Topic 3 - Cells And Viruses Flashcards
What is the cell
The cell is the structural unit of all living organisms
What are the two types of microscopes that are used to study cells
Light microscope and electron microscope
What is the definition of resolution
The ability to discriminate fine detail so that two neighbouring points are seen as separate, rather than as a larger blur
What is the definition of magnification
The increase of the size of the object
Why does an electron microscope have a much greater resolving power than light microscopes
Because electrons have a shorter wavelength than light
What are some advantages of using a light microscope compared to an electron microscope
It’s cheaper
It can be carried about
You can view living specimens under the light microscope
Artefacts can be added
What are some disadvantages of using a light microscope
The magnification and resolution are not high enough to view specific cells
What are the advantages of using a transmission electron microscope
High magnification and resolution than both scanning and light microscopes
You can see in colour
What are some advantages of using a scanning electron microscope
You can see the images on the stand in 3D
You can get a better idea of the volume of the image
What are some disadvantages of using electron microscopes
The specimen must be dead
It requires specialist staff to work
What is the cells ultrastructure
The appearance of a cell viewed under an electron microscope
Give the structure of an animal cell, listing if they have a cell wall, chloroplasts, how they store energy, lysosomes, vacuole, centrioles and plasmodesmata
Cell Wall - No cell Wall Chloroplasts - No chloroplasts Energy Storage - Glycogen granules Lysosomes - Yes Vacuole - No permanent vacuole Centrioles - Yes Plasmodesmata - No plasmodesmata
Give the structure of an plant cell, listing if they have a cell wall, chloroplasts, how they store energy, lysosomes, vacuole, centrioles and plasmodesmata
Cell Wall - Cellulose Cell Wall Chloroplasts - Yes Energy Storage - Starch Grains Lysosomes - No lysosomes Vacuole - Large permanent, central vacuole Centrioles - No centrioles Plasmodesmata - Yes
Give the structure of an fungal cell, listing if they have a cell wall, chloroplasts, how they store energy, lysosomes, vacuole, centrioles and plasmodesmata
Cell Wall - Chitin Cell Wall Chloroplasts - No Energy Storage - Glycogen Granules Lysosomes - Yes Vacuole - Yes Centrioles - No Plasmodesmata - No
What are organelles
The structures that perform particular functions in a cell
What is the structure of the nucleus
Largest organelle; enclose within a double membrane; contains chromatin, consisting of DNA wound round beads of Histones proteins; perforated envelope; contains one or several nucleoli
What is the function of the nucleus
DNA codes for the synthesis of polypeptides in the cytoplasm; pores in the envelope allow large molecules in and out; Nucleolus synthesises ribosomal RNA and manufactures ribosomes
What is the structure of ribosomes
Small bodies of protein and RNA either free in the cytoplasm or attached to RER
What is the function of Ribosomes
Site of polypeptide synthesis; free ribosomes produce proteins that will function within the cytoplasm
What is the structure of the RER
Membrane system of flattened sacs, continuous with the outer nuclear membrane and covered with ribosomes
What is the function of the RER
Polypeptides made on the ribosomes accumulate in the RER and are passed on, in vesicles, to the Golgi
What is the structure of the SER
Separate membrane system of interconnecting tubules
What is the function of the SER
Synthesis of lipids and their distribution throughout the cell
What is the structure of the Golgi apparatus
A stack of membrane-bound sacs(cisternae); forming faces has vesicles from the RER jointing it; mature faces has vesicles pinching off
What is the function of the Golgi apparatus
Dynamic structure in which polypeptides are combined or modified; finished protein is packaged into vesicles either for secretion by Exocytosis or for delivery elsewhere in the cell
What is the structure of Lysosomes
Vesicles produced by the Golgi that contain hydrolytic enzymes
What is the function of lysosomes
Lysosomes combine with membrane-bound degenerate organelles or ingested particles to form secondary lysosomes; hydrolytic enzymes digest the contents
What is the structure of mitochondria
Sausage-shape; surrounded by an envelope, the inner membrane of which is folded to form Cristae; fluid-filled matrix; several to thousands per cell
What is the function of mitochondria
Synthesis of ATP by aerobic respiration
What is the structure of a chloroplast
Ovoid; surrounded by an envelope; elaborate internal membrane system of lamellar with thylakoids stacked into grana: contain lipid droplets and starch grains; found in plant cells
What is the function of chloroplasts
Site of photosynthesis; chlorophyll molecules are attached to the lamellar
What is the structure of vesicles and vacuoles
Bound by a single membrane; vesicles are much smaller than vacuoles; vacuoles are permanent in plant and fungal cells; membrane of the sap vacuole in plant cells is called the tonoplast
What is the function of vesicles
Vesicles may be used for storage and transport of substance
What is the function of vacuoles
Vacuoles are for storage of water and ions
What is the structure of microtubules
Tubular; formed from the protein tubulin; occur within centrioles and throughout the cytoplasm; animal and fungal cells contain a pair of centrioles
What is the function of centrioles
Centrioles form the spindle fibres during cell division of animal and fungal cells; microtubules also form part of the cytoskeleton and allow movement of cell organelles
What is the structure of microvilli
Finger-like folds of the cell-surface membrane
What is the function of microvilli
Increase the surface area for absorption of molecules and ions
What is the structure of plasmodesmata
Strands of cytoplasm between neighbouring plant cells that pass through pores in the walls
What is the function of Plasmodesmata
Facilitate transport of materials between adjacent cells in plants
Give some similarities between prokaryotes and eukaryotes
They are both measured using micrometers
They both contain a cell wall
Both have DNA in them
Both possess ribosomes
Give some differences between prokaryotes and eukaryotes
Eukaryotes have membrane-bound organelles, prokaryotes don’t
In a Eukaryotic cell, the DNA is presented as several linear molecules associated with protein(Histones) to form chromatin, in a Prokaryotic cell, the DNA is a single circular molecule, without associated protein
Eukaryotes have a cell wall made of Cellulose, Prokaryotes have a cell wall made of Peptidoglycan
Prokaryotes posses plasmids, eukaryotes don’t
Why are Viruses not cells
They lack cytoplasm
What is the difference between the Nucleic acid in a bacteriophage and HIV
The nucleic acid in a Bacteriophage is DNA
The nucleic acid in HIV is RNA
What does a Bacteriophage consist of
A core of a double-stranded DNA bounded by a protein coat
How do Bacteriophages work
They invade bacteria and the phage DNA codes for the production of mew viral proteins. The phage DNA replicates to form many copies, which are then packaged in the new protein coats
What does HIV consist of
A core of RNA bounded by a protein coat and a lipid bilayer containing glycoproteins
What group of viruses does HIV belong to, and why
Retroviruses, it has a single strand of RNA
What is the function of Reverse Transcriptase
It uses the RNA as a template to produce single-stranded DNA; double stranded DNA is then created with DNA polymerase activity
How does HIV weaken the immune system
It invade a type of lymphocyte (T-helper)
