Cell Structure

Question 1

features of absorbative cell

Answer 1

microvilli

many cell junctions

Question 2

What is a Cytoskeleton?

Answer 2

A dynamic (changes rapidly) system of protein filaments in the cytoplasm of a eukaryote that gives the cell shape and the capacity for movement of substances

Question 3

What is diapedesis?

Answer 3

The crawling of cells along a surface

allows the passage of white blood cells through capillary walls into the tissues.

Question 4

What are the functions of the cytoskeleton?

Answer 4

Responsible for:

Large-scale cellular movements such as diapedesis and cytokinesis and muscle cell contraction

Changes in cell shape and fluidity that accompany embryonic development

Also provides machinery for intracellular movements e.g movement of organelles/vesicles and anaphase

Question 5

What are the 3 intracellular movements that involve the Cytoskeleton?

Answer 5

Transport of organelles from one place to another

Segregation of chromosomes into 2 daughter cells during anaphase of mitosis

cytokinesis

Question 6

What are the three types of protein filaments within the cytoskeleton?

Answer 6

Microtubules

Intermediate Filaments

Actin Filaments

Question 7

What are the characteristics of Microtubules?

Answer 7

They are…

long stiff, cylindrical intracellular structures

20nm diameter

composed of tubulin protein

grow out of the centrosome and create a system of tracks for transport vesicles, organelles and other cells components

Utilize motor proteins for movement

Question 8

What are motor proteins?

Answer 8

proteins that bind to organelles within a cell and move them along microtubules (and sometimes actin filaments)

Question 9

What are the characteristics of Intermediate Filaments?

Answer 9

Intermediate in size

10nm in diameter

Stable rope-like polymers

Made of fibrous proteins which give mechanical strength

STRONGEST OF THE 3 CYTOSKELETON PROTEINS!

Also found in the nucleus under the nuclear envelope (forming the nuclear lamina)

attach organelles to each other or organelles to the cell membrane

Question 10

Which type of protein filament is rope-like and forms a nuclear lamina under the nuclear envelope of a cell - therefore strengthening the envelope?

Answer 10

Intermediate filaments

Question 11

True or False

Protein filaments participate in cell junctions

Answer 11

True

Question 12

What are the characteristics of Actin Filaments (microfilaments) ?

Answer 12

Small

made of filamentous protein

formed from a chain of globular actin molecules

Found in cross-linked bundles and networks (stronger)

Forming contractile skeleton in cell

used in muscle contraction

involved in regulating cell shape

Question 13

What are integrins?

Answer 13

Cell surface receptors that attach cells to the extracellular matrix and mediate mechanical and chemical signals

Question 14

Which protein filament type forms the cell cortex?

Answer 14

Actin Filaments in a network of cross-linked bundles

Question 15

What are Cell Inclusions?

Answer 15

various nutrients or pigments that can be found within the cell, but do not have activity like other organelles. Examples of cell inclusions are glycogen, lipids, and pigments such as melanin

can be cell products or ingested material

Question 16

What are the 4 types of cell inclusions?

Answer 16

Glycogen

Lipids

Pigment Granules

Secretory Granules

Question 17

What is glycogen?

Answer 17

a large branched polysaccharide found in the cytoplasm of several cell types including liver and muscle

Question 18

What are lipids?

Answer 18

non-membrane bound droplets in the cytoplasm that vary in size

Require special stain to see with LM

Question 19

What are the 2 types of lipid cell inclusions?

Answer 19

Neutral

Metabolic

Question 20

Give an example of Neutral Lipid Cell Inclusions and where they are found in the body

Answer 20

Triglycerides

stored in adipose tissue

Question 21

Give an example of metabolic lipid cell inclusions and where they are found in the body

Answer 21

Steroids as a substrate for estrogen or cortisol

Question 22

What are pigment granules?

Answer 22

Melanin (to block UV damage)

heme (oxygen transport)

Question 23

What are secretory granules?

Answer 23

membrane bound vesicles that contain inactive enzymes, proteins and neurotransmitters

Question 24

What is the nuclear envelope?

Answer 24

The envelope surrounding the nucleus which consists of 2 lipid bilayer membranes and is perforated by nuclear pores

the membranes are continuous with the ER (although structurally different)

Question 25

What is the nuclear lamina?

Answer 25

a network of protein filaments that support the nuclear envelope

Question 26

What do the nuclear pores on the nuclear envelope do?

Answer 26

* Actively transport selected molecules to and from the cytoplasm * Critical role in regulating gene expression * ringed by many proteins

Question 27

What is the Nucleolus?

