Chapter 3 Cell Structure and Function Flashcards
4 basic concepts of the cell theory:
- Cells are the building blocks of all plants and animals
- Cells are the smallest functioning units of life
- Cells are produced through the division of pre-exisitng cells
- Each cell maintains homeostasis
Cytology
The study of the structure and function of cells
Our model body cell is surrounded by a watery medium known as:
extracellular fluid
Cytoplasm can be subdivided into:
a liquid - the cytosol, and intracellular structures - organelles
What is the cell membrane?
the outer boundary of the cell; aka plasma membrane
What are the general functions of the cell membrane?
- physical isolation: separates the inside of the cell from the extracellular fluid
- regulation of exchange with the environment: control the entry of ions and nutrients, the elimination of wastes, and the release of secretions
- sensitivity: it is the first part of the cell affected by changes in the extracellular fluid
- structural support
The cell membrane ranges from ____ to ____ nm in thickness.
6 to 10
Phospholipids are a major component of cell membranes. In a phospholipid, a phosphate group serves as a link between:
a diglyceride and a nonlipid “head”
How do the phospholipids in a cell membrane lie?
with the hydrophilic (soluble in water) heads on the outside, and the hydrophobic (insoluble in water) tails on the inside
Passive processes move ions or molecules across the cell membrane:
without any energy expenditure by the cell
Active processes require that the cell:
expend energy, usually in the form of adenosine triphosphate (ATP)
An ion or molecule can independently diffuse across a cell membrane in one of two ways:
- by moving across the lipid portion of the membrane
2. by passing through a channel protein in the membrane
Osmosis
The diffusion of water across a membrane
Three important characteristics of osmosis:
- Osmosis is the diffusion of water across a membrane
- Osmosis occurs across a selectively permeable membrane that is freely permeable to water but is not freely permeable to solutes
- In osmosis, water flows across a membrane toward the solution that has the higher concentration of solutes, because that is where the water concentration is lower.
Isotonic solution
one that does not cause a net movement of water into or out of the cell
Hypotonic solution
water will flow into the cell
Hypertonic solution
water will flow out of the cell
When placed in a hypertonic solution, a red blood cell will:
lose water by osmosis; called crenation
Carrier-mediated transport
membrane proteins bind specific ions or organic substrates and carry them across the cell membrane
Active transport
the high-emery bond in ATP provides the energy needed to move ions or molecules across the membrane. The cell can import or export specific materials regardless of their intracellular or extracellular concentrations
Sodium ion concentrations are:
high in the extracellular fluid but low in the cytoplasm
Potassium ion concentrations are:
low in the extracellular fluid but high in the cytoplasm
The sodium-potassium exchange pump
maintains sodium and potassium concentration gradients across the cell membrane by ejecting sodium ions and recapturing lost potassium ions. For each ATP molecule consumed, three sodium ions are ejected and two potassium ions are reclaimed by the cell
Vesicular transport
materials move into or out of the cell in vesicles, which are small membranous sacs that form at, or fuse with, the cell membrane
The two major categories of vesicular transport are:
endocytosis and exocytosis
Cytoplasm
a general term for the material inside the cell, from the cell membrane to the nucleus
The cytoplasm contains ____ and ____
cystol and organelles
Microvilli
small, finger-shaped projections of the cell membrane on the exposed surfaces of many cells. They absorb materials from the extracellular fluid
Centrioles
a cylindrical structure composed of short microtubules. They produce the spindle fibers that move DNA strands during cell division
Cilia
relatively long, slender extensions of the cell membrane. Their coordinated actions move fluids or secretions across the cell surface
Flagella
resemble cilia but are much longer. They move a cell through the surrounding fluid
Ribosomes
organelles that manufacture proteins, using information provided by the DNA of the nucleus
Golgi apparatus
consist of a set of five or six flattened, membranous discs.
Lysosomes
vesicles filled with digestive enzymes; perform cleanup and recycling functions within the cell
Mitochondria
small organelles that provide energy for the cell