[3.4] structure of eukaryotic cells Flashcards
what is the function of mitochondria?
aerobic respiration
what are the key features of mitochondria? (7)
- outer mitochondrial membrane
- inner mitochondrial membrane
- inter-membrane space
- mitochondria DNA
- ribosomes
- cristae
- mitochondrial matrix
what is mitochondrial DNA?
- allows mitochondria to be self-sustaining and means they are prokaryotes,
- is the genetic material giving instructions for which proteins to make all the ribosomes
what are ribosomes?
- it is where protein synthesis occurs
- produces key respiratory enzymes in mitochondria
what are cristae?
- infoldings of the inner membrane to increase SA
- where ATP is produced
what is in the mitochondrial matrix?
key respiratory enzymes
what are the key features of chloroplasts? (8)
1.double membrane
2. ribosomes
3. thylakoid
4. granum
5. inter-granal lamella
6. stroma
7. DNA
8. starch grains
what is the function of the double membrane in chloroplasts?
- it is selectively permeable
- it has proteins that determines what can enter
what is the function of the thylakoid?
- it is where the 1st stage of photosynthesis occurs: light absorption by chlorophyll (light dependent stage)
small, pancake-like discs
what is the function of the granum?
to increases surface area cumilatively
what is the inter-granal lamella?
it is a thin rod between grana that connects them
what is the function of the stroma?
- where key enzymes for photosynthesis are found
- where 2nd stage of photosynthesis occurs: glucose production (light independent stage)
(like cytoplasm if it were a cell)
key features of the nucleus (5)
- nucleoplasm
- chromosome
- nuclear envelope (double membrane)
- nuclear pore
- nucleolus
what does the chromosome in a nucleus contain?
DNA wrapped around beads of ‘histone’ protein
what is the function of the nuclear pore?
enables entry and exit of:
- mRNA
- tRNA
- rRNA
- proteins
- ribosomes
what is the function of the nucleolus?
- produces rRNA
- assembles ribosomes
what are the functions of the nucleus? (textbook)
- to act as control centre of cell by producing mRNA and tRNA and hence protein synthesis
- to store the genetic material of the cell in the form of DNA and chromosomes
- make rRNA and ribosomes
key features of the ribosome (4)
- small ribosomal subunit
- large ribosomal subunit
- ribosomal grooves (where mRNA binds)
- binding sites (for tRNA and associated amino acids)
what are ribsomes made of and what size are they?
- prokaryote = smaller (70s)
- eukaryote = larger (80s)
- ribosomes are made of protein and rRNA
what is the endoplasmic reticulum?
an extensive network of flattened interconnected tubes within the cytoplasm
rough ER
- has ribosomes embedded on the surface of the membrane
- used to store and transport proteins
- sometimes found close to nucleus
smooth ER
- no ribosomes
- used to store and transport lipids and carbohydrates
key features of golgi apparatus (2)
close to RER
- cisternae (membrane stacks)
- golgi vesicles
what are golgi vesicles?
small membrane bound sacs that ‘bud off’ from the main membranes due to membrane fluidity
what is the role of the golgi apparatus? (class)
- modifying proteins
- folding & coiling into a specific 3D shape
- addition of non protein components eg. Fe for haemoglobin - packaging proteins
- adding ‘finalised’ protein into golgi vesicles to be transported elsewhere in/out of cell
what are the functions of the golgi apparatus? (textbook)
- add carbohydrate to proteins to form glycoproteins
- produce secretory enzymes eg. in pancreas
- secrete carbohydrates eg. for making cells walls in plants
- transport, modify, and store lipids
- form lysosomes
what is the importance of membrane fluidity/where is it used?
- meiosis
- mitosis
- phagocytosis
key features of lysosome (2)
(example of a vesicle)
- membrane: keeps enzymes tucked away until they are needed
- lysozymes: powerful hydrolytic enzymes that are used in digestion
what are lysosomes used for? (5)
- phagocytosis: to hydrolyse pathogens
- apoptosis: programmed (intentional) cell death for unwanted or damaged cells
- exocytosis: release of enzymes to outside of the cell to destory material around the cell
- autolysis: to completely break down cells after they have died
- digestion of worn out organells so the useful chemicals they are made of can be re-used
key features of the vacuole (2)
- cell sap
> mostly water with dissolved sugars (eg. monosaccharides) and dissolved mineral ions - tonoplast (vacuole membrane)
what is the role of the vacuole? (class)
- storage of the sap
- structural role: full vacuole exerts pressure (‘turgidity’) outwards on the cell wall so the shape of the cell is maintained
what are the functions of the vacuole? (textbook)
- support herbaceous plants, and herbaceous parts of woody plants, by making cells turgid
- the sugars and amino acids may act as a temporary food store
- the pigments may colour petals to attract pollinating insects
what is the cell wall made of?
- cellulose fibrils
- microfibrils bundled together into macrofibrils that form a mesh-like network
> made of multiple straight chains of beta glucose molecules
3 versions of cell wall + vacuole
- turgid (normal) - when no more water can physically enter the cell as vacuole swells and presses cytoplasm against cell wall during osmosis
- flaccid (soft) - when cells are no longer firm and swollen as solution surrounding plant cells is hypertonic so water will leave
- plasmolysed - when too much water is lost by osmosis so the vacuole and cytoplasm shrink, and eventually the cell membrane pulls away from the cell wall
properties of the cell wall (how and why)
- the cell wall is strong and rigid
- this is so it is able to resist turgor pressure of the vacuole and maintain the cell shape
- it is strong and rigid due to long, straight, unbranched chains which have hydrogen bonds between chains
what are the functions of the cell wall? (textbook)
- to provide mechanical strength to prevent cell bursting under pressure created when water enters by osmosis
- to give mechanical strength to the plant as a whole
- to allow water to pass along it, contributing to the movement of water through the plant