Answer 27

non-membrane bound the region of the nucleus where different chromosomes carrying genes for ribosomal RNA cluster (1 per nucleus) are found site of production of rRNA Contains both granular and fibrous material role in cell cycle regulation / sensor for DNA damage

Question 28

features of secretory cells

Question 29

cell membrane structure / function

Answer 29

phospholipid bilayer that is formed spontaneously hydrophobic tails face inwards and are shielded by hydrophilic groups which face outwards on either side fluid allowing lateral diffusion of membrane proteins and cell mobility highly permeable to water oxygen and small hydrophobic molecules e.g ethanol impermeable to large and/or charged ions cell-cell and cell-ECM adhesions (interactions)

Question 30

components of cell membrane

Answer 30

50% phospholipids cholesterol reduces fluidity and improves stability

Question 31

define pinocytosis

Answer 31

when cells take up fluid and small molecules to form small vesicles by budding

Question 32

define potocytosis

Answer 32

type of receptor-mediated endocytosis

Question 33

define endocytosis

Answer 33

general process when cells ingest large molecules to form endosomes (membrane bound vesicle)

Question 34

define phagocytosis

Answer 34

type of endocytosis when cells ingest large solid particles to form a phagosome

Question 35

exocytosis

Answer 35

opposite of endocytosis fusion of vesivles with membrane to discharge its contents buds if cell membrane may also pinch off to form extracellular vesicles that acts as transport vesicles

Question 36

mitochondria functions and structure

Answer 36

site of energy production via oxidative phosphorylation and ATP production metabolism of amino acids and lipids biosynthesis of haem and Fe-S clusters act as a sensor for health of cell and trigger apoptosis Outer (double) membrane smooth Inner (double) membrane folded to form cristae Two compartments: Outer compartment & Inner matrix

Question 37

difference between cilia/flagellae and microvilli

Answer 37

* Cilia (and flagellae): extensions of the microtubule cytoskeleton that actively move * Microvili : extensions of the actin microfilament cytoskeleton, no active movement. they act to increase surface area

Question 38

structure of cilia

Answer 38

microtubule core Each cilium contains nine pairs of microtubules forming the outside of a ring, and two central microtubules known as 9 + 2 arrangement microtubules joined by nexin Between the nine outer pairs are motor proteins called dynein which allow the movement coated in plasma membrane

Question 39

structure of centrioles

Answer 39

Centrioles are cylindrical structures, found in animal cells groupings of microtubules arranged in a 9 (triplets) + 0 pattern help to organize the assembly of microtubules during cell division

Question 40

difference between cell cortex and cytoskeleton

Answer 40

cell cortex provides support to the plasma membrane whereas the cytoskeleton maintains the overall shape of the cell

Question 41

tight junctions

Answer 41

•act as barriers, preventing the passage of substances between adjacent cells * Help maintain position of membrane proteins (called polarity) * found near top of cells

Question 42

adherens junctions

Answer 42

attach cells to each other and to the cytoskeleton e.g •zonula adherens (actin extension) and desmosomes (intermediate fillaments extension)

Question 43

Hemidesmosomes

Answer 43

•type of anchoring junction * they attach epithelia to the basement membrane and hence to the tissues beneath e.g. skin •Made of integrins, laminin, collagen (all ECM proteins)

Question 44

gap junctions

Answer 44

allow direct communication between adjacent cells permits coordinated cell activity e.g cardiac cycle consist of connexins which together form connexons

Question 45

junctional complexes how are the different junction types arranged within a cell?

Answer 45

tight junction , adherens junctions/gap junction , anchoring junctions top of cell bottom of cell

Question 46

RER and SER

Answer 46

ER = series of flatenned membranous channels and vesicles RER is covered by ribosomes that produce proteins for export involved in synthesis, folding, modification, and transport of proteins. SER involved in lipid synthesis and export of large molecules

Question 47

golgi apparatus

Answer 47

series of flattened membrane sacs processes and packages and sorts proteins received from ER into membrane bound vesicles

Question 48

lysosome

Answer 48

vesicle containing digestive enzymes which are kept separated by membrane. Destroys material from outside & within cell Produced from ER and Golgi Apparatus Acid pH inside

Question 49

peroxisome and proteosome

Answer 49

special type of lysosomes containing catalase, converts hydrogen peroxide (toxic) to water (harmless) proteosome - degrades ubiquitinated (degraded) proteins

Question 50

Differences between eukaryotic and prokaryotic cells

Answer 50

**Prokaryotic cells Eukaryotic cells** (bacteria, mycoplasmas, (other algae, fungi, protozoa, blue-green algae) multicellular plants and animals) 1. Size 0.1-5.0 µm - allows ions and organic molecules that enter them to quickly spread to other parts of the cell 1. Size ranging from **10–100 µm –** requires more complex organelles and cytoskeleton 1. No nuclear envelope 1. Prominent nuclear envelope 1. No nucleoli 1. Nucleoli present 1. No histones 1. DNA complexed with histones 1. Few intracellular membranes 1. Many membrane-bound organelles 1. 60-70s ribosomes 1. 70-80s ribosomes