A&P cellular biology (2)

Question 1

cytoplasm

Answer 1

CYTOPLASM**
Includes everything that is between the plasma membrane and the nucleus and consists of 2 parts:
a) Cytosol – the fluid portion of the cytoplasm (makes up *approx 55% of cell volume) which is made of water (70% – 90%) and dissolved solutes.
Major site of chemical reactions that take place w/in the cell.
b) Organelles – “little organs” – specialized structures with characteristic shapes that contribute to the overall functioning and metabolic processes of the cell.

Question 2

organelles–

Answer 2

CYTOSKELETON – the components that make up the shape and structure of a cell.

Question 3

3 types of cytoskeleton a)

Answer 3

a. MICROFILAMENTS – smallest of the 3 cytoskeleton structures
Composed of ACTIN protein usually on the outer edge/part of the cytoskeleton.
Involved in movement and support of shape and structure of a cell.
Play a role in muscle contraction, cell division, cell locomotion.
Helps anchor the cytoskeleton to the integral proteins of the cell membrane.
Helps forms micro-villi (projections of the cell membrane to increase surface areas of certain cells; found mainly in epithelial cells).

Question 4

b)

Answer 4

b.INTERMEDIATE FILAMENTS – medium sized (of the 3)
Made up of several different proteins (inc. keratin).
Aids in internal stability of a cell & keeps organelles in specific positions within the cell.
Helps in cell to cell junctions (connections b/w cells).

Question 5

c)

Answer 5

MICROTUBULES – largest of the 3 cytoskeleton structures
Composed mainly of the protein tubulin.
Long and hollow – produced in the centrosome and helps determine a cell’s shape, movement of organelles (e.g. vesicles) and chromosomes during cell division.
Forms external mobility structures such as cilia* and flagellum*.

Question 6

CENTROSOME makes more sense with cell division

think-microtubules/ nuclear division

Answer 6

Microtubule organizing center*
Involved in mitosis & meiosis (cell division).
There are 2 centrosomes in each cell.
Always found near the nucleus and consists of:
(CENTRIOLES – a pair of cylindrical structures composed of 9 clusters of 3 microtubules.
Pericentriolar material – contains tubulin protein to help build microtubules. Surrounds the centrioles and forms the starting point for mitotic spindles during mitosis )(more later).

Question 7

Motility and Mobility Structures

Answer 7

Composed mainly of MICROTUBULES found on the external surface of cells.

a) CILIA – hair like projections that move in coordination to give the cell mobility (as in egg cells down the fallopian tubes) or to sweep foreign particles along an epithelial lining (as in the respiratory tracts).
b) FLAGELLUM – long, tubular-shaped, whip-like structure that propels the cell forwards. Found only in sperm cells.

Question 8

Ribosomes

Answer 8

Responsible for MAKING PROTEINS AKA protein synthesis
Can be free floating or attached to the endoplasmic reticulum (ER). (rough)
Free floating = make proteins for use in the cytosol.
Attached to ER = make proteins destined for other orangelles, exocytosis, or the cell membrane.
Composed of 2 separate subunits, made in the nucleus but assembled in the cytosol.
Also found in the mitochondria where it helps synthesize enzymes.
Appear as tiny little granules under a microscope.

Question 9

Endoplasmic Reticulum (ER)

Answer 9

Network of flattened tubules or sacs that extend from the nuclear membrane to throughout the cytosol.

*Smooth ER – NO ribosomes – produce FAs and glycolipids
In LIVER cells:
Detoxifies drugs, stores and releases Ca2+
Catabolizes glucose 6-phospate to release “free” form of glucose into the blood stream (glycogen to glucose)
In muscle cells:
The equivalent of the smooth ER is called the sarcoplasmic reticulum, which stores and releases Ca2+

*Rough ER – contains ribosomes – #1 role is PROTEIN SYNTHESIS b/c of the presence of ribosomes.
Continuous with the nuclear membrane
Produces phospholipids and glycoproteins for internal cell use in organelles or plasma membrane or for secretion. ie. Hormones.

Question 10

note

Answer 10

DNA is contained in the nucleus of the cell
Amino acids are organized by ribosomes via protein synthesis from the DNA template (mRNA)
The polypeptide string of amino acids is transported to the golgi body for modification/packaging & shipping out

Question 11

Golgi complex/bodies/apparatus (GBs)

Answer 11

Transports, receives, modifies proteins arriving from the rough ER (LIKE ups PACKAGING)
The more complex and numerous the golgi complex, the more secretory role the cell plays.
Has 3 main steps that pass through CISTERNAE – small sacs in the GB (looks like a stack of pita bread)
–Entry/CIS face – convex side, facing the rough ER, receives the protein via transport vesicles
–Medial cisternae – modifies with enzymes to become glyco(sugar)proteins or lipo(fat)proteins.
–Exit/trans face – concave side that releases the finished product to go onto other processes or to be *EXOCYTOSED from the cell.

