AP Bio Unit 2

  1. What do the structures of a prokaryotic cell consist of?

  • circular DNA, cell wall, plasma membrane, cytoplasm, ribosomes, and plasmids. Other structures worth mentioning are flagella, pili, fimbriae, and capsules.

  • The cell wall is a rigid outer layer that provides structure and protection

  • the plasma membrane is a lipid bilayer that controls the movement of substances into and out of the cell. it acts as a respiratory center, carrying respiratory enzymes.

  • everything is found within the cytoplasm; it contains a gel-like cytosol that contains ions, small molecules, and macromolecules

  • ribosomes are the small structures responsible for protein synthesis; it should be noted that prokaryotic ribosomes are slightly smaller than eukaryotic ribosomes.

  • the nucleoid is an irregularly shaped region that contains the cell’s DNA which is circular and not enclosed in a nucleus

  • plasmids are small, circular DNA molecules that are separate from the main chromosomal DNA. They often carry genes that provide advantages, like antibiotic resistance.

  • Flagella are long, whip-like structures used for movement in some prokaryotes

  • pili and fimbriae are hair-like structures that help the cell adhere to surfaces and in some cases, they exchange genetic material between cells

  • the capsule is a thick, sticky outer layer that provides additional protection and also helps the cell adhere to surfaces.

  1. What do the structures of a eukaryotic cell consist of?

    • the structures of a eukaryotic cell consist of several membrane-bound organelles: the nucleus, the plasma/cell membrane, the cell wall, the cytoplasm/ cytoskeleton, mitochondria, endoplasmic reticulum, ribosomes, Golgi apparatus, lysosomes, chloroplasts, vacuoles, peroxisomes, centrosomes/centrioles

  • the nucleus is the control center of the cell, containing the cell’s DNA which is organized into chromosomes. within the nucleus is the nucleolus, a dense area responsible for ribosome production. the nuclear membrane is a double-layered membrane that protects the nucleus and controls the passage of materials in and out through nuclear pores.

  • the plasma (cell) membrane is a phospholipid bilayer that surrounds the cell, regulating what enters and exits. it is embedded with proteins, carbohydrates, and cholesterol which help with cell communication, structural integrity, and selective permeability.

  • the cytoplasm is a jelly-like substance that fills the cell and provides a medium for chemical reactions and holding organelles in place. the cytoskeleton is a network of protein filaments that gives the cell shape, support, and enables movement of materials within the cell

  • the mitochondria are known as the powerhouse of the cell, where ATP is generated through cellular respiration. the mitochondria is also the primary site of metabolic respiration. it has a double membrane with a highly folded inner membrane called the cristae to maximize surface area for ATP production.

  • the endoplasmic reticulum consists of two: the rough endoplasmic reticulum (RER) and the smooth endoplasmic reticulum (SER). the rough endoplasmic reticulum is studded with ribosomes and is involved in protein synthesis and modification. the SER on the other hand lacks ribosomes and is involved with lipid synthesis (including steroid hormones), detoxification, and calcium storage.

  • the Golgi apparatus modifies, sorts, and packages proteins and lipids for transport. it receives transport vesicles with materials from the endoplasmic reticulum; it packages materials into new transport vesicles that exit the membrane via exocytosis.

  • the lysosomes (which are more prominent in animal cells) break down waste materials and cellular debris. they contain enzymes that digest cellular waste, old organelles, and foreign particles. they are formed by the Golgi apparatus and bounded by a single membrane. they contain hydrolytic enzymes that digest worn-out organelles, food particles, and viruses/bacteria.

  • the chloroplasts are present within plant cells; here, photosynthesis is conducted, converting sunlight into glucose. chlorophyll is what causes the green dye in these plants

  • the cell wall, also present in plant cells, provides additional support, protection, and shape to the cell.

  • the vacuoles store water, nutrients, and waste, as well as prevent cell contamination

  • it is worth noting that peroxisomes break down fatty acids and amino acids and detoxify harmful substances. they also produce hydrogen peroxide as a byproduct and contain catalase to break it down. centrosomes and centrioles are involved in organizing microtubules and are essential for cell division in animal cells.

  1. what are the two domains for prokaryotic cells?

    • The two different domains of prokaryotes are bacteria and archaea

  2. which evolved first: prokaryotic cells or eukaryotic cells?

    • prokaryotic cells evolved first.

  3. where do all the reactions necessary for life take place in a prokaryotic cell? like the production of atp?

    • in a prokaryotic cell, which lacks membrane-bound organelles, all the essential reactions for life take place in the cytoplasm and across the plasma membrane. the ATP is formed through a series of electron transfer reactions within the cytoplasmic membrane. prokaryotic cells rely on their cytoplasm for many metabolic pathways and the plasma membrane for energy production synthesis

  4. why would a large number of ribosomes be needed in a cell?

    • protein synthesis is essential to the function of all cells– large numbers of ribosomes are present in cells that specialize in producing proteins.

  5. What is a phospholipid?

    • a phospholipid is a type of lipid molecule that is a major component of cell membrane. each phospholipid is composed of a hydrophilic head and a hydrophobic tail. phospholipids make up two layers in cell membranes; they organize themselves into a double layer with their hydrophilic heads facing toward the water environments inside and outside of the cell. their hydrophobic tails point inwards, away from the water. proteins are embedded within this phospholipid bilayer

  6. Where are proteins that are to be exported from the cell synthesized?

    • Proteins that are to be exported from the cell are synthesized by ribosomes that are attached to the rough endoplasmic reticulum.

  7. In animal cells, where would you find the DNA?

    • DNA is found in the nucleus of an animal cell.

  8. Describe a feature shared by some organelles that increases the efficiency of their basic functions:

    • both the mitochondria and the endoplasmic reticulum have highly folded membranes that compartmentalize reactions and other metabolic processes

  9. Describe what occurs in the Golgi apparatus:

    • it modifies, sorts, and packages proteins and lipids that are synthesized in the cell for transport to their final destinations, either inside or outside the cell. proteins received from the ER are further processed and sorted for transport to their eventual destinations.

  10. Describe the process of protein synthesis and shipment from the cell:

    • RER → Golgi → cell membrane

    • the DNA in the nucleus contains the instructions for building proteins. the first step in protein synthesis is the transcription of a gene into messenger RNA (mRNA). the mRNA then exits the nucleus through the nuclear pores and enters the cytoplasm where it is translated. proteins that are destined for secretion, incorporation into the cell membrane, or packaging into organelles (like lysosomes) are synthesized by ribosomes that are attached to the surface of the RER. inside the RER proteins begin to fold into a 3D shape and may undergo initial modifications.

    • the Golgi apparatus packages and modifies. once the protein is synthesized and properly folded, it is transported in a vesicle from the RER to the Golgi Apparatus. the Golgi further processes the protein, making any additional modifications; then the Golgi sorts and packages the protein into new vesicles

    • the cell membrane ensures vesicle transport, after the Golgi processes and sorts the protein, the protein is then packaged into a vesicle that will transport it to the cell membrane. the cell membrane is the final vesicle transport to the plasma membrane for secretion or membrane incorporation.

  11. Smaller cells have a high SA:V ratio so they’re able to exchange materials in less time, making them more efficient