Organelles Flashcards by Hector Arredondo

How is the cell wall of a gram negative bacteria arrange?

Outer membrane

Cell wall

Plasma membrane

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How is the arrangement of a gram positive bacteria?

Cell wall

Plasma membrane

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What are the functions of the cell membrane?

Enclose and protect cell
Maintain structural and functional integrity
Selectively permeable membrane
Define inside/outside of organelles
Compartmentalizations of biochemical activity
Intercellular interaction and respond to external signal
Scaffol for biochemical activity

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What is the function of the golgi?

Maturation of glycoproteins and other components of membranes and secretory vessels

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What is the function of chloroplasts (plants)?

Photosynthesis

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What is the function of the mitochondria?

CTA, ET and oxidative phosphorylation

Fatty acid oxidation, amino acid catabolism and pyruvate oxidation

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What is the function of lysosomes?

Segregation of hydrolytic enzymes such as ribonuclease and acid phosphatase

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What is the function of the glycogen granules?

Glycogen synthesis and degradation

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What is the function of the cytoskeleton?

Glycolysis; many reactions in gluconeogenesis, pentode phosphate pathway, activation of amino acids, fatty acid synthesis and nucleotide synthesis

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What is the function of a vacuole?

Water storage

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What is the function of the nucleus?

Replication of DNA, synthesis of tRNA, mRNA and some nuclear proteins

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What is the function of the nucleolus

Synthesis of rRNA

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What is the function of the ER?

Lipid synthesis, direction of biosynthetic products to their ultimate location

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What is the function of ribosomes?

Protein synthesis

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What is the function of microbodies?

Amino cid oxidation, catalase and peroxide reactions, sterol degradations; in plants, glyoxylate cycle reactions

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What are the lipids in the cell membrane?

Phospholipids
Glycolipids
Cholesterol

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What are the proteins in the cell membrane?

(Two classes: transmembrane and peripheral)

Membrane channels/pumps
Transporters
Membrane receptors
Adhesion molecules
Gap junctions

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What are the 3 class of lipids?

Phospholipid (ex: phosphatidylcholine)

Triglyceride (ex: triacylglycerol)

Steroid (ex: cholesterol)

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Where are glycolipids located?

Only on extracellular leaflet

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What forms the glycocalyx?

The carbohydrate residues on the glycolipids

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What is the purpose of cholesterol on the membrane?

For structural stability

Note: it’s on both leaflets

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What determines the properties of a phospholipid?

The tail length and degree of saturation

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What are some important phospholipids?

Phosphatidic acid (phosphate + glycerol)

Phosphatidyl-choline (choline + phosphate + glycerol)

Phosphatidyl-ethanolamine (ethanolamine + phosphate+ glycerol)

Phosphatidyl serine

Phosphatidyl-inositol

Sphingomyelin (choline and serine)

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What do fatty acids form?

Micelles

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What do phospholipids form?

Bilayers Note: circular bilayers are liposomes

What holds the leaflet of a membrane together?

Van der Walls interactions (weak bonds between hydrophobic tails)

In a TEM, membranes appear trilaminar. Why is that?

The polar head groups attract osmium tetroxide and become dark The center lipid section remains clear

How thick is the membrane?

7.5 mm thick

What is the membrane fluidity essential for?

Exocytosis, endocytosis, membrane trafficking and biogenesis

Why aren't the inner and outer leaflets symmetric?

They are composed of different phospholipids

Where are glycoproteins and glycolipids on the membrane?

On the outer leaflet

What increases the fluidity of the membrane?

Unsaturated fatty acid tails (increase cis-double bond kinks) Short chain Increase temperature

What does cholesterol do to the membrane?

Increases stability by "filling in the gaps" when lipids are too fluid I.e. If high unsaturation or high temp

What do steroid rigs do to PL hydrocarbon movement?

Reduces phospholipid movement

What happens when too much cholesterol is within a erythrocyte?

Distorted cell shape called acanthocytes

What does an acanthocyte look like?

Has 5-10 irregular, blunt, fingerlike projections

What is acanthocytosis (spur cells) anemia associated with??

Chronic liver disease

Why is spur cell anemia associated with chronic liver disease?

