LS 7A week 2 (5.1 + 5.3 Questions)

Phospholipids

-glycerol backbone attached to a phosphate group and two fatty acids -The phosphate head group is hydrophilic ("water-loving") because it is polar, enabling it to form hydrogen bonds with water -two fatty acid tails are hydrophobic ("water-fearing") because they are nonpolar and do not form hydrogen bonds with water. -amphipathic

All cells need:

-maintain homeostasis (mech to separate and regulate internal environment) -mechanism to acquire, transform, and use energy -form of information storage and transfer

cholesterol

-major component of animal cell membranes -amphipathic -hydrophilic region is simply a hydroxyl group (-OH) and the hydrophobic region consists of four interconnected carbon rings with an attached hydrocarbon chain -allows cholesterol to insert into the lipid bilayer so that its head group interacts with the hydrophilic head group of phospholipids, while the ring structure participates in van der Waals interactions with the fatty acid chains.

How might you expect these organelles to differ?: -phagocyes - eat a lot of material -RBCs - transport O2 in the body -B cells secrete a lot of antibodies (proteins)

-most lysosomes -least mitochondria -lots of ribosomes bound to ER

The lipid components of cellular membranes often include: -phospholipids. -fatty acids and cholesterol. -phospholipids and cholesterol. -phospholipids and fatty acids.

-phospholipids and cholesterol.

Cells are diverse and have specialized functions

-structure relates to function! -different cell types + cell tissue = different molecules + cells e.g. liver has highest concentration of mitochondria

Organelles

Any one of several compartments in eukaryotes that divide the cell contents into smaller spaces specialized for different functions.

Plasmid

In bacteria, a small circular molecule of DNA carrying a small number of genes that can replicate independently of the bacterial genomic DNA

Cytoskeleton

In eukaryotes, an internal protein scaffold that helps cells to maintain their shape and serves as a network of tracks for the movement of substances within cells.

Nucleoid

In prokaryotes, a cell structure with multiple loops formed from supercoils of DNA. DNA is concentrated in a discrete region of the cell interior known as the nucleoid

Mitochondria

Specialized organelles that harness energy for the cell from chemical compounds like sugars and convert it into ATP.

Fluidity

Strength of the van der Waals interactions between the lipids' tails depends on the length of the fatty acid tails and the presence of double bonds between neighboring carbon atoms. The longer the fatty acid tails, the more surface is available to participate in van der Waals interactions. The tighter packing that results tends to reduce lipid mobility.

Nucleus

The compartment of the cell that houses the DNA in chromosomes.

Cytoplasm

The contents of the cell other than the nucleus.

If cells had single-layer membranes like micelles, how would the structures of transmembrane proteins be affected? Transmembrane proteins would only possess hydrophilic regions. Transmembrane proteins would possess a hydrophilic region in the cell interior and a hydrophobic region in the extracellular space. Transmembrane proteins would only possess hydrophobic regions. Transmembrane proteins would possess a hydrophobic region in the cell interior and a hydrophilic region in the extracellular space. The structures of transmembrane proteins would remain the same as if cells had lipid bilayers.

Transmembrane proteins would possess a hydrophobic region in the cell interior and a hydrophilic region in the extracellular space.

Cytoplasm vs Cytosol

everything in the cell (besides nucleus) vs fluid in cytoplasm

The interior region of a phospholipid bilayer is characterized as: hydrophilic. hydrophobic. hydrophilic and polar. polar.

hydrophobic.

If membrane fluidity needs to be maintained, which of the following would be most important in an animal cell as a response to a decrease in temp? -increase number of long fatty-acid chains -increase number of double bonds -decrease number of cholesterol

increase the number of double bonds

What happens if you dump a bunch of phospholipids into a container of oil?

liposome *air is hydrophobic!

Which one of the following is NOT a component of an animal cell's plasma membrane? nucleic acid carbohydrate protein lipid

nucleic acid

A protein that is temporarily associated with a biological membrane is a(n): transmembrane protein and an integral membrane protein. peripheral membrane protein. transmembrane protein. integral membrane protein.

peripheral membrane protein.

Prokaryote

An organism whose cell or cells does not have a nucleus. Often used to refer collectively to archaeons and bacteria.

Eukaryote

An organism whose cells have a true nucleus.

cholesterol and fluidity

-Cholesterol increases or decreases membrane fluidity depending on temperature. -At temperatures typically found in a cell, cholesterol decreases membrane fluidity because the interaction of the rigid ring structure of cholesterol with the phospholipid fatty acid tails reduces the mobility of the phospholipids. -However, at low temperatures, cholesterol increases membrane fluidity because it prevents phospholipids from packing tightly with other phospholipids. -Thus, cholesterol helps maintain a consistent state of membrane fluidity by preventing dramatic transitions from a fluid to solid state.

Prokaryote vs Eukaryote

-Nucleus: processes of transcription and translation to be separated in time and space --> more complex ways to regulate gene expression -types of lipid that make up their cell membranes (Eukaryotes -- sterols, Prokaryotes -- hopanoids) -Eukaryotes are much larger --> higher SA to V ratio --> absorbs nutrients from environment -most prokaryotes lack the extensive internal organization characteristic of eukaryotes

lipid rafts

?!? For many decades, it was thought that the various types of lipid found in the membrane were randomly distributed throughout the bilayer. However, more recent studies show that specific types of lipid, such as sphingolipids, sometimes assemble into defined patches called lipid rafts. Cholesterol and other membrane components such as proteins also appear to accumulate in some of these regions. Thus, membranes are not always a uniform fluid bilayer, but instead can contain regions with discrete components.

Lysosome

A vesicle derived from the Golgi apparatus that contains enzymes that break down macromolecules such as proteins, nucleic acids, lipids, and complex carbohydrates.

Chloroplasts

An organelle that converts energy of sunlight into chemical energy by synthesizing simple sugars.

Amphipathic

Molecules with both hydrophilic and hydrophobic regions in a single molecule are termed

Peroxisome

Organelles in eukaryotic cells that contain many different enzymes and are involved in metabolic reactions.

Pili

Plasmids are commonly transferred between bacteria through the action of threadlike structures known as pili (singular, pilus), which extend from one cell to another.

Saturated vs Unsaturated

Saturated = straight, single, solid (can pack tightly together) Unsaturated = bent, double bonds, liquid (pack less tightly together)

Most animal fats are solid at room temperature, whereas plant and fish oils tend to be liquid. Both contain fatty acids. Can you predict which type of fat contains saturated fatty acids, and which type contains unsaturated fatty acids?

Saturated fatty acids are less mobile within the membrane compared to unsaturated fatty acids. As a result, saturated fatty acids tend to be solid at room temperature, whereas unsaturated fatty acids tend to be liquid. Margarine and many other animal fats contain saturated fatty acids and are solid, whereas many plant and fish oils contain unsaturated fatty acids and are liquid at room temperature.

Endoplasmic Reticulum (ER)

The organelle involved in the synthesis of proteins and lipids.

Golgi Apparatus

The organelle that modifies proteins and lipids produced by the ER and acts as a sorting station as they move to their final destinations

Cytosol

The region of the cell inside the plasma membrane but outside the organelles; the jelly-like internal environment that surrounds the organelles.