Topic 2 Bio Flashcards
Light vs electron microscope
Light has lower magnification and resolution
Electron is better for dead things and have very small wavelength
Two types of electron micrographs
Transmission electron micrographs are 2D
Scanning electron micrographs are 3D but have a lower magnification
What does a simple phospholipid bilayer allow through with nothing else
Only some fat soluble organic molecules
What determines how freely the proteins float in a membrane (fluid mosaic model)
More unsaturated fats mean membrane is more fluid
What is a gated channel
When a channel formed by a protein can be open or shut depending on cell conditions
What is a vesicle
A membrane bag that holds secretions made in cells
What is the protoplasm
Everything inside cell membrane
What is chromatin
mixture of DNA and proteins that form the chromosomes
What is nucleolus
Extra dense area of nucleus with only DNA and protein
Mitochondria structure and function
Site of respiration. Has an inner and outer membrane. Inner is folded to form cristae to give it a large SA. This has a fluid matrix inside.
What is the endosymbiotic theory of evolution of eukaryotic cells
Some cell organelles have their own DNA and over years have become part of a cell but were alone before
What is a centriole
A bundle of tubules which are used in cell division. They form the spindle fibres
What is the cytoskeleton and its function
A feature of all eukaryotic cells. A dynamic, structure that fills the cytoplasm made up of microfilaments and microtubules.
Keeps things in place, cell movement and transport in cells
What are cytoskeleton tubules mainly made of
Globular protein tubulin
What is a vacuole in an animal cell and what is a specific type
A contractile vacuole is important as they allow water content. Never permanent but can form.
What is endoplasmic reticulum as a whole
A network spread through the cytoplasm.
the site of synthesis for many chemicals
80s vs 70s ribosomes
Both can be present in eukaryotic cells. 70s are found in the mitochondria and chloroplasts so evidence they were independent. Have different rations of RNA to protein
70s are also found in prokaryotes with same job
What is the rough ER
Covered in 80s ribosomes. Makes proteins and then isolates + transports them. Has a very large SA.
What is the smooth ER
Involved in synthesis and transport of steroids and lipids
What does it look like and what is the Golgi apparatus
Made up of stacks of cisternae, formed by vesicles from endoplasmic reticulum fusing together.
Modifies and packages proteins pinched from RER
What is a lysosome and what does it look like
Dark, spherical bodies in the cytoplasm containing a mix of digestive enzymes
What is the process of lysosome destructiomn
Apoptosis. Lysosome ruptures to release cell content
Describe the plant cell wall and what it does, is made up of,
Gives the plant structure. made of insoluble cellulose. Is not a barrier for things getting in/out. Has middle lamella made of pectin, which combines with calcium ions to form strong calcium pectate which binds with cellulose to form cellulose microfibrils. Hemicellulose hardens it more.
How does the cell wall change
Can be inpregnated with Suberin in cork or lignin to make wood. Becomes a barrier
What is the plasmodesmata and what is the interconnected cytoplasm called
A cytoplasmic bridge that allows communication and transport of substances between cells. Symplast exists between cells.
What is the Permanent Vacuole in plants
In non woody plant cells it is a permanent structure surrounded by the tonoplast membrane. Filled with CELL SAP which brings water in by osmosis. Keeps the cell turgid. Used for storage of proteins, pigments, waste products
Describe choloplasts
Site of photosynthesis. Have outer membrane, inner membrane that is folded. Contain chlorophyll.
What is an amyloplast
Colorless organelle that stores starch
What is the order of organisation of cells
Cells - tissues - organs - organ systems
How many main tissue types are there in the body and name them
Four. Epithelial, connective, muscle and nervous
Difference between eukaryotic and prokaryotic cells
EUKARYOTES HAVE NUCLEUS
Describe the bacterial cell wall and its job
Cell wall prevents cell swelling due to lower water potential inside. has peptidoglycan layer. Maintains shape and protection.
What is the capsule of a bacteria
A thin layer that protects the bacteria against phagocytosis. Covers the cell markers that are used to identify it.
What are pilli and major disadvantage
Thread like protein projections that are used for movement, attatchment to host and sexual reproduction.
Make bacteria succeptible to bacteriophage.
What are flagellum
Tail like and is used for movement
Differences between cell membrane in prokaryote and eukaryote
Cell membrane is site of respiratory enzymes because of no mitochondria. Some bacterial cells have infolds called mesosomes.
what is a mesosome
infold in bacertia wall with debated function.
Describe the DNA of a prokaryotic cell
Small circles of DNA called plasmids only code for specific part and can reproduce independently.
Nucleoid contains the single length of DNA.
