Topic 3 Flashcards
What are all living organisms made of?
All organisms are made of prokaryotic or Eukaryotic cells
- Prokaryotic = smaller and simpler (bacteria)
- Eukaryotic = larger and complex (animal cell , plant cell)
What are the features of cells called?
Looking through a microscope you can see the internal structure and the organelles (cell ultrastructure)
What is the ultrastructure of an animal cell?
What is the function of the nucleus
- A large organelle that controls activities like transcription
- Surrounded by the nuclear envelope (Double membrane)
- Nuclear Pores (Allow substance movement in and out nucleus)
- Chromatin (made from DNA and proteins)
- Nucleolus (Makes Ribosomes)
What is the role of lysosome?
- No clear internal structure
- round organelle with membrane (containing digestive enzymes)
- Can be used to digest invading cells or cell waste like Glycosaminoglycans (GAGs)
- Once digested the lysosomes would fuse with the cell membrane
- Then the contents of the lysosomes would be released outside the cell through exocytosis
What is the role of the Ribosome?
- Small organelle
- Free-floating or attached to the rough endoplasmic reticulum
- Made up of proteins
- Not membrane-bound
What is RER?
Rough Endoplasmic Reticulum (RER)
- System of membranes
- Surface covered with ribosomes
- Folds and processes proteins from ribosomes
What is the SER?
Smooth Endoplasmic Reticulum (SER)
- System of membranes
- No ribosomes present
- Synthesises and processes lipids
What is the Golgi apparatus?
- Group of membrane-bound flattened sacs
- Vesicles at end of sacs
- Modifies Proteins (Eg. Adding carbohydrate chains)
- Packages lipids and proteins via Exocytosis
- Makes lysosomes
What is the role of the mitochondrion?
- Oval Shaped
- Double membrane
- Inner membrane folded to form cristae
- Matrix contains respiration-related enzymes
- ATP produces at the site of reparation
What is the role of centriole?
- Small hollow cylinders
- Made of microtubules (tiny protein cylinders)
- Found in all animal cells some plant cells
- Involved in the separation of chromosomes in mitosis
What is the ultrastructure of the bacteria cell?
What is the role of the flagellum in a bacteria cell?
- Long hair-like structure
- Rotates to propel the bacteria cell forwards
- Can be more than one on a cell
What is the role of Nucleoids in a bacteria cell?
- Free-floating DNA
- Circular DNA in a coiled strand
- Not attached to any histone proteins
What is the role of the plasmid in the bacteria cell?
- Small loops of DNA
- Aren’t connected to Nucleoid
- Contains genes for things like antibiotic resistance
- These genes can be passed from one cell to another
What is the role of the mesosomes in the bacteria cell?
- Inward folds in plasma membrane
- May be involved with cellular processes
- Or artefact from using electron microscope
What is the capsule in the bacteria cell?
- Made up of secreted slime
- Helps protect from immune system
What is the role of the pili?
- Help in sticking to other cells
- Help transfer genetic material between cells
What is the role of the Cell Wall?
- Keeps shape
- Made from murein (glycoprotein)
What is the role of the plasma?
- Made up of Lipids and Protein
- Controls movement of substances in and out of the cell
What is the process of protein transport?
- transcription of DNA to mRNA
- mRNA leaves the nucleus
- protein Made on ribosomes enters rough ER
- Protein moves through the ER on a 3D route along cisterna
- Vesicles pinched of rough ER containing protein
- Vesicles from rough ER fuse to form Golgi apparatus sacs
- Proteins modified in Golgi apparatus
- Vesicles pinched off Golgi apparatus containing modified proteins
- Vesicles fuse with the cell surface membrane releasing protein as extracellular enzymes
What is the adaptation of the sperm cell?
