Cell Structure - Animal Cells

Question 1

What is and (what are the characteristics of the cell surface membrane) ?

Answer 1

-thin 7nm.
-trilaminar.
-partially permeable.
-control exchange.

Question 2

What is and (what are the characteristics of microvilli) ?

Answer 2

-finger like extensions of cell surface membrane.
-typically of certain epithelial cells.
-increases surface area.

Question 3

What is and (what are the characteristics of nucleus) ?

Answer 3

-largest organelle.
nuclear envelope -> double membrane, outer membrane continuous with ER.
-nuclear pores -> controls exchange.
-chromatin -> loosely coiled chromosomes organised into functional units called genes.
-controls cells activities.
-nucleolus -> makes ribosomes.

Question 4

What is and (what are the characteristics of nuclear envelope) ?

Answer 4

-nucleus surrounded by two membranes.
-outer membrane -> continuous with ER.
-nuclear envelope has many small pores -> nuclear pores.
*control exchange between nucleus and cytoplasm.
*leaving ->messenger RNA, transfer RNA and ribosomes.
*entering->nucleotides (basic unit of DNA), ATP, hormones (T3).

Question 5

What is and (what are the characteristics of chromosomes and chromatin) ?

Answer 5

-contains DNA -> genetic material.
-organised into functional units -> genes with control activities and inheritance.
-2m of DNA in each cell -> folded in combination with histones into chromatin.

Question 6

What is and (what are the characteristics of nucleolus) ?

Answer 6

-darkly stained, rounded structure in nucleus (1-5).
-makes ribosomes using the information in DNA.
-core of DNA contains genes that code for ribosomal RNA (rRNA).
-also contains genes for making tRNA.
-less dense regions -> ribosomal subunits are assembled by combining rRNA with ribosomal proteins imported from cytoplasm.
-nucleolus disapears when ribosome synthesis ceases (i.e nuclear division).

Question 7

What is and (what are the characteristics of the endoplasmic reticulum and ribosomes) ?

Answer 7

-extensive membrane system.
-sacs.
-separated from cytoplasm.
-interconnected.
-smooth ER -> makes lipids and steroids ; storage for calcium ions.
-rough ER -> ribosomes which are sites of protein synthesis.

Question 8

What is and (what are the characteristics of the ribosomes) ?

Answer 8

-large and small subunit.
-site of protein synthesis.
-free or bound.
-25nm.
-RNA.
-proteins made by ribosomes on rER -> move through ER -> vesicles break off.
-sER -> makes steroids and lipids.
-eukaryotic ribosomes are 80s.
-prokaryotic ribosomes are 70s.

Question 9

How are ribosomes weighed ?

Answer 9

-measurement of weight when settled out in a centrifuge.

Question 10

What is and (what are the characteristics of Golgi apparatus) ?

Answer 10

-stack of flattened discs/cisternae.
-formed at one end, and budding off vesicles at the other.
-collects, processes and sorts molecules ready for transport.
*protein processing -> addition of sugars to protein to glycoproteins.
*glycolipids -> cell membrane structure and cell signalling.
*removal of amino acid methionine from proteins to make a functioning protein.
*in plants -> converts sugars into cell wall components.
*gut/respiratory system -> goblet cells release mucin.
*lysosome.

Question 11

What is and (what are the characteristics of lysosomes) ?

Answer 11

-spherical sacs.
-single membranes.
-no internal structure.
-0.1 to 0.5nm.
-digestive, hydrolytic enzymes (hydrolases-> carry out hydrolysis reactions).
-kept separate to prevent cell damage.
-breakdown of old organelles, bacteria, cartilage, sperm.
-works fastest in acidic environment-> contents ph 4 to 5.
-proteases, lipases, nucleases-> synthesised on rER and delivered to lysosomes by Golgi apparatus.

Question 12

What is senescence ?

Answer 12

growing older.

Question 13

What is apoptosis ?

Answer 13

cell death.

Question 14

How do you get rid of unwanted substances ?

Answer 14

endocytosis, exocytosis and self-digestion.

Question 15

What is endocytosis ?

Answer 15

-endo (bringing in)
-material taken into cell.
-white blood cells engulf bacteria.
-lysosomes may fuse with endocytic vacuoles and release enzymes to digest the contents.

Question 16

What is exocytosis ?

