animal cell structure and function

Question 1

list the components of the cell

Answer 1

• nucleus
• nucleolus
• nuclear envelope with nuclear pores
• chromatin
• lysosome
• smooth endoplasmic reticulum
• rough endoplasmic reticulum
• ribosome
• mitochondria
• golgi body
• cytoplasm
• plasma membrane

Question 2

what is the structure of the nucleus?

Answer 2

• nuclear membrane with nuclear pores
• nucleolus
• chromosomes
• nucleoplasm

Question 3

what is the function of the nucleus?

Answer 3

contains DNA and is the site of DNA replication and transcription

Question 4

what is the function of the nucleolus?

Answer 4

synthesis of ribosomal RNAs (rRNAs)

Question 5

what is the function of a ribosome?

Answer 5

site of protein synthesis

Question 6

what is the structure of a ribosome?

Answer 6

• complex of proteins and rRNAs
• 2 subunits (large and small)

Question 7

where are bound ribosomes located?

Answer 7

endoplasmic reticulum

Question 8

where are the free ribosomes located?

Answer 8

cytoplasm

Question 9

what is the structure of the endoplasmic reticulum?

Answer 9

• continuous membrane system of flattened tubes (cisternae)
• rough ER is studded with ribosomes
• smooth ER has no ribosomes

Question 10

what is the main function of the rough ER?

Answer 10

protein synthesis on ribosomes

Question 11

where do newly synthesized proteins go?

Answer 11

• accumulate in the ER
• then packaged into membrane bound vesicles

Question 12

what is the function of the golgi apparatus?

Answer 12

post translational modifications of proteins

Question 13

what are the post translational modifications?

Answer 13

• formation of disulfide bonds
• addition and processing of carbohydrates
• specific proteolytic cleavages
• assembly into multimeric proteins
• proper folding of the protein

Question 14

list the steps of the ER-Golgi secretory pathway

Answer 14

1. proteins for export are synthesized in the rough ER
2. proteins are then packaged into transport vesicles that ‘bud off’ from the rough ER
3. the vesicles then fuse with the golgi (cis face) and transfer proteins into the golgi lumen
4. secretory vesicles then bud off from the golgi (trans face) and fuse with the plasma membrane for release of proteins (exocytosis) while some proteins are kept for the cell

Question 15

what is the function of the mitochondria?

Answer 15

they are essential for energy production; harness ATP from the oxidation of food molecules

Question 16

which metabolic pathways occur in the mitochondria?

Answer 16

• oxidative phosphorylation
• electron transport chain
• krebs cycle

Question 17

what is the structure of the mitochondria?

Answer 17

• outer membrane
• inner membrane (cisternae)
• inner membrane space between inner and outer membrane

Question 18

what are lysosomes?

Answer 18

organelles involved in degradation of molecules and waste

Question 19

what is the structure of a lysosome?

Answer 19

lipid bilayer membrane with degradative enzymes

Question 20

what do the lysosomal degradative enzymes degrade?

Answer 20

• proteins
• nucleic acids
• carbohydrates
• lipids

Question 21

what is the function of the cytoskeleton?

Answer 21

provide the cell with shape and structure - dynamic not rigid

Question 22

what are the three structures that comprise the cytoskeleton?

Answer 22

• microfilaments
• microtubules
• intermediate filaments

Question 23

what is the structure and function of a microfilament?

Answer 23

• polymers of actin
• give the cell flexibility
• microfilaments can be modified during cell movement (migration, endo/exocytosis)

Question 24

what is the structure and function of a microtubule?

Answer 24

• polymers of tubulin
• provide the cell with shape
• important for mitosis/meiosis where chromosomes attach to microtubules via centromere

Question 25

what is the function of intermediate filaments?

Answer 25

mainly structural function

Question 26

what is the structural basis for all animal cell membranes?

Answer 26

lipid bilayer

Question 27

what is the composition of the plasma membrane?

Answer 27

~ 50% lipid ~ 50% protein

Question 28

what are the 3 main classes of membrane lipids in animal cells?

Answer 28

phospholipids - majority cholesterol - 15% glycolipids- 5%

Question 29

what is the function if cholesterol in the plasma membrane?

Answer 29

provides rigidity to the membrane

Question 30

which factors control the fluidity of cell membranes?

Answer 30

- length of fatty acid chains - degree of saturation - cholesterol content

Question 31

what are the different types of phospholipid movements?

Answer 31

- lateral diffusion - flip-flop (very rare) - rotation - bobbing

Question 32

what is lateral diffusion in phospholipid membrane?

Answer 32

phospholipids move from one part of the membrane to another - only on the same side

Question 33

what is flip-flop movement in the phospholipid membrane?

Answer 33

phospholipid movement from one side of the membrane to the other - very rare and requires specialized enzymes

Question 34

what is rotation in the phospholipid membrane?

Answer 34

each phospholipid can rotate in its place

Question 35

what is bobbing in the phospholipid membrane?

Answer 35

each phospholipid can bob up and down in the same position

Question 36

what are integral proteins?

Answer 36

proteins that extend through the lipid membrane and consist of both hydrophobic and hydrophilic domains - very strong interactions with the membrane

Question 37

what are peripheral proteins?

Answer 37

proteins are bound indirectly to either face of the phospholipid bilayer - weak interactions with the membrane

Question 38

what are the types of transport through the lipid membrane?

Answer 38

- passive diffusion - facilitated diffusion - active transport - endo/exocytosis

Question 39

what is passive diffusion?

Answer 39

transport of molecules into the cell without the need for energy

Question 40

what is facilitated diffusion?

Answer 40

transport of molecules into the cell via transport proteins

Question 41

what is active transport?

Answer 41

transport of molecules into the cell which requires energy in the form of ATP and transport proteins

Question 42

what is endo/exocytosis?

Answer 42

form of transport where the plasma membrane undergoes remodeling to either engulf (endo) or expel (exo) molecules