The Endomembrane System

How do cells increase the chance of Biochemical Reactions?

Concentrate and compertmentalise chemistry

What is Concentration?

Number of molecules in a given time

What is the effect of a decrease in Volume?

Increases probability a chemical reaction happens

What is Cytosol?

Intracellular fluid present inside cells

What is Cytosol comprised of?

Water, ions, small molecules, proteins

What is the role of Cytosol?

Site of all metabolic chemical reactions of prokaryotes

Where is the Cytoplasm?

Contained w/in cell membrane

What is the Cytoplasm compromised of?

Water, nucleic acids, enzymes, lipids, amino acids, carbs

What is the role of the Cytoplasm?

Site of large scale cellular activities including glycolysis & cell division

Describe Cytoplasm

Jelly-llike substance w/ organelles

What is the Plasma Membrane?

Selective barrier that allows sufficient passage of oxygen, nutrients and waste to service the volume of cells

What is the general structure of a Biological Membrane?

Double layer of phospholipids

What is the effect of the logistics of carrying out cellular metabolism?

Sets limits on the size of cells

What do Cell’s compartments provide?

DIfferent local environments that facilitate specific membrane functions, so processes can continue in the cell @ same time

Describe the Phospholipid Bilayer?

• Hydrophobic Tails - Face inward

• Hydrophilic Head - Face outward

Describe the components of the Endomembrane System

Continuous or connected via transfer by alleles

What are the main functions of the Endomembrane System?

Protein synthesis/transport, metabolism and movement of lipids, detoxification of poisons

What is the Endoplasmic Reticulum?

Extensive network of membranes

What is cisternae?

Network of membranous tubules and sacs

What is the internal component of the Endoplasmic Reticulum?

ER lumen, where proteins/lipids are found

What are proteins made by?

Ribosomes on ER’s surface

How are proteins threaded into ER cavity?

Through a pore in ER membrane

What are most secretory proteins?

Glycoproteins

What are Glycoproteins?

Proteins w/ carbs covalently attached, done w/in ER cavity

How do secretory proteins depart from the ER?

In membrane-bound vesicles (transport vesicles)

What is the role of the rER?

Makes enzymes for membrane production and adds membrane proteins/phospholipids to its membrane

What does the Endoplasmic Reticulum account for?

> Half of total membrane in many eukaryotes

How can we identify rER vs sER?

• rER - ribosomes studding its surface

• sER - w/o ribosomes

What does the rER contain?

Bound ribosomes which make glycoproteins

What is the function of the rER?

Distributes transport vesicles - proteins surrounded by membranes

What are Ribosomes?

Complexes made of ribosomal RNA and protein

What do Ribosomes do?

Carry out protein synthesis in cytoplasm and on outside of rER/nuclear envelope

Where are free ribosomes?

Cytoplasm

Where are bound ribosomes?

Outside of rER or nuclear envelope

What happens to proteins made by free ribosomes?

Used in the cell

What happens to proteins made by bound ribosomes?

Often secreted

What is a role of the sER relating to lipids?

Synthesis of lipids by its enzymes

What is a role of the sER relating to carbs?

Metabolises carbs

What is a role of the sER relating to poison?

Detoxification

What is a role of the sER relating to Calcium?

Stores Calcium

What is the relationship between Reproductive Cells and the sER?

Reproductive cells contain sER that produce steroid hormones

What is the relationship between Liver Cells and the sER?

Liver cells contain sER w/ enzymes to detoxify drugs & neutralise toxic compounds by making them soluble and easily removeable

What is the relationship between the sER and Calcium?

Stores Calcium ions, essential for muscle contraction

What is a role of the Golgi relating to the ER?

Modifies products of the ER

What is a role of the Golgi relating to macromolecules?

Manufactures macromolecules

What is a role of the Golgi relating to transport?

Sorts and packages materials into transport vesicles

How do the transport vesicles work?

• Come from ER into cis side

• Pass through cisternae to trans side

• Sent off to various destinations

Where are products of the ER modified?

During transport from the cis face of the Golgi to the trans face

What are Pi Groups?

Molecular identification tags that target protein products to correct part of cell

Where are Molecular Identification Tags added?

Golgi

What is the change in DNA Replication?

DNA to DNA

What is the change in Transcription?

DNA to RNA

What is the change in Translation?

RNA to Protein

What are Lysosomes?

Membrane sac of hydrolytic enzymes that can digest macromolecules

Where are Lysosome Enzymes made?

By rER and transferred to Golgi (cis side), then lysosome buds off from trans face as a vesicle

What are the roles of Lysosomal Enzymes?

Hydrolyse proteins, fats, polysaccharides, nucleic acids

What is a function of the Lysosome relating to engulfment?

Engulf potentially harmful bacteria/viruses

What is a function of the Lysosome relating to Recycling?

Recycle old/worn-out organelles

How does Phagocytosis relate to Vacuoles?

Phagocytosis forms a food vacuole (Phagosome)

How do Lysosomes relate to Phagosomes?

Lysosome fuses w/ phagosome & digests molecules inside

What is Autophagy?

Lysosomes use enzymes to recycle cell’s own organelles/macromolecules

What are Peroxisomes?

Specialised metabolic compartments

What is important about Peroxisome’s Enzymes?

Remove H atoms from various substances & transfer them to oxygen to form H2O2

How do Peroxisomes relate to Fatty Acids?

Some peroxisomes break down FAs to be used in cellular respiration

How are Peroxisomes involved in detoxification?

Some peroxisomes break down FAs to be detoxify alcohol & harmful compounds by transferring H atoms to oxygen

Why is the toxicity of Hydrogen Peroxide not an issue?

Peroxisomes contain an enzyme to convert it to water

What are Vacuoles?

Large vesicles derived from ER and Golgi apparatus

How are Vacuoles formed?

By fusion of multiple, smaller vesicles

How is the Vacuole Membrane selective?

Selective for transporting solutes so solution inside vacuole is different in composition to cytosol

What are food vacuoles used for?

Phagocytosis

What are contractile vacuoles used for?

Freshwater organisms use this to pump excess water out cell, maintaining correct ion concentration

How is the Central Vacuole formed (Plant’s only)?

Joining up many smaller vacuoles

What is the purpose of cell sap in the Central Vacuole?

Cell’s main store of ions (Eg K+, Cl-)

What is the role of the Central Vacuole?

Helps maintain turgor pressure in plants

Why is the Vacuole important in plants?

Contains water, allows structural support due to increased pressures, pushes chloroplasts closer to light

Why is the Vacuole important in animals?

Important in phagocytosis, contractile vacuole pumps water out cells