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A Level Biology > !!!Cell Structure - The Structure Of Eurkaryotic Cells > Flashcards

!!!Cell Structure - The Structure Of Eurkaryotic Cells Flashcards

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1
Q

What makes a cell eukaryotic?

A

It has a distinct nucleus and posses membrane bound organelles

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2
Q

What is the nucleus composed of?

A
  • the nuclear envelope
  • nuclear pores
  • nucleoplasm
  • chromosomes
  • the nucleolus
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3
Q

Describe what makes up the nuclear envelope. What are the functions of the nuclear envelope?

A
  • It’s made up of a double membrane that surrounds the nucleus. It’s outer membrane is continuous with the endoplasmic rectilium of the cell and often has ribosomes on its surface.
  • it controls the entry and exit of materials in and out of the nucleus and contains the reactions taking place within it
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4
Q

What does the nuclear pore do? What’s its diameter and how many of them are in each nucleus?

A

Nuclear pores allow the passage of large molecules like mRNA out of the nucleus. It’s 40-100nm in diameter and there are around 3000 pores in each nucleus

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5
Q

What is the nucleoplasm?

A

A granular jelly like material that makes up the bulk of the nucleus

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6
Q

What do chromosomes do in the nucleus?

A

They contain the protein bound linear DNA

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7
Q

What is the nucleolus and what does it do?

A

It’s a small spherical region within the nucleoplasm. It manufactures ribosomal RNA and assembles the ribosomes
(Note there may be more than one nucleolus in a nucleus)

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8
Q

Give three functions of the nucleus

A
  • act as the control centre of the cell through the production of mRNA and tRNA and hence protein synthesis
  • retain the genetic material of the cell in the form of DNA and chromosomes
  • manufacture ribosomal RNA and chromosomes
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9
Q

What’s the diameter of the nucleus?

A

Between 10 and 15um

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10
Q

What’s the length of the mitochondrion?

A

Between 1 and 10 um

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11
Q

What are the three structures of the mitochondrion?

A
  • a double membrane
  • cristae
  • matrix
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12
Q

What does the double membrane in the mitochondrion do?

A

It controls the entry and exit of material

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13
Q

What are the cistae in mitochondrion and what do they do?

A

They are extensions of the inner membrane which in some species extend across the whole length of the mitochondrion. They provide a large surface area for the attachment of enzymes and other proteins involved in respiration

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14
Q

In the mitochondrion what does the matrix do?

A

It contains the proteins, lipids ribosomes and DNA which allow the mitochondria to control the production of some of their proteins

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15
Q

What do mitochondria do?

A

They are responsible for the production of ATP from respiratory substances like glucose as the mitochondria are the sites of the aerobic stages of respiration

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16
Q

What cells have a high number of mitochondria and a high number of the cistae within the mitochondria? Give an example

A

Cells that have a high level of metabolic acitivity as they require a plentiful supply of ATP e.g. epithelial cells in the intestines as they absorb substances via active transport

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17
Q

What are the main features of chloroplasts?

A
  • the chloroplast envelope
  • the grana
  • the stroma
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18
Q

How long are chloroplasts and what is their diameter?

A

They are 2-10 um long and 1um in diameter

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19
Q

What is the chloroplast envelope and what’s its function?

A

It’s a double plasma membrane that surrounds the organelle and very selectively allows what enters and exits the cell

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20
Q

In the chloroplast, what is the grana? What are the structures they consist of?

A

The grana are stacks of up to 100 disk like structures being thylakoids and is where the first stages of photosynthesis (light absorption) takes place. The thylakoids is where the photosynthetic pigment of chlorophyll is contained and some thylakoids have extensions which join up with thylakoids in adjacent grana.

21
Q

In the chloroplasts, what is the stroma? What does it do?

A

A fluid filled matrix that contains a number of other structures like starch grains. The stroma is where the second stage of photosynthesis (synthesis of sugars) takes place

22
Q

Give three ways chloroplasts are adapted to their function if harvesting sunlight and carrying out photosynthesis

A
  • the granal membranes provide a large surface area for the attachment of chlorophyll, electron carriers and enzymes that carry out the first stages of photosynthesis and these chemicals are attached to the membrane in a highly ordered fashion
  • the fluid of the stroma contains all the enzymes necessary to make sugars in the second stage of photosynthesis
  • chloroplasts contain DNA and ribosomes so they can quickly and easily manufacture some of the proteins needed for photosynthesis
23
Q

What is the difference that can be seen between the rough ER and the smooth ER

A

The rough ER contains ribosomes on the outer surface of the membranes whereas the smooth ER lacks ribosomes on its outer surface and appears more tubular

24
Q

What are the two functions of the rough ER

A
  • To provide a large area for the syntheses of proteins and glycoproteins
  • to provide a pathways for the transport of materials especially proteins throughout the cell
25
Q

What are the two functions of the smooth ER

A
  • to synthesise, store and transport lipids

- to synthesise, store and transport carbohydrates

26
Q

What cells have a lot of ER and give examples?

