Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

as bio > AS Topic 3 > Flashcards

AS Topic 3 Flashcards

(108 cards)

Start Studying
1
Q

What is a eukaryotic cell?

A

A cell containing a nucleus and other membrane bound organelles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a prokaryotic cell?

A

A cell with circular DNA and no membrane bound organelles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the structure and function of the mitochondria?

A

Double membrane with the inner one folded to form cristae.
The mitochondria are the site of the later stages of aerobic respiration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the structure and function of the nucleus?

A

Double membrane (nuclear envelope) perforated by pores. Contains chromosomes and a nucleolus.
Acts as control centre of cell, retains genetic material and manufactures ribosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the structure and function of the nucleolus?

A

Dense body in nucleus
Makes rRNA and assembles ribosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the structure and function of a chloroplast? (PLANT CELL ONLY)

A

Double membrane, filled with grana (disc like stacks of thykaloids). Stroma
Carry out photosynthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

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

A

System of interconnected membrane-bound, flattened sacs with ribosomes attached to outer surface.
Protein synthesis - folds and processes proteins made at the ribosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

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

A

Same as rough ER but doesn’t have any attached ribosomes
Make lipids and steroids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the structure and function of a ribosome?

A

Made of RNA and protein - 2 different subunits
Site of protein synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the structure and function of the Golgi apparatus?

A

Stacks of flattened, membrane-bound sacs formed by fusion of vesicles from ER. Curved/flattened cisternae of different sizes
Modifies proteins and packages them in vesicles for transport

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the structure and function of a lysosome?

A

Spherical sac containing digestive enzymes, bound by a single membrane
Involved in breakdown of unwanted structures within cell, and sometimes in destruction of whole cells when old cells are to be replaced or during development

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

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

A

Phospholipid bilayer containing proteins and other molecules
Forms a partially permeable barrier

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the structure and function of a centrosome?

A

A centrosome is composed of 2 centrioles
It duplicates before mitotic division and moves to opposite poles to start the process of spindle formation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the structure and function of a centriole? (ANIMAL CELL ONLY)

A

Hollow cylinders made up of a ring of 9 protein microtubules
Involved in formation of spindle during nuclear division

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the structure and function of the cell wall? (PLANT CELL ONLY)

A

Outer protective layer composed of polysaccharides
Provides mechanical strength to stop cell bursting, supports cell prevents change in shape

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

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

A

Made of peptidoglycan
Provides cells with support

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the structure and function of the capsule (prokaryotic cells)?

A

Stick outermost layer usually composed of polysaccharides
Helps prokaryotes cling to each other and protects bacteria from attack by cells of the immune system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the structure and function of a plasmid?

A

A small circular double stranded DNA molecule
Carries DNA separate from chromosomal DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the structure and function of the pili?

A

Short hair like structure on cell surface
Involved in adherence to surfaces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the structure and function of a mesosome?

A

Invagination/infolding of plasma membrane
Used in aerobic respiration and cell wall formation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is circular DNA

A

DNA forming a closed loop with no ends/non linear

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How are proteins made and modified? (GOLGI APPARATUS AND ER)

A

Transcription of DNA to mRNA in nucleus, then mRNA leaves nucleus.
Protein is made on the ribosomes of the Rough ER and then moves through the ER, being folded and gaining it’s 3D shape. It is then moved in a vesicle to fuse to form the flattened sacs of Golgi apparatus.
Here the proteins are modified, before being pinched off into vesicles and fused with the cell membrane to be released with exocytosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How is a glycoprotein created from a regular protein by the Golgi Apparatus?

A

The protein arrives and is modified by adding a carbohydrate to become a glycoprotein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the equation for magnification?

