Outer boundary of cell
– Separates the extracellular fluid from the intracellular fluid (cytosol)
• More fluid-like, than rigid, structure
• Creates a selectively permeable barrier
– Allows some, not all, substances across it
• Composed of a phospholipid bilayer
– Type of lipid with hydrophobic and hydrophilic portions
• Contains carbohydrates, proteins, cholesterol
– Carbohydrates are always on the external face
• Attached to membrane proteins and lipids
– Ex. glycoproteins, glycolipids
• Many function as cell “identity” markers for immune system
– Proteins can be integral (embedded) or peripheral (attached to the inner or outer surface)
• Integral membrane proteins function as receptors, channels, transporters, and pumps
– Cholesterol increases the membrane’s strength
The intracellular region containing the cytosol and the organelles, excluding the nucleus. Consists of: Cytosol, Cytoskeleton, & Organelles
Gel-like intracellular fluid. Contains dissolved substances. Bathes the organelles.
The largest organelle. Enclosed by the nuclear membrane. Contains most of the cell’s DNA.
Protein filaments that function in cell support and movement. (A collection of protein filaments including MICROTUBULES, ACTIN FILAMENTS, & INTERMEDIATE FILAMENTS)
Intracellular structures and compartments. Each performs specific functions. Many, but not all, are enclosed by their own membrane
(Ex. The nucleus )
The plasma membrane of some cells contains microscopic folds, called microvilli. They greatly increase the surface area of the cell. Microvilli are present on cells lining the small intestines, where they increase the surface area for nutrient absorption.
Cilia are projections (made of particular cytoskeletal filaments) that move substances across the cell surface. (Examples of ciliated cells: Cells lining the trachea [windpipe] & Cells lining the uterine tube [fallopian tube])
Cell projection (contains particular cytoskeletal filaments) that functions to move the cell. (Only flagellated cell in humans is sperm)
Movement of a substance from an area of higher concentration to an area of lower concentration.
Factors that increase the rate of diffusion
1) Rise in temperature
2) Smaller molecule size
3) Higher concentration gradient
4) Shorter distance
Factors the decrease the rate of diffusion
1) Drop in temperature
2) Bigger molecule size
3) Lower concentration gradient
4) Longer distance
Movement of the solvent from a solution with lower solute concentration to a solution with a higher solute concentration through a selectively permeable membrane.
The concentration of a solution outside of a cell compared to with the concentration of the cytosol.
3 types of Tonicity
A hypotonic solution has a lower solute concentration than the cytosol. A cell placed in a hypotonic solution will gain water by osmosis and may swell and burst. (CELLS SWELL)
An isotonic solution has the same solute concentration as the cytosol. There is no concentration gradient to drive osmosis, so there is no net movement of water into or out of a cell in an isotonic solution. (CELLS STAY THE SAME)
A hypertonic solution has a higher solute concentration than the cytosol. A cell in a hypertonic environment will lose water by osmosis and shrivel or CRENATE, because water will be drawn toward the more concentrated solution. (CELLS SHRINK)
8 types of Organelles
4) Endoplasmic reticulum
5) Golgi apparatus
The small, granular ribosomes are not surrounded by a membrane and are composed of two subunits. Some ribosomes float freely in the cytosol, whereas others are bound to the membrane of another organelle or the nucleus. Ribosomes are the sites of protein synthesis in the cell.
The small, vesicular organelles known as peroxisomes contain enzymes that detoxify chemicals produced by cellular reactions, metabolize fatty acids, and synthesize certain phospholipids.
The bean-shaped mitochondria are double-membrane-bounded organelles that produce the bulk of the cell’s ATP (energy).
The series of membrane-enclosed sacs known as the endoplasmic reticulum may be of two types: ROUGH ENDOPLASMIC RETICULUM, or RER, which has ribosomes on its surface, and SMOOTH ENDOPLASMIC RETICULUM, or SER, which lack ribosomes. RER functions in protein synthesis and modifies proteins that the ribosomes have made. SER has multiple functions, including lipid synthesis and detoxification reactions.
The Golgi apparatus is a stack of flattened sacs near the RER. Its membrane-enclosed sacs receive vesicles from the RER and other places in the cell and process, modify, and sort the products with in the vesicles.
Lysosomes are sacs filled with digestive enzymes that digest particles brought into the cell, old and worn-out organelles, and even the cell itself.
Centrioles are paired organelles composed primarily of microtubules that are located in the central area of the cell called the CENTROSOME. They appear to be microtubule organizing centers and are important in facilitating the assembly and disassembly of microtubules.
Specialized organelle. The nucleus is the cell’s biosynthetic center, which directs the synthesis of all of the body’s proteins, as well as certain nucleic acids. The nucleus is surrounded by a double membrane called the NUCLEAR ENVELOPE, which contain holes called NUCLEAR PORES. Within the nucleus we find CHROMATIN, a ball-like mass of tightly coiled DNA and proteins; RNA; and a dark-staining region called the NUCLEOLUS. The nucleolus contains a type of RNA called RIBOSOMAL RNA and is the “birthplace” of ribosomes.
Composition of the Plasma Membrane
It is composed of a phospholipid bilayer with multiple components interspersed throughout, including INTEGRAL PROTEINS, PERIPHERAL PROTEINS, CHOLESTEROL, GLYCOPROTEINS, & GLYCOLIPIDS. It is a dynamic, fluid structure that acts as a selectively permeable barrier. In parts of the body where rapid absorption is necessary, the plasma membrane is folded into projections called MICROVILLI, which increase its surface area.
Head is polar (Hydrophilic); 2 “tails” are non-polar (Hydrophobic)
What makes cholesterol?