Cells

Question 1

brief history of cells:

Answer 1

Robert Hooke: referred to cells

• Leeuwenhoek ‘father of microbiology’
• Schleiden and Schwann formulated cell theory:
• all organisms made of cells
• cell most basic unit of life
• all cells arise from pre-existing cells

Question 2

microscopy:

Answer 2

• cells too small to be seen with unaided eye
• light microscope magnify 1000x
• but most subcellular structures (organelles) too small to be seen using light microscope

Question 3

eg of electron microscopy:

Answer 3

TEM: transmission electron microscopy

• electron beam through slice of specimen
• 0.05 nm

SEM: scanning electron microscopy

• scans surface of specimen using electron beam
• 0.4 nm resolution

Question 4

plasma membrane features:

Answer 4

• selective plasma membrane allows sufficient passage of oxygen, nutrients and waste
• phospholipid bi-layer

Question 5

organelles found in animal cells only:

Answer 5

• lysosomes

- centrosome with centrioles

Question 6

organelles found in plant cells only:

Answer 6

• chloroplast
• central vacuole
• cell wall
• plasmodesmata

Question 7

features: nucleus

Answer 7

• nuclear DNA
• nuclear double membrane
• each layer lipid bilayer
• pores regulate entry/exit of molecules from nucleus

Question 8

how is nucleus shape maintained? + nucleolus

Answer 8

• nuclear lamina
• protein
• genetic material called chromatin (protein + DNA)
• nucleolus synthesises rRNA (which joined to proteins form ribosome subunits)

Question 9

features: ribosomes

Answer 9

factory of the cell

• rRNA + protein
• carry out protein synthesis in:
• cytosol (free ribosomes)
• on RER or nuclear envelope (bound)

Question 10

list components of endomembrane system:

Answer 10

• nuclear envelope
• endoplasmic reticulum
• golgi apparatus
• lysosomes
• vacuoles
• plasma membrane

Question 11

how are the endomembrane system related?

Answer 11

either continuous or connected via vesicles

Question 12

features: endoplasmic reticulum

Answer 12

• more than half of total membranes in most eukaryotic cells
• continuous with nuclear envelope
• Smooth ER vs Rough ER

Question 13

detail: RER vs SER

Answer 13

ER is a biosynthetic factory:

smooth:

• lipid synthesis
• carb metabolism
• detoxification of poison
• calcium storage

rough:

• glycoprotein synthesis
• membrane production

Question 14

features: golgi apparatus

Answer 14

• flattened membranous sacs (cisternae)
• modification of ER products
• manufactures certain macromolecules
• package materials into transport vesicles

Question 15

features: lysosomes

Answer 15

membranous sac of hydrolytic enzymes- digest macromolecules

- lysosomal enzymes can hydrolyse proteins, fats, polysaccharides and nucleic acids

Question 16

lysosomes: phagocytosis + autophagy

Answer 16

• some cells can engulf another via phagocytosis
• which forms food vacuole
• lysosome fuses with food vacuole to digest molecules
• lysosomes also use enzymes to recycle organelles and macromolecules of the cell, via autophagy

Question 17

features: vacuole and egs.

Answer 17

• plant/ fungal cell may have several
• food vacuoles formed by phagocytosis
• contractile vacuoles: pump excess water out of cells (freshwater protists)
• central vacuoles found in mature plant cells hold organic compounds + water

Question 18

features: mitochondria

Answer 18

• in nearly all eukaryotic cells
• cellular respiration
• smooth out membrane and inner folded one (cristae)
• forms intermembrane space + mitochondrial matrix
• large SA for enzymes to synthesis ATP

Question 19

features: chloroplasts

Answer 19

• photosynthesis

- chlorophyll reside in thylakoid membranes

Question 20

features: cytoskeleton + types

Answer 20

• network of fibres extending throughout cytoplasm
• organises cell structures, anchoring organelles
• microtubules
• microfilaments
• intermediate filaments

Question 21

cytoskeleton contd. function + interactions

Answer 21

• support
• mobility and regulation
• maintains shape
• motor proteins interact to produce motility
• inside cell, vesicles can ‘walk’ along ‘monorails’ provided by cytoskeleton

Question 22

microtubules: function

Answer 22

thickest of the 3

• hollow rods 25nm diameter
• grow from centrosome near nucleus
• shapes cell
• guide movement of organelles
• separating chromosomes during cell division

Question 23

microfilaments: function

Answer 23

aka actin

• thinnest component
• rods 7nm diameter,
• twisted double chain of actin subunits
• bears tension, resist pulling forces of cell
• forms 3D network, support shape
• interacts with myosin for movement

Question 24

intermediate filaments: function

Answer 24

middle fibres

• 8-12 nm diameter
• support cell shape, fix organelles in place
• variety of different proteins
• more permanent than microtubules and microfilaments

Question 25

microtubules: cilia and flagella

Answer 25

• components of cilia and flagella
• motor proteins (dyenin) ‘walk’ along microtubule
• cross links limit sliding = bending of cilia or flagella

Question 26

eg of each cytoskeleton:

Answer 26

microtubule: tubulin dimer
- intermediate filament: keratin protein
- microfilament: actin subunit