CSB (wk 1-10) Flashcards
1
Q
define magnification
A
how many times bigger an object is compared to its actual size
2
Q
define resolution
A
the distance by which 2 points must be seperated for them to be seen as 2 seperate points rather than a single fused image
3
Q
what does resolution depend on
A
- wavelength of radiation (smaller the wavelength= higher resolution)
- numerical aperture of the lens
4
Q
limit of resolution for light and electron microscopes
A
light- 200nm
electron- 1nm
5
Q
millimeter (mm) / micrometer () / nanometer (nm) / picometer (pm) as a fraction of a meter
A
10^-3 10^-6 10-^9 10^-12
6
Q
Define the term “cell” in terms of its structure and function
A
Cells are the basic unit of life. They are small membrane-bound structures containing several smaller structures called organelles.
7
Q
Explain the basic concepts of the cell theory
A
- The structural and functional unit of living organisms is the cell.
- All living things are made up of cells.
- Cells originate exclusively by division of other cells.
8
Q
similarities between animal and plant cells
A
plasma membranes, mitochondria, SER, RER, nucleus, ribosomes, lysosomes, cytoplasm, microtubules, microfilaments
9
Q
differences between animal and plant cells
A
(plants)- cellulose cell wall, chloroplasts, plasmodesmata, permanent vacuole
(animals)- centrioles
10
Q
similarities between prokaryotes and eukaryotes
A
Similarities- both have cytoplasm, cell membrane (phospholipod bilayer)
11
Q
differences between prokarotes vs eukaryotes
A
- free circular dna vs coiled dna
- not associated with histones vs associated
- small ribosomes vs larger ribosomes
- bacterial cell wall (peptidoglycan) vs cellulose/… cell wall
-prokaryotes also have flagella, capsule and plasmid
12
Q
describe a light microscope
A
- uses light waves
- can observe live specimen
- -relatively easy prep
- requires staining
- limited magnification and resolution
- x1500 mag
- 200nm resolution
13
Q
describe an electron microscope
A
- uses beams of electrons - shorter wavelength than light
- higher resolution
- images in black and white
- expensive
- x500 000
- 0.5 nm resolution
14
Q
describe a TEM
A
- Pass electrons through a specimen
- spec has to very thin
- stained with heavy metals
- spec needs to be dead
- dense regions appear darker
15
Q
describe a SEM
A
- 3D images
- spec coated with thin layers of metals so scatters electrons
- not as powerful TEM in mag or res
- can magnify thicker specs
16
Q
describe the steps of cell fractionationation
A
- Homogenisation- homogenate cell in a blender to release organelles
- in buffered (prevents organelles containing proteins denaturing), isotonic (prevents water moving into the organelles by osmosis- stops lysis) and ice cold (reduces the activity of enzymes that may break down the org)
- filter to remove debris
- suspension in centrifuged at a high speed, denser components form pellets at the bottom of the tube
- supernatant spun again at a higher speed to turn the second densest into a pellet- repeat
- nucleus, mitochondria/chloroplast
17
Q
advantages and disadvantages of being multicellular
A
advantages -
- May have complex locomotion – not restricted by a particular environment
- Can grow to large sizes
- May develop NS to be aware of surroundings
- Obtain energy from a wide variety of foods
disadvantages
- Need for a specific transport system
- Reproduction often complex and slow
18
Q
advantages and disadvantages of being unicellular
A
advantages
- No need for a transport system diffusion adequate
- Reproduction is simple and rapid
- Change and evolve more rapidly to adapt to the environment
disadvantages
- Often limited by the environment (and resources within it)
- Limited by size due to diffusion
19
Q
define differentiation
A
a natural process where a cell with less specificity develops and matures to become more distinct in terms of form and function. becomes a specialised cell.
20
Q
define specialisation
A
specialised cells are adapted structurally and biochemically to perform a particular function
21
Q
define stem cell
A
they are unspecialised cells that can reproduce for a large number of generations and under appropriate conditions differentiate into specialised cells
22
Q
what are 2 types of stem cells
A
adult
embryonic
23
Q
describe embryonic stem cells
A
- divide and differentiate into specialised embryonic tissues. i
- in the early embryo - totipotent but from the inner mass of a blastocyst, they are pluripotent
24
Q
describe adult stem cells
A
- Multipotent
- Constant renewal of adult stem cells
- These stem cells are involved in repair and replacement of specialised cells e.g skin, blood, muscle
25
hows does differentiation occur
Determination-
- the initial change in the stem cell happens at the molecular level so the cell still looks the same
- determines what genes will be switched on/off for TSP (tissue-specific proteins)
- TSP determines the structure and function of genes so that cells can be structurally and biochemically specialised
26
what is determination controlled by
- Cytoplasmic determinants
- Induction
27
what is the function of cytoplasmic determinants
- Factors in the cytoplasm of unfertilised egg – proteins and RNA molecules (coded by maternal DNA)
- regulates gene expression
- After fertilisation, early cell divisions distribute the zygote’s cytoplasm into different cells which will now contain different amounts of these factors
- These different cells will therefore begin to produce different proteins
28
function of induction
- the process by which cells within the early embryo produce and release chemicals that signal nearby cells to change their gene expression.
- More frequent/significant cause of differentiation than cytoplasmic determinants
29
what is organisation
- way in which specialised cells are grouped together to form tissues, organs and organ systems within the body
- Occurs within the developing embryo
- essential for multicellular orgs to function effectively
30
steps to organisation
occurs after stem cells divide in developing embryo to differenciate depending on cytoplasmic determinants and inductio.
1.The axis of the embryo are developed.
2.Then segmentation occurs dividing the embryo into specific areas.
3.Apoptosis (cell death) is also involved in this process
31
what is axis establishment
determines which end of the embryo is which
32
def of cranial, caudal, dorsal, ventral
cranial- front
caudal- behind
dorsal- top
ventral- under
33
what is segmentation
- the (cytoplasmic determinant) proteins which determine egg polarity affect the embryo’s genes
- Different concentrations of these proteins lead to a difference in gene expression of other genes involved in segmentation
- products of segmentation genes determine the formation of different segments within the embryo after the major axes have been determined
34
why is apoptosis important
- cell death
- Embryogenesis requires both cell division and controlled cell death for the correct development of body systems, e.g.. Morphogenesis of feet and paws- Webbed feet occur due to a lower apoptosis rate
35
name the different germ layers and name the bodily tissue it forms
Ectoderm- outer external- epidermis/ hair/ nails/ brain
Mesoderm- middle- muscle, bone, connective tissue, kidney
Endoderm- within- stomach, colon, liver, pancreas
36
what are the four classes of animal tissue
- Epithelial tissue
- Nervous tissue
- Connective tissue
- Muscle tissue.
