Eukaryotic cell form & function Flashcards
What is the cell membrane?
Lipid bilayer
Lipids have hydrophobic and hydrophilic regions – form a fluid layer.
Proteins stabilise and allow for selective control of solutes - stops solids from crossing barrier
What Eukaryotes have cell walls? What are they made up of?
Plants - cell walls composed of cellulose (polysaccharide - repeating units of D-glucose)
Fungi - cell wall made of chitin (polysaccharide - repeating unites of N-acetyl-D-glucosamine). *Chitin also makes the exoskeletons of insects
Protists - most lack cell wall
All animals lack cell walls
What is cytoskeleton?
Animals have this instead of cell wall
Microtubules (25 nm), microfilaments (7 nm) and intermediate filaments (8-12 nm):
In multicellular animals also an extra cellular matrix.
Add structural reinforcement.
Internal trafficking.
Movement.
What are flagella and cilia?
Flagella - propel cell with with whip like motion
Functionally/evolutionary different from bacteria flagella which rotate
Cilia - short flagella found mainly on unicellular protists
How big is the nucleus?
~1µM across (bigger than many bacteria)
What are the key features of nucleus?
Outer membrane - continuous with rough endoplasmic reticulum
Inner membrane - nuclear pores (allowing transport in and out the cell)
DNA - packaged around histones and arranged into chromosomes
Nucleolus - site of rRNA synthesis to make ribosomes
What is the function of the nucleolus?
Site of rRNA synthesis to make ribosomes
rRNA added to protein component to make ribosomes
Ribosomes transported to cytoplasm to make proteins from mRNA sequences.
How many RNA and ribosomes do eukaryotic cells have?
18s RNA
80s ribosomes
s - svedbergs unit to measure how fast molecules move in a centrifuge
What are the main roles of the nucleus (3)?
Expression, regulation and replication of genes?
What is transcription?
Transcription of DNA to form mRNA (a template for protein synthesis later used in the cytoplasm).
How do eukaryotes replicate?
Mitosis - asexual replication creating daughter cells.
Meiosis - sexual reproduction
What are the features of the mitochondria?
Generatres ATP
Typical animal cells contain over 100
Composed of inner membrane, outer membrane, Cristal & Matrix
How does mitochondria generate ATP?
Generates ATP using the enzyme ATP synthase. Requires a proton gradient.
Metabolism – the citric acid cycle occurs in the matrix.
Hydrogen ions pushed across membranes in mitochondria.
Difference in hydrogen ions used to power ATP synthase.
ATP created using the flow of hydrogen ions back across membrane.
How and where do prokaryotes generate ATP?
Citric acid cycle occurs in the cytosol with the proton gradient for ATP production being across the cell’s surface (plasma membrane), rather than the inner membrane of the mitochondrion
What are Hydrogenosomes?
Not all cells have mitochondria
Present in certain anaerobic unicellular eukaryotes such as trichomonads.
They specialise in anaerobic respiration.
Phylogenic studies suggest they are a degenerative mitochondria.
What are plastids?
Pigmented plastids found in most plants and seaweeds (chloroplast)
Site of photosynthesis
Double or quadruple membrane structure (endosymbiosis >1)
What are other internal structures present in many eukaryotes that are not membrane bound organell
Endoplasmic reticulum
Golgi complex
Peroxisomes and lysosomes
What is the endoplasmic reticulum?
Rough - due to present of ribosomes, site of protein synthesis (Glycoproteins)
Smooth (lipid metabolism and some aspects of carbohydrate metabolism)
What is the Golgi apparatus?
Glycosylation (addition of sugar residues).
Collects and sorts products for secretion and intracellular transport.
Sugar added to proteins to give extra structure.
What are lysosomes?
Membrane bound compartments containing various digestive enzymes
Compartments fuse with food or ingested pathogens – break down into macromolecules.
What are peroxisomes?
Oxidise compounds in the cell such as alcohols and long chain fatty acids
