Class notes

Human Cell Physiology

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Course
PHGY170 (PHGY170)

Institution
Queen’s University (QU )

Complete set of notes for phgy170 covering: -The cell: Review of structure and function -The Nucleus -The endoplasmic reticulum -The endomembrane system and the Golgi apparatus -Mitochondria and cellular energy production -The plasma membrane and lipids -Cellular communication -The cytoskel...

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Uploaded on July 1, 2024
Number of pages 87
Written in 2020/2021
Type Class notes
Professor(s) Cynthia pruss
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Module 1- The cell: Review of structure and function
Saturday, September 5, 2020 2:21 PM

Section 1 - Introduction to the cell

⚫ Cell theory
○ The 3 tenets of cell theory :
1. All living organisms are composed of one or more cells
2. The cell is the basic unit of structure and organization in organisms
3. All cells come from pre-existing cells

⚫ Cell types
○ Prokaryotic
○ Eukaryotic

⚫ Primary types of cells in the human body
○ Epithelial cells
▪ Form protective barriers in tissues and may be specialized to absorb/secrete specific compounds
○ Muscle cells
▪ Responsible for movement of the skeleton, heart and many internal organs
○ Nerve cells
▪ Conduct electrical signals throughout the body
▪ Control muscle contraction
▪ Responsible for the 5 senses
○ Connective tissue cells
▪ Create extracellular material holding cells together in tissue
▪ Can be specialized to absorb or resist external forces (Ex, tendons; vertebral discs)
○ Bone cells
▪ Give strength and support to the body
○ Secretory cells
▪ Form glands and secrete substances
○ Adipose cells
▪ Fat cells located throughout the body to store fat
○ Red blood cells
▪ Formed primarily in the bone marrow and released into circulation where they work in nutrient exchange
▪ Limited life span

Section 2- Building blocks of the cell

⚫ Water and carbon in the cell
○ Nonpolar carbon-based structures are attracted to each other and repeal water
▪ This allows a cell to form membranes and subcellular compartmentalization

⚫ 5 unusual characteristics of water that make it ideal for supporting life
1. Water is liquid at room temperature
○ Rare due to its molecular mass (ex, CH4 and CO2 gases under standard temp and pressure)
○ Due to its high heat of vaporization and specific heat index, indicating a lot of energy is required to raise the temperature of water, or to ha
it evaporate
▪ Result of hydrogen bonding
2. Water is a polar molecule
○ Oxygen has a slightly negative charge and hydrogen has a slightly positive charge, forming weak but significant hydrogen bonds
3. Water is more dense as a liquid, not a solid
○ All liquids become more dense as they cool, usually extending to their state as a solid
○ Exception = water such that ice (solid state) is less dense than liquid water
4. Water has a high specific heat capacity
○ Specific heat capacity: amount of heat required to change the temp of 1g of substance by 1deg Celsius
○ Water has the highest specific heat capacity of any liquid present within the common conditions of Earth's surface
5. Water has a high heat of vaporization

PHGY 170 Page 1

, 5. Water has a high heat of vaporization
○ Heat of vaporization: quantity of heat that must be absorbed for a liquid to vaporize to gas

⚫ How water supports life
○ Liquid's unique chemistry supports life due to ability to form hydrogen bonds
▪ Allows dissolution of other molecules essential for life
▪ Provides an environment that facilitates complex network of reactions supporting the chemical basis of life
▪ Ice being less dense than water also ensures that water-based habitats remain habitable and sheltered when Earth's ambient temperature
drops below freezing
○ Thermal stability of water
▪ High heat capacity acts as a massive stabilizer for thermal fluctuations, extending from the ocean's effect at a global clima tic level to water
a microscopic cell

⚫ How water supports cells .. And thus life
1. Polar properties
○ Makes water an excellent solvent
▪ Facilitates delivery of nutrients and removal of wastes & provides environment that allows cells to exist within a network by facilitati
the movement of chemical messengers within and between cells
2. High specific heat capacity
○ Allows for thermoregulation by acting as a heat sink for the various chemical reactions that occur within cells and the excha nge of heat
between liquid and air (critical for warm-blooded organisms who must regulate body temp)

⚫ Carbon
○ Building block of important cellular molecules (carbohydrates, amino acids, nucleotides)
○ Small and can form up to 4 covalent bonds
○ Flexibility in bond formation allows it to form a large variety of molecules important to cellular life