- Smaller than egg cell ⇒ Motile
- Flagellum ⇒ Able to swim
- Lots of Mitochondria ⇒ Lots of energy to swim
- Acrosome (Modified lysosome) ⇒ Releases digestive enzymes to break down zona pellucida (targeted to only release on egg)
- Attracted to chemicals released from egg cell ⇒ able to locate egg cell
- Head Shape ⇒ Becomes more streamline as they get closer to egg
- Little cytoplasm
How is an egg cell adapted to its function?
- Lipid droplets ⇒ to supply food to embryo
- Cytoplasm ⇒ contains proteins to feed the embryo
- Released Chemicals ⇒ which attract sperm cells
- Zona Pellucida Hardens ⇒ after one sperm has fertilized the egg a cortical reaction occurs
- Lysosome / Cortical Granules
What are the steps for fertilization
Steps for fertilisation
- Sperm Reach the ovum
- Acrosome reaction triggered from ovum chemicals releasing
- Acrosome Swells, fusion of cell membrane and sperm
- Digestive enzymes released
- Enzymes break down follicle cells
- Enzymes break down zona pellucida
- Sperm and cell ovum membrane fuse
- Sperm nucleus enters ovum
- Lysosome enzymes release thickening zona pellucida preventing sperm from entering
- Nuclei of sperm and ovum fuse
What is the Locus?
- A locus is the location of genes on a chromosome
- Each gene can exist in two or more different forms calledalleles
- Different alleles of a gene have slightlydifferent nucleotide sequencesbut they still occupy thesame position(locus) on the chromosome
What is the structure of a chromosome
What is the linkage of genes on a chromosome?
- Genes on the same chromosome are linked
- They will stay together during independent assortment
- Alleles would be passed off together
- The closer together the loci the more closely they are said to be linked
What is the purpose of meiosis?
- To produce reproductive organs to produce gametes
- These gametes are diploid
- Since these gametes are diploid they produce 4 non-identical daughter cells
What is and Why do we need mitosis?
Mitosis is where a parent cell which divides to produce two genetically identical daughter cells
Mitosis is needed for:
- growth of multicellular organisms
- Repair of tissue
- Asexual reproduction
What is the cell cycle?
Consists of mostly DNA replication and cell growth - INTERPHASE
Divided into 3 growth stages
- Gap phase 1
- Synthesis
- Gap phase 2
What happens in the Interphase?
Interphase
- Cells DNA is unraveled and replicated
- Organelles are replicated
- ATP content is increased
What happens in prophase?
- Chromosomes condense getting shorted and fatter
- Proteins called centrioles move to other ends of cells forming a spindle
- Nuclear envelope breaks down and chromosome lie free in the cell
What happens during Metaphase?
Metaphase
- The chromosomes and chromatids line up
- Then attached to spindle by centromere
What happens during Anaphase?
- Centromeres divide
- Separating pairs of chromatids
- Spindles contract moving chromatids to opposing poles
- Giving the chromatids a shape
What happens during Telophase?
- Chromatids at opposite poles of the spindle uncoil
- Becoming long and thin (THESE ARE CHROMOSOMES)
- 2 nuclear envelopes form around the 2 groups of chromosomes (forming 2 nuclei)
- The cytoplasm then divides (cytokinesis)
- 2 identical daughter cells are then created and both undergo interphase again
Where do stem cells come from in an embryo?
- After five days after conception a blastocyst (a hollow ball of cells form)
- The outer later of blastocyst then forms the placenta
- The inner layer of the blastocyst goes on to form the developing embryos tissue (pluripotent embryonic stem cells)
- These cells can give rise to most cells
- BUT not all 216 for the adult body
How are Embryonic stem cells used in medicine?
- Pluripotent stem cells are isolated and are produced in fertility clinics
- Vitro fertilisation is where the ovum is fertilised outside the body so that embryonic stem cells can be extracted and used
- This has lead to controversy as well as cloning eggs
How are adult stem cells used in medicine?
