Physiology 2130 Lecture Notes - Lecture 3: Secretion, Endoplasmic Reticulum, Membrane Transport
20 May 2018
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Module 3 – The Human Cell
Intro:
• The cell is so small and simple that even under a microscope it is difficult to observe
• The functioning of our organs and systems rely upon these tiny, complex cells
Basic Cell Organelles:
• A: Golgi Apparatus
o Responsible for packaging proteins from the rough ER into
membrane bound vesicles
o Golgi bodies produce two types of vesicles
1. Secretory vesicles – transport proteins for release into the
extra-cellular enviro
2. Storage vesicles – contents are stored within the cell (ex.
lysosomes)
• B: Secretory Vesicles
o Produced by the Golgi apparatus and are used to transport various
types of proteins out of the cell for use in other parts of the body
o Secretion: the process by which the cell releases proteins through the membrane into the extracellular envrio
• C: Free Ribosome
o Ribosomes are dense granules of RNA and protein
o Resposile fo aufatuig poteis fo aio aids ude the otol of the ell’s DNA
o Two types of ribosomes
▪ Fixed: attached to the ER
▪ Free: float in the cytoplasm
o Polyribosomes: groups of free ribosomes of 10-20
• D: Lysosome
o Storage vesicle produced by the Golgi apparatus
o Act as the digestive system of the cell
o Contain several enzymes that are used by the cell to destroy damaged organelles, kill bacteria, and break
down other bio molecules
• E: Mitochondria
o Meaous ogaelle hee ost of the od’s adeosie tiphosphate ATP is geeated
o Number of mitochondria in the cell depends on the energy needs of the cell
o The itohodia a epliate itself, ee if the ell is’t udegoig diisio
• F: Endoplasmic Reticulum (ER)
o Continuation of the cells nuclear membrane
o The site for the synthesis, storage and transport of proteins and lipids
o Two types of ER
▪ Rough or granular: covered with ribosomes
▪ Smooth or agranular: no ribosomes
o Rough ER is the site of protein synthesis
o Smooth ER is responsible for synthesis of lipids and fatty acids
• G: Cell membrane
o Regulates the passage of substances into and out of the cell
o Allows certain molecules in, and keeps other molecules out
o Also plays an important role in detecting chemical signals and forming physical links with other cells
• H: Centriole
o Cylindrical bundles of microtubules that are responsible for directing the movement of DNA strands during
cell division
• I: Nucleolus
o The nucleolus is a dense body within the cell nucleus which contains the specific DNA that produces the RNA
found in ribosomes
find more resources at oneclass.com
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The Cell Membrane:
• The cell membrane separates the intracellular enviro from the extracellular enviro
• Selectively permeable
o Larger molecules cannot penetrate – proteins, nucleotides, etc.
o Smaller molecules and ions can penetrate
Cell Membrane Structure:
• Cell membrane is made up of proteins that form channels and pores
(passage), carbohydrates (cell recognition) and cholesterol (stability)
• The most abundant component of the cell membrane are the
phospholipid molecules
• Figure
o 1 – hydrophilic head of a phospholipid molecule
▪ Phosphate head is situated towards the external and
internal environments
▪ Hydrophilic
o 2 – hydrophobic tail of the phospholipid molecule
▪ Lipid tail is situated away from the external environment and into each other
▪ Hydrophobic
o 3 – cholesterol
▪ Found inserted into the non-polar lipid layer of the membrane
▪ Helps makes the membrane impermeable to some molecules and keeps the membrane flexible over
a wider range of temperatures
o 4 – enzymes
▪ Associated protein that act as catalysts for certain reactions immediately inside or outside the
membrane
o 5 – carbohydrate molecule
▪ Can be found on inside out outside surface
▪ Form a protective layer called the glycocalyx which plays a key role in the immune response of the
cell and recognition of other cells
o 6 – membrane spanning protein
▪ Proteins that are embedded in the bilayer such that they span the entire width
▪ Act as gates or channels that control the movement of specific substances in/out of the cell
o 7 – structural associated proteins
▪ Generally attached to the inside surface of the cell membrane
▪ Structural proteins can support and strengthen the membrane and can anchor cell organelles
Phospholipids:
• Made up of a phosphate head and a fatty acid (or lipid) tail
• Fatty acid tails are hydrophobic – do not like water
o Major barrier to anything that is water soluble
▪ Ions, glucose, urea, etc.
o Fat soluble substances can penetrate this portion of the membrane with ease
• Phosphate heads are hydrophilic – like water
• Because of this when phospholipids are thrown into water they will align themselves into a lipid bilayer so that the
heads groups face out toward the water and the tails avoid the water
Membrane Proteins:
• Many functions including:
o Receptors for the attachment of chemical hormones and neurotransmitters
o Enzymes that help with chemical reactions or breakdown molecules
o Ion channels or pores that allow water-soluble substances into the cell
o Membrane-transport carriers that transport molecules across the membrane
▪ Includes gated channels
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
The cell is so small and simple that even under a microscope it is difficult to observe. The functioning of our organs and systems rely upon these tiny, complex cells. F: endoplasmic reticulum (er: continuation of the cells nuclear membrane, the site for the synthesis, storage and transport of proteins and lipids, two types of er, rough or granular: covered with ribosomes. I: nucleolus: the nucleolus is a dense body within the cell nucleus which contains the specific dna that produces the rna found in ribosomes. The cell membrane separates the intracellular enviro from the extracellular enviro. Selectively permeable: larger molecules cannot penetrate proteins, nucleotides, etc, smaller molecules and ions can penetrate. Cell membrane structure: cell membrane is made up of proteins that form channels and pores (passage), carbohydrates (cell recognition) and cholesterol (stability) The most abundant component of the cell membrane are the phospholipid molecules.
