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0v015 biology & pathology > Cell Biology L25 > Flashcards

Cell Biology L25 Flashcards

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1
Q

What is cytology?

A

The study of cells

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2
Q

What is morphology?

A

The study of cell form.

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3
Q

What are some examples of different types of cells?

A 
Nerve cells 
Red blood cells 
Muscle cells 
Sperm Cells 
Photo receptor cells
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4
Q

What does a general cell consist of?

A

A plasma membrane
Cytoplasm
Organelles
Nucleus

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5
Q

What are the functions of the cell membrane?

A

Maintains the integrity of the cell - not generally permeable but not a simple barrier e.g. surfaces of epithelial cells have different permeabilities.

Ensures the specific regulation of the passage of molecules inwards and outwards i.e. Specific and selective ‘gates’.

Communication - it is the site of receptors for molecules in extracellular fluid e.g. hormones, neurotransmitters, and drugs.

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6
Q

What are the two types of membrane proteins?

A

Integral (transmembrane)- span the entire membrane.
Many act as ‘gates’ for the passage of molecules in and/or out. Whilst others can be components of receptors.

Peripheral proteins - bund to one face or the other- ‘anchors’.

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7
Q

What are the functions of membrane proteins?

A 
Transport 
Enzymatic Activity 
Receptors for signal transduction 
Intercellular joining 
Cell-cell recognition 
Attachment to the cytoskeleton and Extracellular matrix (ECM)
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8
Q

What is the Glycocalyx?

A

Sugar-coating of the cell

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9
Q

What is the role of the glycocalyx and give some examples of this b?

A

It plays a role in cell-cell recognition e.g.

  • enables sperm cell to recognize egg cell
  • signals which cells should be destroyed by phagocytosis
  • determines the ABO blood group of red blood cells

The sugar cell coat also acts as a specific marker for that cell.

(Can be part of recognition of immune system)

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10
Q

What are the three types of junctions?

A

Ones which contain Sticky glycoproteins on cell surface which act as ‘glue’.

Mechanical junctions

Specialised cell-cell junctions

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11
Q

What is a cell junction?

A

Cell junctions are bridge like structures that consist of multiprotein complexes which provide contact between neighboring cells or between a cell and the extracellular matrix.

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12
Q

What is are examples of mechanical junctions in the lens?

A

Ball and socket joint between lens fibres

Tongue and groove- this is also found within the lens.

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13
Q

What are the three types of specialised cell-cell junctions?

A
  • Occluding (tight)
  • Anchoring
  • Gap
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14
Q

What is an occluding junction and how is it formed?

A

An occluding junction is also knwon as a tight junction. It is formed by adjacent proetin molecules in opposing plasma membranes sealing/occluding the space between cells. This prevents the passage of molecules between cells.

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15
Q

What are anchoring junctions and how are they formed?

A

These are called adhering junctions or desmosomes. This is where adjacent cells are joined together by fibres from the cell’s cytoskeleton.

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16
Q

Where are anchoring junctions normally found?

A

Anchoring junctions are very robust and so normally found in tissues subject to severe mechanical stress e.g. skin epithelium, cardiac muscle, uterus.

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17
Q

What is specific about desmosomes?

A

The membranes of adjacent cells thicken into plaques=. Plaques are anchored to the inside of the cell by intermediate filaments.

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18
Q

What is a belt desmosome?

A

When the desmosome goes the entire way around the cell .

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19
Q

What is the scientifc name for a belt desmosome?

A

Zonula Adherens

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20
Q

If the desmosome exsists in just a small area what is it called?

A

Spot Desmosome

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21
Q

What is the scientific name for a spot desmosome?

A

Macular Adherens

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22
Q

What is it called when a desmosome does not link adjacent cells and only links the membrane to the cytoplasm?

A

A hemidesmosome

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23
Q

What are GAP junctions?

A

Junctions whee adjacent cells are joined by their membrane proteins.

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24
Q

What is a key difference between GAP junctions and occluding junctions?

A

GAP junctions allow cytoplasmic continuity between cells i.e. this means certain molecules/ions can pass directly from one cell to the other.

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25
Q

What are the junctions between membrane proetins in GAP junctions known as?

A

Connexons

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26
Q

Why are the cells that make up the lens joined by gap junctions?

A

The lens has no blood supply instead it recieves its nutrients from the aqueous humour. The cells that make up the lens are therefore joined by GAP junctions, so nutrients can diffuse from the lens surface to cells in its interior.

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27
Q

Can a cell posses more than one type of junction?

A

Yes

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28
Q

Wht is the cytoplasm composed of?

A

Cytosol- aqueous component of the cytoplasm (with other components suspended in it). Largely made up of water but also sugars, proteins, salt etc.

Suspended in the cytosol are:

  • cytoskeleton - ‘cell skeleton’
  • membrane bound organelles
  • Inclusions - various substances found in some cells but not others e.g. melanin in retinal pigment epithelium.
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29
Q

What are the functions of the cytoskeleton?

A
  • imparts shape to the cell
  • mediates cytoplasmic movements of organelles
  • crucial in cell division
  • responsible for whole-cell movement
  • provides a framework to organise enzymatic reactions.
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30
Q

What is the cytoskeleton made up of?

A

3 types of protein filaments:

  • microtubules
  • microfilaments
  • intermediate filaments
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31
Q

What is the organising centre of microtubules called?

A

Centrosome - it contains centrioles.

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32
Q

What are cilia made up of ?