2 Types of bacteria: differences
Gram positive has one plasma membrane, thick outer peptidoglycan layer with teichoic acid and surface proteins
Gram negative has two plasma membranes and thin peptidoglycan layer. Has lipopolysaccharides and outer membrane proteins
Different types of bacteria by shape ( 4 types ) how to spot
Cocci - Spherical
Baccili - rod shapes
Spirilla - Twisted
Vibrios - Comma shaped
How to class bacteria by respiratory requirements
Obligate aerobes need oxygen
Facultative anaerobes only use when available
Obligate anaerobic can only respire without oxygen
What is a virus (most scientists define)
obligate intracellular parasite that only exists and reproduces in the cells of other living organisms
Describe the viral protein coat
A capsid made of simple repeating protein units called capsomeres.
How to classify viruses by their genome and mode of replication.
DNA Virus
RNA Virus
RNA Retrovirus
What is a DNA virus and examples
Virus with DNA as genetic material used directly as a template for new viral DNA and mRNA used to synthesise proteins.
Smallpox, adenovirus and lambda phage
What is a RNA virus, the two types and examples
Positive ssRNA virus have RNA that acts as mRNA and is immediately translated by the ribosomes.
Tobacco mosaic, polio
Negative ssRNA has RNA that isn’t directly translated so much be transcribed first.
Measles, influenza, ebola
What is an RNA retrovirus and give examples.
Special type with protein capsid. Reverse transcriptase is used to make DNA molecules which is then incorporated into the host cell DNA and used as template.
HIV
Use of lipid envelope for viruses
makes it easier for viruses to pass from cell to cell
How do plant viruses commonly get into the plant cell
A vector such as an insect
What are the 2 DNA virus replication pathways. State
Lysogenic and lytic.
Describe the lysogenic pathway
Many DNA viruses are non-virulent when they first get into the host cell. They insert their DNA into the host DNA so it is replicated every time the host cell divides. This DNA inserted into the host is called a provirus. Messenger RNA is not produced from the viral DNA because one of the viral genes causes the production of a repressor protein that makes it impossible to translate the rest of the viral genetic material. The virus does not affect the host cell or make the host organism ill at this stage in the life cycle. During this period of lysogeny, when the virus is part of the reproducing host cells, the virus is said to be latent
Lytic Pathway
Genetic material is replicated independent of host DNA immediately. Mature viruses are assembled and host cell will burt. The virus is virulent. Lysogenic state viruses are activated in certain ways
RNA retrovirus replication process
Viral particles leave cell by exocytosis so host remains are a virus producing cell.
How do antiviral drugs work
Cannot target virus particles themselves. 1. Target enzymes that help translate virus DNA or RNA
2. Target receptors viruses use to recognise cells
3. Inhibit production of new virus particles
Stages of mitosis and what happens in each
Interphase - Cell increases in mass and size. DNA is replicated
Prophase - Chromosomes coil up, centrioles begin to move to opposite poles and form spindle fibres. Nucleus breaks down
Metaphase - Chromatids line up along the equator of the cell and spindle fibres attach
Anaphase - Spindle fibres contract and sister chromatids are pulled towards opposite poles
Telophase - Spindle fibres break down, nucleoli and centrioles reform. Chromosones unravel
Cytokinesis - Contractile ring tightens until cell divides in animal cell, in plant cell cellulose just builds up
What do histones do and what do they help form
Pack DNA closely together in clusters known as nucleosomes
Phases of interphase
G1 - Gap is when cell is assimilating material, growing and developing.
S - is when chromosomes replicate to become double stranded chromatids
G2 - time that organelles needed for cell division are synthesised
How is cell division controlled
Small proteins called cyclins. Build up and attached to, cyclin depended kinases CDK’s which brings about the next step in the cell cycle through phosphorylation
Different strategies of asexual reproduction
Producing spore - sporulation involving production of asexual spores that are capable of growing into new individuals.
Regeneration - When organisms replace lost body parts.
Fragmentation - Organsims reproducing themselves asexuals from fragments of their original body.
Producing buds - Budding is when a small new individual forms as part of parent organism
Vegetative propagation - Like budding but with runners, containing stored food and are very resistant.
Differences between mitosis and meiosis
The two chromosomes of each pair stay close together and crossing over occurs (prophase 1).
Centromeres do not split in first meiosis so cell goes straight to mitosis 2.
How does meiosis produce variation
Independent assortment - Different combinations in the assortment of the chromosomes as they line up along the centre means that some will be taken from mother some from father every time in different ratio
Crossing over - Similar sections of genetic material is exchanged between chromosomes forming new mutations
Where does crossing over occur
At the chiasma, usually far from centromere
Gametogenesis in animals
Spermatogenesis - Primordial germ cell divides by mitosis to form spermatogonia
Spermatogonia grow until they are spermatocytes
spermatocytes divide by meiosis to form spermatids
spermatids then differentiate to form spermatozoa
Oogenesis - Primordial germ cell divides by mitosis to form oogonia
One oogonia becomes the primary oocyte
oocyte does meiosis. only does second division after fertilisation
