Cell Structure

Peripheral proteins

On the inside of the cell; can be enzyme; Link the plasma membrane to the internal cytoskeleton to maintain cell shape and act as messengers to relay signals from external receptors to internal cell parts

Integral proteins

A permanent membrane protein that can be channels, receptors, carriers, etc.

What influences membrane fluidity?

Cholesterol; it tends to limit tight packing of phospholipids and maintain intermediate membrane fluidity

What does it mean for the bilayer to be a fluid mosaic?

Lipids and some proteins are not rigidly linked so they can move around, and the many embedded proteins in the membrane appear like a pattern of small pieces

What are the main functions of the plasma membrane?

Regulate the passage of substances in and out of cells

Detect chemical messengers arrive at the cell surface

Link adjacent cells together by membrane junctions

Anchor cells to the extracellular matrix

What are the main functions of the organelle membrane?

Regulate passage of substances between cell organelles and cytosol

What is the function of channels?

Aqueous passageways that are selectively permeable to specific ions or water (some can be physiologically modulated)

What is the function of carriers?

To move specific substances across the membrane (some can be physiologically modulated—iniserted or removed)

What is an important concept about the relationship between cells and their proteins?

The specific proteins in a given cell membrane confers special physiological functions on that cell

Ex. ADH adds water channels (aquaporins) in the kidney

Where can you find nicotinic AcH receptors?

Neuromuscular junctions (in skeletal muscle), autonomic ganglia, some CNS connections

What are nicotinic AcH receptors (nAChRs)?

Specialized protein channels in cell membranes that open when the neurotransmitter acetylcholine or the drug nicotine binds to them, allowing charged particles to flow through

What is the cause of myasthenia gravis?

Autoantibodies bind to and destroy the nAChRs in the neuromuscular junction which impairs muscle contraction and causes weakness and/or paralysis

What are the structural linkages that organize cells into tissues?

Desmosomes and tight junctions

What are the cell to cell linkages that are for efficient signaling?

Gap junctions

What is the difference between desmosome and tight junction?

Desmosomes link cells firmly together with cadherin linkages In areas subject to stretch while tight junctions link cells with no gaps in between and form a selective barrier that prevents the movement of substances

Where might you find desmosomes?

Skin

Where might you find tight junctions?

The blood-brain-barrier and in intestines

Where can you find gap junctions?

Heart muscle cell and intestines

What is the role of gap junctions?

Provide fast cell to cell transmission of electrical activity between cells; especially fast signaling for heart muscle contraction

What is the function of the nucleus?

Storage and transmission of genetic information in the form of DNA to the next generation of cells and protein synthesis

What is the function of the nucleolus?

Site of ribosome synthesis; assemble RNA and protein components of ribosomal subunits, which then move to cytoplasm through nuclear pores

What are the steps to protein synthesis?

DNA is transcribes into mRNA in the nucleus (which dictates the structure and function of cells), then the mRNA is translated to give instructions for protein synthesis in the cytoplasm

What 4 main functions happen in the cytoplasm?

Manufacturing of ribosomes (which synthesize proteins), digestion through lysosomes and peroxisomes, production of energy through mitochondria, and provide cellular shape and movement through the cytoskeleton

What is the function of the smooth endoplasmic reticulum?

Amazon warehouse: contains enzymes for fatty acids and steroid synthesis; stores and releases calcium which controls various cell activities

What is the function of the rough endoplasmic reticulum?

Storage unit: protein synthesis and packaging in ribosomes attached to surface

What is the function of the golgi apparatus?

The distribution center of synthesized proteins; concentrates, modifies, and sorts proteins arriving from the RER prior to their distribution

What is the function of the lysosomes?

Digest and recycle cellular waste, bacteria, etc. mediated by acidic contents and digestive enzymes

What is the function of the peroxisomes?

Use oxygen to remove hydrogen from organic molecules (lipids & alcohols)

What is potentially dangerous about peroxisomes?

The reaction between peroxisomes and oxygen can form hydrogen peroxide which is cytotoxic but destroyed by peroxisomes

What are lysosomal storage disorders?

Enzyme deficiency results in abnormal build-up of toxic material and can affect many different cell types

What are examples of some lysosomal storage disorders?

Gaucher, Pompe (glycogen storage), Tay Sachs diseases

What is the function of the mitochondria?

Generate ATP by consuming O2 via cellular respiration, forming CO2 as a by-product; contains enzymes that are active in the kreb’s cycle and oxidative phosphorylation

What is the function of the cytoskeleton?

Structural support consisting of actin filament (microfilaments), intermediate filaments (keratin in desmosomes), and microtubules

What is muscular dystrophy, particularly Becker Muscular Dystrophy (BMD)?

A rare, inherited genetic disorder that causes progressive muscle weakness caused by a mutation in the dystrophin gene on the X chromosome

What is the role of dystrophin?

Connects the cytoskeleton of a muscle cell to the outer matrix and prevents muscle cell membranes from tearing when muscles contract and relax

What is the function of actin filaments?

Make up a major portion of cytoskeleton in all cells and function to maintain cell shape and ability of cells to move by ameboid-like movements, cell division, and contractile force

What is the function of intermediate filaments?

Internal wires to resist pulling forces and are most extensively developed in the regions of cells subject to mechanical stress (ex. desmosome-linked by desmin)

What is the function of microtubules?

The most rigid of cytoskeleton filaments

In neurons: provide framework that maintains the cylindrical shape & a “highway” for transport (anterograde/retrograde axonal transport)

In cells: form “highways” that move organelles around

What is the function of cilia?

Remove microbes and debris from the interior of the lungs