OCR Biology AS level (f211) flashcards/revision notes


flash cards/ revision notes for nearly all topics in the F211 syllabus. still not completed yet, i have other things yet to add. OCR EXAM BOARD SPECIFICATION
Dariush Zarrabi
Flashcards by Dariush Zarrabi, updated more than 1 year ago
Dariush Zarrabi
Created by Dariush Zarrabi almost 10 years ago

Resource summary

Question Answer
what is the maximum resolution of the light microscope and the electron microscope? light=200nm electron microscope=0.20nm
what is the maximum magnification of the light, TEM and SEM microscopes? light=*1500 TEM=*500,000 SEM=*100,000
actual size= image size --------------------- magnification
magnification= image size ---------------------- actual size
define resolution? the ability to distinguish between 2 separate points clearly.
define magnification? The state of something being magnified or represented by an amplified image.
outline the roles of the cytoskeleton? -keeps the cells shape -allows movement of organelles -supports the cell
outline the process of cilia and goblet cells in removal of waste? cilia- wafts mucus produced by goblet cells up the trachea and into your throat. goblet cells- produces mucus that traps dust and bacteria
role of vesicles? -membrane bound sacs found in cells - transport many different materials around the cell
structure of nucleus? -surrounded by nuclear envelope -nuclear pores in nuc envelope. -nucleolus in the nucleus -has chromatin
role of nucleus? -houses genetic info -contains chromatin that condenses during mitosis. -nucleolus makes RNA and ribosomes.
structure of RER? -flattened sacs called cisternae. -joined to the outer nuclear memb. -littered with ribosomes that make proteins.
structure of SER? -same as RER without ribosomes
role of vesicles? -transports molecules around cell.
role of SER? -involved in making lipids that the cell needs
structure and role of Golgi? structure: flat memb bound sacs role: receives proteins from the ER and modifies them by possibly adding a sugar mol. then packages the modified proteins into vesicles that can be transported. some modded proteins go to the cell surface to be secreted out.
structure and role of mitochondria? structure: 2 membranes separated by fluid filled space. inner membrane is highly folded to form cristae. central part is called matrix. role: produces the energy that drives the cells (ATP)
structure and role of chloroplasts? structure: 2 memb separated by fluid filled space. inner memb is continuous, with elaborate network of flattened memb sacs called thylakoids. a stack of thylakoids are called granum/grana. role: site of photosynthesis, light energy used to drive reactions of photosynthesis, carbohydrate mol are made from carbon dioxide and water. -found on thylakoid memb and in intergranal memb.
structure and role of lysosomes? structure: single memb, spherical sacs. role: contain powerful digestive enzymes. used to break down pathogens ect.
structure and role of ribosomes? structure: some are free in cell and some bound to RER. role: site of protein synthesis, act as assembly line where coded info from mRNA is used to assemble proteins from amino acids.
structure and role of centrioles? structure: small tubes of protein fibres. pair of them next to the nucleus. role: take part in cell devision, form fibres known as spindle fibres that move chromosomes during nuclear division (anaphase)
outline the process of protein synthesis -DNA is part of larger structures (chromosomes), which are unable to move from the nucleus, intermediate messenger molecules are needed. These are messenger RNA molecules. -The completed mRNA molecule detaches from the DNA template and exits the nucleus via the nuclear pores, moving into the cytoplasm. -The mRNA is now ready for translation, which is organised by the ribosomes, which now attach themselves to the mRNA. -the assembled protein leaves the ribosome by pinching off in a vesicle , it may leave the cell or be used in the cell.
outline roles of membranes -separating cell contents from the outside environment -separating the cell components from cytoplasm. -cell recognition and signalling. -holding the components of some metabolic pathways in place. -regulating the transport of materials into or out of the cell.
outline the structure of a phospholipid membrane -hydrophilic head (water loving) -hydrophobic tails (water hating) face inwards. -cholesterol maintains the fluidity of the membrane. -channel proteins allow the movement of some molecules through the membrane. -carrier proteins actively move substances across the memb. -glycoproteins/glycolipids: receptor sites.
define cell signalling? the communication between cells using a hormone and a complimentary receptor site that will bring about a change in other cells.
define diffusion? diffusion is the movement of molecules down a concentration gradient. (from an are of high concentration to an area of low)
define active transport? active transport is the movement of molecules against its concentration gradient with the use of an energy source such as Adenosine tri-phosphate (ATP)
what effects the rate of diffusion? -temperature -concentration gradient -distance -size of molecules -movement/stirring -surface area
outline facilitated diffusion using channel proteins -give an example facilitated diffusion is a passive process, (requires no energy). allows the transport of ions such as sodium and calcium ions.
outline facilitated diffusion using carrier proteins -give an example facilitated diffusion is a passive process, (requires no energy). -larger molecules such as glucose and amino acids.
