Chapter 2 Organelles (2.4) Flashcards
What are prokaryotic cells
- single called organisms with a simple structure of just a single undivided cytoplasm
(Cytoplasm composed of cytosol which is made of water salts etc)
Eukaryotic cell
Make up multicellular organisms like animals and planets , bigger , complex
- complex internal with MEMBRANE bound nucleus , and other membrane bound cellular components
Ultra structure?
Is the structures of a cell you can see with an electron microscope
What does metabolism involve
Both reactions of synthesis and breaking down molecules in cytoplasm
- vital chemical reactions involving enzymes …
What is cytoplasm made up of?
The cytosol, which is salts water and organic molecules
What are organelles
How is cytoplasm separated from external environment?
MEMBRANE bound compartments found in cytoplasm
The cytoplasm is separated from the external environment via cel, surface membrane…
Function of membranes
- selectively permeable
- control what goes in and out of a cell ( thus protects them)
- effective barriers but fragile
What does the nucleus contain and inadvertently do thus?
- genetic material in form of DNA
- biggest part of the cell
- but as DNA directs synthesis of proteins through its info it “controls” metabolic activity of the cell, as many proteins needed are the enzymes needed for reactions to take place, which are made in the nucleus
Membrane of nucleus ? (IMPORTANT)
What is it and why, and also what holes
- DOUBLE MEMBRANE = nuclear envelope
=this protects it from damage from reactions in cytoplasm - these also have nuclear pores, which allow molecules to go in and out of the membrane such as mRNA leaving nucleus .
How is DNA arranged as chromosomes in nucleus?
When is this possible to see
- raw dna associates with proteins called HISTONES to make complex called CHROMATIN
- these then condense and coils to make CHROMOSOMES
However this only possible to see during cell division
What is the function of nucleolus
How are (they) made
Made up of proteins and RNA
- responsible for producing RIBOSOMES
- RNA is used here to make ribosomal rna = rRNA, and this combines with proteins found too to make the ribosomes
Function of mitochondria?
- cite of respiration , where energy stored in glucose is converted into ATP (another chemical store) which cells can use
- the more mitochondria found in an area, the more energy it uses, so like muscles…
Membrane of mitochondria? (IMPORTANT)
HAS A DOUBLE MEMBRANE LIKE NUCLEUS
- inner membrane highly folded to form structure CRISTAE
- fluid interior called MATRIX
- membrane that makes cristae contain all the enzymes needed in respiration
What else does mitochondria have that is evidence for endosymbiont theory?
- have own amount of small CIRCULAR DNA = mitochondrial DNA (mt)DNA
- thus mitochondria can produce their own enzymes and also reproduce themselves
- This is evidence as the fact they have their own circular DNA, like bacteria but also just dna shows they once were their own organism but taken in by complex form later
What function and structure of vesicles
Single membrane made out of phospholipids
- membranous sacs that have storage and transport roles , with fluid inside, transports proteins etc
What is function of lysosomes then? What are they anyways (what do they have)
3 functions
- lysosomes are a specialised form of vesicles that contain HYDROLYTIC ENZYMES
- these allow them to :
1) break down wasted material in cells like old organelles
2) breaking down pathogens ingested by phagocytes in phagocytosis
3) role in apoptosis - programmed cell death (where a lot of lysosomes are made and hydrolytic enzymes are released…)
What are hydrolytic enzymes anyways
Help in catalysing hydrolysis , where it uses water to break chemical bonds made in condensation reactions …
What is the function of the cytoskeleton
Present throughout the entire cytoplasm
= forms a network of fibres necessary for the shape and stability if the cell
- organelles held in place by the cytoskeleton
- cell movement and movement of organelles
Three components = microtubules, microfillaments and intermediate fibres , but also centrioles too…
What is structure and function of micro filaments in the cytoskeleton?
- Contractile fibres made from protein actin
- these are responsible for whole cell movement
- AND also cell contraction during cytokinesis
(where cytoplasm splits and pinch apart to give two daughter cells)
What is structure and function of microtubules in cytoskeleton?
- they are globular tubulin proteins
- they polymerise to form tubes that form a scaffold like structure that determines the shape of the cell
- act like tracks for organelles , including vesicles , to move around the cell (like train tracks)
- The SPINDLE FIBRES MADE for mitosis are made from microtubule too.
What is the function of intermediate fibres in the cytoskeleton?
These are fibres that give MECHANICAL STRENGTH to the cells , maintains their INTEGRITY …
What are centrioles ?
CENTROSOME?
What do they do and from what
Component of cytoskeleton found in most eukaryotic except plants and most fungi
- made up of microtubules like spindle fibres too + flagella/ cilia
- two centrioles make a CENTROSOME, and these actually make the spindle fibres needed for segregation from microtubules
- the centrioles also help position the flagellum and cilia too
What is the function of the flagella (an extension - protuberance )
- cell motility (forward and back movement)
- but also a sensory organelle to detect chemical changes in the environment
Two types of cilia - mobile (again these are extensions - protuberance )
- these best in rhythmic manner creating a current , and these cause FLUIDS/ OBJECTS around to movement (side to side movement) .
- e.g mucus in throat
- E.g eggs in Fallopian tube moving to UTERUS
Two types of cilia- stationary cilia
- present on many surfaces of many cells and have an important function in sensory organs
E.g such as cilia in the nose!
Arrangement of the cilia
How does the cilia move then
9+2 arrangement
- 2 central microtubules as black circles
- surrounded by nine pairs of microtubules arranged like a wheel
- here pairs of parallel microtubules that slide over each other cause the cilia to move in a beating motion
What organelles involved in protein synthesis?
