L.2 Molecular Structures of the Cell ✔️

7 key molecular structures of the cell (subcellular compartments)

1. Plasma membrane

2. Nucleus

3. Cytologie

4. Mitochondria

5. Endoplasmic reticulum

6. Golgi Apparatus

7. Lysosomes

Describe molecular movement within a cell

Molecules can move between compartments, but entry/ exit into various compartments is often regulated (not free flowing)

Membrane permeability function

Keep compartments separate, allows for different functions in each region

Describe movement of hydrophobic molecules and gases across the membrane

Diffuse freely

Describe the movement of small polar molecules (including water) across the membrane

Diffuse to some extent

Describe the movement of large polar molecules and ions across the membrane

Requires channels or transporters to cross

Describe the primary component of the plasma membrane (structure and permeability)

1. Phospholipids

2. Bilayer

3. 5nm thick

4. Impermeable to water-soluble molecules

Within the phospholipid bilayer, what is found in the membrane

Membrane proteins

Membrane proteins can have the following 4 functions and specific type of applicable

1. Transport molecules across membrane (channel)

2. Catalysis of membrane associated reactions (enzyme)

3. Structural links

4. Receptors (receptor proteins)

Plasma membrane functions

1. Barrier to transit of molecules into/out of cell (creates different environments)

2. Contact point where cell senses neighbouring cells, external environment and ECM

Location of cytosol and consistency

1. Liquid* matrix, not enclosed by nucleus/organelles

2. Jelly-like/viscoelastic*

The cell gets structure from what?

Protein structures within the cytosol (micro tubules/actin cytoskeleton)

pH of cytosol

7.4

Ion concentrations in cytosol

1. Not uniform

2. Varies by region due to localization of channels/ transporters/ organelles and slow diffusion

______ concentrations of ions can be very different than______ concentrations

Cytosolic, serum (outside fluid, usually blood plasma)

Asie le from ions cytosol contains ____ and ____

• Metabolic enzymes

• Small organelles

Example of small organelle in cytoplasm and function

• Proteasomes

• Protein-degrading complexes

Types of DNA and who its inherited from

• nuclear → mom and dad

• Mitochondrial → mom (for ion transport and flux in mitochondria)

Most DNA is found where?

In the nucleus

General structure of the nucleus

• surrounded by nuclear membrane/ envelope

  • Has pores

• Nucleolus and DNA within

Function of nuclear pores

• allows transport of proteins in/out

• Export mRNA to cytoplasm

Forms of DNA within Nucleus

compact or open (depending if actively expressing genes or repressed)

__ human cells contain a nucleus except for __

1. all

2. Red blood cells

___ cells have 1 copy of genes, whereas___ cells have 2

1. Germ

2. Somatic

Mitochondrial diseases passed on by ___

Maternal side

Mitochondria function

• Powerhouse of the cell

• Site of energy production (ATP) used by body for metabolic demands

What type of cell has many mitochondria? Why?

• cardiomyocytes (heart muscle)

• Supply needs of constantly contracting muscle

Mitochondria general structure

Double membrane

Mitochondria form what?

Aveint* bacteria that formed a symbiotic relationship with eukaryotic cells

Central dogma of molecular biology

• DNA is genetic code

• Gets transcribed into mRNA (messenger)

• mRNA translated into protein

• Protein = effector of DNA, affect cell function

• What RNA + protein expressed x type of cell

Types of ER + how to define

rough → higher number of ribosomes

Smooth → lower number of ribosomes

mRNA that encode cytosolic proteins are translated by ___

Ribosomes in cytosol

The rough ER’s ribosomes translates into what?

mRNA encoding ER resident, secreted, lysosomal, plasma membrane proteins

ER is adjacent to the ___

Nucleus

After protein (from ER) are formed, they go to___

The Golgi

Which proteins go to the Golgi Apparatus

• secretion

• Lysome

• Plasma membrane

Relative location of Golgi

Adjacent to ER

What happens inside the Golgi

• Proteins are modified with sugars or processed

• Targeted to final destination

Modifying proteins with sugar is called __

Glycosylated

Example of secretion, membranes and lysome destinies

• hormones (insulin)

• Receptors

• Lysosomal proteins

Lysosome function

Acidic organelles for recycling/ degrading cellular component

What is sent to the lysosomes? What happens to them?

• Damaged organelles

• Degraded, amino acids/nucleotides are recycled into other cellular processes

What is autophagy? What is its purpose? Where does it happen

• self devouring

• Survival process activated in starvation to recycle cellular components/use cell parts for energy

• Lysosomes

Too much autophagy can lead to___

Cell death

3 types of “cell eating” by the lysosome

• phagocytosis

• Autophagy

• Receptor-mediated endocytosis

Describe phagocytosis

Large outside cell/parasite engulfed, moves through cytoplasm and into lysosome

describe receptor- mediated endocytosis

• receptors capture specific target (small macromolecules)

• Pinch off coated membrane (endosome)

• Endosome fuses with Golgi vessel

• Goes to lysosome

Most common autophagy target

Mitochondria

Lysosome internal environment

Very acidic (low pH)

What is cystic fibrosis? Prevalence?

• Autosomally recessive lung disease

• Most common fatal genetic disease for children for children in Canada

Cause of CF?

• Mutations in CFTR (regulates flux of Cl-)

• Most common mutation deletion of 1 phenylalanine residue

How does a protein issue cause CF

• misfolded protein trapped within cell

• Cannot work at plasma membrane to regulate ion flow

CF treatment

Treat misfolded protein (does NOT fix DNA) to help be active at surface

• prevents degrading of protein

• Proteins are open to allow flow at membrane