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Cell Dynamics > Cell Organelles > Flashcards

Cell Organelles Flashcards

1
Q

Cytoskeletal filaments

A

provide tracks for moving the organelles around and for directing traffic of vesicles between them.

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2
Q

Motor Protein

A

use energy of ATP hydrolysis to propel the organelles and vesicles along the filaments.

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3
Q

Organelles

A
  • Cytosol
  • Cytoplasm
  • Nucleus
  • Endoplasmic Reticulum
  • Golgi Apparatus
  • Mitochondrion
  • Lysosome
  • Peroxisome
  • Vacuole
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4
Q

Cytosol

A
  • Eukaryotic cell minus plasma membrane, nucleus, mitochondria, ER, GA, chloroplasts =cytosol which is concentrated aqueous gel.
  • Fills largest single compartment in a cell, site of many chemical reactions, e.g. protein manufacture (ribosomes), breakdown of nutrient molecules.
  • Contains host of small and large molecules crowded together, more like a water-based gel than a liquid solution.
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5
Q

Cytoplasm

A

Cytoplasm = cytosol + membrane bounded organelles except nucleus, i.e. contents of cell within plasma membrane, outside nucleus.
* Cytoplasm is not static – in constant motion

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6
Q

Cytoskeleton

A

allows for the movement of organelles around the cell.
a network of protein filaments that extend
throughout the cell: actin filaments, microtubules & intermediate filaments.

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7
Q

Nucleus

A

Usually the most prominent cell organelle – 5μm in diameter.
* Most cells of the body have ONE single nucleus (exceptions are the skeletal muscle cells which have two or more nuclei and mature RBCs which have none)
* Genetic material is made up of nucleic acids (DNA and RNA) and is found in the nucleus. DNA is also found in
the mitochondria and chloroplasts.

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8
Q

Structure of a Nucleus- explanation

A
  • Enclosed within a double membrane (lipid bilayer) that forms nuclear envelope.
  • Envelope perforated by nuclear pores.
  • Protein structure called the pore complex lines the pore and regulates entry and exit of particles.
  • Nuclear side of envelope lined by nuclear lamina: array of protein filaments: anchor-sites for chromatin.
  • Prominent structure in non-dividing nucleus = nucleolus (nucleoli).
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9
Q

Structure of a Nucleus- parts

A

(a) Nuclear membrane
* Inner membrane
* Outer membrane
(b) Nuclear pore
(c) Nucleolus
(d) Chromatin
* Heterochromatin
* Euchromatin
(e) Nucleoplasm

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10
Q

Nuclear Envelope

A
  • a double membrane similar to the cell membrane.
  • Encloses the nucleus to separate contents from the cytoplasm.
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11
Q

Nuclear Pore

A
  • protein-lined channels in the nuclear envelope.
  • Appear as perforations on the surface of the nucleus.
  • Allow for passage of materials from the
    nucleus to the cytoplasm.
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12
Q

Nucleolus

A
  • prominent within the nucleus.
  • It is made up of protein and ribosomal DNA (rDNA).
  • It has no membrane.
  • It is the site of RNA transcription and processing and ribosome assembly.
  • Some cell types and organisms (e.g. Paramecium, Allium cepa) contain more than one nucleolus.
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12
Q

Chromatin

A
  • genomic DNA + proteins.
  • It is found in the nucleus of eukaryotic cells and the nucleoid of prokaryotic cells.
  • The function of chromatin is to package DNA into a smaller volume to fit into the cell.
  • DNA is tightly packed around proteins known as histones in a structure called a ‘nucleosome’.
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13
Q

Types of Chromatin

A

Heterochromatin and Euchromatin

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14
Q

Heterochromatin

A

the condensed (dense patches) form of chromatin organisation and is the inactive form of chromatin

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15
Q

Euchromatin

A

the lighter region of the nucleus and is most abundant in active cells because it is the active form of chromatin.

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16
Q

Functions of the nucleus

A

Replication, Transcription and Translation

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16
Q

Nucleoplasm

A
  • similar to the cytoplasm of the cell but it is found in the nucleus. It is also called nuclear sap.
  • It is a highly viscous liquid that surrounds the chromatin and nucleolus.
  • It contains a network of fibres made up of proteins.
  • It contains substances such as:
    Nucleotides (for DNA replication and transcription)
    Proteins/Enzymes (for all nuclear functions)
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17
Q

Replication

A

mediates copying of DNA in the cell cycle
which is essential for the development and growth of a cell.

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18
Q

Transcription

A

controls the production of messenger RNA (mRNA) is produced in the nucleus using DNA as a template.