⚫ Carbon-based molecules
➢ Lipids
○ Made of hydrocarbon chains
○ Quite hydrophobic and insoluble in water
○ Commonly amphipathic
○ Examples:
▪ Cholesterol
- Regulates cell membrane fluidity and is a precursor for compounds such as steroids, bile acids and some vitamins
▪ Phospholipids
- Forms the lipid bilayer of cells
▪ Triglycerides
- Used for storing energy
➢ Carbohydrates
○ Sugar= simple building block
○ Oligosaccharides are composed of 3-10 monosaccharides linked together, while polysaccharides are much longer chains
➢ Nucleotides
○ Building blocks of nucleic acid and form ATP
○ Composed of: a base, sugar and phosphate group(s)
➢ Amino acids

Section 3- Subcellular compartments

⚫ Overview of cellular structures
➢ Plasma membrane
○ Contains all of the cell's organelles and regulates what enters/exists the cell
○ Phospholipid bilayer
○ Semipermeable
➢ Nucleus
○ Stores DNA
○ Isolated itself in the cell via;
▪ Double layered membrane
▪ Very selective nuclear pores
▪ Unique cytoplasm
➢ Mitochondria
○ Produce energy for the cell in the form of ATP
○ Present in varying amounts depending on energy requirements
➢ Endoplasmic reticulum and Golgi apparatus
○ ER - carries molecules around the cell, synthesizes lipids and proteins, stores ions for the cell
○ Golgi- processes and packages proteins and sends them to their target site
○ ER & Golgi collaborate to control protein and phospholipid traffic in cells
➢ Small, membrane bound organelles
Lysosomes

PHGY 170 Page 2

,○ Lysosomes
▪ Waste management
▪ Enzymes break down waste and debris & digest proteins, lipids, and nucleic acids into their building blocks to be recycled in the cell
○ Endosomes
▪ Waste management
▪ Sort and begin to break down waste before reaching the lysosome
○ Peroxisome
▪ Specialized lysosomes
▪ Breakdown molecules that produce hydrogen peroxide (broken down by catalase which is present in peroxisome)
○ Cytoskeleton
▪ Composed of structural filaments that hold the cell together
▪ Structural filaments stabilize membrane against deformations by forming mechanical resistance
- Actin
- Microtubules
- Intermediate filaments
▪ Motor (force) filaments generate force/motion (ex, myosin generates muscle contraction)
- Myosin
- Kinesin
- Dynein

PHGY 170 Page 3

, Module 2- The Nucleus
Thursday, September 17, 2020 2:56 PM

Section 1- Structure and function of the nucleus

• Primary function of the nucleus: protect DNA

⚫ Function of the nucleus
○ To protect the DNA, the nucleus must accomplish 3 tasks:
1. Regulate what molecules can access the DNA
2. Separate DNA from other cell compartments
3. Keep it organized- DNA is easily damaged
○ 4 key components of the nucleus that work together to fulfill these tasks:
▪ Nuclear envelope
- Controls what molecules have access to the nucleus, and separates the DNA from other cell compartments
- Double membrane structure that encloses nuclear material
- Contains pores which regulate molecular traffic in and out of the nucleus
→ Small molecules (water, oxygen) can pass through the membrane freely
→ Nuclear Pore Complexes (NPCs) in the nuclear membrane regulate movement of large molecules (proteins) into and out of th
nucleus
▪ Nucleolus
- Creates ribosomal RNAs and assembles them into ribosomal subunits used to translate proteins
- Site of high amounts of rRNA gene transcription, and the DNA that encodes these genes is organized here
▪ Nucleoplasm and nuclear matrix
- Nucleoplasm = viscous, water-based fluid enclosed in the nuclear membrane
→ Contains dissolved molecules and ions that are essential for the function of the nucleus
→ Main functions: maintain shape and structure of the nucleus, and serve as a suspension substance for nuclear contents
- Nuclear matrix = network of filaments within the nucleoplasm that helps to organize the DNA in chromosomes into compartments
▪ Chromosomes and chromatin
- Chromatin ; complex of DNA and proteins forming highly organized fibers
- Chromosomes ; highly condensed chromatin found in the nucleus only during cell division

Section 2- DNA and RNA structure

⚫ DNA overview: organization
DNA
- Linear molecules made up of a sequence of smaller molecules
called nucleotides

Gene
- Segments of a DNA sequence contain genetic info (genes)
- Specific set of genes define your personal traits

Chromosome
- All genes are stored in long strands of DNA that complex with
proteins to form highly organized fibers ; chromatin
- Chromatin condenses into chromosomes

⚫ Structure of nucleotides

PHGY 170 Page 4

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