Cells - Key Words

Question 1

Parts of a prokaryotic cell

Answer 1

Parts of a prokaryotic cell: Cell wall, capsule, cell membrane, flagellum, circular DNA, plasmid, ribosomes, cytoplasm, circular DNA.

Question 2

Nucleus

Answer 2

Nucleus – (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

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

Question 4

Circular DNA

Answer 4

Circular DNA - contains genetic information to let cells replicate. Not associated with proteins.

Question 5

Mitochondria

Answer 5

Mitochondria are in cells because:

• 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

Cell wall - Made of peptidoglycan (Murein). Protects cell against damage

Question 7

Cytoplasm

Answer 7

Cytoplasm – contains enzymes for metabolic reactions

Question 8

Capsule

Answer 8

Capsule - 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

Flagellum – tail for movement. Helps spin cell through fluids

Question 11

Rough endoplasmic reticulum

Answer 11

Rough ER (RER) - Surface ribosomes bind to for protein synthesis. Provides pathway for transport of materials around the cell.

Question 12

Smooth endoplasmic reticulum

Answer 12

Smooth ER (SER) - Makes, stores and transports lipids and carbohydrates

Question 13

Comparing prokaryotic and eukaryotic cells

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

Golgi Body - 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

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

Question 16

Lysosomes

Answer 16

Lysosomes - Break down and recycle materials in the cell.

Contain proteases, lipases and lysozymes

Question 17

Centrifugation types

Answer 17

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 à break open cells and release content. Filtered to remove unbroken cells / larger cell debris.

Question 18

Steps in centrifugation

Answer 18

Steps in centrifugation
• 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 19

Adaptions of epithelial cells for absorption

Answer 19

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 20

Cell wall (in plants, algae and fungi)

Answer 20

Cell wall (in plants, algae and fungi)
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 21

Cell vacuole in plants

Answer 21

Cell Vacuole (in plants)
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

Question 22

Magnification

Answer 22

Magnification = Image/Object

Being able to enlarge something in appearance.

Question 23

Light and electron microscopes

Answer 23

Light (optical) and electron microscopes. 2 types of electron microscopes – TEM and SEM

• TEM – Black/white image
• SEM -3D image

Question 24

Benefits of electron microscopes

Answer 24

Benefits of electron microscopes (vs light)

• Have a higher resolution (than light microscopes) because the electron beam has a shorter wavelength
• Thus can see smaller objects – has a higher resolving power

Question 25

Eye piece graticule

Answer 25

Eye piece graticule - is a glass disc fitted into the eyepiece of the microscope. The absolute size of the scale is not important as this is what will be calibrated.

Question 26

Stage micrometer

Answer 26

Stage micrometer - is used to calibrate the eyepiece graticule. A stage micrometer consists of a microscope slide on which is engraved a fine and accurate scale. We use this to calibrate the eyepiece graticule.

Question 27

Using an eye piece graticule

Answer 27

Using an eye piece graticule

1. Measure (each stoma) using eyepiece graticule;
2. Calibrate eyepiece graticule against stage micrometer / ruler / graph paper;
3. Take a number of measurements (to calculate a mean)

Question 28

Benefits of light microscopes

Answer 28

Benefits of light microscopes (vs electron)

• Can look at living cells- don’t have to be in vacuum
• Can produce colour images

Question 29

Artefacts

Answer 29

Artefacts - things that result from the way the specimen is prepared. They are not part of the natural specimen.

Question 30

Parts of a eukaryotic cell

Answer 30

Parts of a eukaryotic cell: 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).