37
describe the function of epithelial tissue
- forms a lining for many structures.
- Can be protective
- Adapted for absorption, secretion, excretion
- Has a basement membrane
- single layer = simple epithelium
- several layers = stratified epithelium
38
name 5 types of epithelial tissue and their structures
1. **simple squamous epithelium** - thin flat cells with flattened nucleus (lining of alveoli)
2. **Simple cuboidal epithelium-** Cube shaped cells with a central spherical nucleus. E.g. the cells lining the kidney tubules
3. **Simple columnar epithelium-** elongated or column shaped, the nucleus is usually found at the base
4. **Ciliated columnar epithelium-** similar shape to simple columnar epithelium but also have cilia on their surface. (lungs, cilia moves mucus along)
5. **Stratified epithelium -** several layers of cells and so provides more protection, top layer of cells becomes flattened and scaly and may be keratinised (skin/ lining of reproductive tract)
39
name the 2 types of nervous tissue and their function
1. **Glial cells**
- Protection against disease.
- Supplying nutrients from the blood to the neurones.
- Maintaining the correct balance of ions in the tissue fluid surrounding the neurones.
- Production of the insulating myelin sheath by specialised glial cells known as Schwann cells.
1. **Neurones**
- transmit information around the body in the form of action potentials, which are also called nerve impulses.
40
What is the function of connective tissue
- binds structures together
- made up of cells and an intercellular matrix
- found throughout the body
- support, protection and repair.
41
what are the 4 types of connective tissue and describe them
1. **Bone tissue**
- Made up of cells within a matrix.
- two types, Compact bone and Spongy bone
- constantly re-modelled through life
- hard because of calcium phosphate in the extracellular matrix.
2. **Blood** - liquid tissue
3. **Cartilage**
- cells called chondrocytes
- produce a matrix which is made up of collagen, glycoproteins and water.
- Unlike bone, cartilage does not contain calcium phosphate and it is therefore more flexible than bone
- continually broken down and renewed throughout life, just like bone.
4. **fibrous**
- contains fibroblast cells and an extracellular matrix
- either dense or loose depending on how many fibres are present in the matrix
- fibres can be collagen (tendons/ ligaments) or elastin (aorta wall)
DENSE
- higher proportion of fibres
- fewer cells
LOOSE-
- less fibres and more cells
- less rigid and more easily distorted
- but due to the presence of collagen, it can still provide resistance when stretched creating a tough barrier.
- eg. adipose tissue / the mesentery
42
what is 5 functions of bone in vertebrates
- Support: maintains upright posture
- Protection: protects the brain and internal organs
- Movement
- produces red blood cells
- stores minerals and fats
43
what are the 3 types of cartilage and where are they found
- **Hyaline:** surfaces of joints
- **Fibrous:** menisci of synovial joints
- **Elastic cartilage**: - ear flaps and larynx
44
whats the function of cartilage
- Structure and support to other tissues
- Cushions joints and smooths movement of joints
- ESSENTIAL for development of long bone
45
whats the outer layer of cartilage called
perichondrium
46
what are the 2 layers of cartilage and their features
- **Fibrous layer**
contains fibroblasts that produce collagenous fibres
Also contain blood vessels which supply the cartilage with nutrients and oxygen
**Chondrogenic layer**
– Remains undifferentiated and can form chondroblast
47
why are chondroblasts important?
Chondroblasts secrete a substance called Extracellular matrix
Chondroblasts mature into chondrocytes
48
what is ossification and
the process of forming bone
49
what is direct ossification
- intramembrane
-Mesenchymal cells → bone
e.g. Flat bones of skull
(primary bone formation in first 2 months)
50
describe the process of bone formation
1. outside becomes cell collar, reduces the diffusion of oxygen, and triggers the chondrocytes to expand and die.
2- The middle of the long bone is invaded by the periosteal bud (POC), bringing blood and OSTEOCLASTS (destroys cartilage) & OSTEOBLASTS(creates bone)
3- process continues. The insides are hollowed out by the osteoclasts and the osteoblasts produce bone. The very ends of the bone remain as cartilage and are not invaded until after birth as cartilage is capable of growing but bone cannot grow- essential for growth in humans
51
what is indirect ossification
-Endochondral
- Mesenchymal cells → Cartilage → Bone
- bone formation after 2 months
- Most of the bones of the skeleton are formed in this manner
52
what is the chemical composition of bone
organic = 1/3 of mass
- OSTEO cells
- matrix- collagen - strength to bone prevents it from brittleness
inorganic = 2/3 of mass
- inorganic mineral salts:
calcium phosphate
calcium hydroxide
calcium carbonate
- provides hardness
- bone is extremely strong but not brittle
53
how are bones classified by shape
- long
- short
- flat
- irregular
54
what is the gross anatomy of a long bone
- diaphysis - shaft
- epiphysis - end
- medullary cavity - canal
- periosteum - covering
- endosteum - canal lining
- articular cartilage - on endsof bones for smooth movement
- marrow
yellow - fat storage
red - blood cell formation
55
what are 4 bone cells and their functions
Osteoclast- resorbs bone (made from macrophage)
Osteogenic/ osteoprogenitor cell- stem cell
Osteoblast- forms bone matrix
Osteocyte- maintain bone tissue
56
describe osteoblasts
Secrete OSTEOID: collagen and non-collagen proteins + calcium binding protein osteocalcin. the osteoblasts become TRAPPED in the matrix. Mature into osteocytes.
57
describe osteocytes
Mature bone cells Are unable to undergo cell division Are networked to each other via long cytoplasmic extensions that occupy tiny channels called canaliculi used for exchange of nutrients and waste
58
describe osteoclasts
Different cell line from the other cells. Actually from monocytes (white blood cells). Multinuclear giant cells – fusion of many cells. Ruffled border – facing towards bone (SA – resorption).
