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Biology > The cell Topic 1 1st year > Flashcards

The cell Topic 1 1st year Flashcards

1
Q

What is a cell?

A

A cell is the basic unit of life.

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2
Q

True or false.
All cells in the body are different.

A

True. The cells that make up our kidneys are different from the ones that make up our skin. Although cells are different they all have the same basic plan.

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3
Q

What does the cell theory state?

A

1) A new cell arises from pre-existing cells
2)Each cell is a basic living unit
3) All organisms are made up of one or more cells.

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4
Q

What do we call organisms which are made up of 1 cell, and organisms which are made up of many cells? Give an example of each.

A

Unicellular and multicellular

unicellular: bacteria
multicellular: plant

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5
Q

True or false. Cells in multicellular organisms become specialised.

A

This means that specialized cells have a distinct shape and a particular function

Ex: sperm or red blood cell

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6
Q

How can we further classify cells? The ones which do not contain a membrane-bound nucleus and no membrane-bound organelles. And the ones which do?

A

Prokaryotic

Eukaryotic

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7
Q

Give an example of a prokaryote and a eukaryote.

A

Prokaryote: bacteria (more primitive)
Eukaryote: animal or human (more complex)

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8
Q

What are viruses?

A

Viruses: particles which do not have a cellular structure but they depend on host cells to replicate

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9
Q

What is an organelle?

A

An organized structure is found in cells with a distinctive shape and function. Ex: mitochondria or chloroplast

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10
Q

Describe the structure and function of the bacterial cell wall.

A

a permeable structure surrounding the cell membrane. This means that substances can pass freely through it.

Made up of peptidoglycan (murein) which is a polymer made up of sugars and amino acids.

Strong and rigid: does not burst when the cell absorbs water

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11
Q

Describe the function of the cell membrane in bacterial cells

A

Thin and flexible layer surrounds the cell.

The cell membrane is semi-permeable because it regulates the exchange of substances into and out of the cell. (and it controls what enters or leaves the cell)

Nutrients are allowed to leave and waste products are allowed to leave

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12
Q

Describe the function of the cytoplasm in the bacterial cell

A

An aqueous jelly-like substance where chemical reactions occur and organelles are suspended in it

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13
Q

Describe the structure and function of the genetic material of the bacterial cell

A

bacteria have a single-stranded nucleic acid. It is a coiled structure attached to the plasma membrane which floats in the cytoplasm

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14
Q

What are ribosomes?

A

structures made up of RNA and proteins,sites of protein syntheis

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15
Q

What is the purpose of the slimy capsule in bacteria?

A

A slimy secretion found in some bacteria which offers protection

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16
Q

What is the purpose of the flagella?

A

Usd for motility. A hollow structure is found at the base of the bacteria.Moves around in a rotating-like way

Made up of flagellin (protein)

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17
Q

What are plasmids in bacteria?

A

Tiny circles of self-replicating DNA which provide the bacteria with a survivable advantage

Plasmids can also be exchanged between living cells.

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18
Q

What is a spore?

A

These are thick protective coats which form when there are bad conditions present,like dryness,heat pr poisions. This provides protection to the bacteria

They can stay in the spare for a long time until conditions have “left”

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19
Q

Draw a well-labelled diagram if a bacterial cell

A
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20
Q

Why do large organisms consist of many cells instead of 1 large cell?

A

Exchange of nutrients and waste products are exchanged between the cell membrane and the cell’s external environment

If an organism was just made up of 1 type of cell only, this would cause 2 major problems.

distance of the cell from its centre to the surface
surface area of the cell:

If the cell si going to increase in size more oxygen and nutrients are needed.and more waste products are produced

Cell size limits cell functioning,becase it limits the exchange of nutrients and wastes between the cell and its environment

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21
Q

Describe the surface area of small organisms vs. large organisims

A

Small organisms: large surface area to volume ratio. (cytoplasm comes into contact with the outside)

Large organisms: small surface area to volume ratio. (however large organisms have developed complex organ systems like the circulatory system and the respiratory system)
The cells deep within the organism are not getting oxygen and nutrients because the cell size is limited

Because of this now the surface area to volume ratio has increased.

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22
Q

What is the nucleus? (in eukaryotic cells)

A

The largest and spherical organelle in the cell. contains chromatin and nucleolus

It controls everything that takes place inside of the cell: protein synthesis or cell division + chemical reactions take place inside of the cell. Contains the genetic material

It is surrounded by a nuclear envelope which contains pores + inner and the outer membrane.

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23
Q

What is the purpose of the pores in the nuclear envelope?

A

It allows communication between the nucleus and the cytoplasm

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24
Q

Describe the structure of the pores in the nuclear membrane.

A

The pores fuse with the inner and outer membranes

The outer membrane is continuous with the endoplasmic reticulum (can be covered with ribosomes)

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25
Q

What is chromatin?

A

Coils of DNA which are bound to basic proteins called histones

Chromatin can stain easily. 9chromatin means coloured material)
During nuclear division, they can be seen easily if stained because it condense into more tightly threads called chromosomes.

