Chapter 2: The Cell and Its Function Flashcards
2 major parts of the cell
Nucleus and Cytoplasm
What structure separates the nucleus from the cytoplasm?
Nuclear membrane
What structure separates the cytoplasm of the cell from the surrounding fluids?
cell membrane or plasma membrane
The different substances that make up the cell is called the:
protoplasm
5 basic substances that compose the protoplasm:
Water Electrolytes Proteins Lipids Carbohydrates
According to Guyton, most cells are comprised mainly of water. With the EXCEPTION of ______ cells
Fat cells (adipocytes)
**In fat cells (adipocytes), triglycerides often account for as much as 95% of the cell mass.
Average water concentration of the cell:
70-85%
Which of the following ions is found only in smaller quantities in the cell? A. Bicarbonate B. Calcium C. Phosphate D. Magnesium
B. Calcium
Important ions in the cell include potassium, magnesium,
phosphate, sulfate, bicarbonate, and smaller quantities
of sodium, chloride, and calcium.
After water, the most abundant substances in the cells are:
Proteins
Proteins constitute what percentage of the cell mass?
10-20%
Which type of proteins present in the cell are mainly in the form of long filaments that are polymers of many individual protein molecules?
Structural proteins
The other type is the functional protein
What structure provides the cytoskeletons of cellular organelles such as cilia, nerve axons, mitotic spindles, and tangled mass of thin filamentous tubules that that hold the parts of the cytoplasm and nucleoplasm together in their respective compartments?
Microtubules
These structural proteins are found outside the cell, especially in the collagen and elastin fibers of connective tissue, and elsewhere, such as in blood vessel walls, tendons, and ligaments.
Fibrillar proteins
- *Microtubules - structural proteins inside
- *Fibrillar proteins - structural proteins outside
These types of proteins are mainly the enzymes of the cell and, in contrast to the fibrillar proteins, are often mobile in the cell fluid.
Functional proteins
Which type of cellular protein is adherent to membranous structures inside the cell and catalyzes specific intracellular chemical reactions?
Functional proteins
**These proteins are mainly the enzymes of the cell and, in
contrast to the fibrillar proteins, are often mobile in the
cell fluid.
Phospholipids and cholesterol together constitute __% of the total cell mass?
2%
Phospholipids and cholesterol are mainly insoluble in water and therefore are used to form the cell membrane and intracellular
membrane barriers that separate the different cell compartments.
Lipid component of the cell that is known as “neutral fat”
Triglyceride
These cells store the body’s main storehouse of energy-giving nutrients that can later be used to provide energy wherever it is needed in the body.
Adipocytes
**In fat cells (adipocytes), triglycerides often account for as much as 95% of the cell mass. The fat stored in these cells represents the body’s main storehouse of energy-giving nutrients that can later be used to provide energy wherever it is needed in the body.
What is the maximum amount of carbohydrates stored in muscle and liver cells? (percentage)
3% in muscle cells and 6% in liver cells
**Most human cells do not maintain large stores of carbohydrates; the amount usually averages only about 1% of their total mass but increases to as much as 3% in muscle cells and, occasionally, to 6% in liver cells.
This is the insoluble polymer of glucose that can be depolymerized and used rapidly to supply the cell’s energy needs
Glycogen
**carbohydrate in the form of dissolved glucose is always present in the surrounding extracellular fluid so that it is readily available to the cell. Also, a small amount of carbohydrate is stored in cells as glycogen, an insoluble polymer of glucose that can be depolymerized and used rapidly to supply the cell’s energy needs.
The loss of which organelle will result to immediate cessation of 95% of the cell’s energy release from nutrients?
Mitochondria
In membranes of organelles, protein molecules often penetrate all the way through membranes, thus providing specialized pathways, often organized into actual ______, for passage of specific substances through membranes
Pores
The approximate percent composition of the cell membrane as to proteins:
55%
55% proteins 25% phospholipids 13% cholesterol 4% other lipids 3% carbohydrates
The approximate percent composition of the cell membrane as to phospholipids:
25%
55% proteins 25% phospholipids 13% cholesterol 4% other lipids 3% carbohydrates
The approximate percent composition of the cell membrane as to cholesterol
13%
55% proteins 25% phospholipids 13% cholesterol 4% other lipids 3% carbohydrates
The approximate percent composition of the cell membrane as to carbohydrates
3%
55% proteins 25% phospholipids 13% cholesterol 4% other lipids 3% carbohydrates
The thin, double-layered film of lipids that is continuous over the entire cell surface
Lipid bilayer
** The basic structure of the cell membrane is a lipid bilayer, which is a thin, double-layered film of lipids—each layer only one molecule thick—that is continuous over the entire cell surface. Interspersed in this lipid film are large globular proteins.
What are the 3 main types of lipids that compose the basic lipid bilayer?
Phospholipids
Sphingolipids
Cholesterol
What is the amino alcohol component of the lipid, found mostly in nerve cell membranes, which serves several functions, including protection from harmful environmental factors, signal transmission, and adhesion sites for extracellular proteins?
Sphingosine
**Sphingolipids, derived from the amino alcohol sphingosine, also have hydrophobic and hydrophilic groups and are present in small amounts in the cell membranes, especially nerve cells. Complex sphingolipids in cell membranes are thought to serve several functions, including
protection from harmful environmental factors, signal
transmission, and adhesion sites for extracellular proteins.
