B2 Flashcards
How do particles in a gas or solution behave?
- They are constantly moving, movement can be random so particles can move in all directions
What is the defenition for diffusion?
Diffusio in the net movement of particles from an area of high concentration to an area of low concentration. Moving down a conc gradient
When does diffusion continue until?
- Concentration gradient is zero, conc of particles same everywhere
Is energy transferred during diffusion?
- No its a passive process as it is the ordinary motion of particles
Where does diffusion occur in the body?
- Glucose and blood for respiration is transported by blood and diffuses into cells
- Some chemical reaction waste products are toxic, eg, CO2, it diffuses out respiring cells
What are 3 factors affecting rate of diffusion?
- Distance
- Conc gradient
- Surface area
How does distance affect rate of diffusion?
To increase rate of diffusion
- Decrease distance particles need to move, less time shorter distance. E.g Capillaries 1 cell thick increases rate of diffusion gasses in and out blood
How does conc graident affect rate of diffusion?
- Steeper conc gradient, greter net movement of particles. E.g. Plants use CO2 in photosynthesis, CO2 conc in plants drop increasig rate ofdiffusion CO2 into cells
How does surface are affect rate of diffusion?
- Allows more space for diffusion, more patricles move in a period of time. E.g. Small intestine wall folde to increase surface area in cnotact with blood, increasing rate of diffusion of molecules
What is defenition of Osmosis?
Osmosis is net movement of water particles across a semi permeable memebrane from an are of high water potential to low water potential
How does water potential work?
- Pure water highest water potential, all molecules free to move
- Conc solution, lower water potential
What is a semi/partially permeable membrane?
- Memebrane with small holes, only tiny molecules like water can pass through
Do water particles move both ways in osmosis?
- Yes, as water molecules move randomly all the time
BUT net movement high water potential to low water potential
What happens to a plant cell if surroundings are more or less concentrated than cell contents?
- Surroundings lower water potential, cell loses water by osmosis - turgor pressure falls, cells becomes flaccid - after cell wall colapses Cell is known as plasmolyed cell
- Surroundings higher water potenial, cell takes water by Osmsis, turgor pressure increases, cell becomes firm and rigid
What happens to an animal cell if surroundings are more or less concentrated than cell contents?
- Surroundings lower water potential, cell loses water by osmosis, becomes crenated(crinkles)
- Surroundings higher water potential, cell takes up water, swells and may burst, lysis
Why is watering a plant extremly important (in terms of osmosis)?
- Watering plant increases water potential of soil around it - plant cells draw in water by osmosis til they’re turgid - contents of cell push cell wall,turgor pressure, this supports plant
- If no water in soil, cells become flaccid, plant starts to droop - but not comlete;y
Whats defenition of active transport?
Active transport is the movement of particles across a membrane against a concentration gradient using ATP released during respiration
What are 3 key features of active transport?
- Particles transported agaisnt a conc gradietn
- ATP is required - that comes from respiration
- Process makes use of carrier proteins in cell memebrane
Why do cells that carry out a lot of active transport have high amounts of mitochondira?
- So they can respire rapidly producing large amounts of ATP, rate at which actove transport occurs depends on rate of respiration to produce ATP
What are carrier proteins?
- Special proteins that span the width of a memebrane
How do carrier protiens work in active transport?
- Particular molecule cell requires binds to sppecific carrier protein
- Energy transferred from energy to store to protein so it can chage shape or rotate
- Carrier protein transports molecule to cell
How is active transport used during digestion?
- In small intestine, carbs broken down to glucose
- Glucose actively transported into bloodstream through villi
- Blood takes glucose to where it is needed in body
How is active transport used in nerve cells?
- Carrier protein pumps sodium ions out cell, same time potassium ions pumped back in
- Sodium potassium pump plays big role in creating nerve impulses
How is active transport used in plants?
To take minerals from soil
- Plants need nitrate ions forgrowth, soil water usually has lower conc of nitrate ions compared to plant
- Root hair cels use active transport to move the ions across cell membrane into root cell
Why does mitosis occur?
- To replace worn out cells, to repair damaged tissue and to enable the organism to increase in size
What is mitosis?
- Process by which cellsdivide, each cell divides to produce 2 indentical daughter cells - that are genetically identical to parent cell, they’re clones
- Mitosis increases number of cellsin a multi cellular organism
What are the 4 stages of the cell cycle
- DNA replication
- Movement of chromosomes
- Cytokinesis
- Growth of daughter cell
Explain how DNA is replicated in DNA replication?
- DNA molecule unzips to 2 strands
- DNA bases in each strand exposed
- Free nucleotides in nucleus line up to each strand, following complementary base pairing
- Forms DNA base pairs
- When strand comlete 2 identical molecules DNA formed
How do chromosomes move in 2nd stage of mitosis?
- Chromosomes line up across centre of cell
- 2 identical copies each chromosome formed when DNA replicated, seperates and moves to opposite ends of cell
- Each end contains full set of identical chromosomes
- 2 new nuclei form
What happens when a cell beocmes specialised?
- its structure chnges so its better adapted to perform its function
- makes organism more efficient as life roceses carried out more effectively
What is differentiation?
- Proccess by which cells changes to become speciaised for its job
How are sperm cells specialised?