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19
Q

Translation

A

mRNA is transported via the nuclear pores to the cytoplasm for the synthesis of specific proteins which in turn have specific cellular functions (e.g. regulating metabolism, initiating mitosis)

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20
Q

Ribosome Structure

A
  • Proteins enter the nucleus, combine with 4 strands of rRNA to make the 2 subunits (large and small) of the completed ribosome.
  • The ribosome leaves the nucleus through the nuclear pore to begin protein synthesis in the cytoplasm of an eukaryotic cell.
  • LSU and SSU are described as Svedberg (s) units.
  • Svedberg (s) values, which are based upon their rate of sedimentation in a centrifuge.
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21
Q

Ribosomes

A
  • technically NOT organelles as they are not bound by a membrane.
  • Ribosomes are 60% rRNA and 40% protein.
  • Ribosomes are found in both eukaryotes & prokaryotes.
  • Can arise as free or bound ribosomes.
  • Ribosomes function in making protein.
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22
Q

Types of Endoplasmic Reticulum (ER)

A

SMOOTH ER and ROUGH ER

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23
Q

Smooth ER

A

Agranular ER- has no ribosomes attached

24
Q

Rough ER

A

Granular ER- has ribosomes attatched

25
Q

Function of Endoplasmic Reticulum

A

in the synthesis, activation and transport of macromolecules in the cell, however depending on the addition of ribosomes or not, the ER has specific functions such as the smooth ER and the rough ER.

26
Q

Specific function of ER: Smooth ER

A

outer surface lacks ribosomes. Contains
enzymes important in synthesis of lipids and steroids, detoxification of drugs and poisons, metabolism of carbohydrates, stores Ca2+, enzyme reactions

27
Q

Specific function of ER: Rough ER

A

ribosomes stud outer surface, proteins produced on ribosomes; protein and lipid transport and secretion.

28
Q

Structure of the ER

A
  • Network of membranous tubules and sacs called cisternae.
  • It is often seen as an extension of the nuclear membrane.
  • Cisterna
  • Lumen/cisternal space
  • Ribosomes
29
Q

Golgi Apparatus

A
  • One of the first cell organelles identified.
  • Distribution and shipping centre for the cell’s chemical processes.
  • Consists of separate flattened membranous sacs called cisternae.
  • Vesicles in vicinity of GA involved in transport between parts of GA and other structures.
  • Golgi stack has distinct polarity: membranes of cisternae on opposite sides differing in thickness and molecular composition:
  • CIS FACE (near ER) ‘receiving’ area
  • TRANS FACE, ‘shipping’ area.
30
Q

Functions of the Golgi (in depth)

A
  • Products synthesised in the ER are transported to the GA for the following functions:
  • Modification of products (with Golgi enzymes).
  • Storage of products.
  • Sorting and Transport of products for various parts of the cell.
  • The vesicles that pinch off from the Golgi apparatus move to the cell membrane and the material in the vesicle is released to the outside of the cell.
  • Some of these pinched off vesicles also become lysosomes.
31
Q

Function of Golgi (basic)

A
  • Stores proteins brought from ER (warehouse).
  • Modifies proteins via enzymes attached to
    golgi membrane.
  • Sorts the proteins by tagging them.
  • Despatches proteins to their final destinations in transport vesicles.
  • Manufactures certain complex carbohydrates.
32
Q

Function of Rough ER

A
  • Makes protein.
  • Makes new membrane - lipids.
33
Q

Function of Smooth ER

A
  • Synthesis of lipids and steroids.
  • Detoxification of drugs and poisons.
  • Stores calcium.
  • Carbohydrate metabolism.
34
Q

Lysosomes

A
  • Membranous sac of hydrolytic enzymes, produced in the Golgi.
  • Digestive enzymes break down cellular waste products, fats, carbohydrates and proteins which sent back to the cell to serve as building blocks for new products.
  • Size of a lysosome: 0.1–1.2x10-6m
35
Q

Lysosomes Functions

A

PHAGOCYTOSIS and AUTOPHAGY

36
Q

AUTOPHAGY

A

recycling of cell’s own organic material, damaged organelle becomes surrounded by membrane, fusion with lysosome: cell continually renews itself.

37
Q

PHAGOCYTOSIS

A

cell engulfs microorganisms/large particles, fusion with lysosome. Digestion products, simple sugars, amino acids pass into cytosol.

38
Q

Lysosomal enzymes

A

They utilise over 40 different types of digestive enzymes.
* Acidic enzymes (low pH).
* Examples include:
* LIPASE digests lipids.
* AMYLASE digests carbohydrates.
* PROTEASES digest proteins.
* NUCLEASES digest nucleic acids.

