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A Level Biology > Cell Ultrastructure > Flashcards

Cell Ultrastructure Flashcards

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1
Q

What are prokaryotic organisms

A

Single celled organisms. Genetic material in prokaryotic cells are not enclosed by a nucleus
eg. bacteria

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2
Q

What are eukaryotic organisms

A

Multi-cellular organisms consisting of one or more cells that contain DNA in a membrane-bound nucleus, separate from the cytoplasm

eg. eukaryotes include animals, plants, fungi, protists

All eukaryotic cells contain a large number of specialised, membrane-bound organelles

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3
Q

3 structural components of the cytoskeleton

A
  • Microfilaments
  • Microtubules
  • Intermediate fibres
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4
Q

Functions of the cytoskeleton

A
  • Providing mechanical strength, support & stability to the whole cell (maintaining cell shape)
  • Allows movement of cilia/flagella
  • Changing shape of cells (cytokinesis, phagocytosis)
  • Organelles can be moved or held in place
  • Movement of chromosomes, chromatids, mRNA
  • Movement of vesicles along microtubules
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5
Q

What are Microfilaments (in cytoskeleton)

A

Fibres made from the protein, actin. They are responsible for movement of the cell & cytoplasm during cytokinesis

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6
Q

What are Microtubules (in cytoskeleton )

A

Formed by the globular protein, tubule. They polymerise to form tubes that determine the shape of the cell. They also act as tracks for organelles moving around the cell

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7
Q

What are Intermediate Fibres (in cytoskeleton)

A

Gives strength to cells & helps maintain integrity

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8
Q

4 components of the Nucleus

A
  • Double Nuclear Envelope
  • Nuclear Pores
  • Nucleolus
  • Chromatin
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9
Q

What are Double Nuclear Envelopes (in nucleus)

A

A double membrane which compartmentalises the nucleus & prevents damage. This protects the DNA

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10
Q

What are Nuclear Pores (in nucleus)

A

Allows molecules to enter (eg. nucleotides for DNA replication) & leave the cell (eg. mRNA leaves the cell)

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11
Q

What is the Nucleolus (in nucleus)

A

Site of ribosome production. Composed of RNA & proteins

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12
Q

What is the Chromatin (in nucleus)

A

Chromatin is the DNA (with associated histone proteins). It contains the genetic code which controls the activity of the cell

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13
Q

Functions of the Nucleus

A
  • Controls all the activity of the cell
  • Where the genetic code (DNA) of the cell is stored, replicated & copied into RNA (transcribed)
  • The nucleus is attached to the Rough Endoplasmic Reticulum so the mRNA can easily get to ribosomes
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14
Q

What does Rough ER stand for

A

Rough Endoplasmic Reticulum

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15
Q

Structure of Rough ER

A

Stacks of membrane bound (fluid filled) sacs which form sheets called cisternae

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16
Q

What is the Rough ER

A

The Rough ER is attached to the nucleus & covered with ribosomes. It consists of an interconnected system of flattened sacs

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17
Q

Function of the Rough ER

A

Site of protein synthesis

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18
Q

What does Smooth ER stand for

A

Smooth Endoplasmic Reticulum

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19
Q

What is the Smooth ER

A

Similar to Rough ER BUT lacks ribosomes. It is a system of interconnected tubules

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20
Q

Function of the Smooth ER

A

Responsible for lipid, carbohydrate & steroid synthesis as well as storage

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21
Q

Difference between Rough and Smooth ER

A
  • Rough ER are studded with ribosomes WHILST Smooth ER does not have ribosomes
22
Q

Similarity between Rough and Smooth ER

A
  • They BOTH have the same structure
23
Q

Structure of Ribosomes

A
  • A 2 subunit organelle
  • Made from RNA & protein
  • Not membrane bound
  • Very small organelles (abt 22nm in diameter)
  • Found free floating in the cytoplasm or attached to the Rough ER
24
Q

Function of Ribosomes

A
  • Site of protein synthesis
  • They assemble amino acids into proteins in chains using mRNA
25
Q

Structure of Mitochondria

A
  • Oval shaped
  • Surrounded by 2 membranes (double membrane)
  • The inner membrane form finger-like structure called cristae, which increases the SA
  • The solution inside is called a matrix, which contains enzymes for respiration
  • Mitochondrial DNA - small amounts of DNA, enable mitochondrion to reproduce & create enzymes
26
Q

Function of Mitochondria

A
  • Site of aerobic respiration
  • As a result of respiration, they release ATP (energy carrier in cells)
  • found in a large no. of cells that are very active & require lots of energy
27
Q

Structure of Golgi Apparatus

A
  • Stacks of flattened, membrane bound sacs (cisternae)
  • These are continuously formed from the ER at one end & budding off as Golgi vesicles at the other
28
Q

Function of Golgi Apparatus

A
  • Allows internal transport
  • Receives proteins from the Rough ER
  • Modifies & processes molecules (sa. new lipids & proteins) & packages them into vesicles. These may be secretory vesicles (if the proteins need to leave the cell) or lysosomes (which stay in the cell)
  • Makes lysosomes as well as lipid synthesis
29
Q