(Nucleus ) ribosomes, ER, (vesicles, ), Golgi apparatus , cytoskeleton too
What is structure of and what does the ER do?
What will secretory cells have
= network of membranes enclosing flattened sacs called CISTERNAE, connected to the outer membrane of the nucleus .
- smooth er = lipid and carbohydrate synthesis and storage
- rough er: ribosomes, synthesis and transport of proteins (for proteins going to be transported out of the cell)
- secretory cells that release hormones / enzymes will have more er as a result as er proteins are transported out of the cell
Ribosomes
Structure + how they made
Who has them
NOT MEMBRANE BOUND
- made of rRNA and proteins combined , which happens in the nucleolus
- site of protein synthesis
As mitochondria and chloroplasts have own dna and can make own proteins, they ALSO HAVE THEIR OWN RIBOSOMES TOO
. (In cytoplasm / on rough er too)
Golgi apparatus structure and roles?
1) similar to ER in the sense that it has flattened sacs folded together to form cisternae again, but no ribosomes
2) - role is to modify proteins (by adding sugar chain) and PACKAGE them into secretory vesicles/ LYSOZOMES if they are staying in the cell (specialised vesicles )
Protein synthesis 4 stages rather than 6 (do this too )
1) transcription , exit nuclear pore and make way to ribosomes
2) translation, proteins are synthesised on ribosomes on rough ER.
- then pass through cisternae of the ER and are packaged into vesicles .
3) vesicles move via the cytoskeleton , so microfilaments for cell movement and microtubules for the tracks , arrive at the cis face of the golgi apparatus. (Or lipids if coming from smooth er)
4) here they are modified (adding a sugar chain ) and repackaged into secretory vesicles
5) exit via trans face of Golgi apparatus , travel to cell membrane
6) fuse with cell membrane as they both have phospholipids, and proteins leave by EXOCYTOSIS
Some may form lysozomes in which case stay in the cell
Cellulose cell wall function and features
- freely permeable so substances can go in and out through cell wall
- contents of the cell will press against the wall making it rigid
- acts as a DEFENCE mechanism against invading pathogens
Vacuoles in plants
What is the membrane called
- MEMBRANE LINED sacs containing cell sap
- plants have permanent vacuoles which are important for tug or pressure
- the membrane in a vacuoles is called a TONOPLAST, selectively permeable
- if snail darter have then small and transient nit permanent
Chloroplasts structure and functions =( only 1 photosynthesis)
What do they have and what do the grana have
What about the internal membrane structure and what it has
- DOUBLE MEMBRANED like mitochondria
- fluid inside is called STROMA
- have an internal network of membranes , which form flattened sacs called thylakoids
- several thylakoids stacked together = granum
- granum joined together by membranes called lamellae
- starch produced is present as starch grains
2) - Here the grana contain chlorophyll, where light dependent reactions for photosynthesis take place
- the internal membranes provide the large surface area needed for alol the enzymes, proteins, Pigment etc for photo
Chloroplasts more on dna and endosymbiont
Like mitochondria, chloroplasts have own
- DNA and RIBSOMES = make own proteins
Supports endosymbiont theory as they have their own dna etc . Mitochondria and chloroplasts are same size and they divide by BINARY FISSION TOO
Prokaryotic 3.5 billion years ago
Lived in extremes of earth
- called extremiphilled , still exist today in hydrothermal vents and salt lakes which have similar conditions to what earth used to be like .
Now found in hospitable environment like soil however
Prokaryotic cells generally
- unicellular small, simple
- DNA not in nucleus, exists in cytoplasm
- fee organelles and NONE ARE MEMBRANE BOUND
DNA in prokaryotes
- one molecules of CIRCULAR DNA, as a chromosome which is supercooled to make it more compact
- genes are grouped into operons, meaning a number of genes are switched of/ on AT THE SAME TIME
, (as opposed to eukaryotic which are at different times)
Ribosomes in eukaryotic
- smaller than eukaryotic, but because they aren’t membrane bound , they exist here
- their size is 70s, compared to 80s of a eukaryotic . Both involved in protein synthesis , but larger 80 s can make COMPLEX proteins
- size is determined on how quickly they settle, or form A sediment in a solution . That’s what (s ) means…
Cell wall prokaryotic
- this is made from PEPTIDOGLYCAN, it cellulose like in plants , also known as MUREIN
- peptidoglycan is a complex polymer for,Ed from amino acids and sugars
Flagella prokaryotic structure + differences
Structure too (alliteration things)
- much thinner than eukaryotic
- does NOT HAVE 9+2 microtubules arrangement
- energy used to rotate the filament that forms the flagella is provided by CHEMIOSMOSIS rather than ATP from respiration
-attached to the cell membrane of a bacterium by a BASAL body, and rotated by a MOLECULAR motor . Here basal body like and anchor attached into the membrane, and molecular motor rotated allowing flagella to have WHIP like motion
Eukaryotic vs prokaryotic
DNA nucleus , rather than circular chromosomes
Genes switched off and on Indiviuslly in eukaryotic, whereas same time on prokaryotic
Membrane bound organelles vs non membrane bound organelles
Endosymbiosis theory
Idea that mitochondria, chloroplasts and potentially other organisms were formerly FREE BACTERIA , but were ingested by another cell as an organism that lived within the body of cells of another organisms . This lead to evolution of complex cell organisms thus
Evidence for endosymbiosis ?
- mitochondria and chloroplasts have double membrane like bacteria
- reproduction is binary fission like bacteria
- Own DNA and ribosomes , so can make own proteins and replicate themselves . Here ribosomes size is 70S, the same
- similar size to prokaryotes
- have same circular DNA
