Week 3 - Chemistry of Life, Cell Structure & Functions, & Cell Metabolism

What are macromolecules?

• Carbohydrates

• Proteins

• Fats

• Nucleic Acids

What are carbohydrates?

• Macronutrient made of monosaccharides

• Composed of C, H, & O

• Used for energy

• Simple CHO: Glucose

• Complex CHO: Fiber, Starch

What are proteins?

• Macronutrient made of amino acids

• Composed of C, H, O, & N

• Structural and functional purposed to the body

What are the 2 types of amino acids?

Essential

• Cannot be produced by the body

• Required intake via diet

Non-essential

• Can be produced by the body

• Not entirely dependent on dietary intake

What is a nitrogen balance?

• The balance or protein intake meeting excretion

• Proteins contain nitrogen

• Neutral balance

  • Intake = Excretion

• Positive

  • Intake > Excretion

  • Required for growth

• Negative

  • Intake < Excretion

  • Starvation

What are fats?

• Macronutrient made up of fatty acids

• Used for structural functions and stored energy

• 3 types

  • Triglyceride

    • Glycerol + 3 fatty acid chains

  • Phospholipid

    • Glycerol & phosphate head + 2 fatty acid chains

  • Steriod/Cholesterol

    • Complex structure

What are the types of triglycerides?

Saturated

• Solid at room temp

• No double bonds

Polyunsaturated

• Liquid at room temp

• Double bonds

What are nucleic acids?

• Biomolecules that store and express genetic information in all living cells and viruses

• DNA and RNA

• Composed of nucleotides (C, H, O, N, & P)

• Blue-print for protein synthesis

What is intracellular and extracellular?

Intra

• Substances contained within the cell wall

Extra

• Substances found outside the cell wall

• Mostly fluid

What are 2 types of cell membranes?

Plasma Membrane

• Separates the internal environment of the cell from the external environment

Membranous Organelles

• Enclose and compartmentalize specific structures within a cell, creating a specialized environment for different cellular functions

What is a phospholipid bilayer?

• A double layer of lipid molecules that forms the fundamental protective barrier of all living cells

• Hydrophilic head on the outside

• Hydrophobic tail on the inside

• Selectively permeable barrier

What is the difference between hydro and lipo?

• Hydro = water

• Lipo = fat

What is the purpose of cholesterol in the lipid bilayer?

Contribute to the fluidity and strength of the membrane

What is the purpose of proteins in the lipid bilayer?

• Transporters/Integral Membrane proteins (passive & active diffusion)

• Identifiers (unique cell markers)

• Receptors

• Connectors (allows cells to bind)

What is cytoplasm

• Gelatinous fluid within cells

• Helps maintain volume and shape of cells

• Facilitated transport of substances within the cell

• Site of numerous crucial functions

What are organelles?

• A tiny, specialized structure inside a cell that performs a specific job

• Membranous & Non-membranous

What are the membranous and non-membranous organelles?

Membranous

• Nucleus

• Mitochondria

• Endoplasmic Reticulum

• Golgi Apparatus

• Lysomes

Non-Membranous

• Ribsomes

• Cytoskeleton

• Centrosomes

What is the nucleus?

• Control centre of the cell

• Contains the cells genetic material (DNA) which codes for all proteins in our body

  • Chromatin threads in non-dividng cells

  • Chromosomes in early stages of cell division

• Enclosed by a double membrane called the nuclear envelope and contains nuclear pores

What is the endoplasmic recticulum?

• Continuous network of membrane action as a crucial site for production of proteins and steroids

• Rough ER

  • Characteristics: Surface is covered in ribosomes

  • Functions: Production of proteins

• Smooth ER

  • Characteristics: Surface lack ribosomes

  • Functions: Production of lipids, cholesterol, and steroids

What are ribosomes?

• Found on the ER

• Non-membranous structure

  • Large subunit and small subunit

  • Each composed of RNA bonded to protein (rRNA)

• Synthesize proteins by translating the genetic code on mRNA into amino acid sequence

What is the Golgi apparatus?

• Membranous organelle that functions to process, modify, and package proteins and lipids

• Consists of a series of stacked flattened membrane-bound sacs called cisternae

What are lysomes?

Membrane-bound organelles that contain enzymes capable of breaking down proteins, carbohydrates, lipids, and nucleic acids

What is the mitochondria?

• Organelle in which ATP generation occurs

  • Converts glucose and oxygen into energy (ATP) through aerobic respiration

• Contain their own DNA

• Folds (cristae) within the inner mitochondrial membrane increases surface area for chemical reactions

What is the cytoskeleton?

