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A Level Biology OCR > Cells And Organelles > Flashcards

Cells And Organelles Flashcards

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1
Q

What are organelles

A

Organelles are structurally distinct from each other and have specific functions

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2
Q

What is the nucleus surrounded by

A

A double membrane or an envelope

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3
Q

What is the largest organelle

A

The nucleus

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4
Q

What is the outer membrane in terms with the rough endoplasmic reticulum

A

The outer membrane is continuous with the rough endoplasmic reticulum

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5
Q

What are the pores in the nuclear envelope for

A

They let mRNA and ribosomes out and nutrients and hormones in

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6
Q

In the nucleus what are the chromosomes present as

A

They are in a loosely coiled state known as chromatin

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7
Q

What is chromatin

A

DNA coiled around proteins called histones

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8
Q

What is the nucleus’ purpose

A

It controls the activities of the cell

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9
Q

What is in the centre of the nucleus

A

The nucleolus

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10
Q

What is the nucleolus’ purpose

A

It makes rRNA (ribosomal RNA) and packages it with ribosomal protein to make ribosomes.

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11
Q

What are the two types of chromatin and how do they appear under an electron microscope

A

Heterochromatin is darker and is densely packed DNA
Euchromatin is lighter and is loosely packed DNA

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12
Q

What is the purpose of euchromatin

A

It acts as a template for mRNA synthesis

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13
Q

What is the Rough Endoplasmic reticulum made out of

A

Lots of membranous tubes are present in the cytoplasm. Many are studded with ribosomes giving it a rough appearance.

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14
Q

When the ribosomes make proteins what happens

A

It is transported within the ER’s flattened sac like sheets called cisternae.

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15
Q

What is the difference between the smooth and rough ER

A

The smooth ER lacks ribosomes

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16
Q

What is the purpose of the smooth ER

A

Makes lipids and steroids (cholesterol and sex hormones)
It contains enzymes that detoxify (remove toxic substances)
It is a storage site for calcium in skeletal muscle cells.

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17
Q

What is the Golgi apparatus made out of

A

A series of tightly packed flattened sacs or cisternae.

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18
Q

What does the Golgi apparatus do

A

it collects and processes protein and lipids

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19
Q

What happens at the maturing face of the Golgi apparatus

A

Vesicles bud off the maturing face and go to either the surface membrane (secretion) or form lysosomes

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20
Q

Do mitochondria have a double or single membrane

A

They have a double membrane or envelope

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21
Q

What happens to the inner membrane of the mitochondria

A

The inner membrane is highly folded to form crystae which project into the internal solution or matrix ( a jelly like substance similar to the cytoplasm.)

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22
Q

What do mitochondria do

A

They complete the later stages of aerobic respiration and synthesise most of the ATP for the cell.

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23
Q

What does the mitochondria have its own

A

It has its own DNA which is (mt)DNA so can produce their own enzymes and can reproduce themselves.

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24
Q

Is a chloroplast surrounded by a double or single membrane

A

It has a double membrane or envelope

25
Q

What is the internal solution called and what runs through it

A

The internal solution is called the stroma and flattened sacs or thylakoids run through it.

26
Q

When the thylakoids are stacked what are they called

A

Grana

27
Q

What is the chloroplasts purpose

A

It’s the site of photosynthesis. Grana trap light energy which is used to fix CO2 in the stroma.

28
Q

Where does the light dependant and independent stages of photosynthesis occur in the chloroplast

A

Light independent occurs in the stroma and light dependant in the Grana/thylakoid.

29
Q

What is a lysosome

A

A round organelle surrounded by a membrane with no clear internal structure.

30
Q

What is a lysosome

A

A round organelle surrounded by a membrane with no clear internal structure.

31
Q

What do lysosomes contain

A

They contain digestive enzymes. They digest invading cells or breaks down worn out cell components.

32
Q

What is the plasma membrane

A

It is a very thin membrane (7-10nm).