A

Cells that manufacture and store large quantities of carbohydrates, proteins and lipids like liver and secretory cells e.g. epithelial cells that line the intestines

27
Q

What is the structure of the Golgi apparatus similar to?

A

The smooth ER except that it’s more compact

28
Q

What does the Golgi apparatus consist of ?

A

A stack of membranes that make up cisternae (flattened sacks) with vesicles (small rounded hollow structures)

29
Q

What does the Golgi apparatus do?

A

Modifies and labels the proteins and lipids from the ER and

30
Q

Describe how the Golgi apparatus works in steps

A
  1. The proteins and lipids produced in the ER are passed through the Golgi apparatus in strict sequence
  2. The Golgi then modifies the proteins and often adds non protein components like carbohydrate to them.
  3. The Golgi then labels the proteins allowing them to be accurately sorted and sent to the correct destinations
  4. The proteins and lipids are then transported in Golgi vesicles which are regularly pinched off from ends of the Golgi cisternae
  5. The vesicles may then move to the cell surface where they fuse with the membrane and release these contents to the outside.
31
Q

Give the 5 functions of the Golgi apparatus

A
  • add carbohydrates to proteins to form glycoproteins
  • to produce secretory enzymes like those secreted by the pancreas
  • secrete carbohydrates such as those used to make cell walls in plants
  • transport modify and store lipids
  • form lysosomes
32
Q

What cells is the Golgi apparatus especially well developed in and give an example

A

Secretory cells like the epithelial cells that line the intestine

33
Q

How many enzymes may be contained in a single lysosome?

A

As many as 50

34
Q

What do lysosomes actually do?

A

They isolate the enzymes contained in the Golgi vesicles from the rest of the cell before releasing them either to the outside or into a phagocytic vesicle within the cell

35
Q

Give the four functions of lysosomes

A
  • To hydrolyse material injected by phagocytic cells like white blood cells and bacteria
  • to release enzymes to the outside of the cell in order to destroy material around the cell
  • to digest worn out organelles so the useful chemicals they are made of can be re used
  • to completely break down cells after they have died
36
Q

Name two cells lysosomes are especially abundant in

A

Epithelial cells and phagocytic cells

37
Q

What are ribosomes and where in the cell may they be found?

A

They are small cytoplasmic granules that occur in all cells. They may be found in the cytoplasm or associated with the rough ER

38
Q

State the two types of ribosomes, what cells they are found in and their size

A
  • 80S found in eukaryotic cells and is around 25nm in diameter
  • 70S found in prokaryotic cells, mitochondria and chloroplasts and are a bit smaller than the 80S ribosomes
39
Q

What are ribosomes composed of?

A

Two subunits (one large one small) and each contains ribosomal RNA and protein.

40
Q

What are ribosomes the site of?

How much of the cell do ribosomes account for?

A

They are the site of protein synthesis and account for 25% of the cell

41
Q

What does the cell wall consist of?

A

Microfibrils of the polysaccharide cellulose embedded in ten matrix.

42
Q

What are the 2 features of cell walls?

A
  • They consist of a number of polysaccharides like cellulose
  • there’s a thin layer (the middle lamella) which marks the boundary between adjacent cell walls and cements adjacent cell walls together
43
Q

What are the functions of the cellulose cell wall?

A
  • to provide mechanical strength in order to prevent the cell bursting under the pressure created by the osmotic entry of water
  • to give mechanical strength to the plant as a whole
  • to allow water to pass along it and so contribute of water through the plant
44
Q

What are the cell walls of algae made of?

A

Cellulose, glycoproteins or a mixture of both

45
Q

What are the cell walls of fungi made of?

A

The nitrogen containing polysaccharide of chitin, the polysaccharide glycan and glycoproteins

46
Q

What is a vacuole?

A

A fluid filled sac bounded by a single membrane

47
Q

What is the tonoplast?

A

the single membrane around the vacuole

48
Q

What does a plant vacuole contain?

A

A solution of mineral salt, sugars, amino acids, wastes and sometimes pigments such as anthocyanins

A Level Biology (36 decks)

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