outline bulk transport -endocytosis (coming into the cell) -exocytosis (leaving the cell) -requires ATP
what are the passive processes? -diffusion -facilitated diffusion -osmosis
what are the active processes? -active transport -bulk transport
define osmosis? -The movement of water down its water potential gradient. (the same process as diffusion just with water travelling from an area of high conc to an area of low concentration. -Across a partially permeable membrane.
what happens to animal cells in a solution with high water potential? -solution has high water potential. - the cell has a lower water potential. -osmosis (diffusion of water down the water potential gradient) -cell swells as water moves down the gradient and fills the cell. -the ANIMAL cell bursts as it does not have a cell wall like a plant cell to withstand the pressure.
what happens to plant cells in a solution with high water potential? -solution has high water potential. - the cell has a lower water potential. -osmosis (diffusion of water down the water potential gradient) -cell swells as water moves down the gradient and fills the cell. -the PLANT cell becomes turgid (filled with water). -plant cells have a cell wall that prevents the cell from bursting. osmosis will stop even if there is still a water potential gradient between the cell and solution.
what happens to animal cells in a solution with a low water potential? - solution has lower water potential than the cell. -gradient from inside of cell to the outside. -water leaves cell by osmosis to fill this gradient. -the cell will shrine, contents will shrink and the membrane will shrivel up.
what happens to plant cells in a solution with low water potential? - solution has lower water potential than the cell. -gradient from inside of cell to the outside. -water leaves cell by osmosis to fill this gradient. -the cell will shrink, as it loses water. -cell surface membrane will pull away from cell wall (plasmolysis)
outline the phases of mitosis -interphase: cell goes about daily activities (growth and development) prophase: replicated chromosomes supercoil (shorten and thicken) metaphase: replicated chromosomes line up down the centre of cell. anaphase: replicase of each chromosome are pulled apart by spindle to opposite poles of cell. telophase: two new nuclie form.
what is a diploid cell containing two complete sets of chromosomes, one from each parent
what is a haploid cell A haploid cell is a cell that contains one complete set of chromosomes.
role of RER? -translates the mRNA that codes for amino acids These secretory proteins (enzymes) are manufactured here. The term secretory just means that these proteins are made for secretion, or delivery outside the cell, into the body. -Once a protein has been synthesized (made), Rough ER creates a bubble around it by pinching off a portion of its own membrane. This bubble is called a “transition vesicle.” The transition vesicle then moves either to the cell membrane or to the Golgi Apparatus.
at what phase in mitosis do the chromosomes line up in the centre of the cell? metaphase
what are the 2 end products called from successful mitosis -2 genetically identical daughter cells.
what is the process where the cell splits in cell division called? -cytokinesis
what are the only plant cells able to divide called? meristem cells
what prevents plant cells from dividing like mammal cells? they have developed a cell wall making the splitting near impossible for the cell. meristem cells have very thin walls.
define clone? an organism or cell, or group of organisms or cells, produced asexually from one ancestor or stock, to which they are genetically identical.
what is an advantage of having genetically identical crops? -will grow at the same rate so will be ready to harvest at the same time. -will produce a known crop as it will lack genetical diversity.
what are the dis-advantages of having genetically identical crops? -same genetics means that adapted viruses/ crop deceases will be able to destroy the whole population as there is little diversity in genetic info.
pros of plants being able to reproduce asexually? asexual means that plants can reproduce quickly even when there are no other plants around to reproduce with. asexual reproduction saves the energy associated with flowers, fruit and seed production.
multicellular organisms need transport systems why? -have a small SA/VOL ratio -not all cells in contacts with external medium. -tissues, organs are created to allow delivery of oxygen and removal of carbon dioxide.
define differentiation? when a cell takes on a particular role/function
how can cells adapt to become differentiated? -increase the number of certain organelles within the cell. -change the shape of the cell -some of the contents of the cell.
role of neutrophils in body? is to ingest invading micro-organisms that are recognised as foreign by the antigen presenting cells (macrophages)
define tissues? collection of cells working together to perform a common function.
define organ? collection of tissues working together to perform a particular function.
define organ systems? number of organs working together to perform an overall function.
outline the xylem tissue structure -xylem vessels with parenchyma cells and fibres. -walls reinforced/waterproofed with deposits of lignin. -ends of the cells making the xylem break down forming a long continuous tube with wide lumen. -where lignin isn't present are sunken pits (allow water molecules to move into live tissue cells around the xylem)
outline the phloem tissue structure -sieve tubes and companion cells. -ends don't fully break down. (form sieve plates) - sieve plates allow movement of materials up & down tubes. -companion cell is very metabolically active -there actives play important role in movement of products produced from photosynthesis up and down the plant in the sieve tubes.