33
Q

What is the purpose of a plasma membrane

A

It is selectively permeable controlling entry and exit of materials.

34
Q

How many layers does a plasma membrane have

A

It has a trilaminar (3-layered) appearance with 2 dark layers separated by a paler middle layer.

35
Q

What is the planet cell wall

A

A rigid structure that surrounds plant cells and it’s made of cellulose.

36
Q

What is the cytoskeleton

A

A complex network of protein structures in cells that run through the cytoplasm

37
Q

What are its three main components in increasing diameter size

A

Microfilaments, intermediate fibres, microtubules

38
Q

what do microfilaments contain

A

they contain the protein actin, allowing the fibres to contract

39
Q

What are microfilaments involved in and an example

A

They are involved in cell movement, for example during cell division the cell membrane is pulled inwards dividing the cell into 2.

40
Q

What do intermediate fibres do and an example

A

They strengthen the cell, for example skin cells are subjected to mechanical stresses due to movement. So intermediate fibres prevent the stresses from damaging the cell.

41
Q

How are microtubules are formed

A

They are formed from subunits of the protein tubulin. Tubulin subunits assemble to form tubular polymers which assemble to form microtubules.

42
Q

What do microtubules do and an example

A

they are responsible for the movement of organelles. E.g vesicle movement during secretion. They also form spindly fibres allowing the movement of chromosomes ion mitosis and meiosis.

43
Q

What is the last thing Microtubules do

A

They also form complex networks to determine the shape of cells.

44
Q

What are centrioles and where are they found

A

A pair of centrioles are present just outside the nucleus set at right angles to each other. Triplets of microtubules form a ring.

45
Q

Are centrioles found in animal and plant cells

A

No they are just found in animal cells

46
Q

What are ribosomes made out of

A

They are made out of a small subunit and a large subunit. They are made of a protein and some ribosomal RNA.

47
Q

Where are ribosomes found

A

They can be attached to a membrane (rough ER) or free in the cytoplasm.

48
Q

What do ribosomes do

A

They translate the instructions carried on mRNA into protein

49
Q

What is the arrangement of cilia

A

They have a 9 + 2 arrangement

50
Q

What are cilia

A

Small hair like projection made of microtubules

51
Q

What is the difference between cilia and centrioles in terms of arrangement

A

Centrioles have 9 triplet tubules. They have no tubules in the centre./

52
Q

What is the difference between cilia and flagella

A

If they are long and few in number they are flagella, if they are short and numerous in number they are cilia.

53
Q

How are proteins produced in terms of organelles in eukaryotes (step 1)

A

The proteins are synthesised on ribosomes on the RER, they then pass into its cisternae and are packaged into vesicles, the vesicles move towards the Golgi via the cytoskeleton, the vesicles fuse with the cis face of the Golgi apparatus and the proteins enter.

54
Q

How are proteins produced in terms of organelles (step 2)

A

The proteins are structurally modified before leaving the Golgi from its trans face. Secretory vesicles carry proteins that are released from the cell. They move towards and fuse with the plasma membrane releasing their content by exocytosis. Some vesicles form lysosomes.

55
Q

What are vacuoles

A

Membrane lined sacs in the cytoplasm containing sap.

56
Q

What is the purpose of the permanent vacuole

A

They are very important in maintaining turgor pressure so that the contents of the cell push against the cell wall and maintains a rigid framework for the cell.

57
Q

What is the membrane of the vacuole called and what’s it function

A

It is called the tonoplast, it’s selectively permeable which means that some small molecules can pass through.

58
Q

What is the plasmodesmata

A

Microscopic channels that traverse the cell walls of plant cells and allow transport and communication between the adjacent cells.

59
Q

What are the enzymes inside a lysosome and what is their PH

A

They are hydrolytic enzymes, and they are acidic.

A Level Biology OCR (15 decks)

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