1.2 Ultrastructure

Question 1

Prokaryote

Answer 1

Prokaryotes: simple organisms which are small in size, do not have a nucleas not membraneous organelles.

Question 2

Typical organelles in prokaryotes

Answer 2

• cell membrane
• cell wall
• slime capsule
• nucleoid
• plasmid
• ribosomes (70S)
• cytosol
• pili
• flagellum

Question 3

Nucleoid vs plasmid

Answer 3

Nucleoid: circular DNA molecule, not aassodiated with proteins which stores all the genetic material of the organism

Plasmid: additional autonomous DNA molecule of circular shape which can be transferred in bacterial conjugation

Question 4

Pili

Answer 4

Attachement pili: used to attach to surfaces and one another

Sex pili: used in bacterial conjugation to exchange plasmids

Question 5

Cytokinesis

Answer 5

Cytokinesis: process in binary fission when the cytoplasm of the mother cells divides into two daughter cells

Question 6

Resolution

Answer 6

Resolution: making separate parts of an object distinguishable by an eye

Question 7

Eukaryotes

Answer 7

Eukaryotes: complex living organisms with a nucleus and single or double membrane compartmentalised ultrastructure.

Question 8

Typical organelles in eukaryotes

Answer 8

• nucleus
• nucleolus
• rER
• sER
• Golgi apparatus
• mitochondria
• plasma membrane
• free ribososmes (80S)
• microtubules
• centrioles
• lysosome
• vacuole
• cilia, flagella
• chloroplasts/amyloplasts

Question 9

Advantages of compartmentalisation

Answer 9

1. Enzymes and substrates for reactions are concentrated
2. Dangerous substances (digestive enzymes) are kept within a membrane
3. Ideal conditions for reactions (pH)
4. Organelles with contents can be moved around the cell

Question 10

Role of nucleus and nucleolus

Answer 10

NUCLEUS: enclose nucleolus, store genetic material, transport mRNA out into cytoplasm - double membrane with pores

NUCLEOLUS: ribosomes are assembled

Question 11

Role of rER and sER

Answer 11

rER: from citernae, ribosomes on surface, synthesise proteins for secretion, carried by vesicles to Golgi

sER: citernae, syntheiss and transport of lipids, steroids, involved in carbohydrate metabolism

Question 12

Role of Golgi app

Answer 12

GOLGI APP: membraneous sacs - cisternae (more curved than ER), process (store, sort, modify) secretory products

Question 13

Role of lysosome

Answer 13

LYSOSOME: spherical, formed from Gogli vesicles, many enzymes inside - appear dark in e micrographs, hydrolyse macromolecules into monomers, can digest organelles, cells

Question 14

Role of mitochondria

Answer 14

MITOCHONDRIA: double membrane (inner invaginated - cristae), fluid inside - matrix, spherical, produce ATP by aerobic respiration, fat is digested of used as E source

Question 15

Role of free ribosomes

Answer 15

RIBOSOMES: made up from rRNA and proteins (appear dark in micrographs), not membraneous, subunits synthesisesd in nucleus, synthesise proteins from mRNA

Prokaryote: 70S

Eukaryote: 80S

Question 16

PROKARYOTE vs EUKARYOTE cell

Answer 16

D: DNA: circular - linear, naked - histones, introns

O: organelles: membraneous, compartmentalisation, nucleous, 70S- 80S ribosomes

R: reproduction; binary fission - mitosis/meiosis, haploid - diploid

A: average size: smaller (1-5 um) - bigger (50-100 um)

Question 17

Role of chloroplasts, tonoplasts, plasmodesmata

Answer 17

CHLOROPLASTS: double membrane, membrane sacs thylakoids, spherical, produce org. comp. by photosynthesis, starch grains if rapid photosynthesis

TONOPLAST: membrane surrounding plant cell

PLASMODESMA: channels in plant cell walls to connect to adjacent cells

Question 18

Role of vacuoles and vesicles

Answer 18

BOTH: single membrane, used for storage

VACUOLES: larger, can be digestive vacuoles, can experll water (Paramecium)

VESICLES: small vacuoles, used for transporting materials inside the cell

Question 19

Role of microtubules and centrioles

Answer 19

MICROTUBULES: small cylindrical fibres, move chromosomes in cell division,

CENTRIOLES: from two gorups of nine microtub., form an anchor for microtub. to attach in cell division, for microtubules in cilia, flagella

Question 20

PLANT vs ANIMAL cell

Answer 20

1. Cell wall
2. Chloroplasts (plastids)
3. Cholesterol in membrane
4. Starch and glycogen
5. Large vacuole
6. Centrioles only in animal cells
7. Shape

Question 21

Role of cilia and flagellum

Answer 21

BOTH: containa ring of nine double microtubules and two central ones, fro locomotion

CILIA: small, many, can be used to create currents in surrounding fluids

FLAGELLUM: larger, in sperm

Question 22

Extracellular components of plant/animal cells

Answer 22

PLANTS: cell wall (support, shape, prevents excess water uptake, against infection)

ANIMALS: from glycoproyeins (support, attach to form tissues, intercellular communication)

Question 23

Palisade mesophyll cell

Answer 23

• typical plant cell of the leaf
• performs photosynthesis - many chloroplasts

Question 24

Exocrine gland cell of the pancreas

Answer 24

• endocrine secrete hormones, exocrine secrete digestive enzymes fro the small intestine
• enzyme - proteins - many ribosomes, rER, Golgi