Which lipid component of the cell membrane determines the degree of permeability (or impermeability) of the bilayer to water-soluble constituents of body fluids?
Cholesterol
**Cholesterol controls much of the fluidity of the membrane as well.
These protein structures on the cell membrane have selective properties that allow preferential diffusion of some substances over others.
Channels or pores (integral proteins)
**Many of the integral proteins provide structural channels (or pores) through which water molecules and water-soluble substances, especially ions, can diffuse between extracellular and intracellular fluids. These protein channels also have selective properties that allow preferential
diffusion of some substances over others.
Which of the following is unable to penetrate the lipid layer of the cell membrane? A. Oxygen B. CO2 C. Urea D. Alcohol
C. Urea
**The lipid layer in the middle of the membrane is
impermeable to the usual water-soluble substances, such as ions, glucose, and urea. Conversely, fat-soluble
substances, such as oxygen, carbon dioxide, and alcohol, can penetrate this portion of the membrane with ease.
Which integral proteins of the cell membrane allow transport of substances that otherwise could not penetrate the lipid bilayer?
Carrier proteins
The process by which carrier proteins transport substances in the direction opposite to their electrochemical gradients for diffusion
Active transport
These molecules bind and interact with cell membrane receptors causing conformational changes in the receptor protein, which in turn enzymatically activates the intracellular part of the part of the protein or induces interactions with second messengers.
Ligands
These are proteins in the cytoplasm that relay signal from the extracellular art of the receptor to the interior of the cell
Second messengers
Which types of cell membrane protein provides a means of conveying information
about the environment to the cell interior?
Integral proteins
This type of cell membrane protein functions almost entirely as enzymes or as controllers of transport of substances through cell membrane pores.
Peripheral proteins
These molecules comprise most of the integral proteins of the cell membrane
glycoproteins
About one-tenth of the cell membrane lipid molecules are:
glycolipids
These compounds, attached loosely to the outer surface of the cell, are carbohydrates bound to small protein cores.
proteoglycans
The loose carbohydrate coat of the entire outside surface of the cell
Glycocalyx
Which of the main molecular compositions of the cell membrane gives it a negative electrical charge?
Carbohydrates
- *The carbohydrate moieties attached to the outer surface of the cell have several important functions:
1. Many of them have a negative electrical charge, which gives most cells an overall negative surface charge that repels other negatively charged objects.
Which of the following is an important function of the carbohydrate moieties of the outer surface of the cell?
A. Allow repulsion to other negatively changes objects
B. Provide a mechanism of attachment to other cells
C. Act as receptors
D. For immune reactions
E. All of the above
Function of carbs of the outer cell membrane:
“NARI”
- Negative charge for repulsion
- Attachment to other cells via the glycocalyx
- Receptors (e.g. insulin)
- Immune reactions
14ed20
This is the jelly-like fluid portion of the cytoplasm in which the particles are dispersed, containing mainly dissolved proteins, electrolytes, and glucose
Cytosol
This is a network of tubular structures in the endoplasmic reticulum
Cisternae
What is the watery medium in the space inside the tubules and vesicles of the ER that is different from the fluid in the cytosol?
Endoplasmic matrix
Electron micrographs show that the space inside the endoplasmic reticulum is connected with the space between the two membrane surfaces which organelle?
Nucleus
“Electron micrographs show that the space inside the endoplasmic reticulum is connected with the space between the two membrane surfaces of the nuclear membrane.”
There are minute granular particles attached to the outer surfaces of many parts of the endoplasmic reticulum
Ribosomes
**The ribosomes are composed of a mixture of RNA and proteins; they function to synthesize new protein molecules in the cell
This organelle functions for the synthesis of lipid substances
Smooth (Agranular) Endoplasmic Reticulum
This organelle is usually composed of four or more stacked layers of thin, flat, enclosed vesicles lying near one side of the nucleus.
Golgi apparatus
The Golgi apparatus is prominent in which type of cells?
Secretory cells
**This apparatus is prominent in secretory cells, where it is located on the side of the cell from which secretory substances are extruded
These are small cellular structures that are pinched off from the ER and shortly thereafter fuse with the Golgi apparatus.
Transport vesicles
also called ER vesicles
What intracellular materials are typically digested by lysosomes?
- damaged cellular structures
- food particles that have been ingested by the cell
- unwanted matter such as bacteria
What is the usual diameter of a lysosome?
250-750 nanometers in diameter
What does the lipid bilayer membrane of the lysosomes contain?
hydrolase (digestive) enzymes
**Lysosomes are surrounded by typical lipid bilayer membranes and are filled with large numbers of small granules, 5 to 8 nanometers in diameter, which are protein aggregates of as many as 40 different hydrolase (digestive) enzymes
This type of enzyme is capable of splitting an organic compound into 2 or more parts by combining hydrogen from a water molecule with one part of the compound and combining the hydroxyl portion of the water molecule with the other part of the compound.
Hydrolytic enzymes
What are the products of the hydrolysis of protein, glycogen, and lipid?
Protein = amino acids Glycogen = glucose Lipid = fatty acids and glycerol
How are peroxisomes believed to be formed?
By self-replication or by budding off from the sER
What enzymes do peroxisomes contain?
oxidases