Cellular Organisation Flashcards
Features of prokaryotic (bacteria) cells
- Absence of membrane bound organelles
- Circular DNA in nucleoid
- Contains ribosomes, cell wall, cytoplasm
- Flagella for movement
Features of Eukaryotic (Animal) cells
- Membrane bound organelles
- Nucleus
- Linear DNA
- No cell wall
Features of plant cells
- Membrane bound organelles
- Chloroplasts
- Cell wall
- Large vacuole
What is the meaning of fluid mosiac model?
- Mosaic -> Phospholipid bilayer, collage of different proteins -> embedded in fluid matrix of lipid bilayer
- Fluid -> lipids and proteins diffuse freely within bilayer
- Flip-flop, lateral, rotational
Role of phospholipids in cell membrane
- Hydrophilic heads -> interact with aqueous outer environment (cytoplasm or tissue fluid)
- Hydrophobic tails -> face inwards creating hydrophobic core
Role of steroids/cholesterol in cell membrane
- Regulates membrane fluidity and permeability at different temperatures
- Prevents packing at low temp -> more fluid
- Restrains movement at high temp -> less fluid
Role of membrane proteins in cell membrane
- Integral (embedded in hydrophobic core) and peripheral (bound to surface)
- Transport, signalling, recognition functions
What is hypertonic?
- Outside is higher water potential as compared to cell, water moves into cell
- Turgid plant cell
- Lysed red blood cell
What is hypotonic?
Outside is lower water potential as compared to cell, water moves out of cell
- Plasmolysed plant cell
- Shrivelled red blood cell
Structure of Nucleus
- Largest organelle in animal cell
- Double membrane nuclear envelope -> nuclear pores on surface
- Dense nucleolus region -> rRNA synthesis
- Aqueous matrix -> contains most genetic info
Function of Nucleus
- Contains most of the cells genetic info
- Synthesises mRNA for protein (Transcription)
Structure and Function of Ribosomes
- Two locations -> bound ribosomes to the Rough Endoplasmic Reticulum (RER) -> synthesise polypeptides for secreted/membrane/lysosomal proteins
- OR free ribosomes suspended in cytoplasm -> synthesise polypeptides for proteins used in cell
- Translation of mRNA into protein
What is the role of mRNA
- Template for translation of polypeptide strand
- Conveys sequence of codons to code for specific amino acids
- Contains start and stop codons to signal beginning and termination of translation
Process of DNA transcription
- DNA template strand used to synthesise mRNA -> complementary to template strand
- DNA non-template strand same as mRNA, replace T with U
- In nucleus
Process of Polypeptide translation
- mRNA codons read by ribosomes to synthesise amino acids
- Peptide bonds formed between amino acids to form polypeptide chain
- Start and stop codons signal beginning and termination fo translation
DNA level mutations
- Base pair substitution
- Base pair insertion
- Base pair deletion
- Three base-pair insertion/deletion
Polypeptide Level mutations
- Silent mutation
- Missense Mutation
- Nonesense Mutation
- Frameshift Mutation
What is a silent mutation?
Does not change amino acids specified by codons -> no change to protein structure
What is a nonsense mutation?
Change in amino acid(s) resulting in EARLY STOP CODON -> shortened polypeptide
What is a frameshift mutation?
Change in reading frame of nucleotide sequence -> Drastic change in sequence of amino acids -> Change in protein structure
Structure of the Endoplasmic Reticulums
- Membrane of ER continuous with nuclear envelope -> encloses ER cisternae
- Internal space filled with endoplasmic matrix -> cisternae space/lumen
- Rough ER -> appears rough due to studded ribosomes
- Smooth ER -> absence of ribosomes
Function of Rough ER
- Ribosomes studded synthesise polypeptides
- Primary structure folded into secondary and tertiary structure -> in cisternae space
- Packages proteins into transport vesicles
Function of Smooth of ER
- Synethesis of lipids
- Carbohydrate metabolism
- Detoxification
Structure of golgi apparatus
- Flattened membrane sacks -> cisternae
- Cis face -> recieves transport vesicles from ER
- Trans face -> packages products into secretory vesicles and vesicles bud off trans face
Function of Golgi Apparatus
- Further modification and folding of proteins/polypeptides
- Packages and stores in secretory vesicles
Structure & Function of Lysosomes
- Bound by lysosomal membrane
- Contains hydrolytic enzyme
- Involved in phagocytosis
Pathway of bound ribosomes to golgi apparatus
- Bound ribosomes -> synthesise polypeptides from amino acids
- Polypeptides released into cisternae space of RER
- In cisternae space -> primary structure folded into Second, Tertiary structure
- Packaged into transport vesicles, buds off RER -> Fuses with cis face of golgi apparatus
- Chemically modified in golgi
Secretory Pathway of Proteins
- Packaged in secretory vesicles -> buds off trans face of golgi
- Exocytosis occurs -> secretory vesicles fuse with membrane to release substances
Membrane bound protein pathway
- Integrated into secretory vesicle membrane -> buds off trans face of golgi
- Fuses with cell membrane -> membrane bound proteins part of cell membrane
Lysosomal Enzymes/Proteins pathway
- Proteins modified to become hydrolytic enzymes
- Packaged in lysosomes -> buds off trans face
Free ribosomes pathway
- Free ribosomes -> synthesise polypeptide chains from amino acids
- In the cytoplasm -> primary structure folds itself into secondary and tertiary structure
- Protein used in the cell
How does sickle cell anemia occur?
Sickle Cell Anemia
- Single base pair substitution of Adenine to Thymine -> glutamic acid replaced by valine
- Alters the shape of red blood cells
- Lack of oxygen in bloodstream
