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Molecules Cells and Disease (MCD) > Introduction to Cells > Flashcards

Introduction to Cells Flashcards

1
Q

Define Cell

A

The basic unit from which living organisms are made. Consists of an aqueous solution of organic molecules enclosed by a membrane. All cells arise from existing cells, usually by division.

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2
Q

What causes a cell to specialise?

A

Particular genes are switched on or off, triggered by signals from their immediate environment, which cause the production of mRNA which then manufactures a protein.

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3
Q

Define Polarity

A

Refers to a structure e.g. a fertilised egg that has an inherent asymmetry so that one side can be distinguished from the other. E.g. the apical and basolateral membranes.

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4
Q

What are the units of the size, volume and mass of cells.

A

Size - 10-20 micrometres in diameter
Volume - nanolitres
Mass - nanogram

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5
Q

What is the nucleus, nucleolus and nuclear pore?

A

Nucleus - Has a double membrane and contains DNA organised into chromosomes.
Nucleolus - Large structure in the nucleus where ribosomal RNA is transcribed and ribosomal subunits are assembled.
Nuclear pores - Specialised protein complex which controls the molecules moving in and out of the nucleus and cytoplasm.

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6
Q

What is the mitochondria?

A

Membrane bound organelle, about 0.5-10 micrometers, that carries out oxidative phosphorylation and produces most of the ATP in eukaryote cells.

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7
Q

What is a vesicle?

A

Small, membrane bound spherical organelles in the cytoplasm of a eukaryote cells

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8
Q

What are secretary granules?

A

Membrane bound organelle where molecules destined for secretion are stored before release.

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9
Q

What is Golgi Apparatus?

A

Membrane bound organelle in eukaryote cells where proteins and lipids made in the endoplasmic reticulum are modified and sorted for transport to other sites around the cell.

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10
Q

What are Ribosomes?

A

Particle composed of ribosomal RNAs and ribosomal proteins that associate with mRNA and catalyses the synthesis of proteins

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11
Q

What is the cytoskeleton?

A

System of protein filaments in the cytoplasm of a eukaryote cell that gives it shape and the capacity for directed movement. It’s main components are actin filaments (microfilaments), microtubules and intermediate filaments.

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12
Q

What is a Lysosome?

A

Intracellular membrane bound organelle containing digestive enzymes.

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13
Q

What is endoplasmic reticulum? Including smooth and rough ER

A

Endoplasmic reticulum is a membrane bound organelle in the cytoplasm where lipids and secreted and membrane-bound proteins are made.
Smooth ER - region of ER not associated with ribosomes involved in the synthesis of lipids
Rough ER - region of ER associated with ribosomes involved in the syntheis of secreted and membrane-bound proteins

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14
Q

Plasma Membrane

A

The membrane that surrounds a living cell.

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15
Q

Define Cytosol

A

Contents of the main compartment of the cytoplasm, excluding membrane-bound organelles and cytoskeletal components

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16
Q

Name some constituents of cytosol

A 
Soluble proteins
sugars
ions (K+, Na+, Ca2+, PO4 2-, Cl-)
Nucleotides (ATP, cAMP, GTP)
Amino acids
mRRNA
tRNA
Lipids
Peptides
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17
Q

Define Basement membrane

A

A thin membrane of fibres which separates two sheets of cells acting as a selective barrier. Type XV collagen is manufactured by the cell and transported out to add strength to it.

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18
Q

Define extracellular fluid

A

Complex network of polysaccharides (e.g. glycosaminoglycans, cellulose) and proteins (e.g. collagen) secreted by cells. It’s a structural component of tissues that also influences their development and physiology.

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19
Q

What can be found in extracellular matrix?

A

Ions (Na+, Cl-, Po4 2-, CO3 2-, Mg2+, Ca2+)
Soluble proteins, carbohydrates and sugars
Vitamins, amino acids, hormones, nucleotides, lipids, cholesterol
Lymph, plasma, saliva, urine, bile, sweat, milk etc

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20
Q

What are characteristics of all cells?

A
  • All have a cell membrane which separates the outside from the organised interior
  • Contain DNA as the genetic material (with exceptions)
  • Have several varieties of RNA and proteins (mostly enzymes)
  • Composed of the same basic chemicals; carbohydrates, proteins, nucleic acids, minerals, fats and vitamins
  • Regulate the flow of nutrients and waste that enter and leave the cell
  • Can reproduce and are the result of reproduction
  • Require a supply of energy
  • Are affected by and respond to reactions occurring within and around them
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21
Q

Define prokaryote

A

Major category of living cells distinguished by the absence of a nucleus or other membrane bound organelles.

