Cell Structure and Function

• Cells have a clear boundary (membrane) that controls the movement of substances in and out.
• Cells contain genes; hereditary material composed of DNA.
• Eukaryotic DNA is transcribed into mRNA to travel to ribosomes because it cannot leave the nucleus.
• Ribosomes synthesize proteins.
• Cytoplasm, located between the membrane and nucleus, houses cellular components, protects from damage, and serves as the site for chemical reactions.
• Cytosol is the liquid component of the cytoplasm, primarily water with soluble molecules.
• Plants, fungi, and bacteria have cell walls for extra protection.
• DNA in prokaryotes is located in a central area called the nucleoid.
• Prokaryotes use flagella for movement.
• Centrioles in animals aid in the formation of spindle fibers during cell division (mitosis).

Cell Division (Eukaryotes)

• Mitosis results in two daughter cells with the same number and kind of chromosomes as the parent nucleus.
• During mitosis, the nucleus divides into two asexually and involves spindle fibers forming protein.
• Sister cells are divided by structure during cell division.
• Meiosis is sexual reproduction.
• Meiosis reduces the number of chromosomes.
• Two rounds of division result in four cells, each with one copy of each chromosome in meiosis.

Cell Division (Prokaryotes)

• Fission involves copying the chromosome (DNA) and separating one cell into two, which is asexual.
• Prokaryotes existed for 1.5 billion years before any other life form.
• Prokaryotes divide by fission, have DNA in a circular format, possess 70S ribosomes, and lack organelles.
• Vesicles use glucose as a food source.
• Eukaryotes are larger, including plants, animals, fungi, and protists.
• Eukaryotes have membrane-bound organelles, divide by mitosis and/or meiosis, have DNA in a linear format, and possess 80S ribosomes.
• Eukaryote nuclei hold DNA wrapped with proteins and are true kernals.
• Both prokaryotes and eukaryotes have double-stranded DNA, cell membranes, ribosomes, and make proteins.
• A prokaryote cell has circular DNA, cell membrane, cell wall and ribosomes.
• Chromosomes travel to ribosomes and assemble amino acids into proteins in prokaryotic cells.
• Nuclear pores allow mRNA molecules to leave the nucleus.
• All living things consist of cells, which are basic functional units and arise from pre-existing cells.

Endomembrane System

• DNA in the nucleus is copied into mRNA, which travels to ribosomes for synthesis.
• A vesicle transports the synthesized product to the endoplasmic reticulum.
• Rough ER folds proteins, and smooth ER detoxifies substances and synthesizes lipids

Golgi Apparatus

• The enzymatic modification of newly synthesized integral membrane proteins takes place in the golgi apparatus.
• Antibodies are proteins exported from the cell.
• Made in the rough ER, they go into the smooth ER.
• The ER then buds off a vesicle transporting the antibody to the Golgi apparatus.
• The Golgi has enzymes that modify the antibody into the correct form to bind/neutralize viruses.
• A vesicle fuses with the cell membrane, releasing the antibody into the bloodstream.
• The antibody floats to bind with and neutralize the virus.
• A single celled eukaryotic amoeba preys on bacteria, using lysosomes to digest food in a process called phagocytosis.
• The amoeba extends its membrane around the prey, forming a food vacuole.
• Lysosomes fuse with the vacuole, and enzymes turn the prey into monomers.
• Monomers are released and used as a food source or energy, and then the lysoosmes deactivate.
• Molecules that cannot be digested are released.
• Lysosomes contain digestive enzymes that can digest proteins, nucleic acids, lipids, and carbohydrates.
• Life consists of three domains: eukarya, archea, and bacteria.
• Archaea use histones (proteins) to package DNA and have membranes made of glycerol-ether lipids.
• Archaea all have a common ribosomal RNA sequence.
• Endosymbiosis occurs when one species lives inside another and can be positive or negative.
• Eukaryotes arose from endosymbiosis; each cell has over 10,000 mutualistic endosymbionts in mitochondria.

Mitochondria and endosymbiosis

• Mitochondria receive food and oxygen, while the host cell receives ATP.
• The merging of mitochondria and archaea is the key component of evolution.
• Eukaryotic compartmentalization evolved first and then endosymbiosis took place.
• A prokaryotic cell lost its cell wall, leaving membrane and genetic material.
• Infolding of the membrane developed an internal membrane system with ER and vacuoles,.
• Loss of the cell wall will enable it to carry out phagocytosis.
• A bacterial cell was not digested and became a mitochondrion.
• Eukaryotic cells engulfed cyanobacteria, which performs photosynthesis.
• Engulfed cells evolved over time into chloroplasts in plants/algae.
• A cell that took up mitochondria would have been archaea.
• Mitochondria and chloroplasts have double membranes and a looped chromosome.
• Double membranes allow for more diffusion to occur.
• Mitochondria and chloroplasts reproduce through binary fission similar to bacteria.
• Evidence for the endosymbiotic origins of mitochondria and chloroplasts includes the fact that they have double membranes and possess their own DNA and looped chromosome.
• Eukaryotic origin model 2- bacterial cell enters archea and becomes proto-mitochondrion, secretes vesicle in new host (archea).
• Vesicles become the source for the nuclear membrane -Nuclear membrane will protect genetic material. Additional vesicles produce the ER and other organelles of endomembrane system.
• In a phylogenetic tree, the gaining of a bacterial cell by a eukarya cell that led to a chloroplast is arrow 5.
• The arrow or letter that indicates the origin of eukarya through the uptake of mitochondria is "A".
• A double membrane provides increased surface area and volume.
• Cell membranes are selectively permeable, only allowing specific substances to pass.
• Membranes are the reason bodies know which cells belong and which don't.
• The hydrophilic phosphate group of phospholipid molecules are attracted to aqueous environment.

