Flashcards in Topic 3 Deck (52):
1
What are the two types of cells
Prokaryotic and Eukaryotic
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What do Prokaryotic cells always have
• No nuclei or membrane bound organelles
• Diameter of 0.5-5ɲm
• DNA is free in the cytoplasm
• Always has a cell wall
• Ribosomes
• Circular DNA
• Cell surface membrane
• Mesosome --> infolding of the cell surface membrane, it is a site of respiration
• Cell wall
• Cytoplasm
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What organisms have/are Prokaryotic cells
Bacteria and cyanobacteria
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What can some Prokaryotic cells have but dont always have u get me
• Plasmid (small circle of DNA)
• Flagellum (hollow thread-like structure that rotates to move the cell)
• Capsule (slimy layer on surface for protection and prevention of dehydration)
• Pili (thin protein tubes that allow the cell to stick to surfaces)
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What do Eukaryotic cells always have
• 20ɲm or more
• Nucleolus --> dense body that makes ribosomes
• Nucleus --> two membranes enclosed in an envelope, it contains chromosomes and nucleolus
• Rough endoplasmic reticulum --> hold ribosomes for transcription, made of flat membrane-bound sacks
• Smooth endoplasmic reticulum --> no ribosomes, makes lipids and steroids
• Golgi apparatus --> modifies proteins and packages them in vesicles for transport. Is made of flat membrane-bound sacks due to the fusion of vesicles from the ER
• Cell surface membrane --> phospholipid bilayer, proteins and molecules that surround the cell contents
• Ribosomes --> made of RNA and proteins, function is in translation for protein synthesis
• Lysosomes --> Spherical sacks with digestive enzymes, breaks down the cell when it dies, or unwanted structures
• Centrioles --> make spindle in nuclear division, made of hollow protein microtubules
• Mitochondrion --> has two membranes and is used for aerobic respiration
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What is the rol of rER and golgi in order
1. Once a protein has been made by the ribosome on the rER or in the cytoplasm, it enters the rER
2. In the rER it folds to gain its 3D shape, enters a vesicle and travels to the Golgi
3. The vesicle fuses with the Golgi and the protein enters the Golgi
4. In the Golgi the protein gets modified
5. After modification the protein is placed into another vesicle and transported to the cell surface membrane
6. The vesicle fuses with the cell surface membrane and the protein is releases
7
What are mammalian gametes
• Gametes are sex cells
• Contain only half of the total genetic material (haploid, n=23)
• When two gametes fuse a diploid zygote (fertilised ovum cell) is formed (2n=46)
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What is an ovum cell, and where does it store its food
• A large cell incapable of independent movement
• Travels along the oviducts via ciliated cells
• Its cytoplasm contains food reserves
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What organisms have/are Eukaryotic cells
All living organisms, that are not bacteria or cyanobacteria
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What can some Eukaryotic cells have but dont always have u get me
Don’t always have a cell wall
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What is the structure of a sperm cell from head to tail
Head contains --> acrosome then haploid nucleus
middle contains --> mitochondiron
Flagellum
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What is the structure of a ovum cell from outside to inside
Follicle cells
Zona pellucida (jelly like coating)
Cell surface membrane
Cytoplasm that contains --> Lipids, lysosomes and a haploid nucleus
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How does fertilisation take place
1. Sperm cell reaches ovum
2. Follicle cells release chemicals and trigger the acrosome reaction
3. Acrosome swells and fuses with sperm surface membrane
4. The digestive enzymes in the acrosome are released
5. The enzymes digest the follicle cells and the zona pellucida
6. Sperm cell fuses with ovum membrane and the haploid nucleus is released
7. Lysosomes release enzymes to harden the zona pellucida preventing any other sperms from entering the ovum membrane
8. The two haploid nucleuses fuse
14
What is meiosis and to what numbers do chromosome replicate to
• Produces haploid cells in the ovaries, testes and anthers (in plants)
• Chromosomes replicate to produce 4n=92 chromosomes, then the cell divides four times to produce four haploid cells/gametes n=23
15
What is independent assortment
• Only one chromosome from a pair ends up in each gamete
• This is how genetically variation is possible
16
What is crossing over
• This is when chromatids that are next to each other break and re-join causing them to mix
• Chiasma --> site where the cross over took place
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Where does crossing over take place
Chiasma
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What is linkage and how does it work
• Genes are inherited individually if the gene is on a different chromosome or if it is far away from another gene on the same chromosome
• If two genes are at the same lotus they will be most likely be passed on to the gamete together (linkage)
• If genes are close together or at the same lotus, crossing over is unlikely
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What is sex linkage and give an example
• Genes that are located on a sex chromosome that will be passed on with a determined sex
• E.g 8%chance of red-green colour blindness in men, only 0.5% in women, this is a sex linked condition as it comes on the X chromosome
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What stage of the cell cycle synthesises the cells contents
Interphase
21
In what stage of the cell cycle do the chromosomes condense and spindels from
