Cells, tissues and organs Flashcards
1
Q
What are cell functions?
A
- structure and activity.
2
Q
How do cells arise?
A
- division of existing cells.
3
Q
In multicellular organisms how are cells organised?
A
- They are organised into tissues, organs and systems.
4
Q
What is histogenesis?
A
- is the formation of different tissues from undifferentiated cells.
5
Q
What is cellular differentiation?
A
- The process by which a cell becomes specialised in order to perform a specific function (e.g. A liver cell or a neurone).
6
Q
What is a stem cell?
A
- An undifferentiated cell of a multicellular organism which is capable of giving rise to indefinitely more cells of the same type, and from which certain other kinds of cell arise by differentiation.
7
Q
What is organogenesis?
A
- The production and development of the organs of an animal or plant.
8
Q
What is the function of a cell membrane?
A
- Support.
- Protection.
- Controls movement of material in/out of cell.
- Barrier between the cell and its environment.
- Maintains homeostasis.
9
Q
What is the function of a nucleus?
A
- Controls cell activities.
- Contains the hereditary material of a cell (i.e. DNA).
10
Q
What is the function of a nuclear membrane?
A
- Controls movement of materials in/out of nucleus.
11
Q
What is the function of a cytoplasm?
A
- Supports and protects cell organelles.
12
Q
What is the function of a ribosome?
A
- synthesises proteins.
13
Q
What is the function of a mitochondria?
A
- Breaks down sugar (glucose) molecules to release energy.
- Site of aerobic cellular respiration.
- Mitochondria has two compartments - an outer membrane which is smooth and an inner membrane which is folded to form cristae.
14
Q
What is the function of a vacuole?
A
- Store food, water, metabolic and toxic wastes (animals have small vacuoles).
15
Q
What is the function of a lysosome?
A
- Breaks down larger food molecules into smaller molecules.
- Digests old cell parts.
16
Q
What is the function of the nucleolus?
A
- Makes ribosomes (and therefore rRNA).
17
Q
What is the function of the golgi apparatus?
A
- Has a cis and trains face.
- Modifies proteins made by the cell.
- Packages and exports proteins.
18
Q
What is the function of the centrioles?
A
- Cylindrical in shape.
- A centriole is a small set of microtubules arranged in a specific way.
- Found in pairs and move towards opposite ends of nucleus when time for cell division.
- Aid separation of chromosome pairs.
19
Q
What is the function of the cytoskeleton?
A
- Strengthens cell and maintains the shape.
- Moves organelles within the cell.
20
Q
What are the two main categories of cell?
A
- Prokaryotic.
- Eukaryotic.
21
Q
Give 3 examples of prokaryotic cells.
A
- Bacteria.
- Mycoplasmas.
- Blue-green algae.
22
Q
Give 3 examples of eukaryotic cells.
A
- Fungi.
- Protozoa.
- Multicellular plants and animals.
23
Q
What are the characteristics of a prokaryotic cell?
A
- No nuclear envelope.
- No nucleoli.
- No histones.
- Few intracellular membranes.
- 60s ribosomes.
24
Q
What are the characteristics of a eukaryotic cell?
A
- Prominent nuclear envelope.
- Nucleoli present.
- DNA complexed with histones.
- Many membrane-bound organelles.
- 80s ribosomes.
25
What is unusual about viruses?
- They are obligate parasites which lack all the characteristics of pro- and eukaryotes.
26
Define the term prokaryote.
- A microscopic single celled organism which has neither a distinct nucleus with a membrane or other specialised organelles.
27
Define the term eukaryote.
- An organism consisting of a cell (or cells) in which the genetic material is DNA in the form of chromosomes contained within a distinct nucleus (all living organisms are eukaryotes except eubacteria and archaea).
28
What is the function of nuclear pores?
- they control traffic to and from nucleus.
- Series of small holes in the nuclear membrane.
- Serves as a channel used for transporting nucleic acids and proteins in/out of the nucleus.
29
What is chromatin made of?
- DNA and nuclear proteins.
30
Name the two types of chromatin.
- Euchromatin and heterochromatin.
31
What are the characteristics of euchromatin?
- Actively transcribing.
| - Pale in colour.
32
What are the characteristics of heterochromatin?
- Not being transcribed.
- "Resting".
- Dark in colour.
33
Define the term protoplasm.
- The colourless material comprising the living part of a cell, including the cytoplasm, nucleus and organelles.
34
What is endocytosis?
- a form of active transport in which a cell transports molecules (such as proteins) into the cell by engulfing them in an energy-using process.
35
What is exocytosis?
- a form of active transport in which a cell transports molecules (such as proteins) out of the cell by expelling them in an energy using process.
36
What is the role of calcium nodules in the mitochondria.