give 2 examples of epithelial tissues -squamous epithelial -ciliated epithelial
give 2 examples of connective tissues -cartilage -bone & blood
list requirements for photosynthesis -light -carbon dioxide -water -chlorophyll presence
how are leaves adapted for photosynthesis? -transparent upper surface layer to allow more light through. - a layer of cylindrical palisade cells (packed with chloroplasts containing chlorophyll) -loosely packed spongy mesophyll layer with many gaps for air flow -lower epidermis has pores called stomata, allows gasses to be exchanged between leaf and air. -2 guard cells swell to open the stomata. (turgid-open vice versa) -leaf vein system stansports H20 to leaf and takes products from pho-syn-sis away to other parts of plant.
why do plants need water in their leaves? -cells need to be turgid to be metabolically active - photosynthesis requires water to produce carbohydrates
why is it important that products of photosynthesis is transported up & down plant? - allows carbs to reach growing leaves/shoots to aid growth
how does SA:VOL ratio effect diffusion? --
define exchange surface? an exchange surface is something that is used to allow transfer or substances. e.g. alveoli in lungs
why do large organisms need special exchange surfaces? -need alot of oxygen for respiration -cannot supply enough through their skin surface as SA:VOL ratio is too low
what makes an exchange surface efficient? -large SA: more space for molecules to diffuse. -thin barrier: short diff distance -permeable membrane: to allow molecules through. -good supply of molecules to exchange surface: keeps conc high so diff grad is high. -removal of molecules from other side: keeps conc of molecules low so diff grad high
list the things that make up the gas exchange system -trachea (has cartilage in C shape to allow flexability and support) -bronchi (has less cartilage,breaks off into 2 separate bronchioles) -lungs -alveoli (exchange surface) -external intercoastal muscles (contract to lift up the ribs) diaphragm (relaxes and contracts to increase/decrease volume of lungs.
role of cartilage? -supports trachea and bronchi -prevents collapse -flexability -allows the oesophagus to expand during swallowing.
role of smooth muscle? -can make lumen of airway narrower (bronchioles) -can help prevent harmful thing sin the air form entering the alveoli by contraction in the bronchioles.
role of elastic fibres? smooth muscle contracts so does the elastic fibres -smooth muscle recoils so does the elastic fibres (helps to increase the lumen of airway)
define tidal volume? amount of air able to move in or out of lungs in a single breath at rest. (allows removal of co2 and enough oxygen to support its resting o2 needs.)
define vital capacity? largest vol of air that can be removed from the lungs in one complete breath.
define residual volume? this is the amount of air that is left in the lungs after the max exhalation of person.
define inpiratory reserve volume is how much more air can be breathed in over and above the normal tidal volume when you take a big breath. (needed when exercising)
define expiratory reserve volume how much more air can be breathed out over and above the amount that is breathed in a tidal volume breath.
what is a double circulatory system? when the blood passes through the heart 2 times in a single circulation.
list features of a good transport system? -medium -pump -exchange surface -tubes/vessels
what is an open circulatory system? blood flows freely in the small animal as it doesn't need the transport system like larger animals. muscles usually force the movement of the blood around the animal.
what is a closed circulatory system? a closed circulatory system is when blood is held in the capillaries. moved around using a pump.
which side of the heart pumps deoxygenated blood away form the heart? right side
which side of the heart pumps blood to the rest of the body? left side (reason the left ventricle is thicker than the right)
in what section of the heart is the atrioventricular valves located? between the atria and ventricles
what makes up the artery? -lumen -endothelium -smooth muscle -collagen fibres -elastic fibres.
what makes up the vein? -lumen -endothelium -elastic fibres -smooth muscle -collagen fibres
what makes up the capillary? -lumen -endothelium
role of elastic tissue? allows the wall to stretch and recoil when the heart pumps.
role of tissue fluid? transports O2 & nutrients from the blood to the cells. -transports CO2 and waste back to the blood.
when haemoglobin binds to oxygen it becomes? oxyhaemoglobin
how are hydrogen carbonate ions formed? -carbonic acid catalysed by carbonic anhydrase. -CO2+H2O=(H2CO3) -carbonic acid dissociates to release H+ ions = (HCO3-) -(H2CO3--HCO3- & H+) -H+ joins Hb -- (HHb) -chloride ion shift into cell to maintain a neutral cell.
what is the Bohr effect? -the Bohr effect is the process of having large quantities of CO2 in repairing tissues causing the erythrocyte to release even more oxygen.
what is the appoplast pathway? water passes through the water filled spaces between cellulose molecules. does not pass through any plasma membranes.
what is the symplast pathway? passes through the plasmodesmata, (gaps in the cell wall that contain a thin strand of cytoplasm).
what is the vacuolar pathway? not confined to cytoplasm, able to pass through the cells and vacuoles.
how does water travel up the stem? -root pressure -tranpiration stream -capillary action
how does H2O leave the leaf? what does evaporation cause? -usually the H20 will leave through the stomata that open when the guard cells are fully turgid. -the evaporation of the cells creates a water potential gradient and so water from surrounding cells move water over through osmosis. (transpiration stream)
define transpiration? the loss of water from the upper section of the plant particularly the leaves.
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