Microanatomy, Cell Structure and Function

What are 2 types of simple cell organisms?

Bacteria

Algae

What are some examples of multiple cells (complex organisms)?

Extracellular matrix (matrix of bone)

What are some examples of a eukaryote?

Plants

Fungi

Animal cells

What 3 things do all eukaryote cells have?

Cytoplasm

Nucleus

nuclear membrane

What are some examples of a prokaryote cell?

Bacteria

Archaea

Which cells, eukaryote or prokaryote, conform to a basic structural model (even though there is extraordinary range of morphological forms)?

Eukaryote cells

What types of external environments do most cells interact with?

Adjacent cells

Extracellular matrix

What organelle is the largest within the cell?

Nucleus

What organelle houses DNA?

Nucleus

What organelle can typically be found near the nucleus?

Golgi apparatus

What organelle is large and elongated and can be found scattered within the cytoplasm?

Mitochondria

What are two additional membrane bound structures within the cell?

Lysosomes

Intracellular transport vesicles

What is embedded in the lipid bilayer that act as channels?

Proteins

The head on the phospholipid molecule is ____ and _____:

Hydrophilic

Polar

The tail on the phospholipid molecule is ____ and _____:

Hydrophobic

Non-polar

What is spingomyelin?

Important and a plentiful phospholipid in cell membranes

The phospholipid bilayer is amphiphilic, what does this mean?

It has both a water-loving and water-fearing region

What are the 2 main functions of unsaturated fatty acids?

Increase the fluidity and flexibility of the membrane

Prevent close packing of the hydrophobic tails

What are the 3 main functions of cholesterol within the phospholipid bilayer?

Prevent overly dense packing of the phospholipid fatty acid tails

Fill gaps between the ‘kink’s of the unsaturated fatty acid tails

stabilize and regulate the fluidity of the phospholipid bilayer

What are transmembrane proteins?

Proteins that span the entire thickness of the membrane to be expose to each surface

What is the function of peripheral membrane proteins?

Cell to cell adhesion

cell to matrix adhesion

intracellular signaling

formation of transmembrane channels (transport materials into and out of the cell)

The RBC does not have this organelle:

nucleus

What is nucleoplasm?

substance of the nucleus (surrounded by the nuclear membrane)

What are histone proteins?

Type of nucleoprotein

low molecular weight, positively charged

What are non-histone proteins?

A type of nucleoprotein

Where are nucleoprotiens synthesized?

Within the cytoplasm, then imported into the nucleus

What are some examples of nuclear RNA?

mRNA

tRNA

rRNA

What is heterochromatin H?

Dense areas of tightly coiled inactive chromatin, in the periphery of the nucleus

What is a barr body?

A small discrete mass that can be formed on the inactivated X chromosome

What is euchromatin E?

Electron-lucent nuclear material

Part of the DNA that is ACTIVE in RNA synthesis

What is chromatin?

a complex mixture of DNA, RNA, and proteins that makes up the chromosomes inside the nucleus of a eukaryotic cell

What occurs in the nucleolus in regard to ribosomes?

Site of ribosomal RNA (rRNA) synthesis and ribosome assembly

What are some functions of the nucleolus?

Site of ribosomal RNA synthesis and ribosome assembly

porcesses transfer RNA

Control of the cell cyle and stress response

What is the function of the ribosomes?

protein factory of the cell

What are some functions of proteins?

Act as enzymes, transport, and regulatory proteins

Structural component

Mediate many metabolic processes

What are the steps of protein synthesis?

Transcription: gene is copied to form a complementary pre-messenger RNA

Post- transcriptional processing causes the excision of introns

mRNA strand passes through nuclear pore complex into the cytoplasm

mRNA binds to ribosomes

Translation: ribosomes synthesize proteins using mRNA strand as a template to determine the specific amino acid sequence of the protein

Each ribosomal subunit is consists of:

a strand of RNA and rRNA

What are polyribosomes?

ribosomes and a single strand of mRNA (small circular aggregations)

Proteins that are destined for the cytoplasm, nucleus, and mitochondria are:

synthesized on free ribosomes (where folding and other post-translational modifications take place)

Proteins that are for export and lysosomal proteins are:

synthesized by ribosomes attached to the surface of the rER

What is degradation?

the natural process by which cells break down old, damaged, or unneeded proteins into smaller peptides and amino acids

What are the steps of the degradation process?

1. Ubiquitin binds to the damaged protein

2. Acting as a signal allowing the protein to be taken up by a proteasome

What is a proteasome?

non-membrane bound arrays of proteolytic enzymes that are plentiful in all cells

What organelle is continous with the rER but lacks ribosomes?

sER

What are the main functions of the sER?

Lipid biosynthesis

Membrane synthesis and repair

sER are prominent in what types of cells?

Liver cells

Cells specialized for lipid biosynthesis

Steroid hormone secreting cells of the adrenal glands and the gonads

Within liver cells, the sER is rich in:

cytochrome P450

How does the sER play a major role within the liver cells?

Major role in metabolism of glycogen and detoxification of various noxious metabolic by-products, drugs and alcohol

In muscle cells, the sER is also known as the:

sacroplasmic reticulum

What is the main function of the sER in muscle cells?

Release and reuptake of Ca+ ions, activating the contractile mechanism

What is the function of the plasma membrane?

Controls the interaction of the cell with the external environment

Mediates the exchange of nutrients and waste products, secretions and signaling mechanisms

What is the function of the lipid membrane?

Separate different compartments within the cell

Contain incompatible biochemical reactions

Passive diffusion is dependent on:

Presence of a concentration gradient ABOVE the membrane

size and polarity of the molecule

What can pass freely through the lipid membrane during passive diffusion?

Lipid and lipid-soluble molecules

Hormones like estrogen and testosterone

gases such as oxygen, nitrogen, and carbon dioxide

What diffuses through the lipid membrane slowly?

Uncharged but polar small molecules

water and urea

What diffuses through the lipid membrane VERY slowly?

Charged molecules

Sodium and potassium

Facilitated diffusion is strictly what kind of process?

Passive process

What is active transport independent from?

Electrochemical gradients

What is an example of active transport?

Continuous movement of sodium out of the cell and potassium into the cell across the membrane by the Na/K pump

What are transport vesicles?

Formed by the assembly of a protein ‘coat’ leading to budding of a section of membrane which is pinched off to form a vesicle

How does bulk transport work within the cell?

moves large molecules or large amounts of materials into and out of a cell using membrane-bound sacs called vesicles

With lipid-soluble molecules like estrogen, how does the signal cross the plasma membrane to deliver information to the cell?

It will diffuse through the plasma membrane to bind to an intracellular receptor

With non-lipid soluble molecules like insulin, how does its signal cross a plasma membrane to deliver information to the cell?

Bind to a protein receptor embedded in the plasma membrane, which is activated

It will then pass the signal on to an intracellular signaling pathway

How does signaling work with neurotransmitters at the nerve synapses?

It will bind to an ion channel in the post synaptic membrane

Allows the ion to enter the cell

Initiates depolarization of the membrane

What does HER2 stand for?

Human epidermal growth factor type 2

The golgi apparatus complex is an important site of:

Protein and lipid glycosylation

The golgi apparatus consists of 4-6 saucer-shaped membrane bound:

cisternae