- maintains calcium at levels required in the cell.
37
What is the difference between the rough and smooth endoplasmic reticulum?
- Rough has ribosomes on it and smooth does not.
38
What is phagocytosis?
- Process by which a cell engulfs a solid particle to form an internal vehicle known as a phagosome.
- This is a specific form of endocytosis (e.g. macrophages and some white blood cells good at this).
39
What is pinocytosis?
- a mode of endocytosis in which small particles are brought into the cell, forming an invagination and then suspended within small vesicles.
40
What is receptor mediated endocytosis (Pinocytosis)?
- Mechanism in which specific molecules are ingested into the cell.
- The specificity results from a receptor-ligand interaction.
- Receptors on the plasma membrane of the target tissue will specifically bind to ligands on the outside of the cell (e.g transferrin -transfer iron from outside to inside the cell).
41
What is the pathway for protein synthesis for secretion?
- Signal sequence on peptide.
- Insertion into ER.
- Modification and processing in ER and Golgi.
- Storage.
- Exocytosis.
42
Name the ways in which cells uptake materials.
- Diffusion.
- Active transport.
- Endocytosis (either phagocytosis or pinocytosis).
- Osmosis (if osmotic imbalance).
43
What is active transport?
- Process by which dissolved molecules move across a cell membrane from a lower to a higher concentration.
- Particles move against the concentration gradient - and therefore require an input of energy from the cell.
44
What is diffusion?
- Diffusion is the net movement of molecules or atoms from a region of high concentration to a region of low concentration (down a concentration gradient).
45
What are the components of the "degradation system" within cells?
- Lysosome.
- Peroxisome.
- Proteosome.
46
What is a lysosome?
- Membrane-bound vehicle containing digestive enzymes.
- Destroys material from in and outside the cell.
- Produced from ER and Golgi apparatus.
- Very acidic with pH of around 4.5.
- Destructive enzymes separated from the rest of the cell by membrane.
47
What is a peroxisome?
- a special types of lysosome containing catalase.
| - it converts hydrogen peroxide (toxic) to water (harmless).
48
What is the function of a proteosome?
- It degrades ubiquitinated proteins.
49
How do cells organise their internal environment?
- by membranes and cellular compartments.
50
How do cells maintain their shape?
- by their cytoskeleton.
51
- what is a cytoskeleton?
- Structure that helps cells maintain their shape and internal organisation, and it also provides mechanical support that enables cells to carry out essential functions like division and movement.
52
What are the structures making up the cytoskeleton?
- Actin microfilaments.
- Microtubules.
- Intermediate filaments.
53
What are actin microfilaments?
- Polar double stranded helical array of G actin.
- 7nm in diameter.
- Involved in shape and movement of cell.
54
What are microtubules?
- Dimers of alpha and beta tubulin arranged as hollow cylinders .
- Involved in movement within the cell.
- 25nm.
55
What are intermediate filaments?
- Rope-like twisted fibres of various proteins.
- 10nm.
- Involved in shape.
56
What are cilia and flagellae?
- These are projections from the cell.
- They are made up of microtubules and are covered by an extension of the plasma membrane.
- They are motile and designed to either move the cell itself or to move substances over or around the cell.
57
What does MTOC stand for?
- Microtubule-organising centre.
58
What is a microtubule-organising centre?
- Structure from which microtubules emerge.
- MTOCs have two main functions: (1) the organisation of eukaryotic cilia and flagella and (2) the organisation of mitotic and meiotic spindle apparatus, which separate the chromosomes during cell division.
59
How do cells interact with each other?
- Via cell junctions.
60
What is a tight junction (also known as zonula occludens)?
- Joins together the cytoskeleton of two adjacent cells (hold cells together).
- Form impermeable barrier to fluid.
- Pentalaminar (5 layer) appearance.
- Continuous lines of intramembranous particles (occludins, ZO-1, ZO2 etc, claudins, junctional adhesion molecules (JAM)).
- Prevent movement of membrane lipids, proteins and signalling molecules from apical surface to the lateral surface of the cell.
- Limit the movement of water and other molecules through intercellular space.
61
What is an endoplasmic reticulum?
- Involved in protein and lipid synthesis. (ribosomes on rough ER are site of protein synthesis, while smooth ER lacks ribosomes and functions in lipid metabolism, carbohydrate metabolism and detoxification of drugs).
62
What is an adherens junction (also known as zonula adherens or intermediate)?
- Protein complexes that occur at cell-cell junctions in epithelial and endothelial tissues, usually more basal than tight junctions.
- Defined as a cell junction whose cytoplasmic face is linked to the actin cytoskeleton.
- 20nm gap.
- Cell adhesion molecules (CAMs) - cadherins, integrins, selectins, immunoglobulin superfamily (VCAM, PECAM) etc.