- Used for leukaemia and related Cancers
- These can be extracted from bone marrow and cultivated into healthy blood cells
- Also used to make cells for transplants like windpipes
- However isolation of stem cells and differentiating of those cells is difficult and costly
What are the main Ethical concerns about the use of stem cells?
- Embryonic cells are controversial because of its collection
- iPSC’s could replace embryonic stem cells
What is meant by epigenome?
All the modifications of that regulate the expression of genes is known as an epigenome.
Epigenetics control determines whether certain genes are expressed by altering phenotype
- Alters how easy the enzymes and proteins needed for transcription
- Involved with cellular processes as changes happen in the environment
Does not alter base sequence of DNA
How can the environment affect a phenotype?
Environmental factors such as medicines, drugs and chemicals in the environment can trigger changes in the epigenome and effect expression of genes
Give an example of the mentioned above
- Overeating lead in one mouse’s pigment to be lighter
- As the agouti gene isn’t methylated like the normal mouse
- Meaning that the agouti protein is made and binds to MSH receptors
How can behaviour effect epigenetic changes?
The behaviour that the mice where exposed to led to or didn’t lead to the methylation to express the GR gene
Where the GR gene produces proteins that bind to stress hormones where if enough is formed stress is prevented and serotonin is released.
How can epigenetic changes can be passed on through cell division?
- During meiosis the sperm and egg cells produced would have helped determine their specialised structure and function.
- This is achieved by the removal of epigenetic changes during development
- Returning these cells to stem cell configuration
- BUT its believed that some epigenetic changes are passed from parent to child.
How does DNA methylation work?
Epigenetic control works by controlling the methylation of DNA
The methyl group is attached to DNA which codes for a gene
Attaches to consecutive Cystine and Guanine bases
Increased amount of Methylation changes DNA structure so proteins can’t bind to the gene in transcription
How does Histone modification work
What is the continuous variation?
When individuals in a population vary within range where there is no distinct categories
- Height
- Mass
- Skin colour
What is discontinuous varaiation?
When there is two or more distinct categories where individuals fall into only one of these categories
- Blood groups
- Genotype of a genetic disease (Carrier, Non sufferer, Sufferer)
How does phenotype influence genotype?
- Different individuals have different genotypes (Different Allele combination)
- So different alleles results in different phenotypes expressed (like blood groups)
- Monogenic characteristics are only controlled by one gene and is found in DISCONTINOUS VARIATION
- Polygenic characteristics are controlled by multiple genes at different loci and is the vast majority of characteristics and is found in CONTINUOUS VARIATION
How does polygenic inheritance work?
How does the environment affect phenotype variation?
Height in as an Influences Phenotype
The next generation of children is taller than the last due to
- Taller men having generally taller children
- Greater movements of people mean a higher gene pool
- Better nutrition since we know a lot more now
- Better heating in houses so energy can be redirected to growing
What is the link between melanin and the environment?
Melanin Production
- Melanin made in specialised cells called melanocyte-stimulating hormone (MSH)
- MSH receptors on melanocyte cells
- Melanin places into melanosomes
- Melanosomes transferred to nearby skin and hair cells protecting DNA in the nucleus from UV light
- UV causes the amount of MSH and MSH receptors
- Leading to darker skin but the removal of melanin by UV in hair cells leads to lighter hair
What is Cancer?
- Damaged DNA
- Caused by Mutations and Carcinogens
- Which leads to uncontrolled cell growth
- Which can lead to a tumours
How is Cancer linked to the cell cycle?
What is the difference between an Oncogene and a Protooncogene?
- A Protooncogene is a gene which allows for cell growth
- An Oncogene is a mutated protooncogene that is responsible for resulting in uncontrollable cell growth
How do Oncogenes work?
Oncogenes result in uncontrollable cell growth by:
- Producing proteins that
- Leads to less methylation of certain genes
- Resulting in indefinite constant cell division
What are Tumour Suppressor Genes
- They stop continuation of cell cycle
- Where the p53 gene stops replication at $G_1$
- So the cell cycle stops at interphase