- They secrete acid and enzymes (acid phosphatase) to breakdown bone tissue
- Dissolve bone
- Release calcium and phosphate yo replace old with new
- To change the shape of bone in response to stress
- Hormones
PTH – increase activity (increase plas. Ca2+)
Calcitonin – decrease activity
59
why is bone remodelling important
1. Homeostasis – maintaining plasma Ca2+ levels in your plasma
2. Removing old damaged tissue and replacing it with new. E.g, breaking a bone, the formation of a bone callus and then shaving away that callus
60
steps to bone remodelling
1. Bone tissue broken down by osteoclasts (acid phosphatase)
2. Releases Ca2+, Phosphate ions
3. Osteoblasts will then arrive.
4. Produce osteoid - mainly collagen and calcium binding proteins
5. This will bind calcium and phosphate ions to produce the hardened bone matrix
61
compact bone vs spongy bone
Compact:
made up of osteons
- cement layer
- lamalle
-haverisan canal
-canalicculi
lacuna
Spongy:
- honeycomb structure
- -Spaces often filled with red bone marrow
- No Haversian system
- no central canals, no perforating canals
- There are blood vessels but they are found in the spaces between the trabecullae
- Nutrients are able to diffuse through the tissue via extracellular fluid
62
what are 5 functions of blood
- Transport: including nutrients, gases, wastes
- Temperature Regulation: by altering blood flow through the skin
- Immunity: protection against pathogens
- Communication: hormones
- Defence: clotting following a wound
63
what is the composition of blood
- plasma (55%)
- red blood cells- eryth
- white blood cells- leuk
- platelets - thrombo
64
what is the process of blood cell production called
haematopoiesis
65
where is blood formed in the fetus vs in adults
in the fetus: liver and spleen and from bone marrow
in adults: **rbc/granular leucocytes/platelets** produced in red bone marrow, **leucocytes** produced in myeloid tissue (red bone marrow) & some mature in lymph tissue
66
RBC: Structure and function
structure
- biconcave disc that is round and flat without a nucleus, mitochondria and endoplasmic reticulum
- contain haemoglobin which combines with oxygen at high partial pressures of oxygen
- can change shape without breaking
- Diameter 7μm
function
- Carry oxygen in the form of oxyhaemoglobin. Each Hb molecule carries eight atoms of oxygen
- Hb readily combines with oxygen when oxygen is at a high concentration eg. lungs
- Hb releases oxygen where it is at a low concentration eg respiring tissue- muscles
- also carries carbon dioxide
some non-mammalian animals may have nuclei, eg, fish
67
WBC : Structure and Function
Structure:
- Contains a big Nucleus
- larger
- irregularly shaped - no cytoskeleton
- contains 5 types
Function:
- combat microbes either by phagocytosis or antibody production
68
name the 5 types of white blood cells and describe their function and shape
**Granular**
- neutrophils- phagocytosis
- Basophils: secrete heparin and histamine (least common) involved in allergic response
- Eosinophils: Combat parasitic infection/allergic response (pink/red granules)
**Non Granular**
- Monocytes: phagocytosis- When leave the bloodstream and transform within tissues = macrophages (one-legged horse)
- Lymphocytes:
T cell – adaptive immune response (cell-mediated immunity)
B cell –humoral immunity (relating to antibodies)
69
platelets: structure and function
- In mammals they have no nucleus
- involved in haemostasis – by forming a platelet plug where fibrin allows platelets to aggregate together.
70
Plasma Structure and function
- straw-coloured liquid that carries the cells and the platelets which help blood clot
- also contains, carbon dioxide, glucose, amino acids, proteins and water (90%) etc
71
define homeostasis
-Maintaining a stable environment within the body. Conditions that need to be controlled within limits include:
- pH
- Blood glucose levels
- Temperature control
- Water content
- Ion content
72
what is the role of blood inn homeostasis
role of blood in homeostasis
- Blood glucose levels are hormone controlled, (insulin & glucagon).
- Temperature control: vasodilation and vasoconstriction
- Water content: hormone control (ADH)
- Ion content: blood is filtered by the kidneys
- Maintaining blood pH (buffer system)
73
what are 3 types of muscle
- **skeletal**
- **smooth**
- **cardiac**
74
function of muscles
- movement- skeletal muscle contraction
- posture- continual adjustment of skeletal muscles
- protection- skeletal muscles in abdominal wall
- sphincter control- skeletal muscle control opening and closing of sphincters eg swallowing
- movement along gi tract- smooth muscle generates peristalsis
- Temperature regulation- shivering, skeletal muscle
75
describe the function of skeletal muscle
- **voluntary control**
- **striated appearance**
- **not electrically connected, each needs to receive a nerve impulse to contract unlike cardiac and smooth**
- attached to bone by tendons
76
structure of skeletal muscle
- muscle fibres (myocytes) are classified as cell- multi nuclei, large, long, many mitochondria
- myofibrils are organelles each contaisn many myofilaments (actin myyosin)
- sarcolemma = plasma membrane contains t tubules
- sarcoplasmic reticulum- endoplasmic reticulum
- T tubules store calcium ions
- Repeating units of overlapping actin and myosin filaments are organised into sarcomeres
77
describe the neuromuscular junction
- specialized form of **synapse** that forms between a neurone and myofibril.
- some motor nuerones only affect one cell while others branch to NMJs causing a cluster of muscles fibres to contract
- action potrntial travels down motor nuerone to muscle which triggers Ach to diffuse across the synapse and causes contraction
78
steps of muscle contacion
1. Calcium ions bind to troponin on actin filament, changes its hape which pushes away tropomyosin, exposing myosin binding sites.
2. Myosin binds to the exposed Myosin binding sites on the actin forming a ‘cross-bridge’.
3. the myosin heads tilts backwards, pulling the actin filament past the myosin filament ‘the power stroke’. (ADP and Pi are released)
4. A new ATP molecule attaches and breaks the cross bridge
5. The myosin head swings back forwards and is ready to bind to another binding site further along the actin
79
describe the structure of smooth muscle
- Smaller than skeletal or cardiac myocytes
- Not striated – myofilaments not arranged in sarcomeres
- Less regular – spindle shaped
- Mononuclear
- No T-tubbules
- Not attached to bone
80
where can smooth muscle be found
-Involved in internal transport
- walls of uterus
- walls of digestive tracts
- blood vessel walls
81
how does smooth muscle function
- Involuntary contraction
- Stimulated by the autonomic nervous system, hormones and in response to stretch
- Slower than skeletal muscle but able to hold for longer
- Less cross-bridges are formed, but for a longer duration*
- Maximum contractile force is the same
- ATP generation is mainly via oxidative phosphorylation
82
describe cardiac muscle
- Involuntary muscle contraction
- Striated muscle
- ATP generated by oxidative phosphorylation
- Branched
- Intercalated disks
83
what are sarcomeres
Repeating units of overlapping actin and myosin filaments are organised into sarcomeres
84
what are the 2 types of muscle fibre and describe them
**Fast twitch**
- Short term
- Fast contraction velocity
- Large diameter
- Increased CP
- More anaerobic production of ATP
**slow twitch**
- Endurance
- More blood capillaries
- Increased myoglobin
- More aerobic ATP production
85
define tonicity, hypotonic and hypertonic
- **Tonicity** = a measure of the effective osmotic pressure gradient; the water potential of 2 solutions separated by a semi-permeable membrane.