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22
Q

Define eukaryote

A

Living organism composed of one or more cells with a distinct nucleus and cytoplasm.

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23
Q

What are the differences between prokaryotes and eukaryotes?

A 
Prokaryotes have
- no organelles
- no nucleus
- external flagella or pili
- cell walls containing peptido-glycan
- no cytoskeleton
Eukaryotes have 
- cilia or microvilli
- no cell wall only cell membrane
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24
Q

Name two passive forms of movement of molecules

A

Diffusion

Brownian motion

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25
Name active forms of movement of molecules. How do they get energy?
Active transport Movement of organelles, movement of cell membranes, growth and migration of cells, muscle contraction etc They need energy from hydrolysis of ATP
26
Define motor protein
Protein which uses energy from the hydrolysis of ATP to propel itslef along a protein filament or polymeric molecule e.g. myosin
27
Why is it important to study cells?
- development and repair is based on the cell cycle and differentiation - cancer is when cellular development programs are failing - infections occur when cellular defence mechanisms fail - viruses take over machinery of cells
28
What mutations can lead to cancer?
- Switch on divide signals - Switch off don't divide signals - Loss of correction mechanism on DNA replication - Loss of escape mechanisms from cell division - Loss of limit on number of times a cell can divide - Loss of control keeping cell within tissue boundaries - Ability to evade body defence mechanisms - Ability to recruit blood vessels to growing tumour - Ability to migrate into blood and lymph vessels - Ability to establish tumours in the wrong tissue
29
List the main functions of blood
- Connective tissue - Transport - Heat distribution - Immunity - Haemostasis (stopping blot flow) - Homeostasis
30
List the major components of blood
Erythrocytes Leukocytes Platelets Plasma
31
Describe the essential features of erythrocytes
- Biconcave disc - No nuclei or organelles - Packed with haemoglobin - 7.5 micrometes and flexible - molecules on the surface confer blood group
32
What is the function of erythrocytes?
Respiratory transport - binds with oxygen to form oxyhaemoglobin for transport to cells.
33
How are erythrocytes regulated?
Low oxygen Kidney (and testosterone) produces erythropoietin Bone marrow stem cells differentiate to form erythrocytes Haemoglobin increases Blood oxygen increases
34
What are reticulocytes, and what are they used to diagnose?
Reticulocytes are precursors to erythrocytes and still contain ribosomes. High levels are indicative of anaemia and chemotherapy
35
What is the life span of erythrocytes and how are they removed?
Lifespan - 120 days | Removed through reticulo-endothelial system by phagocytic macrophages in the spleen
36
What is the structure of haemoglobin?
Globular protein consisting of 4 subunits (polypeptide chains) each with a prosthetic haem group containing a ferrous iron (Fe2+) which can bind to one molecule of oxygen
37
What does haemoglobin form when it associates with O2?
Oxyhaemoglobin
38
Explain cooperative binding
The binding of one O2 molecule makes it easier for subsequent molecules as the compact shape initially means a low affinity but in oxygen rich environments (e.g. lungs) the affinity increases.
39
Why is carbon monoxide dangerous?
It conmbines with haem with 200 times greater affinity compared to O2 forming carboxyhaemoglobin, reducing oxygen binding which can deprive cells of oxygen resulting in cell death
40
What is the average concentration of haemoglobin? (g/l)
Male - 135 - 165 | Female - 115 - 145
41
What is the average red cell count ?
Male - 5.4x10^12 /L | Female - 4.8x10^12 /L
42
What is the average Haematocrit? (Packed cell volume)
Male - 0.4 - 0.54 | Female - 0.35 - 0.47
43
Define anaemia
Low blood haemoglobin concentration
44
List the three main types of anaemia and their causes.
- Microcytic (small MCV) - Failure to produce enough haemoglobin due to iron deficiency as a result of gradual blood loss e.g cancer, infection - Normocytic - Red blood cell production is normal but there is acute blood loss - Macrocytic (Large MCV) - During erythropoeisis cell division fails leaving to fewer but larger orythrocytes. Due to Folic acid and vitamin B12 deficiency (needed for division) caused by pregnancy, autoimmune disease etc
45
What are the main features of Sickle Cell anaemia?
- Haemoglobin point mutation - Causes irregular shaped erythrocytes which are destroyed in the spleen leading to anaemia - Disease only manifests in homozygous genotpype
46
What are the average percentages of different leukocytes?