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26
Q

What are the 2 types of chromatin?

A

Heterochromatin and Euchromatin

Euchromatin: located towards the centre of the nucleus and contains loose coiled chromatin

Heterochromatin: stains intensely, located near the nuclear envelope, tightly coiled chromatin

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27
Q

What is the nucleolus?

A

Rounded darkly stained strcture in the nucleus which contains DNA and RNA

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28
Q

Mention a function of the nucleolus.

A

It makes ribosomes (manufactures ribosomal RNA)

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29
Q

In a eukaryotic cell, we also have a cell membrane, cytoplasm. Mention its functions.

A

Cell membrane: thin flexible layer which keeps together the cell’s internal contents. It is semi-permeable which means that it controls what enters or leaves the cell, and it regulates the exchange of nutrients and waste products between the cell’s cytoplasm and the external environment

Cytoplasm: an aqueous jelly-like substance where chemical reactions occur, organelles are suspended in it

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30
Q

What is the protoplasm and cytosol?

A

Protoplasm: nucleus + cytoplasm

Cytosol: the intracellular fluid

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31
Q

Draw a labelled diagram of the nucleus.

A
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32
Q

What is the endoplasmic reticulum?

A

It is made up of flattened cavities called cisternae made up of parallel membranes

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33
Q

What are the 2 types of endoplasmic reticulum?

A

Rough (with ribosomes)
Smooth (no ribosomes)

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34
Q

What is the function of the rough endoplasmic reticulum?

A

Concerned with the modification and transport of proteins which are made by the ribosomes on its surface

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35
Q

Where do the proteins made by the endoplasmic reticulum get sent after they have been modified?

A

Golgi apparatus

Theere is no continuous membrane between the 2 structures of the rough er and the golgi apparatus. The modified proteins are sent to the golgi apparatus as vesicles. These can be passed on to other organelles in the same cell.

36
Q

What is the function of the smooth endoplasmic reticulum?

A

Concerned with the synthesis of lipids and makes steroids. Transport of substances then takes place.

37
Q

What are ribosomes?

A

Sites of protein synthesis

can be found free in the cytoplasm or on the rough endoplasmic reticulum

They can be either made up of a large subunit or a small subunit

38
Q

What are ribosomes made up of?

A

Ribosomal RNA and protein

39
Q

What is the difference between ribosomes in prokaryotes and in eukaryotes?

A

Prokaryotes: smaller
Eukaryotes:slightly larger

40
Q

What is the Golgi apparatus?

A

Made up of a stack of flattened, memebrane-bound sacs called cisternae and Golgi vesicles.

41
Q

What are the 2 functions of the Golgi apparatus?

A

It makes lysosomes and transports and chemically modifies the materials contained with it ex: carbohydrate is added to proteins to form glycoproteins

42
Q

What are lysosomes?

A

simple sacs which are made up of a single membrane and contain digestive enzymes like proteases or lipases

The enzymes work best in an acidic ph and usually participate in hydrolysis reactions

43
Q

Name 4 functions of lysosomes

A

autophagy: unwanted structures are digested within the cell

autolysis: self-digestion of a cell

release of enzymes outside of the cell (exocytosis)

digestion of material taken by endocytosis

44
Q

What are microvilli?

A

finger-like extensions of the cell surface membrane which are sometimes found in animal cells, increase the surface area. They form a brush border.

45
Q

What are microtubules?

A

structures made up of fibrous protein structures which make up the cytoskeleton (skeleton of the cytoplasm/cell)

46
Q

Mention 2 functions of microtubules.

A

Give the cell’s ability to maintain their shape and are concerned with movement

47
Q

What is the mitochondria?

A

The powerhouse of all eukaryotic cells

An organelle which carries out respiration in the cell and produces atp energy molecules

48
Q

True or false.
The mitochondria contain the inner and the outer membrane. The inner membrane contains many folds called cristae.

A

True

49
Q

Draw a well labelled digram of a eukaryotic cell.

A
50
Q

In what way are plant cells similar to animal cells?

A

They both have a cytoplasm,cell membrane,nucleus and mitochondria

51
Q

Mention some structures which are found in plant cells but not in animal cells

A

Vacuole
Chloroplasts
Cell wall

52
Q

Name 2 other diffrences between plant and animal cells

A

1) Plant cells are larger than animal cells
2) Plant cells are usually cuboidal in shape whilst animal cells are round because they lack a cell wall

53
Q

Describe the cell wall in plant cells

A

Just like bacterial cells,plant cells have a cell wall.

It is a non-living rigid structure which surrounds the cell membrane .

Fully permeable meaning that it allows all substances to pass through it

Made up of cellulose

Consists of a primary and a secondary wall

54
Q

Know how to draw a mitochondria,E.R,chloroplasts, golgi apparatus

A
55
Q

Distinguish between the primary and the secondary cell wall in plant cells.

A

Primary wall: forms first (consists of cellulose microfibrils). It also runs through a mixture of other structures like polysaccharides or hemicelluloses

Secondary wall: forms later on in life
it is much more thicker and contains lignin so it gives rise to wood

56
Q

What is a cellulose?

