TOB S3 - Cell Ultrastructure Flashcards Preview

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Flashcards in TOB S3 - Cell Ultrastructure Deck (35):
1

Define the term 'limit of resolution'

The minimum distance that two objects can be distinguished at

2

Why are electron microscopes capable of finer resolution than light microscopes?

Relate to wavelength, give theoretical limits of resolution.

Limit of resolution is proportional to wavelength

Visible light wavelength = 0.4 - 0.7um
electron at 100,000V accel wavelength = 0.004nm

Theoretical limit of resolution is 0.2um for visible light and 0.002nm for electron microscopy.

3

What are the key features of a bi-lipid membrane?

phospholipid bilayer is relatively impermeable to hydrophilic molecules

Is amphipathic

Protein molecules are dissolved in bilayer to mediate most functions

4

What is the glycocalyx and what is its major function?

Cell wall coat made up of oligosaccharide and polysaccharide side chains on outside of plasma membrane

Side chains give cell specificity

5

The functions of the plasmalemma include?

Selective permeability
Transport of materials along cell surface
Endo/exocytosis
Intercellular adhesion
Intercellular signalling
Intercellular recognition
Signal transduction

6

What are the two major functions of the nucleus?

Stores DNA

Co-ordinates cell activities
Eg metabolism, growth, protein synthesis, mitosis

7

Describe the structure and functions of the nuclear envelope

Double layered membrane w/Nuclear pores

Attached to ER

Separates nuclear contents from cytoplasm

Pores allow molecules of specific types and sizes (eg. mRNA) to pass through

8

Where is the nucleolus found and what is it's function?

Inside the nucleus
Synthesises Ribosomes

9

What is the function of ribosomes and where can they be found?

Translation of mRNA (Protein synthesis)

RER membrane bound or free in cytoplasm

10

How are proteins shuttled from the RER to the Golgi apparatus?

Via transport vesicle

11

What are the functions of the RER?

Production of:

Lysosomal enzymes
Secreted proteins
Initial Glycosylation (-N linked only)

12

In what tissues do the cells possess smooth endoplasmic reticulum and what functions is the SER involved in at these locations?

Found in cells of the liver and mammary glands (Lipid synthesis)

Ovaries, testes, and adrenal glands (steroidogenesis)

13

Describe the structure of a Golgi apparatus

Saucer shaped stacks of cisternae

trans face concave, cis face convex

Polar, proteins migrate from cis to trans

14

What are the functions of the Golgi apparatus?

Modify, sort, concentrate and package proteins

15

What is the fate of the vesicles leaving the Golgi apparatus?

Lysosomal vesicles remain in the cell cytoplasm

Secretory vesicles will condense (secretory granules) and release contents via exocytosis

16

What is contained within a lysosome?

~40 hydrolytic enzymes at pH 5 collectively known as acid hydrolases

Includes:
Nucleases
Proteases
Lipases
Sulphatases
Phosphatases
Glycosidases
Phospholipases

17

How is a lysosomal membrane protected from the enzymes contained within?

Heavily glycosylated

18

Describe how lysomsomes carry out their function

Primary lysosome fuse with:

Phagosomes
Endosomes
Autophagosomes
Endocytosed material
Excess secretory product

forms a secondary lysosome and contents are degraded

19

What are lysosomes that have digested contnents but contain indigestible matter called?

Residual bodies

20

What is a phagosome?

membrane bound vesicle formed via phagocytosis

21

What is an autophagosome

A defunct organelle encircled by ER

22

What is an endosome?

A membrane bound vesicle formed via endocytosis

23

What is the main function of a peroxisome?

H2O2 production

24

Give an equation for H2O2 production in peroxisomes

RH2 + O2 ---> R + H2O2

25

How is H2O2 produced in a cell utilised?

Catalase enzymes utilise H2O2 to oxidise other substrates
Eg. phenols, formic acid, formaldehyde, Alcohol

26

What can be said about the structure and location of peroxisomes?

Single membrane bound
Roughly spherical
Containing granular matrix

Present in all cells but particularly in Liver parenchymal cells and kidney tubules which detoxify toxic molecules entering the bloodstream

27

Describe the structure of a mitochondrion

Double membrane

Lamellar folds in inner membrane (cristae)

28

What is the main function of a mitochondrion?

Generation of energy rich ATP via oxidative phosphorylation

29

what are the main substrates of a mitochondrion?

Glucose and fatty acids

30

What can be found in the matrix of a mitochondrion?

Hint: related to pathways occuring here + some extras

DNA/RNA
Calcium granules
Ribosomes
Enzymes of the TCA and Fatty acid cyles

31

What are the main functions of the cytoskeleton?

Maintaining/changing cell shape

Structural support for organelles and plasmalemma

Provide locomotor mechanisms for ameboidal movement (eg lymphocytes) and for cilia and flagella

Contractibility in cells of specialised tissue (eg. muscle)

32

What are the three types of cytoskeleton?

Microfilaments
Intermediate filaments
Microtubules

33

What are the structural and functional features of Microfilaments in the cytoskeleton

Give an example of where they can be found

5nm diameter

Two actin strings twisted together

Contractile (requires ATP)

Can assemble and dissociate (dynamic)

A core of microfilaments can be found in microvilli (to maintain shape)

34

What are the structural and functional features of Intermediate filaments?

Give examples of where they can be found

Not dynamic (cannot assemble and dissociate)

10-12nm in diameter

Commonly found in nerve and neurological cells

35

What are the structural and functional features of microtubules?

Give an example of where they can be found

13 Alpha and Beta subunits polymerise to form the wall of a tube

They originate from centrosome (where tubulin subunits can be added)

Found at sites where structures in cells are moved

eg. Cores of cilia and flagella or forming the mitotic spindle