Topic 3 Flashcards
Structure and function of different parts of a prokaryotic cell (bacteria/archea)
—>Ribosomes- site of protein synthesis
—>Nucleoid- for prokaryotes they have a single circular length of DNA carrying essential information, DNA is folded into nucleoid.
—>Cell surface membrane- controlling what goes in/out
—>Cell wall- made of peptidoglycan (polymer of sugar and amino acids)
—>Memosomes- Infolding of the inner membrane
—>Flagellum- rotates for movement
—>Pili- thin protein tubes allowing bacteria to stick to surfaces
—>Plasmids- double stranded DNA in a circular structure ( provide toxin producing genes)
—>Capsule- used for production and prevent dehydration
Structure and function of parts in Eukaryotes (fungi/animal cells)
—>rER- series of single/flattened sacs, folds and processes proteins on ribosomes.
—>sER- system of membrane bound sacs, sER produces/processes lipids.
—>Nucleus- surrounded by a double membrane (envelope) contains pores allowing molecules to enter/leave cell. Nucleus contains DNA wrapped around histone proteins in complex called chromatin and a nucleous that produces ribosomes.
—>Centrioles- two hollow cylinders (right angles) creating the spindle for cell divisions
—>Lysosome- enclosed by single membrane, contains digestive enzymes that destroy old organelles and pathogens.
—>Golgi apparatus- single curved sacs enclosed by membrane formed by vesicle fusion from ER. It modifies proteins and packs them in vesicles for transport.
—>ribosomes- protein synthesis
—>mitchrocondria- surrounded by double membrane (envelope). Inner membrane folds into cristae and central area contains jelly called matrix. Mitchrocondria contains DNA and ribosomes it’s also site of respiration.
Steps of Production of proteins and route through cell
1)Transcription of DNA to mRNA, mRNA leaves nucleus
2)Protein on ribosomes enter rER and protein gains 3D shape
3)vesicles fuse to form flattened sacs of Golgi apparatus, here protein is modified and prepared for transport (packed in vesicles)
4)Vesicles pinched and fuse with membrane releasing proteins (exocytosis)
Structure and function of different parts of sperm cell
—>Flagellum- used for movement
—>Haploid nucleus- contains half number of chromosomes (so full amount restored after fertilisation)
—>Acrosome- contains enzymes that digest outer layer of egg
—>Middle region (mitchrocondria) - provide energy (respiration) for movement
Egg cell structure and function
—>lipid droplets- provide energy
—>Folicile cells from ovary- act as protection and hardern after sperm enters
—>Cytoplasm-full of energy
—>membrane
—>Zona pellucida- jell like layer stopping more than one egg fertilising
—>haploid nucleus- half chromosomes
—>Vesilcles (cortical granules)- release substance to harden zona pellucida
Fertilisation steps
1)Sperm reaches ovum so chemicals released triggering acrosome reaction (enzymes digest zone pellucida)
2)sperm fuses with egg membrane and sperm nucleus enters egg
3)cortical reaction occurs hardening zona pellucida
4)full set of chromosomes restored forming diploid zygote
What is a gamete
Contains half the number of chromosomes one from each homologous pair.
What is mitosis
Mitosis produces new body cells as organism grows and develops, it retains full number of chromosomes (diploid)
What is meosis
Produces gametes with haploid. Occurs in ovaries/testies in animals but ovaries/anthers in plants. Meosis creates genetic variance in offspring.
What is crossing over
1) homologous chromosome pair is replicated forming chromatids (the point at which the chromatids break is called chiasma)
2) The chromatids separate and gametes are formed (each with half the amount of chromosomes)
How is genetic variation achieved through meosis
–>Crossing over- exchange of DNA sections between homologous chromosomes
–>Independent assortment- there are various ways paternal/maternal chromosomes can be distributed between daughter cells
Describe what Mendel did with garden pea plants
Mendel analysed patterns of inheritance in garden peas. He crossed homozygous (pure breeding) tall purple plants with short white plants.
-He found that all offspring (f1 generation) were tall purple
-But crossing further he found (F2 generation) there was a mix of different plants.
What did Mendel conclude from his peas experiment
Inheritance of one pair of factors is independent of inheritance of other pairs. However this is only the case if genes are on different chromosomes and independently assorted
What does sex linked mean
Sex linked- genes with loci on the same sex chromosomes (X/Y chromosomes)
What is the cell cycle
Process in which cells divide to produce two genetically identical daughter cells for growth/repair/asexual reproduction
What are the three stages in the cell cycle
-Mitosis (Prophase,metaphase,anaphase,telophase)
-Cytokinesis (cytoplasm divides to form 2 new cells)
-Interphase (Cell grows, new organelles grown,finally chromosomes replicated)
Stages of mitosis explained
1)Prophase- chromosomes become visible and nucleus breaks down and disappears, spindle formed. Then centrioles move to either end of cell.
2)Metaphase-chromosomes with 2 sister chromatids line up and attach to spindle fibres which are attached to centrioles.
3)Anaphase-spindle fibres contract pulling chromatids apart
4)Telophase-chromosomes decondence and membrane of nucleus reform
Stages in interphase
1)G1 (gap 1 phase)- cell grows, DNA replicates and protein synthesis occurs.
2)S phase- chromosomes are replicated and begin to condense to form chromatin
3)G2 (gap 2)- Cell prepares to divide and replicates organelles for a full set in each new cell
How does mitosis ensure genetic consistency
As each daughter cell contains same number and type of chromosomes as parent cell.
This is achieved as DNA replicates prior to nuclear Division and the arrangement of chromosomes on spindle/chroatid separation on poles
What is a multipotent stem cell
Give rise to variety of different cell types
Pluripotent stem cell
Give rise to variety of cells other than placental cells
Totipotent stem cells
Give rise to all types of specialised cells, a cell is totipotent when an embryo consists of 8 identical cells
Ethical issues for using stem cells in medication
-is it acceptable to use human embryos that are created for research
-when does an embryo become a human with rights
What happens during therapeutic cloning (making organs from own cells)
1)diploid cell removed
2)cells nucleus fused with ovum, from which haploid nucleus has been removed and diploid cell results
3)this process is somatic cell nuclear transfer. The stem cells created can be used.