Structure of Lysosomes

A

They are spherical sacs surrounded by a single membrane, w no clear internal structure

30
Q

Function of Lysosomes

A

They contain powerful hydrolytic digestive enzymes known as lysozymes. Their role is to break down worn out components of the cell or digest invading cells

31
Q

Structure of Centrioles

A
  • A component of the cytoskeleton, composed of many microtubules
  • Small, hollow cylinders that occur in pairs next to the nucleus in animal cells only
  • Each centriole contains a ring of 9 triplet microtubules
32
Q

Function of Centrioles

A

Makes a copy of itself during cell division & then helps to form the spindle in cell division

33
Q

Structure of Cilia

A
  • ‘Hair like’ extensions that protrude from some animal cell types
  • In cross section, they have an outer membrane & a ring of 9 pairs of protein microtubules inside w 2 microtubules in the middle (known as a 9+2 arrangement). This arrangement allows movement
34
Q

Function of Cilia

A
  • Sensory function (eg. nose), create a current to move mucous/objects
  • For locomotion - the microtubules allow the cilia to move, used by the cell to move substances along the cell surface
35
Q

Structure of Flagella

A
  • Similar to cilia but longer
  • They protrude from the cell surface & are surrounded b y the plasma membrane
  • Like cilia they have a 9+2 arrangement (2 microtubules in centre, 9 pairs around the edge)
36
Q

Function of Flagella

A
  • ‘Whip like’, enables a cells mobility
  • The microtubules contract to make the flagellum move
  • Propels cells forward (eg. sperm cells)
37
Q

Are chloroplasts found in animal or plant cells

A

Plant cells

38
Q

Structure of Chloroplasts

A
  • Double membrane which encloses the stroma
  • Stroma contains: starch grains, lipid stores, DNA, RNA, ribosomes
  • They contain membrane-bound flattened sacs called, thylakoids in the stroma. Thylakoids stacked tg are called grana
  • Grana are linked tg by lamellae
  • The grana contains chlorophyll
39
Q

Function of Chloroplasts

A

site of photosynthesis
- some parts of photosynthesis happen in the grana & others in the stroma

40
Q

What is the Cell Surface Membrane (or Plasma Membrane)

A

The membrane found on the surface of animal cells & inside the cell wall of plant & prokaryotic cells

41
Q

Structure of the Cell Surface Membrane (or Plasma Membrane)

A
  • A phospholipid bilayer composed of proteins & lipids
42
Q

Function of the Cell Surface Membrane (or Plasma Membrane)

A
  • Regulates the movement of substance into & out of the cell
  • Contains receptor molecules which allow it to respond to chemicals like hormones
43
Q

Structure of the Cellulose Cell Wall

A
  • Made of B-cellulose microfibrils - complex carbohydrate
  • Cell wall is fully permeable to substances
  • Thin layer called the middle lamella which marks the boundary between adjacent cell walls & ‘cements’ adjacent cells tg
44
Q

Function of the Cellulose Cell Wall

A
  • Gives the plant mechanical strength, support & shape
  • Contents of plant cells can ‘push’ against the cell wall (turgid cell). This gives the cell (and whole plant) good support
45
Q

Where is the Large Permeable Vacuole found

A

Plant cells

46
Q

Structure of the Large Permanent Vacuole

A
  • Single membrane bound (membrane is called a tonoplast)
  • Contains a fluid called cell sap (solution of mineral salts, sugars, amino acids, wastes, etc)
  • Selectively permeable barrier
47
Q

Function of the Large Permanent Vacuole

A
  • Stores cell sap
  • Support herbaceous plants by making cells turgid
  • Helps maintain shape & gives support by maintaining turgor pressure
  • Sugars & amino acids act as a temporary food store
48
Q

Describe protein production

A

DNA in the nucleus contains the gene to make proteins. The particular gene is copied by mRNA, which takes the copy of the gene out of the nucleus via the nuclear pore to the ribosomes on the Rough ER. Proteins are synthesised on the ribosomes bound to the endoplasmic reticulum. They then pass into the cisternae of the RER & are packaged into transport vesicles. Vesicles containing the newly synthesised proteins move towards the Golgi apparatus via the microtubules of the cytoskeleton. The vesicles fuse w the cis face of the Golgi apparatus & the proteins enter. The proteins are structurally modified before leaving the Golgi apparatus in vesicles from its trans face. Golgi repackages the protein into secretory vesicles. The vesicles move towards & fuse w the cell-surface membrane, releasing their contents by exocytosis. Some vesicles form lysosomes - these contain enzymes for use in the cell.

49
Q

What are vesicles

A

Small fluid-filled, membrane bound sacs in the cytoplasm

50
Q

Function of vesicles

A
  • Transports substances in & out of the cell (via plasma membrane) & between organelles.
  • Some are formed by the Golgi apparatus or the ER, while others are formed at the cell surface
51
Q

What is the cytoskeleton

A
  • The organelles in cells are surrounded by the cytoplasm.
  • The cytoplasm is more than just a solution of chemicals
  • It’s got a network of protein threads (arranged as microfilaments & microtubules) running through it. These protein threads are called the cytoskeleton

A Level Biology (8 decks)

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