- **Hypotonic**- - The solution has a higher water potential than the cell
- **Hypertonic** - The solution has a lower water potential than the cell
86
what are measurable and immeasurable ways of water loss
- sensibile (measurable) - urine, poo, sweat
- insensible (immeasurable)- respiratory secretio,, diffusion through skin
87
what are 3 abnormal ways of fluid loss
- Urinary (polyuria): Common
- Gastrointestinal (vomiting, diarrhoea): Common
- Respiratory (fever, panting)
- Skin (burns, large wounds)
- Excessive salivation
88
name 3 types of dehydration
isotonic fluid loss, hypertonic fluid loss, hypotonic fluid loss
89
describe isotonic fluid loss
- Water and solute losses are equal eg sweating / haemorraging
- Fluid lost is isotonic so the same concentration as cells
- Extracellular volume decreases. But intracellular no change
- Fluid leaves plasma/extracellular fluid
- The concentration of electrolytes and water is the same as that which remains
- As there is the same water potential in extracellular fluid
- Therefore no driving force to remove fluid from the intracellular fluid
90
describe hypertonic fluid loss
- fluid is lost from the ECF and has high proportion of electrolytes relative to water
- Excessive perspiration, vomiting and diarrhoea, not drinking enough
- The ECF becomes hypotonic relative to ICF
- If more Na+ lost than water (relative)
- The extracellular fluid has a high water potential than intracellular
- Water moves into the intracellular out of the extracellular fluid
- Severe cases the cells will swell and cerebral swelling may occur.
- manifests as neurological symptoms ranging from headaches, nausea, lethargy, and potentially confusion, coma, and death
91
describe hypotonic fluid loss
- Water is lost from the ECF.
- The ECF then becomes hypertonic relative to ICF. - lower water potential
- Results in **HYPERTONIC DEHYDRATION**
- Inadequate water intake, excessive perspiration, osmotic diuresis (diabetes)
- E.G elevated serum sodium concentration Hypernatremia
- Too much water is lost from the extracellular fluid
- Water potential decreases in ECF relative to ICF
- Fluid moves from ICF to ECF resulting in intracellular dehydration
- leads to respiratory arrest and death
92
describe crystalloid and colloid solutions
**Crystalloid solutions:**
This is water and electrolytes that can pass between the membranes of cells easily. There are 3 types
Isotonic
Hypotonic
Hypertonic
**Colloid solutions:**
Contain insoluble molecules that can’t pass between membranes. Eg polysaccharides and proteins
93
define simple diffusion
The net movement of molecules or ions from a region of their higher concentration to a region of their lower concentration until equilibrium is reached. It is a passive process
94
describe exocytosis
process in which water-soluble and/or large substances are transported out of the cell within vesicles, without coming into direct contact with the lipid bilayer- requires energy
95
describe endocytosis
process in which water-soluble and/or large substances are transported into the cell within vesicles, without coming into direct contact with the lipid bilayer’- requires energy
96
what are the processes involving endocytosis
pinocytosis, phagocytosis
96
describe the steps of exocytosis of newly synthesised cells
1.Proteins produced in rough ER are transported to the Golgi in vesicles
2.Proteins are sorted, modified and packaged into vesicles in the Golgi
3.The vesicles are transported to the cell membrane
4.Fusion of the vesicle lipid layers with the cell membrane occurs – this process is dependent on specific proteins in both membranes
5.Vesicle contents diffuse into the extracellular fluid
97
what is endocytosis + examples
process in which water-soluble and/or large substances are transported into the cell within vesicles, without coming into direct contact with the lipid bilayer’- requires energy
e.g. pinocytosis, phagocytosis
98
steps to Pinocytosis (cell drinking)
1. Cells take up **fluid**, dissolved substances, and particles from the extracellular fluid
2. A small membrane invagination forms
3. The invagination develops until it is ‘pinched off’ to form a vesicle
4. It usually results in the formation of many small vesicles
5. The vesicles may then:
fuse with lysosomes and the contents digested by phagocytosis
-break down releasing the vesicle contents into the cytoplasm.
99
Phagocytosis steps
1. Phagocytes have receptor molecules on their surface which bind to unique bacterial chemicals
2. pathogen engulfed by phagocyte
3. enters cytoplams in vesicle
4. fuses with lysosomes which release hydrolytoc enzymes
100
define somatic
body cell
101
define mitosis and its purpose
- *a process where a single cell divides into two identical daughter cells (cell division).*
- major purpose of mitosis is for growth and to replace worn out cells.
102
what are the phases of mitosis
interphase: 90% of the cycle
- G1 (“growth phase” 1) - Cells prepare for DNA replication/ protein syntheisis occurs
- S (“synthesis”) - DNA replication occurs
- G2 (“growth phase” 2)- Short gap before mitosis / organelles grow and divide, energy stores increased
Mitosis (relatively short)
- prophase, metaphase, anaphase, telophase
Cytokenesis
- splits
103
How does CDK control cell cycle
- Cyclins are produced during each phase of the cell cycle
- A CDK will bind to the cyclin if present
- If CDK binds to cyclin it is activated.
- It will then activate another target protein
- The activated target protein is essential for the next phase of the cell cycle
- if CDK is not produced it will enter a non-dividing phase known as G0
104
describe prophase
- chromosomes condense and become visible
- nuclear envelope breaks down and nucleolus disappears
- centrioles move to opposite poles
105
describe metaphase
- centrioles produce spindle fibers
- SF attached to centromeres of sister chromatids
- sister chromatids line up at the equator
106
describe anaphase
- spindle fibres shorten so sister chromatoids are pulled apart
- centromeres split
- chromosomes move to opposite poles
107
describe telophase
- chromosomes decondensed
- nuclear envelope reforms
- the spindle is broken down
108
describe asexual reproduction- binary fission
1. circular DNA replicates
2. cytoplasmic volume increases - cell elongates
3. Circular DNA moves to opposite poles
4. cell wall starts to form in the middle (septum)
5. septum splits down the middle
109
describe the formula for mitotic index
mitotic index = number of cells in mitosis/ total number of cells counted
110
how are nucletide bases split
Pyrimidines: Thymine, uracil, cytosine
Purines: guanine, adenine
111
what is the function of DNA
- Stores and transmits genetic information.
- Instructions for development, functioning, growth, and reproduction.
- Essential for creating proteins that regulate cellular processes.
- Regulates replication and repair of cells.
- Crucial role in inheritance, passing genetic information to future generations.
- Relies on RNA intermediaries (mRNA, tRNA, rRNA) for protein synthesis in the cytoplasm.
112
function of eukaryotic chromosome
- Chromosomes contain genes which code for proteins and polypeptides and so **control all cellular functions**
- made up of “packaged” DNA (DNA can replicate) thereby allowing genetic information to be passed from one generation to another
113
what is the structure of chromosomes
- made of chromatin: DNA and proteins
- **Non-dividing cell** –They partially unravel and chromatin appears as a diffuse mass
- **Dividing cell** –They condense and can be seen as chromosomes
- Chromosomes located in the cell nucleus
- Each duplicated chromosome exists as 2 sister chromatids (after S phase)
- The chromatids are most closely attached at the centromere
- Also have
P-arm = short arm
Q-arm = long arm
114
what are telomeres
**telomeres** are protective regions at the end of each chromosome
- Do not contain genes
- Contain short sections of DNA repeated hundreds or even thousands of times
- act like the plastic caps of shoelaces- prevent chromosome from deterioration at the ends.