Prophase
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In what stage of the cell cycle do the chromosomes more to the equator
Metaphase
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In what stage of the cell cycle do the centrometes spilt and pull DNA to the pols
Late Anaphase
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What is the last stage of the cell cycle
Telophase
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In what stage of the cell cycle does the cell surface membrane constrict around the equator
Cytoplasmic division
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What takes place in Interphase
• Intense organised activity where cells synthesis all their contents
• The length of interphase depends on the role of the cell
• During interphase chromosomes are unravelled for protein synthesis
• DNA must be replicated
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What takes place in Prophase
• Chromosomes condense becoming shorter and thicker
• Spindle forms outside the nuclear envelope due to the centrioles (one on each pole)
• The nuclear envelope breaks down
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What takes place in Metaphase
• The chromatids move towards the cells equator, and spindle fibres attach to the centromeres
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What takes place in Late Anaphase
• Centromeres split as spindles shorten pulling the DNA too the opposite poles
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What takes place in Telophase
• Last stage of nuclear division
• Chromatids unravel and nuclear envelopes form = two separate nuclei
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What takes place in Cytoplasmic division
• The cell surface membrane constricts around the equator, protein filaments bind to the cell surface membrane at the equator to help it split into two new cells
32
What is asexual reproduction
when no production of gametes, they produce copies of themselves with mitosis
33
What is a stem cell
A cell that has the ability to develop into different types of cell.
34
When do stem cells become totipotent and what cells can these cells become
• once a zygote undergoes 3 complete cell divisions and produces 8 identical cells these cells are totipotent meaning they can develop into any type of human cell
35
When do stem cells become a blastocyst and what is a blastocyst
5 days after they become totipotent. It is a hollow ball of cells
36
How does and embryo form and what is an embryp
• The outer layer of this blastocyst forms the placenta which is 50 or so cells also know as an embryo
37
What are the cells in an embryo and what cells can they become
• These cells are pluripotent embryonic stem cells which can become most cells but not all 216
38
most cells specialise into one type of cell but some remain as what
multipotent
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What are multipotent cell
These are adult stem cells that can become a couple of specific cells
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How do cells become specialised
Cells become specialised through gene expression. Different genes are expressed in different types of cells
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What do specialised cells do
These specialised cells produce proteins for cell function and structure
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What does the epigenome do
Influences which genes can be transcribed by mRNA
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How does the epigenome work
• DNA is wrapped around histone proteins, which have chemical markers making the epigenome
• If it is tightly wrapped around the DNA then that gene is inactive
• Histone modification effects how rightly wrapped the DNA is
• These epigenetic markers are also replicated in cell division
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How are genes switched on and off
• The gene codes for the protein
• The gene must be transcribed – RNA polymerase makes mRNA
• RNA polymerase must bind to the DNA
• This happens before the gene, at a region called - the operator (in prokaryotes) – the promoter (in eukaryotes)
• In Eukaryotes --> Regulator proteins (Transcription factors) are needed to assist the polymerase in binding to the DNA or other proteins can block it from binding (repressor molecule)
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What another name for Regulator proteins
Transcription factors
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What is a tissue
These are a cluster of specialised cells all working together
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How are tissues held together
• They have adhesive molecules on their membranes allowing them that recognise the same cell allowing them to stick together
• Some tissues have an extracellular matrix (a collection of extracellular molecules secreted by support cells that provides structural and biochemical support to the surrounding cells.)
48
What does phenotype mean
• Physical characteristics due to the genotype
• Often inherited by genes on a single locus (discontinuous variation)
• Discontinuous variation is not affected by the environment and inherited
• Continuous variation can be controlled by the environment e.g height, hair colour and skin colour
49
What does discontinuous variation mean
not affected by the environment and inherited
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What does continuous variation mean
can be controlled by the environment e.g height, hair colour and skin colour
51
What is polygenic inheritance and give examples
Where multiple genes are responsible for a characteristic e.g height and skin colour alleles effect diseases such as CHD, cancer, diabetes, Alzheimer’s and schizophrenia
• E.g alleles at several loci control eye colour
• E.g 3 three loci can be involved. B=pigment b=no pigment
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