cell communication:

Algae and Protozoans (Protists)

E — Eukaryotic. Protists have a nucleus containing their DNA and membrane-bound organelles.

Bacteria

P — Prokaryotic. Bacteria lack a membrane-bound nucleus and other membrane-bound organelles.

Have ribosomes

A — All cells have ribosomes, which synthesize proteins.

Have a cell membrane

A — All cells have a cell membrane that regulates what enters and leaves the cell.

Have DNA in a nucleus

E — Eukaryotic. Eukaryotic cells have a membrane-bound nucleus containing their DNA. Prokaryotic cells do not have a nucleus.

Have a cytoskeleton

A — All cells have cytoskeletal structures or proteins that help maintain organization and support cellular functions.

Archaea

P — Prokaryotic. Archaea lack a membrane-bound nucleus and membrane-bound organelles.

Fungi

E — Eukaryotic. Fungal cells have a nucleus and membrane-bound organelles.

All eukaryotic autotrophs have chloroplasts. How does the endosymbiont theory explain the origin of the chloroplast? In your answer, describe the symbiotic relationship and cite at least 3 pieces of evidence to support the theory.

The endosymbiont theory states that chloroplasts evolved from photosynthetic bacteria that were engulfed by an ancestral eukaryotic cell. Instead of being digested, the bacteria lived inside the host in a mutually beneficial relationship: the host provided protection and resources, while the bacteria produced sugars through photosynthesis. Evidence includes chloroplasts having their own circular DNA, bacterial-like ribosomes, and a double membrane. Chloroplasts also reproduce through a process similar to bacterial binary fission.

Cells that line the small intestine look like this: How is the cell structure related to its function? Be sure to state the function of these cells.

The function of these cells is to absorb nutrients from digested food in the small intestine. The diagram shows intestinal cells with microvilli, which are tiny projections of the cell membrane. These increase the surface area, allowing nutrients to be absorbed more efficiently.

Three things that plant cells have that animal cells do not are:

Cell walls made of cellulose, chloroplasts in photosynthetic cells, and a large central vacuole. The cell wall provides support, chloroplasts carry out photosynthesis, and the central vacuole stores water and helps maintain turgor pressure.

The diagram below shows the production of insulin in a pancreatic cell. Label the cell parts in the 3 blank boxes.

The three structures are the endoplasmic reticulum, Golgi apparatus, and vesicles. The endoplasmic reticulum helps synthesize and process insulin, the Golgi apparatus modifies and packages it, and vesicles transport insulin for secretion.

What kind of molecule is insulin?

Insulin is a protein hormone, specifically a peptide hormone, produced by pancreatic beta cells to help regulate blood glucose levels.

What kind of molecule is the insulin gene?

The insulin gene is DNA, a nucleic acid containing the instructions for producing insulin.

Label the process shown by the arrow going from the insulin gene to the insulin mRNA.

Transcription. During transcription, RNA polymerase uses DNA as a template to produce messenger RNA (mRNA).

Extra credit (up to 2 points). Choose ONE: Explain the role of transcription factors in the expression of the insulin gene.

Transcription factors are proteins that bind to specific DNA sequences and help regulate gene expression. In pancreatic beta cells, they help control the transcription of the insulin gene into mRNA by regulating the transcription machinery.

Extra credit (up to 2 points). Choose ONE: What step of gene expression is left out of this diagram? Describe that process briefly.

Translation is the missing step. A ribosome reads the codons in insulin mRNA, and transfer RNAs bring the corresponding amino acids to build a polypeptide. The polypeptide is then processed to form functional insulin.

QUIZ: CHAPTER 5 — QUESTION 1. Draw a section of the cell membrane, showing the orientation of the phospholipids and labelling the parts of one phospholipid. Label the inside and outside of the cell.

