Cell biology

Question 1

What is a cell?

Answer 1

the smallest structural and functional unit of an organism which is typically microscopic and consists of cytoplasm and a nucleus enclosed in a membrane.

Question 2

Structure of prokaryotic cell?

Answer 2

No nucleus and no organelles.

Flagellum, Inclusion, Plasmid, Cytoplasm, Cell membrane, Cell wall, Capsule or slime layer, Ribosomes, Plus (fimbria), Chromosome

Question 3

Structure of eukaryotic cell?

Answer 3

Endoplasmic reticulum (smooth and rough), nucleus,, nucleolus, cytosol, ribosomes, cytoskeleton, mitochondrion, peroxisome, Golgi body, lysosome, plasma membrane

Question 4

Key differences between prok and euk cells?

1. Genetic organisation
2. Cell compartmentalisation
3. Metabolism
4. Protein synthesis
5. Protein/lipid transport
6. Energy metabolism
7. Cell structure and transport
8. Cell mobility
9. Water balance.

Answer 4

1. Circular vs linear DNA
2. Cell membrane with subcompartments not membrane enclosed vs Plasma membrane with membrane enclosed organelles
3. Cytoplasm (same)
4. Ribosomes (same)
5. Cytoplasm vs Endomembrane system
6. Cell membrane vs mitochondria/chloroplasts
7. Thin protein filaments in cytoplasms vs protein tubules and filaments in cytoplasm.
8. Bacterial flagella vs eukaryotic flagella or cillia
9. Cell wall

Question 5

Functions of the cell (5)

Answer 5

1. Take up nutrients and generate energy,
2. Remove growth inhibitory or waste products.
3. Synthesise proteins and other components required for structure, growth and/or function.
4. Respond to environment/ stimuli.
5. Control the exchange of material between and/or within cells.

Question 6

What do cells form?

Answer 6

Tissues which form organs which form systems :)

Question 7

Types of tissue?

Answer 7

Neural, muscle, empithelial, connective, blood tissue and Extracellular matrix

Question 8

Glial cells function?

Answer 8

surround neurons for instance astrocytes which regulate the microenvironment of neurons and microglial- the immune cells of the nervous system.

Question 9

What is extracellular matrix?

Answer 9

the non-cellular portion of a tissue produced and secreted by cells and mainly for providing support.

Question 10

Functions of extracellular matrix?

Answer 10

cell adhesion, intercellular communication and segregation of tissues, can form an organized lattice.

Question 11

What is the function of the nervous tissues?

Answer 11

nervous tissues that sense stimuli and transmit signals throughout the body. There are nerve cells on neurons that are specialized for communicating through the initiation and transmittion of the electrical impulses.

Question 12

What is the function of the muscle tissue?

Answer 12

capable of actively contracting thereby causing motion, either local motion or movement within the internal organs.

Question 13

What are the distinct categories of muscle tissues?

Answer 13

• smooth muscle - found in the linings of the organs such as the intestine/arteries or veins.
• Skeletal muscle - moves joints and is voluntarily controlled.
• cardiac muscle – in which the adjacent cells are literally electrically linked so that they can contract synchronously.

Question 14

What does epithelial tissue consist of?

Answer 14

comprised of epithelial cells (which form coherent sheets called epithelia)

Question 15

What is the function of epithelial tissue?

Answer 15

• epithelia line the surfaces of the body, cover the internal organs and act as a barrier as well as having some specialized functions.
• For example: skin, the lining of the mouth and nasal cavity etc. all made out of epithelia.

Question 16

What is endothelia?

Answer 16

specific type of epithelia which also forms the inner lining of all blood vessels.

Question 17

What are types of specialized epithelial cells?

Answer 17

1. Those that line the loomen of the intestine (have numerous hair like microvilli) on the surface which faces the loomen to increase the surface area for absorption of nutrients
2. Secretary type of epithelial cells: can collect together to form glans that specialise in secretion of substance eg. tears, mucus

Question 18

What is an example of connective tissue?

Answer 18

Type of tissue comprised of very few cells held together by the ECM.

Bone is an example of a highly-specialized connective tissue.

Question 19

What is blood tissue?

Answer 19

often considered a subset of the connective tissue, contains several different types of cells eg. erythrocytes, leucocytes, platelets.

Question 20

Building blocks of cells? (4)

Answer 20

Fatty acids, Sugars, Nucleotides, Aminoacids.

Question 21

Describe each of the building blocks?

Answer 21

FA: components of cell membrane, long hydrocarbon chain (hydrophobic) + carboxylic acid group (hydrophilic)- invaluable source of energy.

SU: The food molecules for the cell.

NU: sub-units of DNA, RNA. Phosphate group+ deoxyribose+ nitrogenous base. Joined together by phosphodiester linkage. Can carry chemical energy in their bonds and combine with other groups to form enzymes.

AM: building blocks of proteins, joined together via peptide bond. Can be broken down for energy.

Question 22

How are monomers linked?

Answer 22

Each sugar is linked to the next via the phosphate
group, creating a polymer chain composed of a repetitive sugar-phosphate
backbone with a series of bases protruding from it.

Question 23

How is DNA synthesized?

Answer 23

As a template formed by preexisting DNA strand through templed polymerization.

Question 24

What are the steps of DNA replication?

Answer 24

Step 0:
• DNA is packed into tightly coiled structures called chromatin.
• Prior to DNA replication, the chromatin loosens giving cell replication machinery access to the DNA strands.

Stage 1: Unzipping of the DNA into two strands:

• DNA helicase disrupts the hydrogen bonding between the base pairs to separate the strands into a Y shape known as a replication fork.
• DNA is directional in both strands, signified by 5’ and 3’end.
• The5’ endhas a phosphate (P) group attached, while the3’ endhas a hydroxyl (OH) group attached.
• Replication only progresses in the 5’ to 3’ direction, however, the replication fork is bi-directional; one strand is oriented in the 3’ to 5’ direction (leading strand) while the other is oriented 5’ to 3’ (lagging strand).

Stage 2: Primer binding:

• Leading strand is simplest to replicate.
• Once DNA strands have been separated, a piece of RNA called a primer binds to the 3’ end of the strand.
• Primers are generated by the enzyme DNA primase.

Stage 3: Elongation:

• Enzymes DNA polymerases create a new strand by a process called elongation
• There are five known different types of DNA polymerases in bacteria and human cells.
• In bacteria such as E.coli, polymerase III is the main replication enzyme, while polymerase I and II, IV and V are responsible for error checking and repair.
• DNA polymerase III binds to the strand at the site of the primer and begins adding new base pairs complementary to the strand during replication.
• In eukaryotic cells, polymerases alpha, delta, and epsilon are the primary polymerases involved in DNA replication.
• The lagging strand begins replication by binding with multiple primers. Each primer is several bases apart.
• DNA polymerase then adds pieces of DNA, calledOkazaki fragments, to the strand between primers.

Stage 4: Termination:

• Once both strands are formed, exonuclease removes all RNA primers from the original strands- those are then replaced with appropriate bases.
• Another enzyme called DNA ligase joins Okazaki fragments together forming a single unified strand.
• A special type of DNA polymerase enzyme calledtelomerasecatalyzes the synthesis of telomere sequences at the ends of the DNA. Once completed, the parent strand and its complementary DNA strand coils into the familiardouble helixshape.

Question 25

Differences between DNA and RNA?

Answer 25

Both; nitrogen containing base, phosphate group.

Ribose in RNA vs deoxyribose in DNA.