t2 cells Flashcards
what is the cell wall of a plant made of & it’s function
cellulose - provides structure and support to the cell
what are plasmodesmata
pores that connect two neighbouring plant cells and enable exchange through the cytoplasm
what is the cell surface membrane formed by
phospholipid bilayer - partially permeable to allow exchange (of lipid soluble) substances directly through it
what is a histone
proteins that DNA wraps around to form compacted coil shape
features of the nucleus and their functions
- double membrane called nuclear envelope that has many nuclear pores that allow mRNA and ribosomes to travel out of the nucleus, as well as allowing enzymes and molecules in
- chromatin - material (DNA and histones) which make up chromosomes
- nucleolus - makes ribosomes
structure and function of mitochondria
- site of aerobic respiration
- has double membrane, with inner membrane folded to form cristae
- has liquid called matrix which contains enzymes needed for aerobic respiration, producing ATP and also contains small pieces of DNA and ribosomes
structure and function of chloroplast
- site of photosynthesis in plant cells.
- have double membrane
- grana - thylakoid membranes that stack
- lamellae - think thylakoid membranes that join grana together
- contain small pieces of DNA and ribosomes to synthesise proteins needed for chloroplast replication and photosynthesis
function of ribosomes + how they’re made
- site of translation in protein synthesis
- found freely in cytoplasm or as part of the RER
- formed in the nucleolus and made of rRNA and proteins.
- can be 80S (in eukaryotic cells) or smaller 70S (in prokaryotic cells, mitochondria and chloroplasts)
structure and function of rough endoplasmic reticulum (RER)
- folds and processes proteins made at the ribosomes located on its surface and sends them to the golgi apparatus.
- made of flattened, membrane-bound sacs (cisternae) stacked together around the nucleus
structure and function of smooth endoplasmic reticulum (SER)
- synthesises and processes lipids, carbs and steroids and sends them to the golgi apparatus
- made of flattened, membrane-bound sacs.
- NO ribosomes on surface
structure and function of golgi apparatus
- further processes and packages lipids and proteins from the ER into vesicles or lysosomes
- flattened stack of fluid-filled, membrane-bound sacs (cisternae)
structure and function of vacuole
- maintains pressure in plant cells by pushing cytoplasm against cell wall to keep cell turgid and prevent plants from wilting
- contains cell sap
- has selectively permeable membrane called tonoplast
structure and function of lysosomes
- digest invading cells and break down worn out cells/organelles (autolysis)
- contain lysozymes (digestive enzymes)
- small, spherical sacs formed by the golgi apparatus
structure and function of the centriole
- organises spindle fibres during cell division
- hollow fibres made of microtubules
- 2 centrioles at right angles form a centrosome
what is the cell wall made of in prokaryotic cells
murein/peptidoglycan (protein and polysaccharide combined)
structure and function of mesosomes
- in prokaryotic cells
- invagination of the cell membrane
- permeable boundary that allows for entry and exit of nutrients and waste and may play a role in DNA replication
structure and function of pilli
- in prokaryotic cells
- thin, protein tubes on surface of bacteria
- allow bacteria to adhere to surfaces
structure and function of capsid
- in viral cells
- protein coat
- protects the genetic material
function of attachment proteins on viral cells
- identify and attach to host cells for viruses to replicate inside of
what is the viral genome
- nucleic acid core made of DNA or RNA
what is the lipid envelope on viral cells
- viruses sometimes take a piece of the cell membrane with them as they leave the host cell, causing them to have a lipid envelope around their capsid
why don’t antibiotics work on viruses
- antibiotics target the bacterial enzymes and ribosomes and interfere with the bacteria’s metabolic reactions
- viruses don’t have their own enzymes or ribosomes
definition of resolution
ability to distinguish between two points on an object - minimum distance that this can be done
definition of magnification
how much larger the image is than the specimen
features of optical (light) microscopes
- uses light waves that have a relatively long wavelength, meaning their resolution is lower (max: 0.2 micrometers)
- lower mag (max: x1500)
- can view living organisms
- can view in colour
features of electron microscopes
- uses electron beams that have a relatively short wavelength, meaning their resolution is much higher (max: 0.1 nanometres)
- electron beams directed using electromagnets due to their negative charge
- higher mag (max: x1.5 million)
- can’t view living organisms as required near vacuum so electrons aren’t deflected or absorbed by air particles
- specimen must be extremely thin and go through a complex staining process
- artefacts may appear on photomicrograph eg dust, cotton fibres
features of transmission electron microscopes (TEM)
- beams of electrons pass through specimen. denser parts of specimen absorb electrons and image appears darker on the photomicrograph. less dense parts let electrons pass and appear lighter on photomicrograph.
- higher res (max: 0.1nm)
- sample must be extremely thin
- 2D images only
features of scanning electron microscope (SEM)
- scans beams of electrons across the surface of specimen back and forth in a regular pattern. electrons are then collected in a cathode ray tube and used to produce photomicrograph
- can be used on thicker specimens as electrons can be scattered by specimen
- 3D images
stages of cell fractionation
- homogenisation - grind cell using blender/pestle and mortar to break open cell and release organelles. results in a fluid called the homogenate
- add cold, isotonic, buffered solution
- filtration - filter solution through gauze to remove any whole cells or debris and collect in test tube
- ultracentrifugation- place test tube of homogenate into centrifuge and spin on a low speed. the densest organelle (nuclei) will collect at the bottom of the test tube. pour out remaining supernatant (fluid remaining) into a new test tube.
- repeat step 4 using a higher speed between each separation until the least dense organelles have been separated (ribosomes)
order of pellet formation in cell fractionation
nucleus (densest)
chloroplast
mitochondria
lysosomes
endoplasmic reticulum
ribosome (least dense)
stages of interphase (brief)
- G1 - signal
2.S - DNA rep
3.G2 - check
what happens in G1
-signal received by cell to replicate
-all cell content (except chromosomes) replicate.
-makes RNA, enzymes and proteins needed for growth
what happens in S phase of interphase
-synthesis of DNA (chromosome replication)
-makes 2 identical strands of DNA called chromatids that are joined at centromere
what happens in G2 of interphase
-cell continues to grow
-synthesised DNA is checked for mutations and any copying errors and makes any repairs
stages of mitosis (brief)
1.Prophase
2.Metaphase
3.Anaphase
4.Telophase
5.Cytokinesis
what happens in prophase (mitosis)
-chromosomes condense, become visible
-spindle fibres move towards opposite poles of cell
what happens in metaphase (mitosis)
-chromosomes line up at equator of cell
-spindle fibres attach to centromeres
what happens in anaphase (mitosis)
-spindle fibres shorten
-sister chromatids pulled to opposite poles of cell as centromere divides