Question

review #20
which is most likely true of prokaryotic cells?
they are large, complex cells.
their dna is contained in the nucleus.
their organelles are surrounded by membranes.
they evolved on earth before eukaryotic cells.
which purpose does a cell membrane play in eukaryotic cells?
it digests waste.
it maintains homeostasis.
it translates cellular proteins.
it creates energy to fuel cell processes.
a cow and a frog have similar bone structures in their forelimbs. both have phalanges and radius, ulna, and humerus bones. however, the cow and frog are animals with very different life cycles from each other. which most likely describes why the body structures of these animals are so similar?
both have undergone similar mutations.
both descended from a common ancestor.
both reacted similarly to environmental pressures.
both spread out from the same geographical region.
this diagram shows three different ways molecules can move from one side of a cell membrane to the other. which movement(s) of molecules across the cell membrane is active transport?
y only
z only
x and y
x and z
which factor best explains how many diseases, such as cancer, are formed within the body?
a traumatic injury to the body has occurred.
a disruption in the cell cycle has taken place.
a response by the immune system was triggered by an allergic reaction
a mutation occurred during the process of crossing over.

Explanation:

1. Prokaryotic cells are simple, small cells without a membrane-bound nucleus or membrane-bound organelles. The fossil record confirms they appeared ~3.5 billion years ago, before eukaryotic cells (~2.7 billion years ago).
2. The eukaryotic cell membrane is a selectively permeable barrier that regulates the movement of substances in and out of the cell to maintain a stable internal environment (homeostasis). Lysosomes digest waste, ribosomes translate proteins, and mitochondria produce energy.
3. Similar bone structures in distantly related animals are homologous structures, which form because the organisms share a common tetrapod ancestor that had this forelimb layout.
4. Active transport moves molecules against their concentration gradient (from low to high concentration). Movement Z is the only one moving molecules from an area of low concentration on the top of the membrane to high concentration on the bottom.
5. Most cancers form when mutations disrupt the cell cycle's regulatory checkpoints, leading to uncontrolled, unregulated cell division.

Answer:

1. They evolved on Earth before eukaryotic cells.
2. It maintains homeostasis.
3. Both descended from a common ancestor.
4. Z only
5. A disruption in the cell cycle has taken place.