A

Microtubules

33
Q

What is the function of mitochondria?

A

Powerhouse of the cell
Site of aerobic respiration
Harnesses energy in ATP

34
Q

What is the function of ribosomes?

A

Site of protein manufacture

35
Q

What is the function of the nucleus?

A

The control centre of cells

Consists of a membrane surrounding the nucleoplasm.

36
Q

What does the nucleoplasm contain?

A

Chromatin and the nucleolus within a matrix.

37
Q

Are mechanical junctions structural adaptations of the plasma membrane?

A

Yes

38
Q

What is the structure of the nucleoplasm?

A

It is composed of chromatin and a nucleolus suspended in a matrix.

39
Q

Where would occluding junctions be found for example?

A

On skin because we don’t want water to just leak out of skin.

40
Q

What is the nucleolus responsible for?

A

For making ribosomes

41
Q

What are plaque of adjacent cells linked by in desmosomes?

A

Cadherin

42
Q

What are chromosomes made of?

A

Chromatin ( and intertwined DNA and ‘histone’ proteins)

43
Q

Where is our genetic information stored?

A

Upon chromosomes.

44
Q

Why are GAP junctions important in the heart?

A

They allow quick diffusion of ions across cells allowing for fast simultaneuos contraction.

45
Q

How does DNA exist?

A

As two complimentary chains of nucleotides that form a helical shape.

46
Q

What is the structure of a nucleotide of DNA?

A

A pentose sugar (deoxyribose), phosphate head and nitrogenous base

47
Q

What are the four different bases of a nucleotide?

A

Adenine
Thymine
Cytosine
Guanine

48
Q

What links two DNA strands together?

A

Hydrogen bonds between complimentary bases

49
Q

What is a gene?

A

A piece of DNA that codes for the production of a particular protein.

50
Q

What is each amino acid in a proetin coded by?

A

A triplet codon - which consists of 3 adjacent nucleotides.

51
Q

What are the two stages of protein production?

A

Transcription

Translation

52
Q

What is transcription?

A

When triplet codes of a gene are copied into a molecule of mRNA. This leaves the nucleus.

53
Q

What is translation?

A

When the mRNA that has left the nucleus attaches onto a ribosome. Here the mRNA combines with complementary tRNA molecules. The amino acids on adjacent tRNA molecules join to form proteins.

54
Q

Describe a quick summaary of protein synthesis.

A

The proteins we make are ‘coded’ in the DNA of our genes
The gene’s DNA is ‘transcribed’ onto mRNA
The mRNA leaves the nucleus for the cell’s cytoplasm, where it joins onto ribosomes, located on the endoplasmic reticulum.
Here proteins are made by joining together amino acids in the process of ‘translation’.
Synthesised proteins can be ‘packaged’ by the Golgi apparatus.

55
Q

What are introns?

A

Non coding DNA - i.e. it does not code for proteins

56
Q

What are exons?

A

Coding portions of DNA i.e. code for a protein

57
Q

What are autosomes?

A

Chromosomes holding genetic information relating to the body.

58
Q

What is an allele ?

A

A different form of the same gene i.e. blue eyes and brown eyes are examples of alleles as they are different genes but code for the same characteristic- eye colour.

59
Q

If two alleles are the same what is the term given?

A

Homozygous

60
Q

What are introns used for?

A

Binding sites

61
Q

How many chromosomes do humans have?

A

46 chromosomes - 23 pairs ( 22 autosomes and one sex pair).

62
Q

For homologous traits genes are located at the same what?

A

Loci

63
Q

If two alleles are different what is the term given?

A

Heterozygous

64
Q

What is a genotype?

A

A person’s genetic makeup i.e. the total number of genes they have

65
Q

What is a phenotype?

A

Genes that are expressed

66
Q

What cells do not get replaced?

A

CNS neurones , cardiac muscle , corneal endothelium cells

67
Q

What is mitosis?

A

Cell divison in which the two daughter cells have the same genetic information as the parent.

68
Q

What are the two main phases of the cell cycle?

A

Interphase

Mitotic phase

69
Q

What are the four stages of interphase?

A

G0- normal cell metabolism occurs - the duration is variable
G1- cell growth occurs, duplication of organelles , protein syntheisis
S- DNA synthesis occurs (of histones)
G2- Protein synthesis

70
Q

What happens during the S phase of interphase?

A

Two strands of DNA unwind and DNA polymerase moves along the exposed chains adding complimentary nucleotides from a pool within the nucleoplasm, forming two identical strands of DNA. (semi conservative replication).

71
Q

What occurs during G2?

A

Enzymes needed for cell division are synthesised.

72
Q

What is the splitting of the cytoplasm called?

A

Cytokinesis

73
Q

What is splitting of the nucleus called?

A

Mitosis

74
Q

What are the stages of mitosis?

A

Prophase
Metaphase
Anaphase
Telophase

75
Q

What happens in prophase?

A

Chromosomes condenses and coil forming chromatin. Nuclear envelope disappears.

76
Q

What happens in metaphase?

A

Chromosomes meet at the equator and spindle fibres attach to centromeres.

77
Q

What happens in anaphase?

A

Chromosomes are pulled apart to opposite poles of the cell via contrations of the spindle fibres.

78
Q

What happens in teleophase?

A

Nuclear envelope reforms at either pole and the cytoplasm starts splitting causing a cleavage furrow to occur.

0v015 biology & pathology (57 decks)

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