Cells/Centrifugation

Question 1

Parts of a prokaryotic cell?

Answer 1

Cell wall, capsule, cell membrane, flagellum, circular DNA, plasmid, ribosomes, cytoplasm, circular DNA.

Question 2

Nucleus

Answer 2

(incl. nuclear envelope, nuclear pores, nucleoplasm, chromatin, nucleolus) Storage site of genetic information, the site of DNA replication and its transcription to RNA (mRNA and tRNA). Manufacture ribosomal RNA and ribosomes.

Question 3

Plasmid

Answer 3

Small circles of DNA, used to exchange DNA between bacterial cells.

Question 4

Circular DNA

Answer 4

Contains genetic information to let cells replicate. Not associated with proteins.

Question 5

Mitochondria

Answer 5

Mitochondria release energy/ produce ATP

• From aerobic respiration​
• Double membrane – controls entry and exit of material
• Contain cristae (shelf like extensions of inner membrane – large SA for enzymes in respiration to attach to) & matrix (contains enzymes for respiration)

Question 6

Cell wall

Answer 6

Made of peptidoglycan (Murein). Protects cell against damage.

Question 7

Cytoplasm

Answer 7

Contains enzymes for metabolic reactions.

Question 8

Capsule

Answer 8

Thick polysaccharide layer outside of the cell for protection/helps groups of bacteria stick together for more protection.

Question 9

Ribosomes

Answer 9

Ribsosomes – 80S type in eukaryotic cells (bigger)/70S in prokaryotic.
-Make proteins (remember enzymes are proteins)

Question 10

Flagellum

Answer 10

Tail for movement. Helps spin cell through fluids.

Question 11

Rough endoplasmic reticulum

Answer 11

Surface ribosomes bind to for protein synthesis. Provides pathway for transport of materials around the cell.

Question 12

Smooth endoplasmic reticulum

Answer 12

Makes, stores and transports lipids and carbohydrates.

Question 13

Comparing prokaryotic and eukaryotic cells- like for like

Answer 13

-Bacteria don’t have a nucleus/nuclear membrane, eukaryote does;
-Bacteria don’t have membrane-bound organelles, eukaryote does;
-Bacteria don’t have mitochondria, eukaryote does;
-Bacteria has 70S/smaller ribosomes, eukaryote has 80S/larger;
Bacteria cell- have murein/peptidoglycan cell wall, eukaryotes do not-.
Bacterial cells - smaller than eukaryotic cells;
Bacteria - circular DNA, eukaryotes - linear DNA;
Bacteria may have capsules, eukaryotes don’t;

Question 14

Golgi body

Answer 14

Modifies polypeptide chains into mature proteins. Sorts and ships lipids for secretion or use within the cell. Makes secretory enzymes. Forms glycoproteins. Modified proteins and lipids are transported in golgi vesicles.

Question 15

Centrifugation

Answer 15

Helps to separate organelles. Most dense organelles separate 1st, forming a pellet, which is removed. Supernatant contains other organelles –can spin again.

Question 16

Parts of a eukaryotic cell?

Answer 16

Cell surface membrane, Nucleus (including chromosomes, consisting of protein bound linear DNA and one or more nucleoli), mitochondria, Chloroplasts (in plants and algae) rough endoplasmic reticulum (RER), smooth endoplasmic reticulum (SER), ribosomes, golgi body and golgi vesicles, lysosomes, cytoplasm, cell wall (in plants, algae and fungi), cell vacolue (in plants), starch grains (plants)

Question 17

Lysosomes

Answer 17

Break down and recycle materials in the cell.

Contain proteases, lipases and lysozymes.

Question 18

Centrifugation elements

Answer 18

Centrifugation;
Cold – slows down / stops enzyme activity to prevent digestion of organelles
Isotonic – prevents osmosis –so no lysis/ bursting/shrinking of organelles
Buffer - prevents damage to enzymes / proteins (denaturing); Maintains pH
Homogenised to break open cells and release content. Filtered to remove unbroken cells / larger cell debris.

Question 19

Stages in protein production

Answer 19

Nucleus, then ribosomes, then RER, then golgi body, before leaving the cell via vesicles (exocytosis)

Question 20

Steps in centrifugation

Answer 20

• Chop up cells
• Homogenise
• In a cold, isotonic buffer solution
• Filter and centrifuge filtrate
• Organelle making up most of the pellet after being spun at a low speed = nucleus.
• (If continuing) – Centrifuge supernatant at a higher speed – Mitochondria might come next (refer to question here)

Question 21

Chloroplasts

Answer 21

Double plasma membrane – highly selective
Grana – stacks of disc-like structures called thylakoids. Chlorophyll is contained here.(1st stage of photosynthesis.
Stroma – fluid filled matrix – 2nd stage of photosynthesis.(Starch grains found here).

Question 22

Adaptions of epithelial cells for absorption

Answer 22

Adaptations of epithelial cells for absorption
-Microvilli- large SA
-Many mitochondria; - release energy- active transport
-Carrier proteins for active transport & fac diffusion
-Co-transport of sodium (ions) and glucose
-Membrane-bound enzymes digest disaccharides / produce glucose
(left in because it does come up later in absorption)

Question 23

Cell wall

Answer 23

Plants: Consists of microfibrils of cellulose
-Middle Lamella – thin layer that marks the boundary between adjacent cell walls and cements them together.
Functions: Mechanical strength, pathway for water transport in the plant.
Algae: Cellulose or glycoproteins or a mixture of both.
Fungi: Do not contain cellulose but Chitin, glycan and glycoproteins.

Question 24

Cell vacuole

Answer 24

A fluid filled sac bounded by a single membrane – tonoplast.
Contains salts, sugars, a/a, wastes ad pigments.
Functions: Support – turgid, temporary food store, pigments may colour petals – attract insects.