115
what are the ateps and process of condensation of chromosomes
1. **Naked DNA** - not associated with histone proteins or other molecules and are in their free, unbound form (double helix, sugar phosphate backbone, antiparallel)
2. **Nucleosome**- basic structural units of chromatin, consisting of DNA wrapped around histone protein
3. **Chromatosome** is a number of loosely associated nucleosomes
4. **Solenoid Formation :** Multiple nucleosomes come together to form a solenoid shape (a spiral shape)
5. **30-nm chromatin fibre-** The chromatin fibre undergo further compaction through the coiling of nucleosomes into a 30-nanometer fibre.
116
how is gene expression regulated
- compaction of chromatin can influence gene expression by modulating the accessibility of DNA to transcription factors and regulatory proteins
- The more condensed DNA is the more transcription may be restricted as access to the active gene in DNA is reduced.
- heterochromatin and euchromatin
117
what is heterochromatin
coiled
It helps to maintain the structural integrity of chromosomes, suppresses the expression of repetitive DNA elements
118
euchromatin define
uncoiled
essential for gene expression, transcriptional regulation, and cellular function. It contains most actively transcribed genes and regulatory elements required for cellular processes like growth.
119
describe the steps to semi conservative replication
1. DNA helicase breaks hydrogen bonds between base pairs.
2. This destabilises DNA, causing the two strands to separate into a replication fork.
3. Helicase progresses along DNA, continuing to unwind the double helix, like a zipper
4. SSB proteins bind to single-stranded DNA to prevent it from looping onto itself
5. **Leading strand** formed by :
- DNA polymerase III adds nucleotides ONLY in the 5' to 3' direction.
- Synthesizes leading strand continuously in 5' to 3' direction.
- Continuous replication occurs on leading strand.
1. Lagging Strand formed by:
- synthesized discontinuously in the 5' to 3' direction, which is opposite to the direction of the replication fork movement
- As the replication fork opens, DNA polymerase III synthesizes short fragments of DNA (Okazaki Fragments)
- DNA ligase then joins the adjacent Okazaki fragments together, forming a continuous strand of DNA.
120
what is the role of rna primers and primase in dna replication
- serve as **starting points** for DNA synthesis by providing **a free 3' OH group** for DNA polymerase III to extend from.
- **primase** enzyme synthesizes these short RNA sequences complementary to the DNA template at the replication fork
121
whats the difference between polymerase 1 and 3
DNA Polymerase III
- used in replication of both leading strands and the okazaki frgamets in the laggings strand
DNA polymerase 1
- role is to remove **RNA primers** and replace them with **DNA nucleotides** after DNA polymerase III has synthesized the new DNA strands
- occurs in lagging strands
122
define genetic engineering
involves inserting a foreign gene into an organism’s genome, resulting in the expression of the new gene.
123
how does gel electrophoresis work
separates fragments after a gene has been cut by restriction enzyme.
1. the tank has a positive and negative electrode at each end
2. DNA has an overall negative charge due to phosphate, so it is pulled to positive
3. smallest ones travel the furthest as they’re smaller
124
what are the steps to gene cloning
1. isolation - of DNA containing the target gene
2. insertion - of DNA into vector
3. transformation - transfer of DNA into a suitable host
4. identification - finding those host organisms containing the vector and DNA using gene markers
5. cloning - of the successful host cells
125
ISOLATION- restriction enzymes steps
1. restriction enzymes cut genes at specific recognition sites to isolate the target gene
2. recognition sites are normally palindromic
3. forms sticky ends which are complimentary to each other
4. They will join with another sticky end (i.e. from a gene to be inserted) but **only if it has been cut with the same restriction enzyme.**
5. Sticky ends are joined together using **DNA ligase**
6. forms recombinant dna
126
ISOLATION- reverse transcriptase steps
1. **Modification**: Eukaryotic DNA is first transcribed into mRNA
- The mRNA is then modified as necessary and then obtained from the eukaryotic cell e.g once introns removed
- RNA however cannot be inserted and used for transcription- a dsDNA is need for this
1. **Reverse transcriptase:** RNA → complimentary DNA (cDNA)
2. **DNA polymerase :** cDNA → dsDNA
127
INSERTION
1. the plasmid is cut by the same restriction enzyme as DNA
2. forms complimentary sticky ends
3. The target gene can be inserted and joined by dna ligase
4. Genetic transformation occurs when a cell takes up DNA and expresses the genes on that DNA. Many different types of cells can be transformed – plant, animal, human, bacterial.
5. bacteria divides and new bacteria gets plasmid
6. genes are transcribed and translated to make protein
128
how does IDENTIFICATION work
gene markers can be added to vectors (antibiotic ressistance, fluorescent, enzyme)
Usually a gene marker is disrupted if the DNA fragment is present.
129
TRANSFORMATION- Heat shock steps
- Cells are incubated with the vector in a solution containing calcium ions at 0°C. The temperature is then suddenly raised to about 40°C. This heat shock causes some of the cells to take up the vector.
1. dna is negatively charged
2. CaCl2 transformation solution
3. Ca shields negative charge
4. incubate on ice for 10 mins
5. heat shock at 42 degreees for 50 secs
6. incubate on ice for 2 mins
130
TRANSFORMATION- electroporation
- Cells are subjected to a high-voltage pulse, which temporarily disrupts the membrane and allows the vector to enter the cell.
1. cells and plasmids are mixed together
2. an electrical pulse is applied, causing pres to form
3. plasmids eneter the cell through the pores
4. pores seal with the plasmid insode transformed cell
131
steps to PCR
1. heat to 95- breaks the weak hydrogen between bases so strands separate (denatures DNA)
2. the mixture is cooled to 55, causing primers to anneal with their complimentary bases- DNA polymerase attaches
3. raise temp to 72 - optimum for DNA polymerase- adds complementary nucleotides
4. repeat, DNA doubles each time
132
define non overlapping, degenerate and universal
nonoverlapping code:
- each base is only used once in one triplet
degenerate:
- more than one triplet can code for the same amino acid
universal:
- can be applied to the DNA of all living organisms from bacteria, to plants to animals
132
what are the stop and start codons
There is a start (AUG) codon and 3 stop codons (UAA, UGA and UAG)
133
which way is the code syntheisied and ehich way is it read
code is always read 3→5 so mrna can be synthesised in 5→3 direction
134
Describe automated Sanger sequencing
1. In **automated Sanger sequencing**, all dideoxynuclueotides (ddNTPs) are combined into a single reaction, with each of the four ddNTPs being uniquely labelled with a fluorescent tag.
