bio paper 1

what is the definition of homeostasis

maintenance of a constant internal environment

what changes can result in denaturation

pH - too high or low

temperature- too high

what do cellular activities rely on

enzymes

which factors are considered with the changes of an organism

internal

external

what is a stimulus

change in the environment

what is the response when the stimulus is a decrease in temperature in humans

shivering

what is the response when the stimulus is a increase in temperature in humans

sweating

what is the response when the stimulus is a increase in UV in humans

more melanin production

what is the response when the stimulus is danger in humans

flight or flight response- e.g. increased hr

what are cells surrounded by

tissue fluid

what are the factors that cause changes to the internal environment of an organism

o2, glucose, sodium, temperature, pH

how are changes to the internal environment detected

hypothalamus

what maintains the composition of tissue fluid

blood

what are the waste products that must be excreted from cells

carbon dioxide and urea

what is the response to an increased concentration of urea

increased urine production

what is the response to a decreased blood pH

increased heart rate and an increased breathing rate

what is the response to an increased glucose concentration

release of insulin to convert glucose to glycogen

increased respiration

what is negative feedback

detects a stimulus and issues a response to bring the value back to normal

what is positive feedback

detects a stimulus and brings about a response that moves the factor further away from the normal level

give an example of a positive feedback reaction

oxytocin

triggers contractions during labour- when detected, more is secreted leading to increasingly strong contractions

what are hormones

chemicals that send information around the body

describe endocrine glands

ductless

hormones travel in the blood to their target organ or tissue and binds to cells within the complementary receptor

how are exocrine glands different to endocrine glands

exocrine glands have ducts to secrete products into specific locations, endocrine glands are ductless and release hormones to blood stream

give an example of exocrine glands

sweat and salivary glands

which organ is endocrine and exocrine

pancreas

describe steroid hormones

can pass through cell membranes to act directly on DNA

describe how steroid hormones act on dna

diffuses through plasma membrane

hormone binds with receptor in cytoplasm to form a receptor hormone complex

complex enters nucleus and triggers gene transcription

transcribed mRNA is translated into proteins that alter cell activity

describe non-steroid hormones

hydrophobic

cannot pass through cell membranes

bind to receptors on cell surface membrane of target cell

describe how non-steroid hormones act on a cell

• binds to receptor protein

• activates secondary messenger

• ATP changes in structure to cAMP

• effect on cellular function

what are the aspects of the adrenal gland

adrenal medulla

adrenal cortex

what is the function of cortisol

helps regulate metabolism

regulates blood pressure and cardiovascular function

what type of hormone is cortisol and corticosterone

glucocorticoids

what is the function of corticosterone

regulates immune system response and suppresses inflammatory reactions

where are glucocorticoids released from

adrenal cortex

what type of hormone is aldosterone

mineralcorticoids

where is aldosterone released from

adrenal cortex

what is the function of aldosterone

helps control blood pressure by maintaining balance between salt and water concentrations in the blood

where are androgens released from

adrenal cortex

what is the function of androgens

male and female sex hormone

especially important for women after the menopause

where is adrenaline released from

adrenal medulla

what is the function of adrenaline

increases hr

sends blood quickly to the muscles and the brain

increases blood glucose by converting glycogen to glucose in the liver

where is noradrenaline released from

adrenal medulla

what is the role of noradrenaline

works with adrenaline in response to stress

e.g. increased hr, widening of pupils, narrowing of blood vessels in non-essential organs

describe the histology of the pancreas

islet of langerhans- alpha cells

tubule in the centre of a group of enzyme secreting cells

acinus

why is the pancreas an endo and exocrine gland

digestive enzymes- amylase, lipase, protease→ exocrine

glucagon and insulin→ endocrine

what do alpha cells do in the pancreas

secrete glucagon

what do beta cells do in the pancreas

secrete insulin

what is it called when blood glucose is too high

hypoglycemia

what is it called when blood glucose is too low

hyperglycemia

what are the target cells for insulin and glucose

hepatocytes

skeletal muscle cells

what does insulin do

increases the cells permeability to glucose

causes glucose to transport protein channels to open

secreted from beta cells

how is blood glucose detected

by the pancreas

what is glycogenesis

glucose stored as glycogen

what is glycogenolysis

glycogen is broken down into glucose

what cells is glucagon secreted by

alpha cells

what is gluconeogenesis

formation of glucose from non-carbohydrate carbon stores

e.g. lactic acid, glycerol from fats, prolonged fasting→ amino acids from muscles

describe insulin secretion

glucose enters b cells

atp is produced- potassium ion channels close

K ions cant diffuse out- membranes potential becomes less negative

change in membrane potential- calcium channels open- calcium ions rush in

calcium ions cause vesicles to release insulin by exocytosis

describe the function of the nucleus

• contains coded genetic info- in the form of DNA molecules

• directs the synthesis of all proteins required by the cell

• controls metabolic activities

• DNA associations with histones to form chromatin→ coils and condenses to form chromasomes

describe the structure of the nucleus

• DNA contained within the nuclear envelope (double membrane)