A

Magnification = size of image/size of object

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What is the difference between resolution and magnification?
Resolution is the ability to distinguish between 2 points, whereas magnification is how enlarged an image is compared to a specimen
26
How do you prepare a microscopic slide?
Liquid sample - add a few drops to slide and cover with coverslip Solid sample - cut a thin layer of tissue cells from the sample, apply a stain to make cells more visible and cover with a coverslip
27
What are the common stains, what do they colour?
Methylene blue - stains animal cell nuclei blue Iodine - stains starch-containing material in plant cells blue-black Toluidine blue - stains tissues that contain DNA and RNA blue Phloroglucinol - stains lignin found in some plant cells red/pink
28
What are gametes?
Sex cells
29
What are the adaptations of a sperm cell?
Acrosome - contains digestive enzymes to hydrolyse the zona pellucida Flagellum - propels the sperm forwards (motility) Large amounts of mitochondria - provide ATP for respiration, energy for swimming Haploid - sexual reproduction Hydrodynamic
30
What is the acrosome reaction?
When the acrosome in the head of the sperm swells, fuses with the head of the cell surface membrane and releases digestive enzymes. This then hydrolyses the zona pellucida
31
What are the adaptations of an egg cell?
Zona pellucida hardens after fertilisation to prevent polyspermy Follicle cells (corona radiata) provide protective coating Cytoplasm contains nutrients for the embryo
32
What happens when the sperm and egg nuclei meet each other?
Egg nuclear envelope breaks down and the 2 haploid nuclei fuse, which produces a fertilised egg (zygote - diploid)
33
How do the events following the acrosome reaction prevent more than 1 sperm fertilising an egg?
sperm cell fuses with cell membrane cortical granules are released by ovum via exocytosis cortical granules released into the zona pellucida this causes the zona pellucida to harden, preventing polyspermy
34
What are the similarities and differences between the acrosome and cortical reaction?
Similarities = both involve exocytosis, both involve vesicles Differences = acrosome digests zona pellucida, cortical hardens it
35
What is meiosis?
A type of cell division that produces gametes
36
How does meiosis ensure genetic variation?
through the production of non-identical gametes as a consequence of independent assortment of chromosomes and crossing over of alleles between chromatids
37
Explain how meiosis gives rise to genetic variation in gametes?
Independent assortment gives rise to different/new combinations of chromosomes Crossing over is the process by which non sister chromatids exchange alleles
38
What is crossing over and how does it create genetic variation?
When sections of DNA are exchanged between non sister chromatids (chiasmata) This gives rise to a large amount of genetic variation
39
What is independent assortment and how does it create genetic variation?
When chromosomes line up randomly on the cell equator during mitosis This means either chromosome from each pair could be in any gamete
40
What happens during meiosis?
Original cell - diploid Before Meiosis I, chromosomes replicate. During Meiosis I, the homologous pairs of chromosomes are split up (still remain as 2 chromatids) to produce 2 haploid nuclei. During Meiosis II, the chromatid pairs are pulled apart to produce 4 haploid nuclei (each chromosome is a single chromatid)
41
What is the locus of a gene?
The position of a gene on a chromosome
42
What is autosomal linkage?
When genes that are on the same autosome are not assorted independently (as they have a similar locus) so they become linked and stay together during original parental combination - meaning they are passed on to offspring all together.
43
What is the autosome?
All chromosomes except from the sex chromosomes
44
What sex chromosomes do females have?
XX
45
What sex chromosomes do males have?
XY
46
Why is colour blindness more common in males than females?
Colour blindness is caused by a recessive allele on the X chromosome Males only need 1 recessive allele to be colour blind whereas females need 2
47
Why does males only having one X chromosome make it more likely they will inherit sex linked conditions?
Because it means they are hemizygous for any genes present on the X chromosome and therefore it will be expressed even if it is a recessive allele
48
What is sex linkage?
When genes are linked due to the locus of the allele that the gene codes for being found on a sex chromosome
49
What are the 3 stages of the cell cycle?
Interphase Nuclear division (mitosis) Cell Division (cytokinesis)
50
What are the 3 phases in interphase?
G1 S G2
51
What happens in each of the 3 interphase stages?
G1 = signal received to divide again, cells make DNA, enzymes and proteins for growth S = DNA replicates G2 = cell continues to grow, new DNA checked, preparations for cell divison
52
What happens to cell growth in mitosis?
It stops
53
What happens in cytokinesis?
The whole cell divides to create 2 genetically identical daughter cells
54
What is mitosis?
The process of nuclear division forming 2 genetically identical daughter nuclei (which are also identical to the parent nuclei)
55
What happens during metaphase?
Chromosomes line up along the equator of the spindle Spindle fibres attach to the centromere