Sperm cellsare specialised to transfer gentetic material to ovum. Adaptations include:
- Flagellum - Whips side to side propelling sperm 2 ovum
- Lots of mitochondria - Respiration occurs in mitochondria, respiration transfers energy from chem store so flagelum can move
- Acrosome - Stores digestvie enzymes that break vum wall, so sperm can incorporategenetic material
Why is the cell cycle a cycle?
- Following growth of daughter cell, the daughter cells will begin replicating their DNA and the cell cycle will continue
How are fat cells specialised?
- Small layer of cytoplasm currouning fat resevoir
- They can expand to 1000 times original size to store fat
How are red blood cells specialised?
- Bioconcave discs, pushed on each side mkaing bioconcave shape, increasing sa:vol, increasing rate of diffusion of oxygen into and CO2 out cell
- Full of haeoglobin, protin binds to form oxyhaemoglobin - red
- No nucleus, space for more haemoglobin
How are cilliated cells specialised?
- Located in airways, in between these are goblet cells, that porduce mucus - trapping dirt and bacteria
- Cillia on topof cell sweep mucus to backof throat where swallowed
How are palisade cells specialised?
- Specialised for carrying out photosynthesis
- Near surface of leaf, full of chloroplasts
- Regular shapeallow close packing within leaf, maximising sunlight absorption
What are stem cells and what do they do?
- Stem cells are undifferentiated cells, that depending on intructions they are given - they can divide by mitosis to become newcells that can differentiate becomin specialised
What are stem cellsused forin the body?
- Used during development growth and repair
What is special about embroynic stem cells?
- They can divide by mitosis to produce all cells needed to makean organism - have ability to differentiate into all cell types
Where are adultstemm cells found?
- In various body tissues, brain, bone, marrow, skin, liver
What can adult stem cells specialise into?
- Only certain ones from the tissue they originally came form
What happens to adult stem cells when an animal is fully grown?
- Remain in non dvodding state for years
- If activated by disease, tissue injury they can start to divide and regenerate
What are the cells that divide by mtosis in plants called?
- Meristems, found in growing parts ofplant, roots and shoots
Why can differentited plant cells not divide?
- Their cell walls are too thick
What type of cells do meristems produce?
- Unspecialised stem cells able to specialise onto any plant cell, but can onoly do this when plant is alive
Why is SA: VOL ration important?
- Small organism have large sa: v, nutrients can diffuese directly into organism to live as diffusion distances are small
- Larger organism, smaller sa:v, most multicellular rgasnism can’t rely on smple diffusion tolive, diffusion over great distance isn’t fast enough tomeet standaards
How are alveoli specialised to maximise diffusion of CO2 and O2?
They have:
- Enourmous surface area, lots of ubstance can move at once
- Vey thinwalls, short distance to travel
- Goodblood supply, maintains concentraiton gradient by removing 02and bringing in CO2
How is absorption from digested food in small intestine to blood maximised? (diffusion rate)
- They contain villi
- Villi increase SA, s dissolved food molecules absorbed much quicker
- Vili specialised, single layer of surface cells, very good blood supplyto assist quick absorption
Why is crculatory system known as a closed system?
- Blood remains within the structures
What happens in the doubecirculatory system?
- Deoxyganated blood first umped from heart to lungs, to take in O2, oxygenated blood returs to heart
- 2nd, Heart pumps oxygenated blood to all other organs of body, bloodgives oxygen at cells, deox bloodreturnto heart to repeat
Pros of double circulatory system?
- returning blood to heart once ixygenated allows pumping of high pressure
- increases rate of blood flowin tissues, more oxygen delivered to cells
Why do ateries have a thick outer arteial wall?
- To widthstand high pressurewaves caused from bloood leaving heart at high pressure
- Wall expands with each contraction, then snaps back pushing blood forward
What is blood made upof?
- Red blood cell, fit through luen of capillary 1at a time
- White blood cells, contain nucleus, fight disease making anti bodies or changing shape
- PLasma, many materialstransported in, amiino acids, glucose, hormones, antibodies
- Platelelts, tiny structures that help bloodclot
What transport systems do plants have?
- Plants have 2 seperate types of transport vessels - xylem and phloem, for transporting things around
- Both types of vessels goto every part of plant but are completely seperate
What do xylem tissue transport and how do they get the materials?
- trasports water and miner ions from roots to stem leaves and flowers in transpiration stream
- Water diffuses to roots by osmosis, mineral ions taken up by active transpot
What do phloem tissues transport and how do they get thematerials?
- Transport dissolved sugars made in photosynthesis and other soluble food molecules from leaves to all areas of plant
- This is translocation
What is the vascular bundle?
- Structure formed by phloemand xylem tissue
What is the structure of the xylem?
- Made of dead cells, joined with no end walls between and lumen down middle
- Thick side walls made of cellulose - strong and stiff, giving plant support - cell walls also stregthened by lignin
What is the structure of phloem?
- Columns of living cells, ‘sieve tube elements’, with seive plates - allowing sugars to flow through
- Sieve tubes can’t survive on their own, have no nucleus, rely on companion cell, carrying out living functiosn
How do vascular bundles provide support?
- In leaf, form network supporingsifter leaftissue
- in stem, located outer edgegiving resistance to bendign in breeze
- in root, found in centre, root canact as anchor - rootcan bend and plant moves in wind
