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Organelles, Structure and Function
Relationships
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Describe the role for named subcellular organelles in creating specialised
microenvironments;
Explain the differences between prokaryotic vs
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The Cell Surface
Nucleus & Nucleolus
Mitochondria
Synthetic Organelles
Digestive Organelles
Prokaryotes vs Eukaryotes
Variations on a Theme

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The plasma membrane is a complex structure that consists of:
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Lipids (amphioathic)
Proteins
Carbohydrates (CnH2nOn)
Glycolipids- lipid with sugar attached
Glycoproteins- protein with sugar attached
Peptidoglycans
Glycosaminoglycan- repeated chain of disaccharide (don’t need to know much about)

Why is the plasma membrane partially permeable?
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Because the lipids are amphipathic!
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Amphipathic- has a hydrophobic end and hydrophilic end, thus this creates a phospholipid
bilayer
So because it is amphipathic, it is not easy to pass things through the membrane, so this is
where protein channels and carrier proteins come in
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This describes the plasma
membrane as a fluid combination of phospholipids, cholesterol, and proteins
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The lipid can ‘flip-flop’ from one monolayer to the other
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It has to be
digested by cellulase, which animals don’t have!
Bacterial cell walls are composed of peptidoglycans; this can be surrounded by gelatinous
polysaccharide layer known as the capsule, glacocalyx or “slime layer” depending on its
arrangement

We can stain bacterial cell wall with Gram’s stain
The cell walls stained (the Gram positive bacteria) have a single cell wall, whilst those not stained
(the Gram negative bacteria) means the bacteria has several layers to the cell wall
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It is an antenna-like structure and it is on the plasma
membrane and picks up signals from other cells
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Damage to
cilia such as in the fallopian tubes can be problematic in pregnancy, as the egg may not move to the
correct place after fertilisation
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Nucleus and Nucleolus
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Contains DNA
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DNA is essential for the production of proteins
DNA is essential for reproduction (biogenesis) by cell proliferation
DNA consists of chromosomes= condensed chromatin
Chromatin= histone proteins and DNA
Nucleolus contains DNA
The nucleolus is an electron-dense area
Nucleolus is the site of transcription and also ribosome synthesis and rRNA
Nucleus is needed for DNA replication for interphase in mitosis
In a non-dividing cell, DNA is used for protein synthesis by;
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Translation- RNA to protein in ribosome (either free in cytoplasm or studded on
endoplasmic reticulum)
The nucleus is separated from the cytoplasm by the nuclear envelope which is a double
membrane, it has nuclear pores
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It doesn’t need a
plasma membrane as the nuclear pores facilitate the movement of substances in and out of
the cell instead
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They are a perpendicular pair
of specialist microtubules (made of tubulin
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Mitochondria
Has a double membrane
(Study diagram)
Inner membrane space is convoluted into cristae to increase surface area for metabolic
pathway: respiration and this is the area that contains oxidative enzymes for respiration
Has its own DNA so it can make its own proteins (don’t need to know why)
(Don’t need to know about respiration pathways for this lecture)
Its role is to HARNESS energy- ATP for respiration
It harnesses energy from carbon-based fuels by oxidative phosphorylation
It contains oxidative enzymes to oxidise glucose
It catalyses aerobic catabolism- break down carbohydrates, fats, proteins to harness ATP
(aerobic respiration)
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The mitochondria mediates apoptosis
It generates and metabolises reactive oxygen species (ROS) and free radicals
Mitochondria evolved from bacteria
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Chloroplasts- for photosynthesis
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ER- lipid synthesis, protein synthesis on ribosomes on RER
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This method can be exploited using antibiotics
Polysomes- several ribosomes translating same mRNA sequence
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Golgi apparatus
 Series of specialised, membrane bound sacs, stacked cisternae through which proteins and
lipids are processed before insertion or secretion to the plasma membrane
 Molecules enter the cis face
 Molecules exit via the trans face
 Molecules move between the cis and trans face via vesicular trafficking
Vesicle- small, fluid filled (ICF), single-membrane bound sac
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this allows the trafficking of the vesicle content
 Enzymes in Golgi Apparatus can add a carbohydrate group;
Lipid + carbohydrate= glycolipid
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Protein + carbohydrate= glycoprotein
 Golgi Apparatus sorts, processes and packages into vesicles for their final destination- target
cell
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Endosomes
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Peroxisomes
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Lysosomes
 Late endosome fuses with lysosome- vesicle containing digestive enzymes (acid hydrolases)
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lysosomes
 At low pH, the digestive enzymes hydrolyse the chemical bonds and thus degrade the
contents of the lysosome
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Prokaryotes vs
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Some prokaryotes are
multicellular at certain life cycle stages;
 Archaea is always unicellular
 Bacteria is USSUALLY unicellular e
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Variations on a Theme
 Not all eukaryotes have nuclei e
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erythrocytes in mammals, whilst some non-mammalian
vertebras have nucleated red blood cells
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If these cells had nuclei, it would interfere with their functions; erythrocytes would
have decreased surface area for carrying oxygen, whilst there would be cloudy vision due to
the lens having nuclei
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