
  • The protein binds to operator region
  • RNA polymerase is unable to bind
  • No lactase is produced
65
Q

What happens to Lac Operon when lactose is present?

A
  • Lactose is present to binds to repressor protein and distorts it
  • Prevents it binding to operator region
  • RNA polymerase is able to bind to promotor region
  • Lactase is produced
66
Q

What is cancer?

A
  • The abnormal growth of mutant cells
  • Derived from genes regulating cell division
  • Either benign or malignant
67
Q

What are proto-oncogenes?

A
  • They code for many products including growth factors, receptor proteins and cell cycle
68
Q

What happens if there is a mutation of proto-oncogenes?

A
  • Form oncogenes which cause constant cell division
  • Causes division and growth into a tumour
69
Q

What are tumour suppressor genes?

A
  • They inhibit cell growth
70
Q

What happens if there is a mutation of tumour suppressor genes?

A
  • Cells grow at an increased rate as it is not inhibited.
  • Cells accumulate.
71
Q

What are the genetic risks of cancer?

A
  • Inherit mutations of oncogenes or tumour suppressor genes
72
Q

What are the lifestyle risks of cancer?

A
  • Age
  • Genetics
  • Smoking
  • Diet
  • Obesity
  • Exercise levels
73
Q

What is natural selection?

A
  • Process of evolution in which the environment can apply a selective force on individuals within a population
74
Q

What is the 6 steps of natural selection?

A
  • Genetic mutations create multiple alleles of genes within a population
  • Creates intraspecific competition
  • Particular, advantageous alleles are able to face challenges
  • These characteristics are able to survive
  • Reproduce and pass on advantageous alleles
  • Next generation has higher proportion of it.

A Biology A Level (8 decks)

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