• Internal supporting framework of cell that is composed of tiny, flexible fibres and rigid, rod-like pieces

  • Provides shape and support

  • Holds organelles in place

  • Assists in cell signalling and movement

What are centrosomes?

• An organelles that acts as the primary microtubule-organizing centre playing a major role in cell division

• The control centre for the cytoskeleton

• Centrioles:

  • Central component of centrosomes

  • Highly active in cell division

What are 3 types of cell extensions?

Microvilli

• Present in the small intestine as they increase surface area enhancing absorption of nutrients

Cilia

• Present in respiratory passages for movement of mucous out od the airways

Flagella

• Used for cell motility in sperm

What is membrane transport?

• Transportation through the cell directly through phospholipid bilayer or by proteins

• Passive Transport

  • No energy

  • Follows concentration gradient

• Active Transport

  • Requires energy

  • Against concentration gradient

What are examples of passive transport?

• Simple diffusion

• Osmosis

• Facilitated diffusion

• Filtration

What are examples of active transport?

• Pumps

• Endocytosis

• Exocytosis

What is diffusion?

• Passive transport

• Solutes move from an area of high concentration to an area of low concentration until they are evenly spread out

• Concentration gradient

• Involves a permeable membrane

What can and cant get thorough a phospholipid bilayer

Can

• Small unchanged molecules

Can’t

• Large uncharged molecules

• Ions

What is osmosis?

• The spontaneous movement of solvent molecules through a semipermeable membrane from a region of lower solute concentration to a region of higher solute concentration

• Concentration gradient

What effect does osmosis have on cells?

• Changes cell volume and shape by moving water across the cell membrane depending on the surrounding solution's concentration

• Hypo

  • Cell swells

  • Cell concentration is higher than the fluid

• Isotonic

  • Balances

• Hyper

  • Cell shrinks

  • Cell concentration is lower than the fluid

What is facilitated diffusion?

• A type of passive transport that moves polar molecules and ions across a cell membrane with the help of specialized transport proteins

• Concentration gradient

• Use of transport channel or carrier protein

• Selectively permeability

What is channel-mediated passive transport?

• A type of facilitated diffusion where specific ions or polar molecules move down their concentration or electrochemical gradient through water-filled protein pores across a cell membrane

• Creates a hydrophilic tunnel

• Only one type of solute

• Open and closes in response to a specific stimulus

What is carrier-mediated passive transport?

• The movement of specific polar molecules or ions across a cell membrane down their concentration gradient with the help of specialized transmembrane carrier proteins, requiring zero cellular energy

• Carriers attract and bind to the solute, change shape, and release the solute out the other side of the carrier

• Reversible depending on concentration gradient

What is the active transport process?

• Require the expenditure of metabolic energy by the cell

1. Pumps

   • Against the concentration gradient

2. Vesicles

   • Endocytosis (bring into the cell)

   • Exocytosis (remove from the cell)

What are active transport pumps?

• Sodium Potassium

  • Uses ATP to push Na+ out/bring K+ in against the concentration gradients

• Calcium

  • Uses ATP to push Ca out of the cell against the concentration gradient

What is endocytosis and exocytosis?

Endo

• Phagocytosis

  • Cell eating

• Pinocytosis

  • Cell drinking

Exo

• Cells transport molecules out of the cell by secreting them in membrane-bound vesicles that fuse with the plasma membrane releasing its contents to the exterior of the cell

What are the types of cell metabolism?

• Metabolism

  • Sum of all chemical reactions that occur within the cells of a living organisms

• Catabolism

  • Breaking down molecules for energy

• Anabolism

  • Building complex molecules needed by cells

What are enzymes?

• Catalysts for cellular reactions

  • Make them easier/brings extra energy/reduces energy required

• Does not change in reaction and can be reused

• Often, multiple are needed in sequences

• End in “ase”

What is catabolism?

• Cellular respiration

  • Metabolic process in cells that converts chemical energy from nutrients (primarily glucose) into ATP, which cells use for energy to perform life functions

• 3 chemically linked pathways

  • Glycolysis

  • Citric acid cycle

  • Electron transport system (ETS)

What is glycolysis?

• First series of chemical reactions in carbohydrate catabolism

• Takes place in the cytoplasm

• Anaerobic

• Glucose → Pyruvate and small amount of ATP

What is the citric acid cycle (Kreb’s Cycle)?

• Second series of chemical reactions in the process of glucose metabolism

• Takes place in the mitochondria

• Pyruvate → small amount of ATP, CO2, H2O, FAD (FADH)

• Also produces highly charged electrons

What is the Electron Transport System?