Question 12

Enzyme Vesicles a)

Answer 12

a. LYSOSOMES
Contain DIGESTIVE and HYDROLYTIC enzymes that digest absorbed substances in vesicles.
Acidic pH for optimal enzyme functioning (most enzymes function in a pH <7)
May be autophagy – destroys the organelle it engulfs
May be autolysis – destroys the entire cell with it
e.g. Suicide (APOPTOSIS) white blood cells in an immune response (the WBC engulfs the entire microbe but self-destructs in the process).

Question 13

Enzyme Vesicles b) and c)

Answer 13

b. PEROXISOMES – aka microbodies
Similar in function to lysosomes; these contain oxidase enzymes that remove H+ from organic molecules
As a by-product of normal metabolism in the presence of O2 & H2O, oxidative enzymes create H2O2 (hydrogen peroxide) which is toxic to cells (it causes rusting in metals, & oxidation of apples).
BUT it also contains catalase enzymes, which in turn break down or neutralize the H2O2.

c. PROTEOSOMES
Contain protein degrading enzymes called proteases.
Useful in cleaning up the cytoplasm once PROTEINS have performed their function, allowing the amino acids from the degraded proteins to be recycled.

Question 14

Mitochondria

Answer 14

The “POWERHOUSE” of the cell – generates ATP through aerobic metabolism (requires O2).
Present in all cells but much more numerous in highly active cells (i.e. muscle and nerve cells).
Has an outer and inner membrane; convolutions found throughout called CRISTAE (folds). The internal space between cristae (folds) called matrix is where most reactions take place.
Contains ribosomes & its own set of DNA as part of its ability to self-replicate proteins for normal functioning.

Question 15

note

Answer 15

Ribosomes present in the mitochondria help in the synthesis of proteins involved in metabolism.
Cells that aren’t as metabolically active have few mitochondria (e.g. adipose and skin cells). other highly active cells have many (e.g. nerve and muscle cells).

Question 16

Nucleoli (pl) - Nucleolus (sgl)

(this is where ribosomes are made)

Answer 16

Nucleoli (pl) - Nucleolus (sgl) – spherical bodies made up of clusters of RNA, DNA & protein, that produce rRNA and ribosomal subunits (present normally in cell as spherical bodies, scatters prior to and during cell division, reorganizes afterwards).

Question 17

Chromatin

Answer 17

– the DNA, RNA, & proteins scattered throughout the nucleus prior to cell division. Appears as a diffuse, granular mass when the cell is not dividing. The chromatin will cluster and form chromosomes prior to cell division.

Question 18

Genes

Answer 18

– segments of DNA that encode for specific traits and characteristics (i.e. hair color, eye color, skin tone, etc.)

Question 19

DNA

Answer 19

– double helix – the coiled structure of nucleotides (pentose sugars, phosphate groups and nitrogenous bases)

Question 20

Chromosomes

Answer 20

– the arrangement of chromatin fibers during cell division (exists only during cell division).
Humans have 46 chromosomes in total, or 23 pairs (1 set from each parent). These pairs are called homologous chromosomes (#1 - #22) -autosomes
The sex chromosomes (pair #23), may be XX (female) or XY (male).

Question 21

Genome

Answer 21

– the total genetic information of the organism carried in the nucleus of cells.
The Human Genome Project (HGP) was completed and the entire genome (approx 30,000 genes) was mapped out in 2003 (it took 13 years and the combined efforts of scientists and geneticists from all over the world)

Question 22

Histones

Answer 22

– protein balls that a DNA double helix coils around to help organize its coiling and folding.

Question 23

Nucleosome

Answer 23

– combination of histones & clusters of double-stranded DNA.
Linker DNA – the section of double-stranded DNA that links nucleosomes together.

Question 24

Chromatin fiber

Answer 24

– section of many nucleosomes & linker DNAs in a row.

Question 25

Chromatids

Answer 25

– ½ of a chromosome. 1 pair of chromatids = 1 chromosome.

Question 26

Centromere

Answer 26

– the central portion of a chromosome that holds the 2 sister chromatids together.

Question 27

Telomeres

Answer 27

– the terminal (end) portions of the chromosomes (believed to protect the gene sequences found there).

Question 28

DNA polymerase

Answer 28

the enzyme that copies the DNA template of 1 strand to form a new strand which is:
Complementary to the original strand
Identical to the partner of the original strand
DNA H holds HELICASE the DNA strands in place

Question 29

C. NUCLEUS

Answer 29

The “Brain” of the cell – responsible for genetics & protein synthesis which guide the functioning and survival of the cell (analogous to the CPU of a computer).

Most cells have at least 1 nucleus, some have more (i.e. muscle cells), and some have NONE (i.e. mature red blood cells).

The nucleus has its own double membrane nuclear envelope that separates it from the cytoplasm (similar to plasma membrane).

Extending throughout the nuclear envelope are tiny nuclear pores made of proteins which allow molecules to enter/exit the nucleus (e.g. proteins coming in, RNA going out).