cells Flashcards
What organelles does a eukaryotic cell contain?
*nucleus
*cell surface membrane
*mitochondria
*80s ribosomes
*cytoplasm
*rough endoplasmic reticulum
*smooth endoplasmic reticulum
*golgi apparatus
What is the structure of the nucleus?
*double membrane with pores
*nucleolus
*contains chromatin
What r the functions of the nucleus
*stores genetic info for polypeptide production
*site of DNA replication
*site of production of mRNA and tRNA and rNA (nucleolus)
Structure of mitochondria
*double membrane
*inner membrane folded to form cristae (high SA)
*liquid part (matrix) contains ribosomes, lipids, proteins and mitochondrial DNA
Function of mitochondria
Site of ATP production
Structure of RER
*highly folded membrane with 80s ribosomes
*membrane folded into flattened sacks (cisternae)
Function of RER
*ribosomes on the surface synthesise proteins
*proteins packed into vesicle
Structure of SER
*highly flattened sacks called cisternae
Function of SER
*recombines fatty acids and glycerol to produce triglycerides
*packages triglycerides into vesicles and transports them to golgi
Structure of cytoplasmic ribosome
- 2 subunits of long strands of rNA and ribosomal proteins
Function of cytoplasmic ribosome
*site of protein Synthesis
Structure of Golgi Apparatus
*flattened sacks of membrane filled w fluid
*golgi vesicles pinch off from main membrane
Function of golgi appartus
*sorts, and packages proteins, triglycerides into vesicles
*modifies proteins and lipids by adding carbohydrates to them and turning them into glycoproteins/lipids
Structure of lysosome
*membrane bound organelle with hydrolytic enzymes
Function of lysosomes
*hydrolyse pathogens and worn out components
Example of cell that contains a lot of lysosomes
*phagocytes because they hydrolysed a lot of invading pathogens
Function of cell surface membrane
*Selectively permeable → enables control of passage of substances in / out of cell
* receptors on surface → allow cell recognition
Structure of centrioles
Microtubules
Function of centrioles
*form network of spindle fibers that chromosomes attach to
*pull chromosomes apart during mitosis
Structure of chloroplasts
*granum
*thylakoid membranes
*strach grains
*stroma
*DNA and ribosomes
*lamella- thick lining around granum
Function of granum
stack of thylakoid membranes
Function of thylakoid membranes
*has chlorophyll for photosynthesis
*has ATP synthase for ATP production
Function of stroma
*fluid part
*light indep photosynthesis occurs here
Function of starch grains
*energy storage in plants
Function of DNA and ribosomes in chloroplasts
*have their own DNA and 70s ribosomes for synthesis of enzymes that are needed in photosynthesis
How do TEM microscopes work
*electrons pass through the specimen. allowing to see all the organelles
How do SEM microscopes work
*elctrons bounce off the specimen producing 3D image
What type of specimens do light and TEM microscopes work on
*light microscope- living or dead
*TEM- Dead – they are fixed in resin and sliced very thinly. Must be in a vacuum.
LImitations of TEM
- Cannot look at living material / Must be in a vacuum;
- Specimen must be (very) thin;
- Artefacts present;
- Complex staining method
advantage of using a TEM rather than a
SEM.
*Higher resolution
*allows internal details of specimen to be seen
advantage of using a SEM rather than a
TEM.
*Thin sections do not need to be prepared
*shows surface of specimen
*can have 3-D images;
How do scientists study organelle function?
Cell Fractionation & differential-centrifugation
What are the steps of homogenising?
*tissues are homogenised in blender to break the cells releasing the organelles into the solution
What type of solution is required for homogenising?
*ice cold
*isotonic
*buffered
Why does the solution needs to be ice cold?
- reduce enzyme action of enzymes that would digest organelles
Why does the solution need to be isotonic (same water potential)?
prevents osmosis of water in and out the cell so it doesnt burst or shrivel
Why does the solution need to be buffered?
*stop pH changes that could denature proteins
What is the last step of homogenising?
*Filter mixture to remove any large pieces of tissue/cells producing a solution of suspended organelles (supernatant).
What are the steps of differential centrifugation of the supernatant?