- Neutrophils 40-75% - Lymphocytes 20-45% - Monocytes 2-10% - Eosinophils 1-6% - Basophils
47
What are the terms for raised and low levels of leukocytes, and reasons for it?
Leukocytosis - raised. Infection, cancer etc | Leukopenia - low. Chemotherapy, HIV etc
48
What leukocytes are polymorphic granulocytes? What are their functions and features?
- First on scene, adhere to blood vessels and migrate into infected tissue. Release inflammatory mediators: digestive enzymes, vasodilators, chemotaxins - Neutrophils - phagocytic - Basophils - produce histamine - Eosinophols - Allergic and asthma response
49
What are the key features of B-lymphocytes?
- Mature in the bone marrow - Involved in humoral response - Foreign antigen causes immunoglobulin (antibody) production - Immunoglobilins: IgM, IgG, IgA, IgD, IgE - Antibodies involved in: Precipitation, agglutination, opsonisation and neutralisation - Secondary response much stronger due to memory cells
50
What are the key features of T-lymphocytes?
- Dervied from bone marrow, matures in the thymus - Cellular immunity - Circulate body to recognise foreign antibody -> blast transformation (cloning) - When activated release chemotaxins, lymphotoxin, interferon - Include Cytotoxic T-cells, helper T-cells, supressor T-cells
51
What are the key features of Monocytes?
- Large, single horse-shoe nucleus - Appear after granulocytes - In tissue become macrophages - Engulf micro-organisms, tissue debris and dead polymorphs - Secrete inflammatory mediators and stimulate angiogenesis (vessel growth=repair)
52
What are the key features and functions of platelets?
- Derived from megakaryocytes - 2-3 micrometers in diameter - Life span 8-10 days - Many organelles, no nucleus - Release of granules promotes platelet aggregation
53
What initiates haemostasis?
- Platelet activators which platelets express surface receptors for - E.g. collagen in vessels, or thrombin from coagulation cascade
54
What is the definition of plasma and serum?
Plasma - fluid component of blood, acts as transport carrier | Serum - plasma without proteins
55
What are the functions of plasma proteins?
- Exert osmotic pressure to maintain blood volume - Akbumins and Globulins, carrier molecules e.g. hormones - Fibrinogen: clotting, platelet aggregation
56
List the steps for haemostasis
- Adhesion to exposed collagen in wound - Release of granules promoting platelet aggregation - Platelets produce thromboxane A2 from cycloxygenase enzyme - Which is involved in clot or thromus formation
57
What structures do phospholipids form in an aqueous environment?
- Micelles | - Bilayers
58
What affects the fluidity of a membrane?
- Unsaturated hydrocarbon chains has cis-double bonds forming a kink in the fatty acid chains so cannot be packed as densely - Amount of cholesterol increases rigidiity
59
How are phospholipids amphiphilic?
They contain a polar (hydrophilic) phosphate head and a non-polar (hydrophobic) fatty acid chains
60
What are key properties of the membrane?
- Selectively permeable - Impermeable to macromolecules and biochemical intermediates - permeable to nutrients and waste products - Transfer of information (signal transduction)
61
Describe the structure of a phospholipd
- The polar head group is made up of choline, phosphate and glycerol - The non polar tail is two fatty acids
62
What are the features of cholestererol?
- Modulates membrane rigidity | - Affects interactions with cytoskeleton
63
What causes the inside of the cell to be negative?
The majority of the membrane closest to the cytosol is made up of negatively charged phospholipids, whereas the extracellular membrane is neutral phospholipids and glycolipids
64
How is membrane protein movement controlled?
By intracellular actin cytoskeleton fences which limits their movement
65
In what ways does the bilayer move?
- Phospholipids can switch sides in the layer but it's rare because it needs a lot of energy - Most movement is lateral within a monolayer
66
What are lipid bilayers are permeable to?
- Water molecules - Small uncharged molecules - Lipid soluble molecules
67
What are lipid bilayers not permeable to?
- Ions - Small hydrophilic molecules - Macromolecules
68
Through what processes of movement can molecules cross the membrane?
Diffusion Facilitated Diffusion Active Transport
69
What are the two types of coupled transporters?
- Symporters: molecules move in the same direction e.g. Na+ and glucose - Antiporters: molecules move in the opposite direction e.g. Na+ and H+
70
What two forces are movement of ions dependent on?
- Concentration gradient | - Electrochemical gradient
71
Explain the movement of Na+ and K+ ions across the cell membrane
- 3 Na+

Molecules Cells and Disease (MCD) (1 decks)

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