BIO-250 Microbiology Lecture Test Study Guide

All cells share basic features:
- Bounded by a selective barrier called the plasma membrane (or cell membrane).
- Contain a semifluid substance known as cytosol, in which subcellular components are suspended.
- Contain chromosomes that carry genes in the form of DNA.
- Possess ribosomes, which are tiny complexes that synthesize proteins according to gene instructions.

Major differences in DNA location:
- In eukaryotic cells, most DNA is localized in an organelle called the nucleus, which is surrounded by a double membrane.
- In prokaryotic cells, DNA is located in a region called the nucleoid, which is not membrane-enclosed.
Cytoplasm:
- Refers to the interior of both prokaryotic and eukaryotic cells.
- In eukaryotic cells, cytoplasm includes the region between the nucleus and plasma membrane.
- Eukaryotic cells have various membrane-bound organelles suspended in cytosol.
- Prokaryotic cells typically lack membrane-bounded structures, although specific reaction regions surrounded by proteins may exist.

Two primary types of eukaryotic cells exist:
- Animal cells
- Plant cells
Example: Humans are composed of eukaryotic animal cells.

Function: Acts as a selective barrier allowing the passage of oxygen, nutrients, and wastes necessary for cell function.
This property is termed Selective Permeability.

The plasma membrane and organelle membranes are composed of:
- A double layer (bilayer) of phospholipids.
- Various proteins either attached to or embedded within the bilayer.
Distribution of Phospholipids:
- Hydrophobic regions are located internally with hydrophilic portions exposed to aqueous solutions on both sides.
Carbohydrates:
- Carbohydrate side chains can be attached to proteins or lipids on the outer surface of the plasma membrane.

Description: The most prominent organelle within the cell; contains the majority of genes in eukaryotic cells (some genes also exist in mitochondria and chloroplasts).
Characteristics of the nucleus:
- Typically the most noticeable organelle.
- Surrounded by a nuclear envelope, which is a double membrane consisting of two lipid bilayers with associated proteins.
- Contains nuclear pores—structures that perforate the nuclear envelope.
Nucleolus:
- The dark center of the nucleus responsible for ribosome synthesis.
Ribosomes:
- Composed of ribosomal RNAs and proteins; vital for protein synthesis.

Function: Major biosynthetic factory within eukaryotic cells; it makes up over half the total membrane.
Consists of two distinct regions:
- Smooth ER:
- Lacks ribosomes on its surface, hence appearing smooth.
- Importance: Synthesizes lipids, including oils, steroids, and phospholipids.
- Key products include sex hormones and various steroid hormones secreted by adrenal glands.
- Rough ER:
- Studded with ribosomes on its outer surface, causing a rough appearance under an electron microscope.

Function: Acts as a warehouse for receiving, sorting, shipping, and manufacturing molecules.
Process:
- Transport vesicles containing products from the ER, such as proteins, travel to the Golgi apparatus.
- Proteins in the Golgi are modified, stored, and directed towards various destinations.

Definition: Membranous sacs filled with hydrolytic enzymes.
Functions:
- Used by eukaryotic cells for intracellular digestion (hydrolysis) of macromolecules.
- Some human cells, such as macrophages, utilize lysosomes to perform phagocytosis, which involves engulfing and destroying bacteria and other pathogens.

Definition: Organelles referred to as the powerhouses of the cell.
Function: Sites of cellular respiration, utilizing oxygen to facilitate the production of ATP by extracting energy from sugars, fats, and other fuels.