Cytology: Cell Size Limitation and Components

Cell Biology

• The ability of a solution to affect the fluid volume in a cell is referred to as its tonicity.
• Insulin is transported across endothelial cells through a process called transcytosis.
• White blood cells engulf bacteria through phagocytosis.
• cAMP activates enzymes called kinases, which regulate other enzymes by adding phosphate groups to them.
• Hepatocytes have large amounts of smooth endoplasmic reticulum for detoxifying drugs or other chemicals.
• The cytoskeleton provides structural support, determines the shape of a cell, and directs the movement of substances through a cell.
• Microvilli increase a cell's surface area, cilia act as sensory "antennae" in many cells, and flagella provide motility to a sperm cell.

Cellular Transport

• Na+-K+ ATPase is a countertransport antiport carrier that always requires energy.
• Facilitated diffusion does not require energy and can transport molecules down a concentration gradient.
• The greater the concentration gradient, the faster the diffusion rate.

Cell Structure and Function

• The nucleus and the mitochondrion are surrounded by a two-layer membrane.
• In the plasma membrane, glycolipids and glycoproteins face toward the outside, while peripheral proteins face toward the cytoplasm.
• Most human cells range from 10 to 15 micrometers in diameter, and the limit to how large a cell can get is the relationship between the cell's volume and surface area.
• The three basic components of a cell are cytoplasm, nucleus, and plasma membrane.
• Phospholipids are the most abundant molecules in the plasma membrane.

Cell Signaling and Communication

• Membrane proteins that bind to signals by which cells communicate are called receptors.
• The term selectively permeable refers to a membrane that allows some things to pass through it, but not others.

Osmosis and Filtration

• Osmosis is the process by which hydrostatic pressure forces water and small solutes through narrow clefts between capillary cells.
• The number of particles of a solute in a solution is described by its osmolarity.