Lecture 6: INTRO Cell structure and function Flashcards
What is cell theory?
- All living organisms are composed of one or more cells
- The cell is the basic unit of structure and organisation
- All cells arise from pre existing cells (via mitosis or meiosis)
What are the common features of prokaryotes and eukaryotes?
Both have cell surface plasma membrane
Have ribosomes
Have cytosol
Have DNA, RNA and protein
What are the differences between prokaryotes and eukaryotes
Eukaryotes have membrane bound organelles and are larger
Prokaryotes have no membrane bound organelles and are smaller
What is cytoplasm?
Everything inside the plasma membrane including the organelles, but not including the nucleus
What is cytosol?
The fluid in the cytoplasm - composed of water and dissolved substances (ions, ATP, proteins, lipids)
What is the endomembrane system?
The organelles of a cell involved in packaging, labelling, and shipping molecules around the cell
Made up of: Nucleus ER smooth and rough Golgi apparatus Lysosomes
Plasma membrane function
The plasma membrane is a selectively permeable barrier controlling the passage of substances in and out of the cell
Plasma membrane structure
Double layer of phospholipids with embedded proteins
Phospholipid structure
Made up of a hydrophilic phosphate head and two hydrophobic fatty acid tails arranged as a tail to tail bilayer
What are integral proteins
proteins embedded partially or fully in the plasma membrane
What are transmembrane proteins
Type of integral protein that spans the whole membrane coming in contact with extracellular and cytoplasmic areas
What are peripheral membrane proteins
Associated with the membrane but not embedded in them
What is function of peripheral membrane proteins
Cell to cell identification and facilitate intercellular communication
What is function of integral proteins
Mediate movement of hydrophilic substances
What are 6 functions of plasma membrane proteins?
Transport Enzymatic activity Signal transduction Cell-cell recognition Intracellular joining Attachment to cytoskeleton and extracellular matrix
Nucleus function
House DNA in eukaryotic cells
Make RNA and assemble ribosomes
pores regulate movement of substances (protein and mRNA) in and out
molecule segregation to allow temporal and spatial control of cell function
Nucleus structure
The largest distinct structure in the cell Made up of: nucleolus nuclear envelope nuclear pores
What is nucleolus
Dark region of nucleus where rRNA are produced later forming ribosomes
What is nuclear pores?
Gaps in the nuclear envelope controlling exit and entry into nucleus
What is nuclear envelope
Membrane surrounding nucleus
What is DNA
Deoxyribonucleic acid - encodes our phenotype
What is a histone
Protein which DNA binds to
What is nucleosome
Structure formed from DNA wrapped twice around 8 histone proteins
What is chromatin
A length of nucleosomes (structures with DNA wrapped around 8 histone proteins)
What is chromosome
Fully condensed form of DNA where chromatin condenses further to chromatin fiber which condenses into loops then stacking to form chromosomes
What are genes
A length of DNA that codes for a phenotype/function
What is diploid organism
Organisms with two sets of chromosomes
What determines accessibility of DNA in the nucleus
Extent of coiling - more coiling reduces accessibiltiy
What are ribosomes
Two subunits, small and large made up of rRNA in complex with many proteins
Assembled in nucleolus and exited through nuclear pores
What do ribosomes do
Protein synthesis, they are found in two places
free in the cytoplasm- making cytosol proteins
attached to RER- making endomembrane proteins
What is ER
An extensive network of tubes and tubules, extending from the nuclear membrane
What are the 2 types of ER
Rough and smooth
What is rough ER
Extension of nuclear membrane dotted with attached ribosomes
What is rough ER function
Ribosomes produce proteins which enter the lumen of ER for folding. Then rough ER membrane surrounds protein forming transport vesicles destined for golgi
Production of secreted proteins, membrane proteins, organelle proteins
What is smooth ER
Extension of rough ER with no ribosomes
What is smooth ER function
Lipid synthesis
Storage of cell-specific proteins
Function of smooth ER varies a lot from cell to cell
What is golgi appartus
A complex made up of 3-20 flattened membranous sacs called cisternae stacked on top of one another
What is golgi apparatus function
Modify sort package and transport proteins from rough ER using enzymes present in each cisternae
Formation of vesicles (3types):
secretory vesicles
membrane vesicles
transport vesicles
What are lysosomes
Vesicles produced by golgi apparatus containing digestive enzymes
Highly acidic due to constant pumping of H+ ions via membrane proteins
What is lysosome function
Digestion of:
substances entering cell
cell components
entire cells
What are mitochondria
Membrane bound organelles that generate ATP through cellular respiration
Made of inner and outer membrane where the inner membrane folds to form cristae. Inside of mitochondria is filled with fluid called mitochondrial matrix
Carry own genome
Number of mitochondria depend on ATP needs
How does mitochondria produce ATP
ATP -> ATP + phosphate
Energy is released in this process
What is cytoskeleton
Structural support system of cell - determines size shape integrity of cell
What is cytoskeleton function
Act as scaffolding across cell
Involved in intracellular transportation and cell movement
What are the 3 types of fibers that make up cytoskeleton
Microfilaments
Intermediate filaments
Microtubules
What is the diameter of microfilaments
7 nm
What are microfilaments and where are they found
Comprised of actin molecules assembled in two long chains, twisted around each other
Found around the periphery and lining the interior of cell
What is microfilament function
Bear tension and weight by anchoring cytoskeleton to plasma membrane proteins
Promote amoeboid motility if required (movement of cell)
What is the diameter of intermediate filaments
8-12nm
What are intermediate filaments and where are they found
Comprised of diverse range of different materials and found in cytoplasm
What is intermediate filament function
Bear tension and weight throughout the cell
Act as scaffold for cellular organelles
What is the diameter of microtubules
A tubular structure, 25nm in diameter with a central lumen of 15nm
What is microtubule
Comprised of tubulin dimers coiled to form a tube
Extends from centriole into cytoplasm/nucleus
What are functions of microtubules
Support cell shape and size
Guide for movement of organelles
Chromosome organisation - cell division
Support and movement of cillia and flagella