The cell membrane is a phospholipid bilayer. Draw two rows of phospholipids with hydrophilic phosphate heads facing the watery environments outside and inside the cell and hydrophobic fatty acid tails pointing inward toward each other. Label one hydrophilic phosphate head and its two hydrophobic fatty acid tails. Label the extracellular side as outside and the cytoplasmic side as inside.

The enzyme lactase is a transmembrane protein that converts lactose to glucose and galactose inside the lumen of the large intestine. Why can't glucose and galactose simply diffuse across the cell membrane? For full credit, refer to properties of glucose and galactose as well as the molecules that make up the cell membrane.

Glucose and galactose cannot easily diffuse through the phospholipid bilayer because they are relatively large, polar molecules. The membrane's interior is made of hydrophobic fatty acid tails, which restrict the passage of polar substances. Therefore, glucose and galactose need membrane transport proteins to cross the cell membrane.

People who do not produce the lactase enzyme often have diarrhea (too much water in their stool) if they drink milk. Using what you know about osmosis, explain why this would happen. Use scientific vocabulary.

Lactase normally breaks lactose into glucose and galactose, which can be absorbed by the small intestine. Without enough lactase, lactose remains in the intestinal lumen and increases its solute concentration. Water moves by osmosis toward the region with the higher effective solute concentration, so more water remains in the intestine. This causes watery stool and diarrhea.

The sodium potassium pump moves ___ (give a number) sodium ions ___ (in or out) for every ___ potassium ions ___ (in or out).

The sodium-potassium pump moves 3 sodium ions out of the cell for every 2 potassium ions into the cell. It uses energy from ATP to move these ions against their concentration gradients.

A white blood cell (macrophage) engulfs a virus-infected cell through the process of ___.

Phagocytosis. This type of endocytosis allows a cell to engulf large particles or entire cells by surrounding them with its plasma membrane.

The difference between having blood type A and blood type B has to do with what type molecules on membranes?

The difference involves carbohydrate antigens on the surface of red blood cell membranes. Type A blood has A antigens, while type B blood has B antigens. These carbohydrate structures are attached to membrane glycoproteins and glycolipids.

What hormone instructs cells to take glucose out of the bloodstream? What kind of cell signaling is this an example of?

Insulin instructs responsive cells to take up glucose from the bloodstream. This is endocrine signaling because the hormone travels through the blood to reach target cells.

A cell releases a growth factor instructing another cell to divide. This is an example of what kind of cell signaling?

Paracrine signaling, assuming the growth factor acts on a nearby cell. The signaling cell releases a chemical messenger that binds to receptors on the target cell and stimulates a response such as cell division.

Neurons communicate through synaptic signaling. One neuron releases ___ by the process of ___. These chemical signals then bind to the receptors of the receiving cell.

A neuron releases neurotransmitters by exocytosis. The neurotransmitters cross the synaptic cleft and bind to specific receptors on the receiving cell, triggering a response.

True/False: All cells in our body respond the same way to the same hormone.

False. Different cells have different receptors and intracellular signaling pathways, so the same hormone can cause different responses in different target cells. Cells without the appropriate receptor generally do not respond to that hormone.

What is the point of a phosphorylation cascade in signal transduction?

A phosphorylation cascade relays and amplifies a signal inside the cell. Protein kinases phosphorylate downstream proteins, allowing the signal to activate additional signaling steps and produce a larger cellular response.

Proteins are activated when they have been ___ (phosphorylated or dephosphorylated).

Proteins can be activated by phosphorylation or dephosphorylation, depending on the specific protein and pathway. Adding or removing a phosphate group can change a protein's shape and activity, but phosphorylation does not always activate every protein.

Use the diagram below to explain how the signal molecule testosterone results in a cellular response. Scientific vocabulary please.

The diagram shows testosterone crossing the plasma membrane and binding to an intracellular receptor. The hormone-receptor complex then interacts with DNA and regulates gene transcription, producing mRNA. The mRNA is translated by ribosomes into a new protein, which contributes to the cellular response.