Module 1

What are the three unifying themes of biology?

Energy and matter transformations
Genetic information storage and transmission
Interactions with the environment

What is the purpose of lipids in the phospholipid bilayer?

creating a hydrophobic barrier between inside and outside the cell

What is the purpose of the proteins within the phospholipid bilayer?

Mediating transport, facilitating structure-function relationships (e.g. connecting to the extracellular matrix)

What is the basic path from DNA to protein?

DNA → pre-mRNA → mRNA → mRNA → protein

Examples of endgoals of post-translational targeting

mitochondria, chloroplasts, peroxisome, nucleus

Examples of endgoals of co-translational targeting

Golgi, cell membrane/secretion, lysosomes, vacuoles, storage vesicles

Where are the eukaryote’s genetic instructions held?

the nucleus

What proteins organize DNA?

histones

What surrounds the nucleus of a eukaryote?

A double bilayer (nuclear envelope) perforated with pores large enough to let macromolecules in and out

What gives the nucleus its shape?

a protein network called the nuclear lamina

What is the nucleolus of a cell?

Located inside the nucleus, produces the ribosomes needed for protein synthesis

What is chromatin?

The combination of DNA strands and histone proteins

What are ribosomes?

RNA-protein complexes produced by the nucleus which work in the cytoplasm to translate nuclear-encoded mRNA or in chloroplasts/mitochondria to produce the proteins encoded in those genomes

What two locations can ribosomes be found in?

Free-floating in the cytoplasm or bound to the ER

What organelles are contained in the endomembrane system?

ER, golgi, cell membrane/secretion, lysosomes, vacuoles, storage vesicles

What is the term for the first layer of the golgi apparatus?

cis golgi

What happens to molecules that go through the ER?

they make their way through layers, each of which have different enzymes that modify their structure

What is the ER?

A normally smooth surface (smooth ER), but if it is active in protein synthesis, ribosomes associate with the membrane, giving it a rough appearance (rough ER)

How do the ER’s products leave it?

Via vesicles

What do the smooth ER’s enzymes mostly do?

lipid synthesis and detoxification

Why is the ER important in signalling?

It is a major intracellular store of calcium, particularly in muscular cells

If a cell’s main purpose is protein synthesis and secretion, what will there be an abundance of?

Rough ER

What is the golgi apparatus?

Processes vesicles and determines where their constituents should be directed

Steps of the golgi apparatus

1. Vesicles move from ER to Golgi

2. Vesicles coalesce to form new cis Golgi cisternae

3. Golgi cisternae move in a cis-to-trans direction to mature

4. Vesicles form and leave the golgi

5. Vesicles transport some proteins backward to less mature Golgi cisternae

Which side of the golgi faces the ER?

cis

What is PTM?

Post-translation modification

What is glycosylation?

adding monosaccharides to other molecules

Where does glycosylation occur?

endomembrane system

What can PTMs change?

• affinity for ligands

• catalytic activity

• stability

• targeting

What are lysosomes?

Produced by the golgi and contain enzymes that degrade macromolecules. Degrade material internalized by endocytosis and damaged intracellular products

What is autophagy?

the degradation of damaged or excess intracellular components by lysosomes

How do lysosomes “digest”?

They contain active hydrolytic enzymes. they fuse with the food vacuole and these enzymes digest the food particles

What are vacuoles?

Large vesicles separated from the cytoplasm and used primarily for storage. Most important in plants, where they store water, solutes, and nutrients

What is cytoplasm?

A viscous fluid with consistency between a liquid and gel. It is the solution in which ions, metabolites, and enzymes are dissolved, diffuse, and react

Describe the osmotic activity of cytoplasm

It is osmotically active, being diluted by movement of water into the cell and concentrated by loss of water. Total volume = cell volume

How is the chemical nature of cytoplasm controlled?

By transporters that move molecules in and out of the cell across the cell membrane

What is the cytoskeleton?

An internal protein framework that determines the shape of the cell and changes the shape as needed by adding and removing monomers

Where do motor proteins walk?

On the cytoskeleton

Virtually all forms of biological movement depend on what?

cytoskeletal proteins and molecular motors

What does myosin walk on?

actin microfilaments

What do dynein and kinesin walk on?

microtubules

Name the three main cytoskeletal polymers

microtubules, microfilaments, and intermediate filaments

Basic steps of evolution of eukaryotic cells

1. the use of membrane to separate genetic information from the cytoplasm

2. the acquisition of organelles via endosymbiosis

How does mitochondrial shape change?

Dynamically from single organelles to complex networks

What are chloroplasts?

Plastids that contain the pigment chlorophyl, an enzyme that permits photosynthesis by using light energy to produce carbohydrates

What are peroxisomes?

Organelles specialized to handle a subset of redox reactions, including those involving hydrogen peroxide. Cells protect themselves from damage by collecting the enzymes that produce and degrade hydrogen peroxide in this compartment

What are peroxisomes essential to produce?

ethanol, long fatty acid chains, uric acid, other toxic compounds

What is the extracellular matrix made of?

Fibres and mesh (collagen), gels (proteoglycan), crosslinkers (fibronectin), connections (integrins)

How is the ECM related to tumours?

When solid tumours metastasize, they secrete enzymes that break down the ECM

How do cells connect to one another?

Cells produce proteins to connect (cell junctions) which determine tissue integrity and restrict molecular movement between cells and within a membrane

What do tight cell junctions do?

Prevent things from passing through tissues between cells and restrict free movement of membrane proteins, which prevents proteins diffusing from end to end of the cell