topic two Flashcards
cell surface membrane
- made of lipids and proteins
- regulates movement of substances in and out of the cell/has receptor molecules on it which allow it to respond to hormones.
nucleus
- surrounded by nuclear envelope which contains pores. pores allow RNA to move between cytoplasm.
-chromatin consists of DNA RNA and proteins. nucleolus consists of DNA RNA and proteins too - controls cells activities by controlling DNA transcription/ controls gene expression, protein synthesis and storing DNA.
ribosome production and protein synthesis in nucleolus.
mitochondria
- oval shaped structure with outer and inner membranes. inner is folded to form cristae and inside is called matrix which contains enzymes for respiration
- site of aerobic respiration, releases energy
chloroplast
- have a double membrane that surrounds the stoma. inside the stoma there is fluid filled sacs called thylakoids.
- site of photosynthesis; light independent reactions in sacs, light dependent reactions in stoma
golgi apparatus
- composed of small vesicles, a membrane bound structure filled with fluid
- processes and packages lipids & makes lysosomes
lysosome
- surrounded by a membrane with no clear internal structure.
- contains lysozyme, kept separate from cytoplasm by surrounding membrane, used to digest invading cells
ribosome
- floats free in cytoplasm/or attached to RER, made of proteins and RNA
- site where proteins are made
rough endoplasmic reticulum
- system of membranes enclosing a fluid filled space, surface covered with ribosomes
- folds/processes proteins made at ribosome
smooth endoplasmic reticulum
- no ribosomes, but similar to RER
- synthesises and processes lipids
cell wall
- rigid, surrounds membrane. cellulose in plants and chitin in fungi
- supports cells, protection against pathogens
vacuole
- membrane bound (called the tonoplast), contains cell sap (solution of sugars and salts)
-maintains osmotic pressure, stops plants wilting, stores unwanted chemicals
differences between prokaryotic compared to eukaryotic
- cytoplasm has-no bound organelles
- no nucleus, circular DNA instead
- plasmids
- capsule surrounding the cell
- flagellum
structure of virus particles
- genetic material surrounded by capsid
- lipid envelope with attachment proteins
formula for magnification
image = actual size x mag
how high can a light microscope measure resolution
0.2 micro metres
why can light microscopes only measure a small amount of resolution
the microscope cant produce the image of an object that is smaller than the wavelength of light
how high can an electron microscope measure resolution to
0.1 nm
what are the two types of electron microscopes
- scanning electron microscope
- transmission electron microscope
how do TEMs work
a beam of electrons passes through a thin piece of the specimen.
areas that absorb electrons appear darker
how do SEMs work
a beam of electrons passes across the surface and scatters.
this builds up a 3D image
limitations of SEMs
- lower resolution
- specimens have to be dead
strength of SEMs
- can produce 3D images
limitations of TEMs
- samples need lots of prep
- very expensive
- cant produce 3D images
strengths of TEMs
- high resolution
specimens can be alive
what is cell fractionation
separating cells and organelles to study them in detail
explain homogenisation
- cells are blended in a homogensier to form a fluid called homogenate.
- this is added to a centrifuge
- the heaviest organelles are forced to the bottom where a sediment forms (lowest speed)
- the fluid at the top is called the supernatant, this is removed and added to a different tube
- the supernatant is then spun at higher speeds to force the smaller organelles
- the last organelle to be forced to the bottom is ribsomes.
why is the solution ice cold
to stop the organisms from breaking down organelles
why is a buffer solution used
to maintain pH
why is an isotonic solution used
to prevent bursting and shrinking
what is mitosis for
- division of cells for growth and repair and reproduction
how many cells does mitosis produce
2 genetically identical daughter cells
what are the three stages of the cell cycle
- interphase
- mitosis
- cytokinesis
what are the four stages of mitosis
- prophase
- metaphase
- anaphase
- telophase
what happens during interphase
the cell grows and prepares to divide
what happens during cytokinesis
the organelles moves to opposite ends of the cell and the cytoplasm divides to form 2 separate cells
prophase
- chromosomes condense
- spindle fibres appear
- nuclear membrane breaks down
metaphase
- chromosomes align
anaphase
- sister chromatids move to opposite poles
- centrometers divide
telophase
- nuclear membrane reforms
- spindle fibres disappear
- chromosomes decondense
what is the process by which prokaryotic cells divide called
binary fission
steps of binary fission
- circular DNA replicates and attach to the cell membrane, plasmids also replicate
- cell membrane begins to grow inbetween the DNA molecules and pinches inwarsd to form 2 cells
- a new cell wall forms between the two divided DNA molecules
- the identical daughter cells both have a copy of circular DNA and mulitple copies of the plasmids
why do viruses not replicate
the are not living
what happens after a viruses injection of nucleic acids
the infected host cell replicates the virus particles
what do receptors on cell membranes allow molecules to do
enables adjacent cells to stick together
why is was it given the name ‘fluid mosaic model’
the fluidity of the membrane and the arrangement of the proteins
how do the hydrophil/phobic heads and tails point
- hydrophilic head = points outwards
- hydrophobic tail = points inwards
why do the head and tail point these ways
- allows lipid soluble substances to pass through, but not water soluble
- means membrane is flexible and self-sealing
what are the two types of proteins in the cell membrane
- intrinsic = throughout the membrane
- extrinsic = along the surface
what is the function of intrinsic proteins (carrier proteins)
- carriers = allow substances to cross the membrane
- provide mechanical support
- act with glycolipds as receptors
what is the function of cholesterol in the membrane
- makes the membrane more rigid and reduces movement of phospholipids
- prevents leakage of water and dissolved ions, since it is hydrophobic
what are glycolipids made of
a carbohydrate that is bound to lipids
what is the function of glycolipids in the membrane
- act as cell surface receptors for certain substances
- allow cells to adhere together to form tissues
what are glycoproteins made from
carbohydrates attached to extrinsic proteins
what is the function of glycoproteins in the membrane
- act as cell surface receptors and neurotransmitters
- also allow cells to adhere together to form tissues
what is diffusion
passive movement of small non polar molecules from an area of high conc. to an area of low conc.
molecules move through the phospholipid bilayer
what is osmosis
diffusion of water molecules from an area of high conc. to an area of low conc. through a partially permeable membrane
what is facilitated diffusion
requires channel proteins in membrane to transport water soluble and polar molecules
what is active transport
transports all types of molecules through carrier proteins, from an area of low conc. to an area of high conc. requires lots of ATP
exocytosis and endocytosis
- transport large molecules
what happens in endocytosis
particles are enclosed in vesicles and transported into the cell
what happens in exocytosis
the vesicles containing large particles are fused with the cell membrane and released into the cell
what is co transport
uses ions to moe substances in and out of the cell
where does co transport occur
epithelial cells of the ileum
what happens during co transport
sodium and potassium ions are pumped out of the epithelial cells by AT, into the blood which leaves a lower concentration in the cell. this causes these ions to move in by facilitated diffusion which brings glucose and amino acids into the cell. thse then diffuse from high conc in epithelial to low conc in blood.
DNA in bacteria and prokaryotes
- circular
- short
DNA in viruses
- consist of only nucleic acid in a protein coat
- can take the form of DNA or RNA
what cell do viruses require
host cell
what do viruses not have
- organelles
examples of bacterial infections
- TB
- whooping cough
- strep throat
example of viral infection
- HIV
- common cold/flu
- covid-19
- bronchitis