55
What happens during prophase?
Chromosomes condense, centrosomes move to opposite ends of the cell and spindle fibres begin to form. Nuclear envelope and nucleolus break down
56
What happens during anaphase?
Sister chromatids separate at the centromere and are pulled away by shortening spindle fibres (microtubules) to opposite poles
57
What happens during telophase?
Chromosomes arrive at opposite poles and start to decondense. Nuclear envelope reforms around each set of chromosomes, remainder of spindle breaks down
58
Why is mitosis biologically significant?
-for the growth of multicellular organisms from unicellular zygotes -replacement of cells and repair of tissue (cells are constantly dying so need to be replace by genetically identical cells) -asexual reproduction
59
What is a stem cell?
An undifferentiated stem cell that can give rise to specialised cells and divide to produce more stem cells
60
What is potency?
The ability to differentiate into more specialised cell types
61
What are totipotent stem cells?
Stem cells that can differentiate into any cell type
62
What are pluripotent stem cells?
Embryonic stem cells that can differentiate into any cell type found in an embryo, but not the cells forming placenta and umbilical cord
63
What are the differences between totipotent and pluripotent stem cells?
totipotent can differentiate into any cell type pluripotent can only give rise to most (not all cells in the body or totipotent cells) totipotent can give rise to an entire human, pluripotent cannot
63
When do totipotent cells change to pluripotent
Totipotent are only present in mammals in the first few divisions of an embryo. After this point the embryonic stem cells become pluripotent, losing the ability to become cells that make up the placenta and umbilical chord
64
What are the uses of embryonic stem cells, and where are they taken from?
Huge potential in development of therapeutic treatments of diseases Taken from embryos, and can therefore be pluri or totipotent
65
What are the uses of adult stem cells, and where are they taken from?
Can be injected into damaged tissue to treat diseases such as leukaemia and also injuries - but must match blood type and antigen or there is a risk of rejection Taken from bone marrow and brain
66
How do official regulatory authorities make decisions about the use of stem cells?
-review proposals for stem cell resarch -licensing and monitoring of research centres -providing guidelines and codes for practice -monitoring new developments -providing governments and other professional bodies with correct and up to date advice and info on stem cell research
67
What are the benefits of stem cells?
Potential to treat a range of diseases, can develop treatments from a patient’s own organs, adult stem cells are already successful
68
What are the risks/issues with stem cells?
Stem cells could become infected in lab, can develop into cancer cells due to mutations, there are low numbers of donors
69
What are the social issues associated with the use of stem cells?
* embryonic stem cells are totipotent and can be used in a wider range of therapies (1) * source of embryonic stem cells has to be {considered/ regulated} (1) * {moral / ethical} issues as the use of embryonic stem cells destroys embryos (1) * need for research establishments to be {regulated / licensed} (1)
70
What are the ethical objections to the use of stem cells?
Amounts to killing an unborn child/abortion/murder, intefering in nature, may have genetic consequences for future generations, pressure to harvest human eggs for medical use, money could be used for other types of research
71
What are the advantages of using stem cells from a patient rather than a donor?
Genetically identical cells to the patient therefore there is no risk of rejection. No need to take immunosuppressant drugs, and less risk of infection
72
How do cells become specialised?
Stimulus (e.g. chemical) causes some genes to be switched on/expressed. This leads to transcription of active genes, the mRNA produced is then translate to create the protein. This protein modifies the cell/determines cell structure
73
What is a transcription factor?
A protein that binds to dna and activates or deactivates genes by increasing or decreasing rate of transcription
74
What are the 2 types of transcription factor?
Transcription factors increasing rate of transcription = activators Transcription factors decreasing rate of transcription = repressors
75
How do transcription factors control gene transcription?
Binding to promotor region of a gene They interact with RNA polymerase, either assisting or preventing it from binding so beginning/stopping transcription
76
What is an operon?
A group or cluster of structural genes that are controlled by the same promoter
77
What is the lac operon?
Section of genes that controls production of enzyme lactase, which is ‘inducible’ and only synthesised when lactose is present
78
What happens when lactose is absent? (lac operon)
regulatory gene is transcribed and translated to produce the lac repressor protein (transcription factor) the protein binds to the operator site when no lactose present blocking transcription as RNA polymerase is unable to bind NO LACTASE PRODUCED
79
What happens when lactose is present? (lac operon)
lactose is present so binds to lac repressor protein and distorts it this means it can no longer bind to the operator region RNA polymerase is able to bind to the promoter region LACTASE IS PRODUCED