Cell Membranes

• Some integrals span the entire width of membranes and act as pumps.
• Peripheral proteins bind or unbind from the membrane on the polar exterior and are involved in cell signaling.
• Alpha helices run through and act as signal receptors.
• Integral proteins are built into the hydrophobic portion of the membrane.
• Channels help molecules that otherwise would not get in get through cell membrane.
• Carbs play a role in cell recognition, therefore the membrane knows which cells belong to it .
• Diffusion refers to the movement of particles from a high to low concentration area.
• Osmosis is diffusion involving water.
• Simple diffusion does not require energy or a channel, and molecules are small and nonpolar like oxygen.
• Facilitated diffusion is passive but requires protein pores to diffuse polar molecules, such as proteins, because interior phospholipid tails of cell membrane are nonpolar.
• Small nonpolar molecules can diffuse directly through the cell membrane.
• Osmosis occurs when water will move from an area of higher water concentration to an area of lower water concentration, therefore cell will likely swell.
• Active transport requires ATP to work and flows up the concentration gradient.
• Na+, Cl, Ca*+, Cl- or H⁺ can only pass through membranes through protein channels because they're big, charged and and polar.

Endocytosis and Exocytosis

• Endocytosis is when the membrane pinches in, creating a pocket that surrounds material, and requires energy.
• Pinocytosis involves the small piece of the membrane pinching in until a vesicle forms.
• Phagocytosis involves a large piece of the membrane surrounding a particle/cell, which is then swallowed into the cytoplasm.
• Phagocytosis is used by white blood cells to swallow invaders.
• In receptor-mediated endocytosis, a molecule binds with a receptor embedded in the membrane
• Exocytosis is the opposite of endocytosis; a vesicle fuses with the cell membrane, releasing its contents.
• B cells export proteins they've manufactured through exocytosis.
• Hypertonic solutions have more solute and less solvent, causing cells to shrink.
• Hypotonic solutions have less solute and more solvent, causing cells to swell.
• Isotonic solutions have equal concentrations, thus cells remain the same size.
• Water potential is potential energy of water per unit area compared to pure water.
• It measures how easy water is to move between areas.
• Water potential is built on solute potential and pressure potential, which are added together.
• Osmosis refers to the concentration of solutes.
• Water flows from hypotonic to hypertonic.
• If there are more solute molecules, there have to be fewer water molecule
• Osmotic pressure happens after osmosis and amount of pressure stops solvent from moving.
• Since the left side has a lower water potential, water will move to that side.
• In the experiment to determine water potential, adding solute lowers water potential.
• The force will counteract the force of solution potential and is known as gravity.
• Downward increases pressure potential, which increases water potential.
• Therefore, water moves from a high to low potential.
• Charged oxygen binds with a charged solute and keeping it stuck.
• Water molecules are randomly moved in both directions, however, once water molecules diffuse into hypertonic side, interact and get stuck.
• In animal cells, water will go outside the cell causing it to cell. in hypotonic its ideal for animals. In hypertonic it is a ideal state causing loss of water & the cell will deflate.
• In plant cells, having cell walls, therefore has diff reactions.
• Plasmolyzed cells have a loss of water which cause the vacuoles contrac.
• Flaccid cells are limp because nothing else happens when in a cell because there is no water, is a constand volune.
• Turgid state is when the vacuole expands and the cell is also pushign causing an ideal condition for plants, since its solid and firm, and will not burst.
• Bigger surface gives more space for diffusion, diffusion happen better.
• Cells that have smaller siE sizes have SA bigge SA:V ratious.

Volume and Surface Area

• During diffusion, smaller area and volume is what helps be better at diffusion. But when the cell grows bigger, the surface area is bigger volume and makes it be faster during diffusion.
• Cells need to be big enough in surface and water to thrive.
• Volume grows much bigger than surface area.
• The area will provide most resources to supply and maintain with more resources.
• Osmolarity: is the water and concentraiotns, therefreo water moves because if much solitu, better with low concentration (passive transport)
• The ratio is what determines if surfacea is better thatn diffusion, diffiusion ocicur faster since much bigger.
• As cells grow, their surface area and volume increase but not to the same rate. The volume increases more and is more cubi, therefore it is getting ready for diffusion to get to cell.