39
Q

Peroxisomes

A
  • Specialised metabolic compartment bounded by single membrane.
  • First isolated from liver cells.
  • Contain enzymes that transfer hydrogen from various substrates to oxygen, producing hydrogen peroxide (H2O2) as a by-product.
  • Oxidative reactions (+O2, -H) include:
    * break down fatty acids into smaller
    molecules that can be transported to
    mitochondria.
    * destroy toxic molecules.
  • H2O2 is itself toxic: enzymes contained in peroxisome that converts it to water.
40
Q

How to identify Peroxisomes and Lysosomals

A

Lysosomes
* Larger
* Darker in colour
Peroxisomes
* Smaller
* Lighter in colour

41
Q

Vacuoles

A
  • a membrane-bound sac.
  • Formed by pinching in of the plasma membrane.
  • Storage of food and waste.
  • Transport of products around the cell.
  • Examples:
    • Small vacuoles – animals.
    • Large central vacuoles – plants.
42
Q

What is the endomembrane system?

A

A group of cell membranes and organelles that are mutually interconnected, either by being directly continuous with one another or by sending one another vesicles.

42
Q

What organelles form the endomembrane system?

A
  • Nuclear envelope
  • Endoplasmic reticulum
  • Golgi apparatus
  • Lysosomes
  • Vacuoles
  • Plasma membrane X
43
Q

Mitochondrion

A
  • Powerhouse of the eukaryotic cell- produces almost all ATP to drive cellular reactions.
  • Semi-autonomous cell organelle (division, fusion, own genetic system).
  • Imports > 99% of proteins from cytoplasm.
  • Outer membrane is permeable to small molecules.
  • Inner membrane is site of cellular respiration and ATP synthesis.
44
Q

Structure of the Mitochondrion

A
  • Outer and inner membrane
  • Intermembrane space
  • Cristae
  • Matrix
  • Matrix granules
  • Ribosomes
44
Q

Where did Mitochondria evolve from?

A

Prokaryotes-
* Nucleated cell engulfed a prokaryote.
* Symbiosis developed – cell dependent on prokaryote and vice versa.
* Development into an energy producing mitochondrion.

45
Q

Outer Membrane (Mitochondrial)

A

Contains integral proteins called porins (allow molecules to freely diffuse from one side of membrane to other).

46
Q

Inner Membrane (Mitochondrial)

A

Double phospholipid layer, site of ATP
production. Cristae folds allows more surface area so that ability to produce ATP enhanced.

47
Q

Inter-membrane Space (Mitochondrial)

A

Between outer and inner membrane. Outer membrane is freely permeable to small
molecules so concentrations of ions and sugars in this space is same as cytosol.

48
Q

Matrix (Mitochondrial)

A

Fluid that fills area inside inner membrane. Also important for ATP production with the aid of ATP synthase contained in inner membrane.

49
Q

ATP (adenosine triphosphate)

A

the energy-carrying molecule used in cells because it can release energy very quickly.

50
Q

Functions of the Mitochondrion

A
  • Energy production: This is the main function which involves the conversion of nutrients into energy yielding molecules (ATP) to fuel the cells activities. This is known as aerobic respiration.
  • Produce enzymes for the metabolic conversion of food to energy.
  • Heat production: From proton leakage.
  • Signal transduction (calcium ions).
  • Cell proliferation/growth.
51
Q

Mitochondrial DNA

A
  • Mothers give genes (nucleus) and cytoplasm (mitochondria) to their children in their egg cells.
  • Fathers only give genes (nucleus).
  • Each cells contains:
    • 1000s of copies of the mitochondrial
      genome.
    • 1 copy of the nuclear genome.
  • mtDNA has a high mutation rate compared to nuclear DNA.
  • Used to study maternal family lines and recent evolutionary events.
52
Q

Chloroplast

A
  • Found in plant cells ONLY
  • Chloroplasts replicate autonomously.
53
Q

Photosynthesis

A

converting light energy to chemical energy and thus food for the plant.

54
Q

The stroma

A

contains the chloroplast DNA and ribosomes.

54
Q

Structure of the Chloroplast

A
  • Membrane
  • Stroma
  • Granum (stack)
  • Thylakoid (individual units)
  • Lamella
55
Q

The lamella

A

internal membranes with stacks of individual hollow disks called thylakoids. The stack is called a granum.

55
Q

Chlorophyll

A

contained in the thylakoids which absorbs the light and begins the process of photosynthesis.

Cell Dynamics (4 decks)

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