Lec 8: Eukaryotic Structure & Function Flashcards
Anatomy of eukaryotic cells’ functions
Protection and retention of cell contents
Controlling cell activities and processes
Generating energy
Cellular assembly and transport
Creating movement
Plasma membrane
Similar structure and function to prokaryotes
Retains cell contents
Controls exchange with external environment
Consists of phospholipid bilayer with transport and other proteins
Cell wall
Only plants, algae and fungi have cell walls
Animal, protozoan and other eukaryotes lack cell walls -> less rigid cell shape
Composition varies. Different from prokaryotes
Plants: cellulose
Fungi: chitin, glycans, protein, cellulose
Algae: pectins, cellulose, mannans or minerals (silica)
Cell shape in eukaryotes that lack cell wall
Cell shape maintained by:
Chemicals (sterols) embedded in plasma membrane
Cytoskeleton (network of flexible fibres)
Some protozoans (protists) have thin protein ‘pellicide’ supporting membrane
Glycocalyx
External cell coating
Usually carbohydrate
Anchored to membrane -> strengthen cell surface. Help attach cells together. Cell-cell recognition/signalling
Nucleus
The cell control centre determining cellular activities
Generation of energy
Synthesis of chemicals necessary in cell reactions (e.g enzymes)
Synthesis of structural materials
Excretion of wastes
Chromosomes
Long, linear
Encodes information for cell control
Appear as diffuse network in non-dividing cells (chromatin complex of DNA & proteins)
In dividing cells DNA condenses around histones -> chromosomes become visible
Nucleolus
Nuclear subdomain
Assembles ribosomal subunits
Directs rRNA synthesis thus, essential for protein synthesis
Nuclear envelope
Double membrane system encloses nucleus
Pores allow exchange with cytoplasm
Ribosomes
Eukaryotes and prokaryotes have ribosomes
70S and 80S ribosomes
70S: inside certain organelles (mitochondria, chloroplasts)
80S: free in cytoplasm or associated with rough endoplasmic reticulum
Sites of protein synthesis
Mitochondria
Generates energy (ATP)
In prokaryotes, generates energy in plasma membrane
Smooth outer membrane
Highly convoluted inner membrane -> cristae
Fluid matrix: have chemicals necessary to make ATP from nutrient chemicals in cell
Divide independently of cells (have 70S ribosome and own circular DNA)
Chloroplasts
Photosynthesis
Double outer membrane enclosing membrane sacs called thylakoids
70S ribosomes, have own circular DNA -> divide independently of cell
Thylakoids
Have light harvesting pigments
Sites of ATP formation
Max cell size determined by..
Physical & chemicals problems:
Combination of surface to vol ratio, chemical diffusion rates, chemical conc effects
Surface to volume ratio
Needs to sufficient ratio -> nutrient uptake and waste removal
As cell gets bigger -> increase in V exceeds increase S -> exchange becomes limiting
Chemical diffusion rates
Diffusion takes longer with increasing size -> increased diffusion distance
Chemical conc effects
To maintain chemical conc, 8 times more chemical must be made for every doubling size
Endoplasmic reticulum
Continuous, interconnected network of membrane sacs throughput cytoplasm
Involved in protein & lipid synthesis
Transport proteins
Rough endoplasmic reticulum
Studded with ribosomes on outer surface
Ribosomes synthesise protein into rough ER
Protein modification in lumen of ER
Proteins
May be used for:
Membrane synthesis
Export from cell
Transport within cell
Smooth ER
Site of lipid synthesis
Also for cell membrane phospholipids, cholesterol
Golgi Apparatus
Prepares materials for secretion
ER buds off transitional vesicles for transport of ER products to GA -> vesicles fuse with GA
Consists of stacked membrane sacs
ER products further modified in GA for specialised use by cell
Sorts packages & delivers specialised products to sites via vesicles
Flagella and cilia
To find food/prey/new hosts, orientate in environment, enable mating and aid in dispersal
Generate currents -> allow swimming & capture of food particles
Flagella and cilia structure and action
Extensions of plasma membrane
Whip like, beat cell to move cell along
Movement driven by sliding of microtubules -> wave-like motion
Difference between prokaryotic and eukaryotic flagella
Prokaryotic flagella: rigid protein spirals
Action occurs by rotation