A

An unbranched polymer of glucose.

The main constituent of cell walls in plant cells

Provides rigidity and support

57
Q

What is the middle lamella?

A

holds adjacent cells together

made up of cellulose and hemicellulose

58
Q

True or false

Not every plant cell has a secondary cell wall

A

True

59
Q

True or false.

The secondary wall will form when layers of cellulose are added to the primary wall

A

True

60
Q

Give 2 functions of lignin

A

Protects the cell from physical and chemical damage

Acts as a very hard a rigid substance giving the cell wall extra tensile strength

61
Q

True or false

A plant cell will burst if excess water is absorbed

A

False

Because of the presence of cell walls. Even if a plant cell does not have a secondary wall it will not burst due to strong cell walls because it provides lot of support,turgidity,strength and rigidity.

62
Q

What is the apoplast?

A

A system of interconnected cell walls which allows the movement of dissolved minerals and movement of water

63
Q

What is the plasmodesmata?

A

Living connections between neighbouring plant cells which run through very fine pores in the cell wall

64
Q

What is the symplast?

A

The movemet of dissolved mnerals and water between plant cells protoplasts.

When this movement occurs it occurs also thorugh vacuole to vacuole in a sytsme called the vacuolar

65
Q

What is the importance of the plasmodesmata?

A

Communication and coordination is made easier between plant cells instead of the dissolved minerals having to cross from the cell membrane

66
Q

What is the chloroplast?

A

A membrane bound organelle which contains a green pigment called chlorophyll

67
Q

Function of chloroplasts

A

They give the plant the green colour and this is where photosynthesis occurs

68
Q

What is the vacuole in plant cells?

A

A fluid -filled sac bounded by a single membrane

69
Q

What is the membrane in large central vacuoles in plant cells called?

A

Tonoplast

70
Q

What is cell sap?

A

Sugary fluid found in plant vacuoles. The fluid is made up of oxygen,carbon dioxide,pigments,some waste products,sugars and mineral salts

71
Q

True or false

The vacuole provides turgor pressure. The pressure pushes on the cytoplasm,cell wall and cell membrane helping plant cells to become firm

A

True

72
Q

What is the endosymbiotic theory?

A

It tries to explain how the eukaryotic cell arose. That eukaryotic cells evolved from prokaryotes.

73
Q

Explain the endosymbiotic theory

A

Prokaryotes are the most primitive, oldest and simplest form of cells.

Eukaryotes evolved from prokaryotes because they have only been existing for 1.4 billion years, whilst prokaryotes have been existing for longer

74
Q

Explain more

A

Over a billion years ago prokaryotes were present. Different prokaryotes had different modes of nutrition. Some ate other prokaryotes, some had photosynthetic pigments and some others absorbed food directly

A small prokaryote was englufed by a larger prokaryote. Then it started to divide. The small prokaryote was ingested but not digested

This could have led to the formation of the first chloroplast

75
Q

Name some similarities between eukaryotic and prokaryotic cells to show evidence regarding the endosymbiotic theory.

A

The functions of bacterial plasma membranes are similar to those of inner mitochondrial membranes

Similarities between the enzymes of bacteria and mitochondria

A chloroplast has a double membrane, its own DNA and ribosomes are similar in size to those of prokaryotes

The ribosomes of eukaryotes are slightly larger than those of prokaryotes

However the theory has not been proven yet because other factors still need to be studied such as the nuclear membrane

76
Q

How might the double membrane have risen?

A

When the smaller prokaryote was engulfed by the larger one the membrane of the larger prokaryote might have stretched around the plasma membrane of the smaller cell

77
Q

True or false.

Eukaryotic cells may have cilia or flagella like bacterial cells

A

True

Cilia and flagella are similar structures.

Both of these structures are outgrowths in eukrayotic cells. The cilia can move in one directon,whilst the flagella waves.

9+2 arrangment of microtubules in both structures which causes their movement

78
Q

Draw a well-labelled diagram of a plant cell

A
79
Q

What is differentiation?

A

The process that cells undergo in order to become specialized

80
Q

What is division of labour?

A

When cells become specialized to carry out a particular job

81
Q

What is a tissue?

A

A group of same cells carrying out the same job.

82
Q

What is an organ?

A

A group of tissues working together to do a particular job. EX: the heart is made up of different tissues that work together to pump blood

83
Q

What is an organ system?

A

When different organs are working in harmony together. Ex: the heart and blood vessels form part of the circulatory system

84
Q

Extra notes on endosymbiosis

A

The small prokaryote might have provided crucial nutrients to the larger prokaryote which might have led to the formation of the chloroplast or the mitochondrion.

This theory states that once the mitochondria and the chloroplasts were once prokaryotes

85
Q

Mention the S.I units of a molecule,membrane,virus,bacteria,organelle and a cell

A

molecule: 1nm
membrane:10nm
virus:100nm
bacteria: 1 micrometre
organelle: up to 10 micrometres
cell: up to 100 micrometres

Biology (19 decks)

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