B2.2 Organelles and compartmentalization Flashcards

1
Q

B2.2.1 What are organelles and why are they useful?

A
  • Discrete structures in cells adapted to perform one or more vital functions.
  • Efficient because they are specialized.
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2
Q

B2.2.1 Cell components that aren’t organelles

A
  • Cell walls = extracellular structures (outside PM)
  • Cytoskeletons = narrow protein filaments spread throughout cell, not discrete enough.
  • Cytoplasm = not a discrete structure, many different structures and performs many functions.
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3
Q

B2.2.1 Organelles membranes (no, single, double)

A
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4
Q

B2.2.2 Advantage of the separation of the nucleus and cytoplasm - DNA + RNA

A
  • Chromosomes in nucleus = safeguards DNA
  • Transcription and RNA processing is in the nucleus, transport cytoplasm for translation: better quality control + gene regulation.
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5
Q

B2.2.3 Advantages of Compartmentalisation - enzymes

A

Enzymes and substrates for a particular process can be much more concentrated than if they were spread throughout the cytoplasm.

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6
Q

B2.2.2 Advantage of the separation of the nucleus and cytoplasm - signalling

A

Cytoplasm receives signals, e.g. hormones, relays to nucleus. This regulates transcription, altering gene expression.

Allows the cell to adjusts protein production to adapt to different conditions.

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7
Q

B2.2.3 Advantages of Compartmentalisation - organelles (conditions, substances, contents)

A

Substances that could damage the cell can be kept inside the organelle membrane. E.g. digestive enzymes of a lysosome could digest a cell.

Conditions e.g. pH can be maintained at optimal levels for specific process, different from other cell parts.

Organelles with their contents can be moved around within the cell.

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8
Q

B2.2.3 Advantages of Compartmentalisation - membrane potential

A

There is a larger area of membrane available for processes that happen within or across membranes.

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9
Q

B2.2.4 (HL) Adaptations of the mitochondrion - outer membrane

A

Contains transport proteins that enable the shuttling of key materials from the cytosol.

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10
Q

B2.2.4 (HL) Adaptations of the mitochondrion - inner membrane

A

Contains the electron transport chain and ATP synthase (used for oxidative phosphorylation).

Arranged into cristae that increase the SA:Vol ratio.

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11
Q

B2.2.4 (HL) Adaptations of the mitochondrion - intermembrane space

A

Small space between membranes maximises hydrogen gradient upon proton accumulation.

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12
Q

B2.2.4 (HL) Adaptations of the mitochondrion - matrix

A

Central cavity that contains appropriate enzymes and a suitable pH for the Krebs cycle to occur.

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13
Q

B2.2.5 (HL) Adaptations of the chloroplast for photosynthesis - thylakoids

A

Flattened discs = small internal volume to maximise hydrogen gradient upon proton accumulation.

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14
Q

B2.2.5 (HL) Adaptations of the chloroplast for photosynthesis - grana

A

Thylakoids are arranged into stacks to increase SA:Vol ratio of the thylakoid membrane.

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15
Q

B2.2.5 (HL) Adaptations of the chloroplast for photosynthesis - photosystems

A

Pigments are organised into photosystems in thylakoid membrane to maximise light absorption.

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16
Q

B2.2.5 (HL) Adaptations of the chloroplast for photosynthesis - stroma

A

Central cavity that contains appropriate enzymes and a suitable pH for the Calvin cycle to occur.

17
Q

B2.2.5 (HL) Adaptations of the chloroplast for photosynthesis - lamellae

A

Connects and separates grana, maximising photosynthetic efficiency.

18
Q

B2.2.6 (HL) Nucleus structure

A

The semifluid matrix found inside = nucleoplasm.

DNA within the nucleus is found as chromatin, less condensed form that organizes to form chromosomes during prophase of mitosis/meiosis.

A nucleolus/nucleoli, organelle synthesizes ribosomes.

19
Q

B2.2.6 (HL) Functional benefits of the double membrane of the nucleus - nuclear envelope

A

A system of two concentric membranes, inner and outer nuclear membrane.

Outer = continuous with endoplasmic reticulum.

Are phospholipid bilayers, which are permeable only to small nonpolar molecules.

20
Q

B2.2.6 (HL) Functional benefits of the double membrane of the nucleus - nuclear pores

A

Create a selective passageway through which molecules are able to travel between the nucleus and the cytoplasm.

21
Q

B2.2.6 (HL) Functional benefits of the double membrane of the nucleus - nuclear pores transport

A

Proteins for genome structure and function, e.g. histones, made in cytoplasm + imported into nucleus.

mRNA and tRNA transcribe in the nucleus, exported for translation. Ribosomes synthesized in nucleolus exported to the ER or cytoplasm to aid translation.

22
Q

B2.2.6 (HL) Nucleus During Cell Division

A

Disassembles and re-forms when most cells divide.

Prophase: nuclear membrane and ER are fragmented into vesicles which are moves to the edge of the cell.

Telophase: vesicles moved around the daughter chromosomes, nuclear membrane and ER reformed.

23
Q

B2.2.7 (HL) Structure of free ribosomes and of the rER

A

Site of polypeptide synthesis. Protein (stability) and rRNA.

  • Small subunit: binds to mRNA
  • Large subunit: binds to tRNA

Two subunits form a complex = translation of an mRNA sequence occurs.

24
Q

B2.2.7 (HL) Function of free ribosomes and of the rER

A
  • Free ribosomes synthesise proteins for use within the cytosol (i.e. intracellular proteins).
  • rER Ribosomes: synthesise proteins to be packaged into vesicles + sent to organelles.

Vesicles transported to Golgi a. = proteins secreted for extracellular use.

25
Q

B2.2.8 (HL) Function of the Golgi apparatus

A

Sorts, stores, modifies and exports cellular material.

Proteins (from rough ER) and lipids (from smooth ER) arrive in vesicles at the Golgi body and are modified into functional molecules.

26
Q

B2.2.8 (HL) Structure of the Golgi apparatus

A

Composed of flattened sacs (cisternae) located between the ER (cis facing) and PM (trans facing)

Different sacs = responsible for specific chemical modifications based on the enzymes involved.

27
Q

B2.2.8 (HL) Secretion from the Golgi apparatus

A

Materials for secretion are packaged into vesicles at the Golgi body for extracellular release (exocytosis).

  • Constitutive secretion: immediate release.
  • Regulatory secretion: stored in secretory vesicles for a sustained release. Triggered by a ligand binding to a specific receptor.
28
Q

B2.2.9 (HL) Structure and function of vesicles in cells

A

Membrane-wrapped containers involved in shuttling materials between cellular compartments.

Large molecules are packaged into vesicles that fuse with membranes to deliver extracellular material.

29
Q

B2.2.9 (HL) Structure of vesicles - Clathrin

A

Some vesicles form with the help of a triskelion-shaped coat protein called clathrin.

Adaptor proteins recruit C to membrane. C proteins link into a rounded lattice, pulls membrane into a bud.

Bud is cleaved by dynamin (protein) to form a vesicle, clathrin architecture disassociates.

30
Q

B2.2.9 (HL) Receptor-Mediated Endocytosis

A

Ligand binds to a receptor, which recruits clathrin.

Advantage: only the specific ligand internalised, allows greater regulatory control over what enters the cell.