2. In **automated** Sanger sequencing, all oligonucleotides are run in **single capillary gel electrophoresis** within the sequencing machine
3. **computer** reads each band of the capillary gel, in order, **using fluorescence** to identify of each terminal ddNTP. In short, a laser excites the fluorescent tags in each band, and a computer detects the resulting light emitted. Because each of the four ddNTPs is tagged with a different fluorescent label, the light emitted can be directly tied to the identity of the terminal ddNTP. The output is a **chromatogram**, which shows each nucleotide’s fluorescent peak along the template DNA's length.
135
what is DNA profiling
- introns contain VNTRs
- Minisatellites vary in the number of repeats and the exact sequence of bases in the core sequence. People who are related are more likely to have the same number of repeats and the same core sequences
136
describe the 5 steps to gene fingerprinting
1. Collection and Extraction-
- most commonly collected by bucal swab, break cells,
- remove proteins, and then precipitate out and **extract** the DNA using ice-cold ethanol
2. Digestion-
- **Restriction digest** the DNA, cutting into bits. Important that you choose restriction enzymes that don’t cut in your minisatellites as you want to compare the number of repeats in different animals
3. Separation
- **Separate** out the DNA bits by length using electrophoresis. After separating the fragments of DNA you need to make them single stranded. Do this by immersing the gel in alkali solution.
- Transfer the single stranded DNA (in their exact positions to a nylon sheet by placing the nylon sheet on top of the gel and then placing blotting paper on the nylon. This draws the DNA upwards so it sticks on the sheet. Remember its single stranded now
4. Hybridization
- Now that the DNA is on the nylon sheet a probe can be added. The probe has the complementary sequence to the core sequence and will bind to it whenever it encounters it. The probe has a radioactive label so after it binds you can take an AUTORADIOGRAPH
5. Development
- Image – x ray
137
describe transcription
1. RNA polymerase II binds to promoter region of the gene and unwinds the DNA to expose the bases
2. Free ribonucleotides base pair with the exposed bases of the unwound template strand.
3. RNA polymerase links nucleotides to the 3’ end of the with the growing mRNA strand via phosphodiester bonds.
4. Once RNA polymerase reaches the transcription termination site, it detaches from the DNA template
5. mRNA is released, DNA winds back in a dsDNA form.
6. mRNA is transported to the cytoplasm via a nuclear pore.
7. introns are spliced out
138
describe translation
1. mRNA attaches to the small subunit
2. Initiation tRNA carrying Methionine loaded into the P site of small subunit
3. Anticodon UAC in tRNA aligns with codon AUG on mRNA
4. Large subunit binds to complete the ribosome
5. Complementary tRNA enters the A site, bringing its amino acid with it.
6. Anticodon in the A site tRNA aligns with codon on mRNA
7. The two amino acids are aligned
8. A peptide bond is formed, catalysed by peptidyl transferase
9. Ribosome moves along the mRNA.
10. The earlier tRNA enters E site to exit the ribosome.
11. Remaining tRNA moves to P site, exposing A site codon for a new tRNA
12. The process continues, until the ribosome reaches a stop codon
13. At the stop codon in A site, translation termination factors (release factors) signal the ribosome to split into subunits.
14. It dissociates from the mRNA.
15. Newly synthesised protein is released.
139
what are the different types
- Lethal mutation – causes organism to die prematurely
- Conditional mutation – produces phenotypic effect only under certain conditions (e.g. temperature sensitive)
- Loss-of-function mutation – reduces or abolishes (**null mutation**) activity of gene
- Gain-of-function – increases activity of gene
140
what are mutagens and examples
- Certain environmental factors, known as **mutagens**, can increase the rate at which mutations occur:
- Ionising radiation
- Viruses and microorganisms
- Chemicals
141
describe gene mutations
- changes or alterations in the DNA sequence-
- Base substitution (point mutation)
- Base insertion or deletion - Frameshift
142
what does silent, missense and nonsense mean
silent- no change
missense - changes the amino acid
nonsense- creates a stop codon
143
describe chromosome disorders and examples
- changes in the number or structure of the chromosome
- e.g. Down’s Syndrome (Trisomy 21)
- Inversion, duplication, deletion, translocation, non-disjunction
144
what's the difference between gametic and somatic mutations
**Gametic mutations**
- Take place in the reproductive organs within cells producing gametes
- They are inherited by subsequent generations
**Somatic mutations**
- “Acquired” mutations
- Occur in a body cell after fertilisation
- They are not inherited
145
describe alkanes, (structure, formula, stability, bonds)
- Simple carbon skeleton
- General formula: CnH2n+2
- forms four single covalent bonds with atoms of hydrogen or carbon.
- All the bonds are “full;- so are saturated
-This makes them very stable and not very reactive.
146
name the first 10 prefixes for number of carbons
Meth-
eth-
prop-
but-
pent-
hex-
hept-
oct-
non-
dec-
147
describe alkenes (structure, function, formula, reactivity)
- Alkenes are hydrocarbons containing at least one carbon double bond
- **Unsaturated**
- **General Formula:** CnH2n, where "n" represents the number of carbon atoms.
- **Reactivity:** Carbon-carbon double bond is reactive, undergoes addition reactions, polymerization, and oxidation.
148
describe an alcohol group
Compounds with an –OH group
149
describe carbonyl compounds and the 2 types
- aldehydes and ketones contain C=O (the carbonyl group)
- Aldehydes: the C=O is joined to at least one hydrogen and (usually) a hydrocarbon chain
- Ketones: carbonyl group is joined to two other carbon atoms
150
describe carboxylic acids
Carboxylic acids contain a -COOH group
151
describe amine groups
contain NH2 groups
152
describe amide group
Derivative of carboxylic acid where –OH group replaced by amine group (NH2)
153
describe the general formula of carbohydrates.
(CH2O)n.
