Lec 8: Eukaryotic Structure & Function

Question 1

Anatomy of eukaryotic cells’ functions

Answer 1

Protection and retention of cell contents

Controlling cell activities and processes

Generating energy

Cellular assembly and transport

Creating movement

Question 2

Plasma membrane

Answer 2

Similar structure and function to prokaryotes

Retains cell contents

Controls exchange with external environment

Consists of phospholipid bilayer with transport and other proteins

Question 3

Cell wall

Answer 3

Only plants, algae and fungi have cell walls

Animal, protozoan and other eukaryotes lack cell walls -> less rigid cell shape

Composition varies. Different from prokaryotes

Plants: cellulose

Fungi: chitin, glycans, protein, cellulose

Algae: pectins, cellulose, mannans or minerals (silica)

Question 4

Cell shape in eukaryotes that lack cell wall

Answer 4

Cell shape maintained by:

Chemicals (sterols) embedded in plasma membrane

Cytoskeleton (network of flexible fibres)

Some protozoans (protists) have thin protein ‘pellicide’ supporting membrane

Question 5

Glycocalyx

Answer 5

External cell coating

Usually carbohydrate

Anchored to membrane -> strengthen cell surface. Help attach cells together. Cell-cell recognition/signalling

Question 6

Nucleus

Answer 6

The cell control centre determining cellular activities

Generation of energy

Synthesis of chemicals necessary in cell reactions (e.g enzymes)

Synthesis of structural materials

Excretion of wastes

Question 7

Chromosomes

Answer 7

Long, linear

Encodes information for cell control

Appear as diffuse network in non-dividing cells (chromatin complex of DNA & proteins)

In dividing cells DNA condenses around histones -> chromosomes become visible

Question 8

Nucleolus

Answer 8

Nuclear subdomain

Assembles ribosomal subunits

Directs rRNA synthesis thus, essential for protein synthesis

Question 9

Nuclear envelope

Answer 9

Double membrane system encloses nucleus

Pores allow exchange with cytoplasm

Question 10

Ribosomes

Answer 10

Eukaryotes and prokaryotes have ribosomes

70S and 80S ribosomes

70S: inside certain organelles (mitochondria, chloroplasts)

80S: free in cytoplasm or associated with rough endoplasmic reticulum

Sites of protein synthesis

Question 11

Mitochondria

Answer 11

Generates energy (ATP)

In prokaryotes, generates energy in plasma membrane

Smooth outer membrane

Highly convoluted inner membrane -> cristae

Fluid matrix: have chemicals necessary to make ATP from nutrient chemicals in cell

Divide independently of cells (have 70S ribosome and own circular DNA)

Question 12

Chloroplasts

Answer 12

Photosynthesis

Double outer membrane enclosing membrane sacs called thylakoids

70S ribosomes, have own circular DNA -> divide independently of cell

Question 13

Thylakoids

Answer 13

Have light harvesting pigments

Sites of ATP formation

Question 14

Max cell size determined by..

Answer 14

Physical & chemicals problems:

Combination of surface to vol ratio, chemical diffusion rates, chemical conc effects

Question 15

Surface to volume ratio

Answer 15

Needs to sufficient ratio -> nutrient uptake and waste removal

As cell gets bigger -> increase in V exceeds increase S -> exchange becomes limiting

Question 16

Chemical diffusion rates

Answer 16

Diffusion takes longer with increasing size -> increased diffusion distance

Question 17

Chemical conc effects

Answer 17

To maintain chemical conc, 8 times more chemical must be made for every doubling size

Question 18

Endoplasmic reticulum

Answer 18

Continuous, interconnected network of membrane sacs throughput cytoplasm

Involved in protein & lipid synthesis

Transport proteins

Question 19

Rough endoplasmic reticulum

Answer 19

Studded with ribosomes on outer surface

Ribosomes synthesise protein into rough ER

Protein modification in lumen of ER

Question 20

Proteins

Answer 20

May be used for:

Membrane synthesis

Export from cell

Transport within cell

Question 21

Smooth ER

Answer 21

Site of lipid synthesis

Also for cell membrane phospholipids, cholesterol

Question 22

Golgi Apparatus

Answer 22

Prepares materials for secretion

ER buds off transitional vesicles for transport of ER products to GA -> vesicles fuse with GA

Consists of stacked membrane sacs

ER products further modified in GA for specialised use by cell

Sorts packages & delivers specialised products to sites via vesicles

Question 23

Flagella and cilia

Answer 23

To find food/prey/new hosts, orientate in environment, enable mating and aid in dispersal

Generate currents -> allow swimming & capture of food particles

Question 24

Flagella and cilia structure and action

Answer 24

Extensions of plasma membrane

Whip like, beat cell to move cell along

Movement driven by sliding of microtubules -> wave-like motion

Question 25

Difference between prokaryotic and eukaryotic flagella

Answer 25

Prokaryotic flagella: rigid protein spirals

Action occurs by rotation