Cell Biology for Nursing School Entrance Exam Study Guide

Practice questions for this study guide can be found at:

Cell Biology for Nursing School Entrance Exam Practice Problems

1. Definition of a Cell

The cell is the structural and functional unit of life. The Cell Doctrine, generally credited to Schleiden (1838) and Schwann (1839), maintains that:

• All living things are made up of cells and the products formed by cells.
• Cells are units of structure and function.
• All cells arise from preexisting cells.
2. Two Types of Cells
   1. Prokaryotic Cells

   Prokaryotic cells: cells found only in bacteria and cyanobacteria (formerly known as blue-green algae). These cells lack a true nucleus and organelles, and have a cell wall and a cell membrane.

   2. Eukaryotic Cells

   Eukaryotic cells: cells found in all organisms except bacteria. These cells are differentiated by membranes into subcellular structures called organelles, including a nucleus.

3. Organization of a Cell
   1. Prokaryotic Cells

   Prokaryotes (bacteria and cyanobacteria) do not have:

   • a nucleus (DNA is throughout the cell and in rings called plasmids.)
   • mitochondria
   • chloroplasts
   • Golgi apparatus
   • lysosomes
   • vacuoles
   • cilia or flagella
   • centrioles

   Prokaryotes do have:

   • a cell membrane
   • a cell wall
   • single chromosome, with DNA only
   • ribosomes
   2. Eukaryotic Cells

   Eukaryotes include animals and plants.

   Animal cells do not have:

   • a cell wall
   • chloroplasts

   Animal cells do have:

   • a cell membrane
   • a nucleus
   • chromosomes (multiple, with DNA and protein)
   • ribosomes
   • mitochondria
   • Golgi apparatus
   • lysosomes (often)
   • vacuoles (sometimes—they may be small or there may be none)
   • cilia or flagella (often)
   • centrioles

   Plant cells do not have:

   • cilia or flagella
   • centrioles

   Plant cells do have:

   • a cell membrane
   • a nucleus
   • a cell wall
   • chromosomes (multiple, with DNA and protein)
   • ribosomes
   • mitochondria
   • chloroplasts (in photosynthetic cells)
   • Golgi apparatus
   • plastids
   • lysosomes
   • vacuoles (one large single vacuole in a mature cell)
4. Energy Transformation in a Cell
   1. General Discussion of Energy

   The two concepts most basic to science are matter and energy.

   Matter: anything that has mass and takes up space (volume).

   Energy: the capacity to do work; a more abstract concept that can be described only as it affects matter.

   There are two types of energy: kinetic and potential.

   2. Thermodynamics

   Thermodynamics: the physics of what is and is not possible with regard to energy.

   First law of thermodynamics: Energy can be transferred and transformed, but it cannot be created or destroyed (conservation of energy).

   Second law of thermodynamics: Every energy transfer or transformation results in the release of heat from the system to the rest of the universe.

   3. Cell Metabolism

   Cell metabolism: energy management by a cell. The complex structure of a cell includes pathways along which metabolism proceeds, aided by enzymes.

   Bioenergetics: the study of how organisms manage energy, including heat production and transfer; and regulation of body temperature (endothermy and ectothermy).

   Metabolism: the totality of chemical reactions that take place in an organism.

   Anabolism: the metabolic synthesis of proteins, fats, etc., from simpler molecules; requires energy in the form of adenosine triphosphate (ATP).

   Catabolism: the metabolic breakdown of molecules (for example, respiration).

   Cellular respiration: a catabolic pathway for the production of ATP, in which oxygen is sometimes consumed as a reactant along with an organic fuel (food). At other times, the process proceeds without atmospheric oxygen, but this is less efficient.

   • Anaerobic pathway of cellular respiration: Food (especially carbohydrates) is partially oxidized and chemical energy is released; however, atmospheric oxygen is not involved in the process.
   • Aerobic pathway of cellular respiration: Food is completely oxidized to carbon dioxide and water, and chemical energy is released; atmospheric oxygen is involved in the process. The Krebs cycle, electron-transport chain, and oxidative phosphorrylation are important concepts here.

   Photosynthesis: conversion of light energy into chemical energy, on which, directly or indirectly, all living things depend. Photosynthesis occurs in plants, algae, and certain prokaryotes.

   4. Enzymology

   Enzymology: the study of the speed of the process of transformation of energy in a cell; enzymes change the rate of a reaction without themselves being consumed by that reaction.

   5. Movement of Molecules

   Small molecules are steadily transported across the cell membrane. Types of transport include diffusion and passive transport; osmosis (a special case of passive transport); and active transport.

5. Cell Reproduction
   1. General Discussion of Cell Reproduction

   All cells arise from other cells. The basis of all biological reproduction is cell division. A single, intact chain of life extends backward from today to the first bacteria on Earth.

   Prokaryotes often reproduce simply, by binary fission, or division into identical halves. Eukaryotes have much more complicated genomes, and therefore, the process of reproduction is more complex.

   2. The Cell Cycle

   The cell cycle describes the entire life cycle of a cell including reproduction that occurs in an orderly sequence.

   M phase—division of nucleus and cytoplasm.

   • Mitosis: division of the nucleus; distribution of nuclear materials, particularly chromosomes. For descriptive purposes, mitosis is divided into phases: prophase, prometaphase, metaphase, anaphase, and telophase.
   • Cytokinesis: division of the cytoplasm into two identical daughter cells, which occurs during the telophase stage of mitosis.

   Interphase—cell grows and copies chromosomes.

   • G1 phase: vegetative, non-reproductive functions. The "restriction point'' is here, just before DNA synthesis—if "no-go,'' the cell exits from cell cycle and enters G0 phase, the resting phase.
   • S phase: DNA of nucleus doubles.
   • G2 phase: mitosis proper.
   • Back to M phase.
   3. Control of Cell Division

   A certain timing and rate of division are necessary to normal growth. Cell division can be interfered with by lack of nutrients, poisons, lack of growth factors (for example, platelet-derived growth factor or PDGF), cell size, and density.

   4. When Things Go Wrong

   In abnormal cell division (e.g., cancer), cells do not heed the restriction point in GI phase; they may divide excessively, invading surrounding tissue. If given enough nutrients, they may divide "forever'' (see "immortal'' or HeLa cells); or abnormal cells may stop dividing at any point in the cell cycle, not just at the restriction point.