154
what are the 5 and 6 carbon rings called
5- furan
6- pyran
155
describe the structure and function of glucose molecule
- hexose
- pyranose
- OH group on carbon 4 is pointing down
- C6H12O6
- the main energy source for many cells
- highly soluble so is the main form in which carbs are transported around the body
156
describe the structure and function of a galactose molecule
- OH group on carbon 4 pointing up
- pyranose
- not as soluble as glucose
- important role in the production of glycolipids and glycoproteins
157
describe the structure and function of a fructose molecule
- furanose
- very soluble
- main sugar in fruit and nectar
- sweeter than glucose
158
describe the difference between alpha and beta glucose molecules
Alpha glucose- OH on carbon 1 pointing down
Beta glucose- OH on carbon 1 pointing up
159
describe the benedicts test for reducing sugars and why this works
1. Heat the sample (90oC) with an equal volume of benedict's reagents for a few mins.
2. if solution turns red, it contains reducing sugar
- All of the monosaccharides are reducing sugars if they have an aldehyde group or a ketone group. This means that they will turn the Copper 2+ ions in benedict's solution to Cu+ . The copper goes down in oxidation state as it is reduced. In real terms it is gaining an electron from the sugar
160
describe the non reducing sugar benedicts test
do benedicts and observe a negative result
1. add acid- hcl and heat
2. nuetralise with alkali
3. this hydrolyses the glycosidic bond
4. so now benedicts can be added and heated again to form a red precipitate if non reducing sugar is present
161
why is sucrose a non-reducing sugar
sucrose isnt a reducing sugar because unlike maltose and lactose it cannot open up one of the cyclic monomers that make it up to expose its ketone group. It would need to break the glycosidic bond to do this.
162
define structural isomers and stereoisomers and name examples for each
- **Structural isomers** have different structural formulae. Three types of structural isomerism are **chain isomerism**, **positional isomerism** and **functional group isomerism**
- **Stereoisomers** have the same structural formula, but the 3D arrangement of atoms is different. Two types are ***cis–trans* isomerism** and **optical isomerism**.
163
define, chain, positional and functional group isomers
**Chain isomers**, the carbon chain is arranged differently. For example, hexane has several chain isomers, all with the molecular formula C6H14:
- **positional isomers**, the functional group is attached to a different carbon atom.
- **Functional group isomers** contain different functional groups and so are members of different homologous series
164
defien optical isomerss
- Optical isomers: molecule can exist as two isomers that are non-superimposable, mirror images of each other, just like a left hand and right hand.
- Optical isomers have the same physical properties, but they rotate polarised light in opposite directions.
165
defien chiral and achiral
- Chiral- Any molecule with 4 different groups bonded to a carbon exhibits this asymmetry and are described as **chiral**. Only chiral molecules can have optical isomers:
- Achiral- A molecule or ion is achiral if it is superimposable, i.e. it can be superimposed on its mirror image. They have a plane of symmetry or a centre of symmetry
166
What does the D and L mean on d-glucose
refer to the configuration of the chiral carbon farthest from the aldehyde or ketone group and whether it is the same as D-glyceraldehyde (-OH on right) or L-glyceraldehyde (-OH on left).
167
Describe the function, properties, structure and test for Starch
function:
- Storage of carbohydrate in plant cells, produced and stored in plastids
- Source of carbohydrate for animals
properties:
- Inert – this means that it does not readily react
- Relatively insoluble in cytosol of the cell, so it does not affect the water potential of the cell.
- Compact – which means it stores lots of glucose in a small space
- Transportable - throughout the plant when converted to sucrose
- Energy rich - stored energy in plants
- Accessible and digestible by animals – it can be readily hydrolysed (by enzymes) into smaller lengths and eventually di and monosaccharides.
structure:
- Polymer consisting of α-glucose monomers
- Joined by 1-4 glycosidic bonds
- Hydrogen bonding within the chain results in helical structure
- Starch is made up of 2 different molecules in varying ratios
- Amylose – unbranched (1-4) & Amylopectin - branched (1-6)
starch test:
- Because amylose has a spiral shape iodine molecules can fit into the centre of the spiral producing the blue/black colour
168
Describe the function, properties, and structure for cellulose
function:
- Plant structure, present in cell walls
- Particularly important in non-lignified plants
properties:
- Stable and inert
- Flexible with a high tensile strength
- Strength
- Insoluble
structure:
- Structural polysaccharide
- Monomers of β-glucose, joined with 1-4 glycosidic links
- Every other Beta-glucose monomer must rotate about 180 degrees to form glycosidic bonds:
- Straight chains not helix due to the bond angle created by rotating the monomers
- H-bonds are also formed between glucose units of parallel molecules ensuring straight chains.
fibresµfibrils:
- The parallel arrangement of cellulose chains in plant cell walls contributes to the formation of microfibrils, which in turn assemble into larger fibres
169
Describe the function, properties, and structure for glycogen
function:
- Storage of carbohydrate in animal cells
- Also known as “animal starch”
- In vertebrates found mainly in liver and muscle cells as granules in the cytoplasm
- Only provides a short-term store
properties:
- Readily and specifically degraded for use in the animal
- Insoluble in cytosol of the cell
- Compact
- Energy rich
structure:
- Polymer made up of **αglucose** monomers
- Similar in structure to **amylopectin**
- **Extensive branching** and so less spiralling
- With greater branching there is greater surface area for enzyme activity, so it is more easily hydrolysed into monosaccharides
170
Describe the function, properties, and structure for chitin
function:
- Exoskeletons of made up of layers of protein with chitin
- Some fungal cell walls used to provide strength and structure in place of cellulose
properties:
- Tough
- Flexible
- Readily forms H-bonds with other polar macromolecules
structure:
- Chitin is a polymer of *N*acetylglucosamine, a sugar that contains an amide functional group
- Similar structure to cellulose, but the hydroxyl groups of the second carbon of each glucose unit have been replaced with acetamido (**NH(C=O)CH3**) groups.
- The monomers are linked by β 1-4 glycosidic bonds, which gives the molecule strength and rigidity as in cellulose
- The amide groups form strong H-bonds between parallel chains
171
Describe the function, properties and structure for pectin
function:
- Plant cell walls – It provides structural support to plant cell walls.
- Fruits – in fruits helps cells bind together - which is known as cell to cell adhesion, giving the cells firmness and shape.
- **Acts as a gelling agent.** In certain foods like jam, it will **help hold water** and this contributes to the consistency of the jam – basically makes things thicker.
properties:
- Soluble / interacts with water molecules or positive ions depending on the degree of esterification
- However, pectin’s solubility is variable because of the carboxyl being esterified. The ester group is less able to interact with positive cations and has less ability to interact via hydrogen bonds with water.
structure:
- Pectin is a polymer of α-galacturonic acid with a variable number of **methyl ester groups**
- The Degree of Esterification (DE) affects the gelling properties of pectin
172
describe the electron transport chain
1. NADH interacts with an enzyme of Complex I that catalyses a redox reaction:
- Oxidises NADH → NAD+
- Hydrogen atoms are released as H+ and electrons
- The coenzyme is reduced (by accepting the electrons released by NADH)
1. The electrons are passed down the chain of proteins in the ETC, in a series of redox reactions - reducing molecules as they flow through the chain.
- Each electron acceptor is slightly more electronegative than the one before
1. As they pass down the chain, the electrons exist at lower energy levels – the energy “lost” by the electrons is used later!.