- E-cadherin binds to catenin, vinculin and a-actinin.
- a-actinic binds to tonofilaments of actin in cytoskeleton.
- E cadherin link to E cadherin requires Ca++.
- Provide mechanical stability by linking cytoskeleton of adjacent cells.
63
What are desmosomes (also known as macula adherens)?
- Is a cell structure specialised for cell to cell adhesion (junctional complex).
- They are localised spot-like adhesions randomly arranged on the lateral sides of plasma membranes.
- They help to resist shearing forces and are found in simple and stratified squamous epithelium.
- The intercellular space is very wide (about 30nm).
- They are also found in muscle tissue where they bind muscle cells to one another.
- Discoid.
- Specialised cadherins: desmocollin and desmoglein between cells.
- Intracellular attachment plaques anchor.
- Link to intermediate filaments in cytoplasm.
- Perpendicular to basement membrane.
64
What is a gap junction (also known as communicating junction)?
- Specialised intercellular connection between a multitude of animal cell types.
- Directly connect the cytoplasm of two cells, which allows various molecules and ions and electrical impulses to directly pass through a regulated gate between cells.
- One gap junction channel is composed of two connexons which connect across the intercellular space.
- Gap junctions expressed in virtually all tissues of the body except adult fully developed skeletal muscle and mobile cell types such as sperm and erythrocytes.
- Allow direct communication between adjacent cells.
- Permits coordinated cell activity.
65
Name the junctional complexes?
- Tight junction (zonula occludens).
- Adherens junction (zonula adherens/intermediate).
- Desmosomes (macula adherens).
- Gap junction (communicating junction).
66
What is an extracellular matrix?
Is a collection of extracellular molecules secreted by cells that provides structural and biochemical support to the surrounding cells.
- Provides structural support for cells embedded within the tissue.
- Functions of ECM: providing support, segregating tissues from one another and regulating intercellular communication.
- Regulates the cells dynamic behaviour.
67
What is the extracellular matrix made up of?
- Proteoglycan, water, minerals and fibrous proteins. (A proteoglycan is composed of a protein core surrounded by long chains of starch like molecules called glycosaminoglycans (GAGs).
68
What are the two main classes of molecule found in the extracellular matrix?
- Fibrous proteins and proteoglycans.
69
What is a proteoglycan?
- Proteins that are heavily glycosylated.
- The basic proteoglycan unit consists of a core protein with one or more covalently attached glycosaminoglycan (GAG) chain(s).
- They occur in connective tissue.
- 90-95% carbohydrate.
70
What is a glycosaminoglycans (GAGs)?
- Long unbranched polysaccharides consisting of a repeating disaccharide unit.
- Highly polar and attract water therefore useful to the body as a lubricant or a shock absorber.
- Acidic.
- Negatively charged hydroxyl, carbonyl and sulphydryl groups (e.g. heparan sulphate and hyaluronic acid).
71
What is 'Ground substance'?
- The ground substance of the extracellular matrix is an amorphous gelatinous material.
- It is transparent, colourless, viscous and fills the spaces between fibres and cells.
- Consists of large molecules called glycosaminoglycans which link together to form even bigger molecules called proteoglycans.
- Hydrophilic: attracts water and Na+ (extracellular fluid).
72
How do tissues arise?
- Zygote (sperm and egg) (which is the single cell) undergoes cleavage to form a blastula.
- Blastula undergo gastrulation to form three germ layers which will develop into various tissues of the body.
- The germ layers: ectoderm will develop into skin and nervous system, mesoderm will develop into muscle, most internal organs and connective tissue including bone and cartilage and the endoderm develops the lining of the digestive tract and gut.
73
Explain the journey from cells to systems.
- Cells, simple tissues, compound tissues (e.g. Cortex of kidney), organ (e.g. Kidney), system (e.g. Urinary system).
74
Which fibrous proteins/molecules are found in the extracellular matrix of different tissues?
- Collagen: strong, stretch resistant fibre provides tensile strength to tissues. Most abundant protein in human body, principle constituent of your tendons and ligaments and provides support for your skin. Secreted as troop collagen and polymerised extracellularly to form collagen (at least 11 different types).
- Elastin: stretchy and resilient protein. Returns to original shape after being stretched. Tropoelastin polymerises to elastin. Requires fibrillin for assembly.
- Fibronectin: necessary for cellular division and specialisation in many tissues. Secreted from fibroblasts in a water soluble form but is quickly assembled into an insoluble mesh work. Other cells use fibronectin mesh work to migrate through a tissue (important during embryonic development)
- Laminin: principle protein in basement membranes.
75
What are the 2 forms of structural glycoproteins?
- Filamentous and non-filamentous (links cells and ECM).
76
Name structural glycoproteins (filamentous).
- Fibrillin: microfibrils 8-12nm (links to elastin).
| - Fibronectin: deposition and orientation of collagen and its links to cells via integrin.
77
Name structural glycoproteins (non-filamentous).
- Lamin: major component of basement membrane.
- Entactin: binds laminin to type found collagen.
- Tenascin: binds to integrins.
78
What are the three primary germ layers?
- Ectoderm (most exterior or distal layer).
- mesoderm (middle layer).
- endoderm (most proximal layer).
79
The body contains four primary tissues, name them.
- Epithelial.
- Connective tissues.
- Muscular tissues.
- Nervous tissues.
80
What is epithelia?
- Sheets of closely packed cells derived from one of the 3 germ layers (ectodermal, meso and endoderm) and which cover or line a surface of an organ.
- Sheets may be simple (one cell thick) or compound (made of several layers).
81
Where are connective tissues derived from?
- Comprising cells derived from mesoderm and producing an extracellular matrix of fibres and ground substance (e.g. fetal mesenchyme and cartilage).
82
What muscular tissues derived from?
- Derived from mesoderm and composed of cells (or multinucleated syncytia) whose cytoplasm contains filaments made of contractile proteins (actin, myosin etc) (e.g skeletal, cardiac and smooth).
83
Where are nervous tissues derived from?
- Develop from neuro-ectoderm (neurectoderm) and consist of cells of which the main type possesses processess called neurites (axons and dendrites) which conduct impulses when stimulated (e.g a neuron).
84
How do cells respond to their environment?
- Change in cell environment will either lead to a successful cell response to change (e.g. cell returns to normal or cell adaption) or an unsuccessful cell response to change (e.g. Cell death or neoplasia).
85
What are the major factors affecting tissue repair and regeneration?
- Type of tissue.
- Presence of stem cells.
- Blood supply.
- Nutrient supply.
- Environment.
86
Name the systems of the body.
- Nervous.
- Respiratory.
- Circulatory.
- Digestive.
- Reproductive.
- Musculoskeletal.
87
What is neoplasia?
- The new and abnormal development of cells that may be benign or malignant.
88
What are pathological stimuli?
- Severe changes in the cellular environment, which lie outside the acceptable range of normality.
89
How do cells adapt to their environment?
- Cells adapt to acceptable changes in their environment by modifying metabolism or growth pattern.
- Metabolic changes are physiological adaptions (increased cellular activity/decreased cellular activity).
- Growth pattern changes are structural adaptions (alteration of cell morphology).
90
How do cell growth patterns change in response to disease?
- Changes in size of cells (atrophy: reduction in size/hypertrophy: increase in size).
- Change in number of cells (hyperplasia: increase in number/hypoplasia: decrease in number (involution).
- Change in differentiation of cells (metaplasia: stable change to another cell type).
91
What are the changes in functional demand that can take place due to a change in environment or disease?
- Increased functional demand and reduced functional demand.
- Increased functional demand: increase in cell number (hyperplasia)/increase in cell size (hypertrophy).
- Reduced functional demand: reduction in cell number (involution)/reduction in cell size (atrophy).
92
What is necrosis?
- Form of cell injury which results in the premature death of cells in living tissue by autolysis.
- Necrosis is caused by factors external to the cell or tissue such as infection, toxins or trauma which result in the unregulated digestion of cell components.
93
What is autolysis?
- Also know as self-digestion.
| - Refers to the destruction of a cell through the action of its own enzymes.
94
What is apoptosis?
- Is a naturally occurring programmed and targeted cause of cellular death.
- Has beneficial effects to the organism.
95
Do different types of tissues have different or similar capacities for repair?
- they have different capacities for repair.
96
What is the epithelial tissue capacity for repair?
- continuous capacity for renewal.
97
What is the connective tissue capacity for repair?
- dependent on blood supply.
98
What is the muscle tissue capacity for repair?
- Poor capacity for renewal.
- Some evidence of skeletal muscle satellite cell proliferation and migration of stem cells into heart.
- Some smooth muscle proliferation.
99
What is the nervous tissue capacity for repair?
- Poor capacity for renewal.
| - Stem cells present but do not undergo mitosis.
100
Name some tissues at risk of aberrant repair?
- Liver: production of toxic drug metabolites give rise to cirrhosis of the liver.
- Burns: abnormal support tissue repair gives rise to shrinkage and scarring.
- Irritants: cause tissue damage e.g. Contact lenses on non-epithelial cornea (extra protective layer).
- Massive injury: cutting off blood supply e.g tissue death of muscle leading to fibrous scar tissue.
- Cardiac muscle: due to blood supply being cut off by blockage of coronary artery (cell death and fibrous or fatty tissue).