Answer 16

-lysosomal enzymes released from cell for extracellular digestion.
-replacement of cartilage by bone during development.
-heads of sperm -> acrosome digest path through the layers of cells surrounding ovum.

Question 17

What is self-digestion ?

Answer 17

-contents released into cytoplasm.
-autolysis/apoptosis.

Question 18

What is and (what are the characteristics of ATP) ?

Answer 18

-ATP (adenesine tri-phospate)
-aerobic respiration, in aerobic respiration there is:
*link reaction
*Kreb cycle.
-lipid synthesis.
-energy needed from sugars/fats -> ATP (energy carrying molecule).
-Rxn takes place in matrix and the cristae.
-matrix contains enzymes for Krebs cycle which supply H+ and e- required in the cristae.
-flow of e- and e carriers in the membranes of cristae provides power to generate ATP.
-folding of cristae increases SA.
-ATP leaves mitochondrion -> cell where it’s needed -> ADP (hydrolysis reaction).

Question 19

What is phosporylation ?

Answer 19

-the addition of phospate.

Question 20

What is ADP ?

Answer 20

-the energy in the reaction of aerobic respiration.

Question 21

What is the Endosymbiont Theory ?

Answer 21

A) a prokaryote ingested some aerobic bacteria. The aerobes were protected and produced energy for the prokaryote.
B) over a long time, the aerobes became mitochondria no longer able to live on their own.
C) some primitive prokaryotes also ingested cyanobacteria, which contain photosynthetic pigments.
D) the cyanobacteria became chloroplasts, no longer able to live on their own.

Question 22

What is and (what are the characteristics of mitochondria) ?

Answer 22

-1nm.
-sausage shaped.
-outer membrane -> porin allows small water-soluble molecules through.
-inner membrane -> folded into cristae -> selectively permeable.
-interior solution or matrix.
-intermembrane space.
-aerobic respiration therefore cells with high energy demand -> more mitochondria.

Question 23

What is the measurement of Cytoplasmic ribosomes ?

Answer 23

80s.

Question 24

What is the measurement of Mitochondrial ribosomes ?

Answer 24

70s.

Question 25

What are ribosomes ?

Answer 25

-small, circular DNA responsible for coding/synthesis of proteins.

Question 26

What is and (what are the characteristics of microtubules) ?

Answer 26

-they are made up of Alpha-Beta tubulin.
-long, rigid, hollow tubes 25nm.
-make up cytoskeleton -> cell shape.
-𝝰-tubulin and 𝝱-tubulin-> dimers-> protofilaments (polymerisation).
-13 protofilaments line up in a helical ring (microtubule).
-intracellar transport.
-forms spindle-> nuclear division.
-controlled by MTOC’s.
-movement of cilia and flagella.

Question 27

What is and (what are the characteristics of centrioles and centrosomes) ?

Answer 27

-just outside nucleus -> 2 centrioles.
-lie at right angles in a region -> centrosomes.
-hollow cylinder -> 500nm.
-ring of short microtubules arranged in triplets.
-found at bases of cilia and flagella -> basal bodies.

Question 28

What is and (what are the characteristics of cilia and flagella) ?

Answer 28

-whiplike beating extensions of many eukaryotic cells.
-composed of 600 different polypeptides.
-cilia:-
*2 central microtubules and a ring of 9 microtubule doublets (9+2).
*each MTD contains an A and B microtubule.
* A microtubule wall ->13 protofilaments.
*B microtubule ->incomplete ring with 10 prtofilaments.
*A tubule has inner arms and outer arms made of dynein ->connects with B tubule of neighbouring MTD’s during beating.
*the whole cylindrical structure ->axoneme.
-basal body ->centriole.

Question 29

Explain the beating mechanism of cilia and flagella ?

Answer 29

-motion caused by dynein arms making contact with, and moving along, neighbouring.
-produces the force needed for cilia to beat.
-As neighbouring MTD’s slide past each other, the sliding motion is converting into heading by other parts of cilium.

Question 30

What are the functions of the beating mechanism of cilia and flagella ?

Answer 30

-if the cell is attached ->fluid will move past the cell.
-if the cell is free ->move through the fluid.

Question 31

What is an example of the beating mechanism of cilia and flagella ?

Answer 31

-Epithelial cells lining airways ->maintain the flow of mucus which remove debris (dust/bacteria) from respiratory tract.