• nuclear envelope contains nuclear pores- allows molecules in and out

• DNA is too big to leave through nuclear pores for protein synthesis- so it is transcribe into smaller RNA molecules

what is the function of the nucleolus

• responsible for producing ribosomes

• composed of protein and RNA 

• RNA is used to produced ribosomal RNA (rRNA) then combines with proteins to form ribosomes

describe the function of mitocondria

• site for final stages of respiration

• energy stored in bonds of organic molecules is made available for cell to use to produce ATP 

• no. mitocondria in a cell is a reflection of how much energy it uses

describe the structure of mitocondria

• double membrane

• fluid interior= matrix

• membranes forming cristae contains enzymes used for aerobic respiration

• contains a small amount of DNA (mtDNA)

• can produce own enzymes and reproduce themselves

what is the function and structure of vesicles

• membranous sacs- single membrane with fluid inside

• storage and transport roles- used to transport materials inside of cells

what is the function and structure of lysosomes

• speciallised forms of vesicles that contain hydrolytic enzymes

• responsible for breaking down waste materials in cells 

• important role in the immune system→ breaks down pathogens ingested by phagocytic cells 

• role in apoptosis (cell death) 

what is the cytoskeleton?

• present in cytoplasm of all Eukaryotic cells

• network of fibres- needed for shape and stability of cells 

• organelles held in place by cytoskeleton 

• composed of microfilaments, microtubules, and intermediate fibres

describe microfilaments

• contractile fibres- form from protein actin

• responsible for cell movement + cell contraction in cytokinesis

describe intermediate fibres

gives mechanical strength to cells and helps them maintain integrity 

describe microtubules

• globular tubulin proteins polymerise to form tubes used to determine shape of cell 

• act as tracks for movement of organelles 

• spindle fibres are composed of microtubules

describe centrioles

• composed of microtubules

• plays a role in positioning flagella+ cilia

describe the endoplasmic rectillium

• network of cisternae

• connected to outer membrane of the nucleus 

describe the smooth ER

responsible for lipid and carbohydrate synthesis and storage

describe the rough ER

has ribosomes bound to the surface, responsible for synthesis and transport of protein

describe ribosomes

• can be free floating in cytoplasm or attached to the rough ER

• constructed of RNA molecules

• site of protein synthesis

describe the golgi apparatus 

• similar to structure of smooth ER 

• formed of cisternae- doesnt contain ribosomes

• modifyes proteins and packs them into vesicles

• secretory vesicles or lysosomes

describe cellulose cell walls 

• freely permeable 

• gives the cell shape- contents of cell press up against wall

• cell wall acts as defense mechanism against invading pathogens

describe vacuoles

• membrane lines sacs

• plant cells have permenant vacuoles

• membrane of vacuole= tonoplast 

• selectively permeable 

describe chloroplasts

• responsible for photosynthesis 

• double membrane structure 

• fluid enclosed= stroma 

• light dependant reactions take place in photosynthesis 

• able to make own proteins 

what are the functions of the cytoskeleton?

• establishes cell shape

• provides mechanical strength 

• movement

• chromosome separation in mitosis and meiosis 

describe microtubules

• 25nm in diameter

• globular tubulin proteins polymerise to form tubes 

• involved in the transport of organelles

describe microfilaments

• 7nm in diameter

• contractible fibres formed from the protein actin 

• responsible for cell movement and cell contraction in cytokinesis 

describe the structure of undulipodia and cilia

• cylinder of 9 pairs of microtubules in a circle and 2 in the middle 

• 9+2 arrangement

what is the function of undulipodia and cilia

• move liquid past the surface of the cell 

• enables them to swim 

describe flagella

• only present in bacterial cells 

• structurally different to undulipodia

• made of a spiral of flagellin protein attached by a hook to a protein disk that can rotate

describe division of labour 

• each organelle in a cell is speciallised to carry out a specific role

what is the first step of protein synthesis

• nucleolus produces ribosomes and mRNA 

what is the second step of protein synthesis

• mRNA and ribosomes leave through nuclear pores

what is the third step of protein synthesis

• ribosomes bind to ER

• mRNA travels to the roughER 

• ribosomes that synthesis the proteins mRNA codes for 

what is the fourth step of protein synthesis

• proteins passed into cisternae and packaged into transport vesicles

• vesicles then move towards the golgi apparatus 

what is the fifth step of protein synthesis

• vesicles fuse with cis face of golgi apparatus- modification of proteins occur 

• vesciles leave from trans face

cells

cells

describe prokaryotic cells

• no membrane bound organelles 

• 1-10 micrometers

• divide by binary fission 

• unicellular 

• genetic material= single looped chromosome

what happened in 1600-1800 with microscopes

• lenses were developed

• light microscopes became available

what did Robert Hooke do

• used microscope to observe a cork

• saw that the cork was made of cells

What did schleiden do

suggested all plants are made of cells

what did Schwann do

• proposed all animals are made of cells

what is the cell theory

• all living things consist of cells 

• new cells are formed only by the division of pre existing cells 

• cells contain DNA that acts as instructions for growth

what is a temporary mount

a specimen that will only last a few hours to be seen under a microscope

what is a permenant specimen

• prepared by dehydrating the specimen

• fixed in wax→ then thinly sliced

what is a dry mount

• solid specimens are viewed whole or cut into very thin slices

• placed on slide+ covered with a coverslip

what is a wet mount

• specimens suspended in liquid 

• coverslip placed on an angle to avoid airbubbles