2. Between complexes, electrons are shuttled by the molecules ubiquinone and cytochrome c which diffuse rapidly within the membrane
3. FADH2 does not deliver its electrons at the start of the chain, but at Complex II.
4. During the last step, oxygen atoms are the final electron acceptors (complex IX) and O2- ions are formed. These ions react with H+ ions and water is formed.
173
where does each stage of respiration occur
glycolysis- cytoplasm
link reaction- mitochondrial matrix
krebs- mitochondrial matrix
ETC- mitochondrial membrane
174
whats the balanced equation for respiration
C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP
175
Describe the steps of glycolysis
1. 6C glucose is converted to fructose-1,6- biphosphate by the addition of 2 phospates from 2ATP-> 2 ADP reaction
2. fructose 1,6 biphosphate splits into 2 triose phosphate as it is unstable
3. each triose phosphate becomes pyruvate by converting 2 ADP -> 2ATP and 1 NAD-> NADH
4. NET: 2 ATP, 2 NADH, 2 Pyruvate
176
describe both anaerobic pathways of glycolysis
**Lacatate fermentation:** Pyruvate is reduced to lactate as NADH is oxidised to NAD (regenerated)
The NAD can then be used in glyclysis again
**Ethanol**
- pyruvate undergoes a decarboxylation first, becoming ethanal.
- Then the ethanal is reduced
and NADH is oxidised so NAD can be reused in glycolysis
177
Describe the link reaction
1. Carbon is removed as the waste product CO2.
2. The second thing to happen is another hydrogens are removed and more NADH + H+ is produced. Again 2 NADHs as there are two pyruvates
3. The third thing is the remaining 2 carbon molecule is added to Co-enzyme A, to produce acetyl-CoA
178
Describe the Krebs cycle
1. Acetyl CoA (2C) is added to Oxaloacetate (4C) to form Citric acid (6C)
2. Citric acid goes through decarboxylation (loses CO2), and oxidation as NAD is reduced to NADH- becomes 5C compound
3. 5C compound is decarboxylated (loses CO2) and is oxidised x3 (2 NADH is formed and 1 FADH) and is dephosphorylated (1x ATP)- forms oxaloacetate (4C)
4. NET: 4x CO2, 6x NADH, 2x FADH, 2x ATP
179
Describe the processes in the liver
Glycogenesis: Stores excess glucose as glycogen
glycogenolysis: the breakdown of glycogen to glucose for transport around body
gluconeogenesis convert amino acids, lactate, pyruvate and glycerol into glucose too
High blood pressure- pancreas releases insulin- glucose moves into rissue cell and liver- liver converts glucose to glycogen- lowers blood sugar + inverse with glucagon
180
describve the sructure of triglycerides
-Glycerol molecule: has three OH groups
- Fatty acids react with the carboxyl groups (COOH-)
- ester bonds - a triglyceride is generated
181
how are triglycerides hydrolysed and what are the components are used for
Lipase enzymes breaks teh ester bonds, 3 h2os are added to form 1 glycerol and 3 fatty acis
fatty acids used for:
- energy via Beta oxidation pathway.
- chopped into 2 carbon chain units- make acetyle coA- krebs cycle
Glycerol used for:
- can be converted into glyceraldehyde 3-phosphate which is an intermediate on the glycolytic pathway
182
what are adipose cells
Adipose cells (adipocytes) are cells in mammals specialised for the synthesis & storage of triglycerides and for their mobilisation (via blood) into fuel molecules
183
Describe the structure of phospholipids and its functions
- similar to triglyceride but third hydroxyl group of the glycerol is joined to a phosphate (PO43-) group, which has a negative electrical charge (2 fatty acids, glycerol and phosphate)
- All phospholipids contain both a hydrophilic and hydrophobic moiety
- Polar head group (phosphate group)
- Non-polar hydrocarbon tails
- Inside water, phospholipid molecules arrange themselves in bilayers or micelles (globular structure)
- Hydrophilic head “likes” to be in contact with water
- Hydrophobic tail tries to avoid water
- Fatty acid chains too bulky to fit inside micelle so phospholipids tend to form bilayers
- Extensive bimolecular sheet can form – cell membrane
184
describe the process of ipid absorption
1. Large lipid droplets in your intestines
2. Bile from the bile duct, stored in the gall bladder and produced by the liver will emulsify the fat top form micelles
3. Pancreatic lipase will then have a greater surface are to hydrolyse the triglyceride
4. breaks ester bonds and forms Monoglyceride and 2 fatty acids
5. Absorbed directly into the intestinal epithelial cell – lipid soluble
6. Enter the SER, where the recombine to form triglycerides
7. then at the golgi they have protein added to them and they form a lipoprotein called a chylomicron.
8. This then travels into the lymph vessel (lacteal) via exocytosis
9. - Chylomicrons transport triglycerides in the bloodstream
- to adipose tissue and liver for storage
- to active muscle for energy supply
185
what's the absorptive state and how are fats metabolised in this state
**Absorptive- utilise nutrients**
**Chylomicrons**
- Transport TG from the GIT into the lymph and then into blood
- Large, lighter, mainly TG
- **VLDL** (very low density lipoprotein)
- Synthesized in liver, high in TG
- TG transport in post-absorptive state
- **LDL** (loe density lipoprotein)
- Transports cholesterol to cells
- **HDL**
- Transports cholesterol from tissues to liver
density determined by ratio of protein to lipids, lipids are lower density so the more lipids there are the lower the density but as lipds are lost the density increases
186
what is the post absorptive state and what are the 3 steps to this
**Post Absorptive- utilise energy stores**
1. hydrolysis of trigkycerides
2. beta oxidation of long chain fatty acids
3. formation
187
describe beta oxidation of long chain fatty acids- post-absorptive
Beta-Oxidation of long-chain fatty acids
1. Activation- CoA molecule is added to the fatty acid to produce acyl-CoA, converting ATP to AMP in the process
2. Activated fatty acids cross the mitochondrial membrane in a process that requires carnitine- stimulates the oxidation of fats
3. Fatty acid has two carbons chopped off the end to make acetyl CoA by enzyme called **thyolase**. This leaves the rest of the fatty acid (with another CoA) which goes through the cycle again
4. produces 1 FADH and 1 NADH
188
describe formation of ketone bodies in the liver - post absorptive
1. when loots of acetylcoA is generated, theres ot enough oxalacetate to combine so theres a surplus
2. surplus is converted to the ketone bodies by the liver
- Acetoacetate (first)
- β-hydroxybutyrate (second)
- Acetone (third)
3. ketone bodies cant be reconverted in the liver- doesnt contain the enzymes
4. ketone bodies are water soluble so can be exported to other cells which can convert- brain/heart
5. If many ketone bodies are present in the blood, the condition is called ketosis- can change the pH of the blood