Abnormal lipoproteins with high cholesterol content and high plasma cholesterol levels in these patients

What does the decreased deformability of acanthocytes lead to?

Sequestration and destruction by spleen (haemolytic anemia)

What are lipid rafts rich in? (Butter islands in oil)

They are rich in cholesterol and glycosphingolipids (long saturated tails) and are less guild and thicker

What is a glyosylphosphatidylinositol anchor?

GPI: glycolipid that attaches proteins to PM

What kind of proteins are found in lipid rafts?

Integral and peripheral membrane proteins Note: clustering enables proteins to function together and for transport into endocytic vesicles E.i. GPI

What maintains the asymmetry of the phospholipid bilayer?

Flippases Note: these enzymes selectively "flip" particular phospholipids across the membrane

What does flip-flop require? ( a type of movement within the bilayer)

Flippases | Scrambalases

What do scrambalases do?

Non-specific scrambling In ER membrane: mix up newly synthesized PLs At plasma membrane: activated during apoptosis

What is the functional importance of lipid movement?

Phosphatidyl serine will be flipped to outer leaflet during apoptosis

What are glycolipids used for?

Cell to cell recognition Protection (exposed apical surface of epithelial cells) Nerve conduction

What is the receptor for Cholera toxin found on the intestinal epithelial cells?

Gm1 ganglioside

What are integral proteins bound to?

Actin cytoskeleton

What is the difference in protein concentration in myelin and mitochondrial membrane?

Myelin : 25% protein Mitochondrial: 75% protein

What are the functions of membrane proteins?

Transport (nutrients, metabolites, ions across bilayer) Anchor membrane to macromolecules on either side Receptors: signal transduction Enzymes (lactase in apical membrane of GI epithelial cells) Cell identity markers: MHC

What are the 3 classes of membrane proteins?

Integral transmembrane proteins Peripheral proteins Lipid-anchored (peripheral) proteins

What are the characterisitcs of integral transmembrane proteins?

Single/multipass proteins Often alpha-helical in secondary protein structure Receptors (signaling and adhesion), channels, transporters/pumps

What are the characteristics of peripheral proteins?

Located entirely outside but associated with inner/outer leaflet by noncovalent interactions Part of cytoskeleton, cytochrome C

What are the characteristics of lipid-anchored (peripheral) proteins?

Located either side of bilayer, have lipid group that inserts into bilayer Signaling and adhesion proteins

What does protein 4.1 link?

Actin to glycophorin (single pass transmembrane glycoprotein) Note: also binds spectrin and band 3

What is band 3?

Multipass transmembrane protein

What does ankyrin bind?

Binds band 3; attaching spectrin cytoskeleton to membrane

What is hereditary spherocytosis?

An autosomal dominant disorder in RBC cytoskeleton membrane This is due to non-functional skeletal membrane protein; spectrin, ankyrin or protein 4.1

What is dysfunctional in hereditary spherocytosis?

Spectrin, ankyrin or protein 4.1 (spectrin deficiency)

What is the treatment for hereditary spherocytosis?

Folate supplement, splenectomy

What are the effects of hereditary spherocytosis?

Unstable membrane, loses fragments = RBCs sphenoidal, decreased deformability -vulnerable to splenic sequestration and destruction -hemolytic anaemia (splenomegaly, jaundice, gall stones)

What is the function of the apical plasma membrane?

Regulation of nutrient and water intake Regulated secretion Protection

What is the function of the lateral plasma membrane?

Cell contact and adhesion Cell communication

What is the function of the basal membrane?

Cell-substratum contact Generation of ion gradients

What does the glycocalyx repel?

Negative charges from sialic acid sugars

What are the substances found in the glycocalyx?

Glycoproteins, glycolipids, proteoglycans

What is different in the glycocalyx of a cancer cell?

Different sugar coat than noncancerous cells

What are the primary marker for cell recognition ?

Carbohydrates

What do carbohydrates provide for cell recognition?

Attachment for bacteria, viruses, toxins, other cells Activated endothelial cells express selectins which bind to oligosaccharides on WBC & platelets L-selectins recognise addressins on lymphoid organ endothelial cells

Organelles Flashcards

(70 cards)