*centrifuge at high speed- densest organelles like nucleus go to the bottom into a pellet thats removed
*centrifuge at higher speed- the next densest organelles go to the bottom to the pellet and are then removed
What is the most dense, second densest, and least dense organelle
*most dense- nucleus
*second- mitochondria/chloroplasts
*least- ribosomes
What is the structure of the cell vacuole and function
*tonoplast membrane
*cell sap
Cell vacuole contains sugafr, proteins and waste materials. Maintains turgor pressure in cell (stopping plant wilting)
What is a tissue
*group of SPECIALISED cells with similar structure that work for a specific function
Whats an organ
aggregation of tissues performing specific function
Whats an organ system
group of organs working together for a specific function
Describe how you can apply your knowledge of cell features / organelles to explain adaptations of eukaryotic cells
● [Named cell] has many [named organelle, eg. ribosomes]
● To [link organelle function to cell function eg. increase rate of protein synthesis, making many antibodies]
for eg
*respiring cells have many mitochondria, fo aresobic respiration that release energy from ATP formation
Features that are ALWAYS in prokaryotic cells
*cell wall of chitin and membrane
*circular DNA
*70s ribosomes
*cytoplasm
Features that are SOMETIMES in prokaryotic cells
*plasmids
*capsule
*flagella
Explain why viruses are described as acellular and non-living
*Acellular - not made of cells,
*no cell membrane/ cytoplasm / organelles
● Non-living - have no metabolism, cannot independently move / respire / replicate / excrete
General structure of viruses
*nucleic acid - RNA or DNA surronded by capsid
*attachment proteins- bind to receptors on host cell
*no organelles
Structure of HIV
*nucleic acid- RNA/DNA
*reverse transcripstase
*capsid
*attachment proteins
*lipid envelope
Describe the stages of the cell cycle in eukaryotic cells
*INterphase- S phase is where DNA replicates semi-conservatively
G1/G2- number of organelles and volume of cytoplasm increase, protein syntheis
2nd-Mitosis-
*nucleus divides
* produce 2 nuclei with identical copies of DNA produced by parent cell
3rd- Cytokinesis
*Cytoplasm and cell membrane divide
*form 2 new genetically identical daughter cells
why does the number of the organelles and the volume of the cytoplasm increase in the G1/G2 interphase
cell grows in size. As it grows, it needs more organelles to support the increased cellular functions. This is because a larger cell requires more energy,
volume of cytoplasm increases so after division, each of the two new daughter cells will have enough cytoplasm and organelles to function properly.
Describe the Prophase
*chromosomes condense and supercoil and appear as 2 identical sister chromatids
*centrioles move to opposite poles create spindle network
*nuclear envelope breaks down
Describe Metaphase
*spindle fibers attach to chromatids by centromere
*align down equator
Describe Anaphase
*spindle fibers shorten
*centromere divides
*equal sister chromatids on opposite ends of cell
Describe Telophase
*chromosomes uncoil- larger and thinner apperance
*spindle fiber breaks down
*nuclear envelope reforms
Explain the importance of mitosis in the life of an organism
Parent cell divides to produce 2 genetically identical daughter cells for…
*Growth of multicellular organisms by increasing cell number
*Replacing cells to repair damaged tissues
*Asexual reproduction
Describe how tumours and cancers form
Mutations in DNA / genes controlling mitosis can lead to uncontrolled cell division
● Tumour formed if this results in mass of abnormal cells
○ Malignant tumour = cancerous, can spread (metastasis)
○ Benign tumour = non-cancerous
Suggest how cancer treatments control rate of cell division
*some disrupt spindle fibre formation
*chromosomes can’t attach to spindle by their centromere
* So chromatids can’t be separated to opposite poles (no anaphase)
*So prevents / slows mitosis
● Some prevent DNA replication during interphase
*can’t make 2 copies of each chromosome
○ So prevents / slows mitosis
Describe binary fission
*DNA/ plasmid replicate
*cytoplasm divides
*produces 2 daughter cells
*single copy of circular DNA
● Variable number of copies of plasmids
Describe how viruses replicate
*attachment proteins bind to host cell
*secretes nucleic acid in host cell
*Infected host cell replicates virus particles:
a. Nucleic acid replicated
b. Cell produces capsid
c. Virus assembled then released
Outline the role of organelles in the production, transport and release of proteins from eukaryotic cells.
Do not include details of transcription and translation in your answer.
- DNA in nucleus is code (for protein);
- Ribosomes/rough endoplasmic reticulum
produce (protein); - Mitochondria produce ATP (for protein
synthesis);
4 Golgi apparatus package/modify;
OR
Carbohydrate added/glycoprotein produced by
Golgi apparatus;
5 Vesicles transport
OR
Rough endoplasmic reticulum transports; - (Vesicles) fuse with cell(-surface) membrane;
Describe and explain how you would use cell fractionation and ultracentrifugation to obtain sample of nucleus from muscle tissue
Homogenise (tissue) to break open cells
OR
Homogenise (tissue) to release
organelles/nuclei;
2. Filter to remove (intact) tissue/cells/debris;
3. Cold (solution) to prevent enzyme activity;
4. (Solution with) equivalent water potential to
prevent osmosis
OR
(Solution with) equivalent water potential to prevent organelles bursting/shrinking;
5. Buffered (solution) to stop enzymes/protein denaturing;
6. Centrifuge/spin at low(er) speed so nuclei in pellet/move to bottom
OR
Centrifuge at low(er) speed and
supernatant/solution discarded;
Describe the role of organelles in the production and release of enzymes by animal cells
- DNA in nucleus codes for enzyme/protein
(production); - Ribosome produce enzyme protein
- Rough endoplasmic reticulum
modifies protein; - Mitochondria produce ATP;
- Golgi apparatus modify/process/
package/transport protein forms/releases vesicles; - Vesicles move (protein) to cell(-surface) membrane
OR
Vesicles fuse with cell(-surface) membrane;
Use Figure 6 and your knowledge of enzyme action and DNA replication to explain why new nucleotides can only be added in a 5’ to 3’ direction.
- Reference to DNA polymerase;
- (Which is) specific;
- Only complementary with/binds to 5’ end (of strand);
- Shapes of 5’ end and 3’ end are
different/description of how different;