• Charged electrons flow through the mitochondria, pulled by O2, to make massive amounts of ATP

• If O2 is unavailable process breaks down, bogs down Kreb’s cycle

What is the Lactic Acid Cycle?

• A metabolic pathway where lactate produced by muscles during rapid exercise is converted back into glucose by the liver

• Occurs when not enough cellular oxygen to run Citric Acid Cycle + Electron Transport System

• Occurs in cytoplasm

• Pyruvate + NAD = very low yield ATP

• Byproducts: lactic acid (cramps), ketones (with diabetes)

What is a rough summary of cellular respiration?

Process for producing energy (ATP)

1. Glycolysis

   • Takes place in the cytoplasm

   • Anaerobic

   • Glucose → Pyruvate and small amount of ATP

2. Citric Acid Cycle + Electron Transport System

   • Takes place in the mitochondra

   • Needs pyruvate + oxygen → lots of ATP

   • Byproducts: CO2, H2O, and Hear

What is cellular growth and reproduction?

• Most fundamental of all living functions

• Constitute the cell life cycle

• Growth

  • Depends on the use of genetic information in DNA to make the structural and functional proteins needed for cell survival

• Reproduction

  • Ensures that genetic information is passed from one generation to the next

What is protein synthesis?

• The process cells use to build proteins

  • Transcription

  • Translation

• DNA (genes) contains the “blueprints” for synthesizing specific proteins

• RNA are a copy of these plans/blueprints

How do different organelles contribute to protein synthesis?

Nucleus

• Part of DNA “unzips”, binds with RNA

• Transcription (copy), becomes mRNA, leaves nucleus

Cytoplasm

• mRNA binds with Ribosome

• tRNA brings in amino acid

• Translation: mRNA uses code to build protein in ribosome

ER/Golgi Apparatus

• Ribosomes bind to ER

• More complex protein synthesis occurs, leaves via Golgi

What is transcription?

• Process in which DNA molecule is used as template to form mRNA, thus making a temporary “working copy” of the gene

• Occurs in the nucleus

• Segment of DNA “unzips”

• An RNA copy of unzipped segment is made

• the RNA copy is mRNA

What is translation?

• Occurs in the cytoplasm

• mRNA binds with ribosome

• tRNA brings in amino acid

• mRNA uses code to build protein chain (polypeptide)

What are the end stages of protein synthesis?

• Once translation is complete, polypeptide chains are combined with others in the ER to make larger and more complex proteins

There are further refined and then distributed via the Golgi Apparatus

What is the life cycle of cells?

1. G1 Phase

   • G0 phase (Non-dividing cells)

2. S Phase

   • Interphase

3. G2 Phase

4. Cell Division

   • Prophase

   • Metaphase

   • Anaphase

   • Telophase

   • Cytokinesis

What are chromosomes?

• Thread-like structures made of tightly wound DNA and proteins that live inside cell nuclei and carry your genetic blueprint

• Each chromosome has one centromere (specialized region of a chromosome that holds sister chromatids together and helps direct cell division) and two chromatids one of the two identical halves of a replicated chromosome

• During cellular replication, the cell duplicates its genetic material

What is mitosis?

1 cycle of cellular division resulting in 2 identical copies of the parent cells

1. Interphase

   • Not always considered part of mitosis

   • Cell grows, produces more organelles to accommodate its size

1. Prophase

   • DNA organizes into chromatids

   • Two new chromosomes replace each original chromosome

   • Nuclear envelope begins to breakdown

   • Centrioles begin to create spindles

2. Metaphase

   • Centrioles arrange condensed chromosomes along the midline of the cell

   • Spindles attach to chromosomes via centromeres

3. Anaphase

   • Sister chromatids separate, with each half moving to the opposite end of the cell

   • Ensures each daughter cell will receive an identical set of chromosomes

   • Cleavage furrow begins to form

4. Telophase

   • Nuclear envelope begins to form around genetic material

   • Chromosomes unravel back into DNA strands

   • Cytokinesis: Division of cytoplasm and it’s contents

   • Results in 2 identical daughter cells

What is meiosis?

• 2 cycles of cellular division resulting in 2 daughter cells with 50% of genetic material

• Reproductive cells (gametes) only

• Allows for genetic variability

• Results in haploid cells

What are the key difference with meiosis?

Prophase I

• Crossing over of genetic material happens, allowing for variability

Metaphase I

• Homologous pairs of chromosomes line up in pairs, not single file

Anaphase I

• Full pairs of chromosomes pulled to opposite ends of the cells, not individual chromatids