Cell structure Flashcards
What are the different types of microscopes?
— light microscope
— scanning electron microscope
— transmission electron microscope
what is the equation to work out magnification?
Magnification = size of image/ size of real object
What is cell fractionation?
The process where cells are broken up and the different organelles they contain are separate out.
For cell fractionation the solution must be?
— cold
— same water potential as the tissue
— buffered so pH doesn’t fluctuate
What is homogenation?
cells are broken up by a homogeniser
How does the process of ultracentrifugation occur in animal cells?
— tube of filtrate is placed in the centrifuge and spun at low speed
— the heaviest organelles are forced to the bottom of the tube, form the sediment/ pellet
— the fluid at the top of the tube is removed (supernatant)
— the supernatant is transferred to another tube and spun in the centrifuge at a faster speed than before.
— next heavier organelles are forced to bottom
— process is continued
What are 2 advantages of the electron microscope?
— electron beam has a very wavelength and the microscope can therefore resolve object well
— as electrons are negatively charged the beam can be focused using electron agents
What are the main limitations of the TEM?
— the whole system must be in a vacuum so living species cannot be observed
— a complex staining process is required
— specimen must be extremely thin
— image may contain artefacts
what do you calibrate a eyepiece graticule?
— use a stage micrometer, line up scales,
What do you find inside the nucleus?
— nuclear envelope
— nuclear pores
— nucleoplasm
— chromosomes
— the nucleolus
Describe the nuclear envelope?
A double membrane that surrounds the nucleus
describe the nuclear pores
Allow the passage of large molecules out of the nucleus
describe the nucleoplasm
Granular, Jelly-like material
Describe the chromosomes
Consorts of protein-bound linear DNA
describe the nucleolus
A small spherical region within the nucleoplasm.
What are the functions of the nucleus?
— control centre of the cell though the production of mRNA and tRNA
— retain the genetic material of the cell in the form of DNA and chromosomes
— manufacture ribosomal RNA and ribosomes
what structures make up the mitochondrion?
— double membrane around the organelle
— cristae are extensions of the inner membrane
— matrix makes up the remainder of the mitochondrion
What are the main features of the chloroplasts?
— the chloroplast envelope - double plasma membrane
— the grana - stacks of thylakoids which have chlorophyll on them
— the storma is a fluid-filled matric where the second stage of photosynthesis takes place
How are chloroplasts adapted for photosynthesis?
— Granal membrane provide a large surface ares for the attachment of chlorophyll
— the fluid of the storms possesses all the enzymes need to make surgery in the second stage of photosynthesis
— Chloroplasts contain both DNA and ribosomes so they can quickly and easily manufacture some of the proteins needed for photosynthesis
what is the function of the rough endoplasmic reticulum?
— provide a large surface area for the synthesis of proteins and glycoproteins
— provide a pathway for the transport of materials, especially proteins.
what are the functions of smooth endoplasmic reticulum?
— synthesise, store and transport lipids
— synthesis, store and transport carbohydrates
What are the functions of the Golgi apparatus?
— add carbohydrate to proteins to form glycoproteins
—produce secretory enzymes
— secrete carbohydrates
— transport, modify and store lipids
— form lysosomes
what are the functions of lysosomes?
— hydrolyse material ingested by phagocytes cells
— release enzymes to the outside of the cell in order to destroy material around the cell
— digest worn out organelles so that the useful chemicals they are made of can be re-used
— completely break down cells after they have dies
What are the features of the cell wall?
— consist of a number of polysaccharides, such as cellulose
— thin layer (lamella) which marks boundary between cell walls
What are the functions of a cellulose cell wall?
— Provide mechanical strength in order to prevent cell from bursting
— give mechanical strength to the plant as a whole
— to allow water to pass along it and so contribute to the movement of water through the plant
what functions do plant vacuoles have?
— they support herbaceous plants
— the sugars and amino acids may act as temporary food stores
— the pigments may colour petals to attract pollinating insects
What is a tissue?
Cells normally aggregated together to work efficiently
what is an organ?
Tissues aggregated together to work efficiently
What are the three organ systems in humans?
— the digestive system
— respiratory system
— circulatory system
What are the main structural features of a bacteria cell?
— cell wall (murein)
— capsule
— cell-surface membrane
— circular strand of DNA
— plasmids
what are the differences between prokaryotic and eukaryotic cells
— P has no true nucleus / E does
— P DNA no proteins / DNA proteins
— P has no membrane-bound organelles E does
What is the structure of a virus?
— genetic material (RNA)
— attachment protein
— capsid
— lipid envelope
— matrix
— reverse transcriptase
what is Mitosis?
Produces 2 daughter cells that have the same number of chromosomes as the parent cell and each other
What is meiosis?
Produces 4 daughter cells
what are the 4 phases of mitosis?
— prophase
—metaphase
— anaphase
— telophase
What happens in the prophase?
Chromosomes become visible, spindle fibres develop
What happens in the metaphase?
Chromosomes make up 2 chromatids, joined by centromere
What happens in the anaphase?
The centromeres divide into two and the spindle fibres pull the individual chromatids making up the chromosome part
What happens in the telophase?
Chromosomes reach their respective pole and become longer and thinner
What is cell division in prokaryotes called?
Binary fission
what is the process of binary fission?
— circular DNA molecule replicates and both copies attach to cell membrane
— plasmids also replicate
— cell membrane begins to form between the two DNA molecules and begins to pinch forwards
— new cell wall forms.
What are the three stages of the cell cycle?
— interphase
— nuclear division
— division of the cytoplasm
How does chemotherapy usually disrupt cell cycle?
— prevents DNA from replicating
— inhibits the metaphase stage of mitosis by interfering with spindle formation.
