module I - red flags

function of carbohydrates

primary energy source

structure of carbohydrates

sugar monomers (monosaccharides) that form chains (di-, tri-, poly-saccharides)

function of lipids

energy, can meet 80-90% of resting metabolic needs, superior to carbs as stored energy

structure of lipids

hydrophobic with long hydrocarbon chains (triglycerides - glycerol + 3 fatty acids) (phospholipids - glycerol +2 tails + phosphate head) (steriods - four fused carbon rings)

function of nucleic acids

to store and transfer information

structure of nucleic acids

1 or 2 chains of nucleotides (backbone of phosphate + sugar molecules - nitrogenous bases off to the side)

function of proteins MIC STEM C

movement, immune defence, catalyst, structural support, transport, enzyme, metabolic regulation, communication

structure of proteins

polypeptide chain of amino acids, folded into a 3D structure

nuclear envelope =

double membrane that protects and is continuous with RER

nucleolus =

Amembranous (held together by surface tension), contains DNA, RNA & proteins. The site of rRNA synthesis and initial ribosome assembly

Transcription =

DNA uncoils (gene sequence exposed), RNA polymerase enzyme binds and creates a copy (single-stranded mRNA), the completed mRNA copy moves outside the nucleus into the cytoplasm

Translation (mRNA into protein) =

Initiation, elongation then termination.

Translation (initiation phase)

mRNA enters cytoplasm and binds with ribosome, when start codon is recognised tRNA begin delivering specific amino acids (protein building blocks)

Translation (elongation phase)

Amino acids are linked together to form a polypeptide chain (protein)

Translation (termination phase)

when a stop codon is reached, the polypeptide chain is released from the ribosome

Whats the main difference between nucleolus and nucleus?

Nucleus contains all genetic material (chromatin, chromosomes), Nucleolus job is to produce ribosomal RNA and assemble ribosomes

Passive transport =

can be simple diffusion or facilitated (carrier-mediated diffusion) that follows the concentration gradient.

Active transport =

carrier-mediated transport that goes against the concentration gradient (can also be endocytosis and exocytosis)

simple diffusion (passive) =

molecules move through membrane freely to achieve equilibrium (lipids and soluble gases can move through)

facilitated diffusion (passive) =

molecules are helped across the membrane via channels (for water/ions) or carrier molecules (for hydrophilic or large molecules)

active transport =

requires energy, involved the movement of substances across the membrane against their concentration gradient

signaling molecule =

ligand

types of ligands

hydrophobic (water insoluable, can cross plasma membrane and bind to intracellular receptors eg. steroid hormones) or hydrophilic (water soluble, bind to extracellular receptors eg. peptides and small proteins)

ligand-gated ion channel

Ligand binds → channel physically opens → ions flood into the cell → changes the electrical charge across the membrane (gate opens from the ligand key that allows ions to rush through)

enzyme linked receptor

Ligand binds → receptor activates an enzyme on the inside of the cell → enzyme adds phosphate groups to signalling molecules (phosphorylation) → triggers a chain of cellular responses (light-switch, once turned on enzyme activity activates inside cell)

G protein-coupled receptor

Ligand binds → receptor activates a G protein middleman → G protein triggers a cascade of cell signalling (telephone, ligand makes a call, G protein passes the message along)

Intracellular receptor

Ligand is small and lipid soluble so it passes directly through the membrane → binds to receptor inside the cell → complex travels to the nucleus → directly activates or silences gene transcription (VIP access, skips the door and goes straight to control room)

Hydrophilic molecules =

cannot cross the membrane without support

Hydrophobic molecules =

can pass across the membrane and bind to receptors inside the cell

Stages of interphase in cell cycle

G0 resting phase → G1 generation of organelles, normal cell function → S replication of DNA and synthesis of histones and nuclear proteins → G2 final protein synthesis, centriole replication

Early prophase =

chromosomes condense, spindle fibres emerge, nuclear membrane disappears

late prophase

spindle fibres organise chromosomes and centrosomes move to opposite sides of cell

metaphase

chromosomes align along centre and each sister chromatid is attached to microtubules

anaphase

centromeres split in two, microtubules pull chromatids away from the centre, spindle fibres begin to elongate the cell

telophase

nuclear membrane reform around each set of chromosomes, chromosomes begin to decondense and uncoil

cytokinesis

a ring of actin protein pinches the cell along crease (cleavage furrow) to divide the cytoplasm equally between two daughter cells

four key characterstics of epithelial cells

avascular, have polarity, highly cellular and attached to basement membrane

Apocrine =

a type of gland where secretion occurs through the loss of part of the cell, often found in sweat glands.

Merocrine =

a type of gland where secretion occurs through exocytosis without loss of cellular material, commonly found in salivary glands.

tight junction =

located apically, membrane fused

adherens junction =

join actin filaments of adjacent cells forming a belt

desmosomes =

join skeletal protein filaments of adjacent cells (spot junctions)

gap junctions =

allow direct passage of nutrients and signaling molecules between adjacent cells.

hemidesmosomes

located on basal surface, protein fibres connect cells to basement membrane

keratinocytes

most predominant cell in epidermis, found throughout all epidermal layers and produce keratin

langerhans cells

antigen presenting immune cells, mainly in stratum spinosum, encounter pathogen, digest it then migrate to lymph nodes to alert immune system

merkel cells

mechanoreceptors (detection of touch, pressure, stretch), reside in stratum basal

melanocytes

reside in stratum basal, produce pigment, endocytosed by keratinocytes, and shield DNA from UV damage

amorphous ground substance

Viscous fluid secreted by fibroblasts that fills spaces in connective tissue, providing support and aiding nutrient and waste exchange. contains glycans, proteins and water

collagen =

most abundant CT, function strength, located in tendons and ligaments

elastin =

highly elastic CT, provides flexibility and elasticity, located in skin, arteries

reticulin =

similar to collagen but finer, located lover and bone marrow (provides netting/shape/support)

Fibroblast cells =

fibres and ground substance, responds to injury by secreting collagen and forms scar tissue (long cytoplasmic projections)

adipocytes =

fat cells that store energy in the form of lipids, contributing to insulation, shock absorption. Involved in thermoregulation, contains lots of mitochondira.

macrophanges =

scavenger defence cells that engulf and digest bacteria, pathogens and cancer cells

plasma cells =

originate from B-lymphocytes, produces antibodies to fight infection

mast cells =

Immune cells that release histamine play a key role in the inflammatory response. Dont just remain in blood, locaslise in mucosal and epithelial tissue.

leukocytes =

defence cells circulating via blood

four main tissue types

connective (connects), muscle (movement), nervous (communication and control) and epithelial (protection, absorption, secretion and filtration)

dermis is composed of

papillary dermis (loose CT) and reticular dermis (dense CT)

what are hair follicles involved in?

touch sensation and thermoregulation, controlled by arrector pili muscle

sebaceous gland =

secretes sebum/oil associated with hair follicles

sweat gland =

merocrine (duct empties onto skin surface) and apocrine (duct empties into hair follicles)