celulas, partes y función

Question 1

CHEMICAL LEVEL -

Answer 1

includes all chemical substances necessary for life (see, for example, a small portion - a heme group - of a hemoglobin molecule); together form the next higher level

Question 2

CELLULAR LEVEL -

Answer 2

cells are the basic structural and functional units of the human body & there are many different types of cells (e.g., muscle, nerve, blood, and so on)

Question 3

TISSUE LEVEL

Answer 3

a tissue is a group of cells that perform a specific function and the basic types of tissues in the human body include epithelial, muscle, nervous, and connective tissues

Question 4

ORGAN LEVEL -

Answer 4

organ consists of 2 or more tissues that perform a particular function (e.g., heart, liver, stomach, and so on)

Question 5

SYSTEM LEVEL -

Answer 5

an association of organs that have a common function; the major systems in the human body include digestive, nervous, endocrine, circulatory, respiratory, urinary, and reproductive.

Question 6

membrane

Answer 6

Functions include:
supporting and retaining the cytoplasm
being a selective barrier
The cell is separated from its environment and needs to get nutrients in and waste products out. Some molecules can cross the membrane without assistance, most cannot. Water, non-polar molecules and some small polar molecules can cross. Non-polar molecules penetrate by actually dissolving into the lipid bilayer. Most polar compounds such as amino acids, organic acids and inorganic salts are not allowed entry, but instead must be specifically transported across the membrane by proteins.
transport
Many of the proteins in the membrane function to help carry out selective transport. These proteins typically span the whole membrane, making contact with the outside environment and the cytoplasm. They often require the expenditure of energy to help compounds move across the membrane
communication (via receptors)

Question 7

Cytoplasm

Answer 7

Cytoplasm consists of a gelatinous solution and contains microtubules (which serve as a cell’s cytoskeleton) and organelles (literally ‘little organs’)

Question 8

Endoplasmic reticulum -

Answer 8

comes in 2 forms: smooth and rough; the surface of rough ER is coated with ribosomes; the surface of smooth ER is not
functions include: mechanical support, synthesis (especially proteins by rough ER), and transport

Question 9

Golgi complex -

Answer 9

consists of a series of flattened sacs (or cisternae)
functions include: synthesis (of substances likes phospholipids), packaging of materials for transport (in vesicles), and production of lysosomes
consists of a series of flattened sacs (or cisternae)
functions include: synthesis (of substances likes phospholipids), packaging of materials for transport (in vesicles), and production of lysosomes

Question 10

Lysosomes -

Answer 10

membrane-enclosed spheres that contain powerful digestive enzymes
functions include destruction of damaged cells (which is why they are sometimes called ‘suicide bags’) & digestion of phagocytosed materials (such as bacteria)

Question 11

Mitochondria -

Answer 11

• Have a double-membrane: outer membrane & highly convoluted inner membrane
• Inner membrane has folds or shelf-like structures called cristae that contain elementary particles; these particles contain enzymes important in ATP production
• Primary function is production of adenosine triphosphate (ATP)

Question 12

Ribosomes-

Answer 12

composed of rRNA (ribosomal RNA) & protein
may be dispersed randomly throughout the cytoplasm or attached to surface of rough endoplasmic reticulum
often linked together in chains called polyribosomes or polysomes.
primary function is to produce proteins

Question 13

Centrioles -

Answer 13

paired cylindrical structures located near the nucleas

play an important role in cell division

Question 14

Flagella & cilia -

Answer 14

hair-like projections from some human cells
cilia are relatively short & numerous (e.g., those lining trachea)
a flagellum is relatively long and there’s typically just one (e.g., sperm)

Question 15

Villi -

Answer 15

projections of cell membrane that serve to increase surface area of a cell (which is important, for example, for cells that line the intestine)

Question 16

DNA (Deoxyribonucleic acid) -

Answer 16

controls cell function via transcription and translation (in other words, by controlling protein synthesis in a cell)

Question 17

Transcription -

Answer 17

DNA is used to produce mRNA

Question 18

Translation -

Answer 18

mRNA then moves from the nucleus into the cytoplasm & is used to produce a protein

requires mRNA, tRNA (transfer RNA), amino acids, & a ribosome
sequence of amino acids in a protein is determined by sequence of codons (mRNA). Codons are ‘read’ by anticodons of tRNAs & tRNAs then ‘deliver’ their amino acid.
Amino acids are linked together by peptide bonds (see diagram to the right)
As mRNA slides through ribosome, codons are exposed in sequence & appropriate amino acids are delivered by tRNAs. The protein (or polypeptide) thus grows in length as more amino acids are delivered.