80
What is an organelle?
A component within a cell that carries out a specific task
81
What is a cell?
The basic functional and structure unit within a living organism
82
What is a tissue?
A group of cells that works together to perform a particular function
83
What is an organ?
Made from a group of different tissues working together to perform a particular function
84
What is an organ system?
Made from a group of organs with related functions, working together to perform body functions within the organism
85
What is phenotype?
The observable characteristics of an organism
86
What is phenotype determined by?
The expression of an organism’s genotype and it’s interaction with it’s environment
87
What is genetic variation?
The small differences in DNA base sequence between individual organisms within a species
88
Why is the variation in phenotype due to genetics inherited but the variation in phenotype due to environmental factors not?
Genetic variation directly affects the DNA of the gametes but variation in the phenotype caused by the environment does not
89
What in the genotype can determine the phenotype?
The different alleles an organism has at a single gene locus can determine the phenotype
90
What are environmental factors that can affect the phenotype of plants?
Living conditions: - availability of water - supply of nutrients - temperature range - oxygen levels - length of sunlight hours
91
How do changes in environmental factors affect changes in the phenotype of an organism?
Because environmental factors change how an organism grows and develops Environmental factors determine the achievement of the genetic potential
92
How can the height of an adult human demonstrate how environmental factors interact with genotype (diet)?
Malnutrition - prevents a nutrient being taken in for specific growth - e.g. bone growth/muscle growth Other environmental factors can determine expression of genotype (such as health) Environmental factors determine the achievement of genetic potential
93
What are the features of discontinuous variation, and what type of variation in the phenotype gives rise to it?
Generally monogenic inheritance causing qualitative differences Features: - distinct classes/categories - characteristics cannot be measured over a range - individuals cannot have features that fall in between categories
94
What are the features of continuous variation, and what type of variation in the phenotype gives rise to it?
Caused by multiple different genes or multiple alleles for the same gene at many different loci as well as the environment (polygenic inheritance causing quantitative differences) Features: - no distinct classes or categories - characteristics can be measured and fall within a range between 2 extremes
95
What is epigenetics?
The control of gene expression by factors other than an individual’s DNA sequence. This involves switching genes on and off without changing the actual code
96
What are histones?
Proteins around which nuclear DNA is wrapped to form chromatin
97
How can chromatin be chemically modified to alter gene expression?
-methylation of DNA -histone modification via acetylation of amino acid tails
98
What is DNA methylation and what change does it cause?
The direct addition of methyl groups (CH3) to DNA Causes the inactivation of genes
99
How does DNA methylation cause the inactivation of genes?
Methylation suppresses the transcription of the affected gene by inhibiting binding of transcription factors and the enzymes needed for transcription
100
What can DNA methylation be affected by?
Environmental, lifestyle or age related factors
101
What is the acetylation of histones and what change does it cause?
The addition of acetyl groups (-COCH3) to lysine amino acids on histone proteins It causes genes to be activated
102
How does histone acetylation cause gene expression?
On lysine amino acid, there is normally a positively charged R group which forms iocnic bonds with the phosphate backbone - so DNA coils tightly. Adding an acetyl group removes the positive ion, removing a bond between the histone protein and DNA so it becomes less tightly wrapped. Less tightly wrapped DNA means RNA polymerase and transcription factors can bind more easily and the gene is activated
103
Can epigenetic changes be passed on?
Yes, via cell divison EXAMPLE - during gamete production, DNA in parent cells usually undergoes de-methylation, but often methyl groups are not removed and therefore are present in DNA on sperm or egg cells Epigenetic changes due to environmental factors therefore can be passed down to the next generation
104
Why does increasing the number of stem cell divisions increase the risk for cancer?
Greater number of cell divisions = more opportunities for errors in DNA replication Therefore more mutations may occur, creating a greater chance of cancer.
105
What are the comparisons/contrasts between the acrosome and cortical reaction?
SAME: both involve vesicles, both involve release of a substance via exocytosis DIFFERENT: acrosome causes digestion of zona pellucida, cortical causes thickening of zona pellucida
106
What is molecular phylogeny?
Study of molecular differences/similarities in DNA/RNA and proteins to determine evolutionary relationships between organisms

as bio (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions