Week 1 Flashcards
Describe the types of membrane proteins
The types of membrane proteins found in the membrane depend on the cell type. Hay:
Structural proteins: Proteins which attach cytoskeletal filaments to cell membrane. Adhesion molecules which attach cells to extracellular matrix
Transport proteins: eg carrier, pump and channel proteins.
Receptors: for chemical signalling between cells
Proteins with enzymatic activity
Receptor proteins are more likely to be glycoproteins
Proteins can be embedded in the membrane or associated with the membrane surface.
What are conjugated proteins?
have a chemical group associated w/ their polypep chain. Eg haemoglobin has an Iron containing heme group.
What are carrier proteins?
facilitate diffusion of large polar molecules.
A molecule/ ion combines with the binding site of a carrier protein.
ATP then transfers a phosphate group to the carrier protein on the inside of the membrane.
The carrier has a shape change, carrying and then releasing the molecule in the membrane before reverting back to its original shape.
Describe Cholesterol
Cholesterol occurs dentro the membrane and limits movement of the phospholipids, making the membrane more rigid. The organic lipid fits between the phospholipids, maintaining membrane strength.
At higher temps it stabilises cell membrane structure, and at lower temps maintains fluidity. The more unsaturated the lipids, the more fluid it will be.
Describe glycolipids
Glycolipids, occur on the outer surface of the membrane with their associated sugars. They may be involved in intercellular communication.
Describe centrioles
Each centriole is composed of nine sets of 3 microtubules.
In a pair of centrioles, the individual centrioles are arranged perpendicular to each other.
Centrioles occur in pairs and are found in an area of the cell near the nucleus called the centrosome (cell center).
The centrioles organise the microtubular network within the cell. And organises the development of the microtubules in the cilia
Describe ribosomes
Ribosomes consist of 2 subunits.
Site of mRNA translation for protein synthesis. Occurs either in cytosol (cell protein synthesis) or attached to ER (membrane or secretion protein synthesis)
Describe the rER
A network of tubules, vesicles and flattened cisternae continuous with the nuclear envelope
Function: protein synthesis in conjunction with ribosomes and modification of newly synthesised protein by glycosylation and structural changes
Describe the smooth ER
An irregular network of tubes and vesicles continuous with the rough ER
Lipid and steroid biosynthesis, protein processing and intracellular transport by packaging of products into vesicles
Describe the GApp
Vesicles from the ER fuse to form flattened, membrane bound sacs.
The GA modifies and packages proteins in vesicles for transport
Hay transport vesicles, which move within the cell, and secretory vesicles which move molecules out of the cell, (exocytosis).
The Golgi apparatus has 3 main roles:
Modification of proteins by addition of sugars
Proteolysis, activation of peptides
Sorting and packaging of macromolecules into vesicles for transport within cell and for secretion
Describe exocytosis of proteins
Transcription forms mRNA, which leaves the nucleus and joins onto a ribosome on the rough ER.
Protein moves through the ER assuming its 3-D shape en route.
Vesicles containing the protein are pinched off the rER.
These pinched off vesicles fuse to form flattened sacs of the Golgi apparatus. Proteins are modified within the Golgi apparatus.
Vesicles containing the MODIFIED protein are pinched off the G. ap.
Vesicle fuses with the cell membrane and releases the protein.
Describe microtubules
Microtubules are hollow fibres present in all cells except RBCs. Formed from 2 protein subunits, α and ß tubulin, which join alternatively to form protofilament chains. These arrange into groups of 13, forming the microtubule.
Microtubules are constantly forming and unforming w/in the cell. They grow out of the centrosome and are stabilised by associating w various proteins.
Microtubules have many functions:
Intracellular transport
Present in cilia and flagella
Form cell cytoskeleton
Form filaments of the mitotic spindle
Form centrioles and basal bodies
What are intermediate filaments?
Intermediate filaments are intermediate in size between microtubules and microfilaments. They vary slightly according to which cell type they appear in.
For example cells showing muscle differentiation contain the intermediate filament desmin and epithelial cells all contain cytokeratin.
How can intermediate filaments be used to detect breast cancer?
The cells contain cytokeratin, the epithelial type of intermediate filaments
All the cancer cells have stained black/brown with immunoperoxidase using an antibody which reacts with human cytokeratin.
The connective tissue around the cancer does not stain as these cells contain a DIFF type of intermediate filament, which doesn’t react w the cytokeratin antibody.
What is the cytoskeleton?
The cytoskeleton is made out of proteins like microfilaments, microtubules, and intermediate filaments, which all provide structural stability.
The cytoskeleton is v dynamic, allowing the cell to change shape by selectively contracting and extending filaments. This is important in some cell functions like muscle contraction, cell division, cell movement
The cytoskeleton also helps structures within the cell move from one area to another.
What are microfilaments?
Microfilaments are composed of actin and are the smallest proteins of the cytoskeleton. Various isoforms of actin occur in various amounts in diff cell types.
The majority of the microfilaments occur just below the cell membrane where they form a crosslinked mesh which provides mechanical support to the cell membrane.
Actin molecules can form bundles which protrude the cell membrane to form microvilli.
In some cells actin interacts with Myosin to generate motion.
What are microvilli? Draw a diagram in your answer
Microvilli are small finger like projections found on the apical surface of most epithelial cells.
The no and shape of the microvilli correlates w the absorptive capacity of the cell. Mircovilli increase SA of the cell.
Draw and describe mitochomdria
Mitochondria provide energy to cells through oxidative phosphorylation. They are present in all cells except red blood cells. Their morphology varies with cell type.
What does this image show and can you label it?
Histological section of breast tissue (low power). Breast tissue is mostly adipose tissue in which a few glandular elements are found. Fat stored in fat cells is usually dissolved by alcohol used during prep of cytology and histology samples so they appear as empty balloons.
What does this image show and can you label it?
Histological section of breast tissue with secretions in ducts (high power).
What are transitional cells?
Transitional cells line the whole urinary tract from the inside of the kidney, down the ureters, into the bladder and all but the last part of the urethra (lined by squamous epithelium).
Similar to squamous epithelium but can also stretch and recoil to accommodate urine and is resistant to urine’s adverse affects.
Umbrella cells are the most superficial layer of transitional epithelium.
Describe and identify the types of fibrous connective tissue.
Loose (areolar): contains elastic fibers and collagen bundles imbedded in ground substance. Found in the mucosa and submucosa of various organs and surrounding many blood vessels, nerves and muscles.
Dense irregular: course, irregularly arranged thick bundles of collagen fibers. Below is a section showing connective tissue in the dermis of the skin. Blood vessels also present.
Dense regular: regular parallel collagen fibre bundles with rows of fibroblasts between. Below is a section showing a tendon.
Describe bone
Bone is laid down by osteoblasts onto a preformed structure of cartilage or fibrous tissue by ossification.
Other cells (osteoclasts) ‘remodel’ the bone in response to weight or other forces. Bone consists of a large amount of extra-cellular calcified connective tissue w mature bone cells (osteocytes), osteoblasts and osteoclasts.
What is squamous cell carcinoma?
A type of skin cancer associated with sun exposure causing damage to the DNA in the nuclei of the squamous cells.
This can lead to uncontrolled cell division w mas cells being produced than needed, resulting in a squamous cell carcinoma.
What is arthritis and how is gout a cause of it?
Arthritis is the inflammation of joints and has many aetiologies (causes).
One cause, gout, is when the body’s ability to deal with uric acid is impaired; uric acid crystals are laid down in soft tissues and within joints.
In joints they cause an inflammatory reaction w neutrophils entering the joint, causing pain and swelling. Gout typically affects the joint of the big toe (first tarso-metatarsal joint).
Diagnose gout by looking at joint fluid under polarised light microscopy. The fluid is full of WBCs and crystals of uric acid. (see images)
What is a myocardial infarction?
When the blood supply to the muscle of the heart is obstructed by fatty deposits of atheroma in the walls of the blood vessels, the heart muscle cells die. This is called a myocardial infarction or heart attack.
Describe how diabetes can affect the nervous system.
Diabetes over mucho time affects the small blood vessels supplying organs of the body, but also affects sensory nerve endings.
It can cause lack of sensation in the feet, which impairs protective reflexes so that bones and joints of the feet become damaged and very distorted and it is difficult to walk.