Question 19

Water:

Answer 19

comprises 60 - 90% of most living organisms (and cells)

important because it serves as an excellent solvent & enters into many metabolic reactions

Question 20

ION

Answer 20

atoms or molecules with unequal numbers of electrons and protons:
found in both intra- & extracellular fluid
examples of important ions include sodium, potassium, calcium, and chloride

Question 21

Carbohydrates:

Answer 21

about 3% of the dry mass of a typical cell
composed of carbon, hydrogen, & oxygen atoms (e.g., glucose is C6H12O6)
an important source of energy for cells
types include:
-monosaccharides (e.g., glucose) - most contain 5 or 6 carbon atoms.

-disaccharides
monosaccharides linked together
Examples include sucrose (a common plant
disaccharide is composed of the monosaccharides glucose and fructose) & lactose (or milk sugar; a disaccharide composed of glucose and the monosaccharide galactose)

-polysaccharides
several monosaccharides linked together
Examples include starch (a common plant polysaccharide made up of many glucose molecules) and glycogen (commonly stored in the liver)

Question 22

PROTEINS

Answer 22

about 50 - 60% of the dry mass of a typical cell
subunit is the amino acid & amino acids are linked by peptide bonds
2 functional categories = structural (proteins part of the structure of a cell like those in the cell membrane) & enzymes
Enzymes are catalysts. Enzymes bind temporarily to one or more of the reactants of the reaction they catalyze. In doing so, they lower the amount of activation energy needed and thus speed up the reaction.

Question 23

LIPIDS

Answer 23

about 40% of the dry mass of a typical cell
composed largely of carbon & hydrogen
generally insoluble in water
involved mainly with long-term energy storage; other functions are as structural components (as in the case of phospholipids that are the major building block in cell membranes) and as “messengers” (hormones) that play roles in communications within and between cells

Question 24

Nucleic Acids:

Answer 24

DNA

RNA (including mRNA, tRNA, & rRNA

Question 25

Simple diffusion

Answer 25

net movement of a substance from an area of high concentration to an area of low concentration. The rate of diffusion is influenced by:
concentration gradient
cross-sectional area through which diffusion occurs
temperature
molecular weight of a substance
distance through which diffusion occurs

Question 26

Osmosis =

Answer 26

diffusion of water across a semipermeable membrane (like a cell membrane) from an area of low solute concentration to an area of high solute concentration

Question 27

Facilitated diffusion =

Answer 27

= movement of a substance across a cell membrane from an area of high concentration to an area of low concentration. This process requires the use of ‘carriers’ (membrane proteins). In the example below, a ligand molecule (e.g., acetylcholine) binds to the membrane protein. This causes a conformational change or, in other words, an ‘opening’ in the protein through which a substance (e.g., sodium ions) can pass.

Question 28

Active transport =

Answer 28

= movement of a substance across a cell membrane from an area of low concentration to an area of high concentration using a carrier molecule

Question 29

Endo- & exocytosis -

Answer 29

moving material into (endo-) or out of (exo-) cell in bulk form

Question 30

Glycolysis

Answer 30

involves the breakdown of glucose. Cells obtain glucose from the blood. Blood glucose levels are maintained by the interaction of two processes: glycogenesis and glycogenolysis

Question 31

Glycogenesis

Answer 31

Glycogenesis is the production of glycogen from glucose and occurs (primarily in the liver and skeletal muscles) when blood glucose levels are too high (for example, after a meal).

Question 32

Glycogenolysis

Answer 32

Glycogenolysis is the reverse process - the breakdown of glycogen to release individual molecules of glucose. This occurs when blood glucose levels begin to decline (for example, several hours after a meal). The interaction of these two processes tends to keep blood glucose levels relatively constant.