B2 - scaling up Flashcards
what are new cells needed for?
growth and repair
what is diffusion?
- the net movement of particles from an area of higher concentration to an area of lower concentration
- a consequence of the random movement of individual particles, until the molecules are evenly spread out and a dynamic equilibrium is reached
in what states must the particles be if they are going to be able to diffuse?
- gas
- liquid
- in solution
how does difference in concentrations affect the rate of diffusion?
bigger difference = faster rate as particles collide more often/steeper slope
how does a larger surface area affect the rate of diffusion?
faster because there’s more surface area to diffuse to
how does a shorter distance affect the rate of diffusion?
there is less area for the particles to diffuse to/they can diffuse more quickly if they aren’t going far (less to travel)
how does a higher temperature affect the rate of diffusion?
the particles can move faster as they have more energy to move and collide
how does a barrier which is permeable to a substance affect the rate of diffusion?
faster if permeable diffusion can happen
true or false: molecules are able to diffuse because they are constantly moving around
true
true or false: only molecules in liquids and gases can diffuse
true
true or false: diffusion is the movement of molecules from an area of low concentration to an area of high concentration
false
true or false: molecules move down a concentration gradient during diffusion
true
true or false: molecules diffuse until they are evenly spaced apart
false
true or false: diffusion requires energy
true
what is osmosis?
the nett movement of water molecules from an area of high water potential to an area of low water potential through a selectively permeable membrane
what is a selectively permeable membrane?
a membrane that only lets certain molecules pass through and stops others
what’s the name for a concentrated solution?
hypertonic solution
what’s the name for a dilute solution?
hypotonic solution
what is a concentrated solution?
a lot of solute molecules (e.g. sugars or salts) dissolved in little water
what is a dilute solution?
very few solute molecules dissolved in lots of water
what happens to a animal cell in a hypertonic solution?
it becomes crenated
what happens to a plant cell in a hypertonic solution?
it becomes plasmolysed
what happens to a plant cell in an isotonic solution?
it becomes flaccid
what happens to a plant cell in a hypotonic solution?
it becomes turgid
what happens to a animal cell in a hypotonic solution?
lysis
what does being crenated mean?
shrivelled
what does being plasmolysed mean?
the cell has lost so much water that the cytoplasm pulls away from the cell membrane
what does lysis mean?
the cell swells up until it bursts open (bursts because it doesn’t have a cell wall)
why do plant cells become turgid rather than experience lysis?
the cell wall stops it from bursting
how do you calculate percentage change?
(new result-original result)/original result x100
what does active transport mean?
the transport of substances using energy in the form of ATP, up or against the concentration gradient (uses transport proteins); not across a membrane
what do plants need all the time?
mineral ions
how are root hair cells adapted to their function?
it has a large surface area to provide contact with soil water and also thin walls so that the movement of water is not restricted
does active transport require energy?
yes
how do plants take up mineral ions?
to take up mineral ions, the ions are moved into root hairs, where they are in a higher concentration than in the dilute solutions in the soil; then active transport occurs across the root so the plant takes in the ions it needs from the soil around it
what is the function of transport proteins?
they are found in the cell membrane and help in active transport of substances in and out of the cell
what occurs during the cell cycle?
- DNA replication
- movement of chromosomes
- cytokinesis
- growth of daughter cell
which enzyme carries out DNA replication?
helicase
how is DNA replication carried out?
- the DNA unwinds and unzips
- following the complementary base pairing rule, free DNA nucleotides line-up against the separated DNA strands
- another enzyme called DNA polymerase joins the free nucleotides together
- the DNA molecules now twist back into a double helix
what is mitosis?
a form of cell division which divides the chromosomes and the cell itself into 2 genetically identical daughter cells
what are the stages of the cell cycle?
- interphase
- prophase
- metaphase
- anaphase
- telophase
- cytokinesis
which are the named stages of mitosis?
prophase, metaphase, anaphase, telophase
what happens during interphase?
each chromosome replicates so it contains two identical chromatids
what happens during prophase?
chromosomes become visible by shortening and thickening
(chromosomes become present)
what happens during anaphase?
the two chromatids in each chromosome are pulled apart by spindle fibres to opposite poles of the cell
(pulled apart)
what happens during metaphase?
the chromosomes align up along the centre/equator of the parent cell, moved by spindle fibres
(in the middle)
what happens during telophase?
there are now two nuclei
(two collections of chromosomes are visible)
what happens during cytokinesis?
the cell splits in two to produce two daughter cells, each containing the same chromosomes
(vision or splitting of the cytoplasm)
what are genes?
sections of DNA
what is a specialised cell?
a cell adapted to perform a particular function
what are some examples of specialised cells?
- sperm cells
- fat cells
- red blood cells
- ciliated cells
- palisade cells
what is the function of a sperm cell?
transfers genetic material from the male to the ovum
how is the sperm cell adapted for its function?
- flagellum; whips from side to side to propel the sperm
- lots of mitochondria; respiration, to transfer energy from chemical stores so the flagellum can move
- acrosome; stores digestive enzymes to break down the outer layers of the ovum to allow the sperm to transfer and incorporate its genetic material
what is the function of a fat cell?
to store fat (used as a source of energy), provide insulation and form a protective layer around some organs
how is the fat cell adapted for its function?
- small layer of cytoplasm surrounding a fat reservoir
- can expand up to 1000x their original size as they fill with fat
what is the function of a red blood cell?
to carry oxygen around the body (found in the blood which flows around the circulatory system)
how is the red blood cell adapted for its function?
- contain haemoglobin (carries oxygen molecules)
- no nucleus (more space to carry oxygen)
- bi-concave shape which gives a large SA and the best chance of absorbing as much oxygen as they can
what is the function of ciliated cells?
to move mucus/liquid past the cells (found in lining of airways and fallopian tubes)
how are ciliated cells adapted for their function?
- cilia; hair-like projections that move
- lots of mitochondria to provide energy from respiration for cilia to move
what is the function of palisade cells?
to carry out photosynthesis (found in the top of the leaf)
how are palisade cells adapted for their function?
- lots of chloroplasts which contain the light absorbing pigment chlorophyll
- regular shaped closely packed cells from a continuous layer for efficient and maximum absorption of sunlight
what is a stem cell?
- an undifferentiated cell
- a cell that divides by mitosis forming cells which can differentiate and become specialised
- a cell which can develop into any type of specialised cell
- used by the body during development, growth and repair
what are some different types of stem cell?
- embryonic stem cells
- adult stem cells
- plant stem cells
where do embryonic stem cells come from?
they are derived from 5-7 day old blastocysts
how many cells can embryonic stem cells differentiate into?
they are totipotent; capable of generating any cell in the body (including any cells that make up the embryo or placenta)
what does totipotent mean?
can differentiate into anything
what happens to cells when an adult is fully grown?
once an animal is fully grown, many adult cells remain in a non dividing state
where are adult stem cells found?
in various body tissues e.g. brain, bone marrow, skin and liver
how many different cells can adult stem cells differentiate into?
they are able to develop into some different types of cell, but not as many as embryonic stem cells
where are plant stem cells?
plant stem cells are in the meristems of the plant; these are the regions of the plant that continue to grow throughout their lives (root tips and shoot tips)
what do meristems look like?
meristems look very different to normal plant cells; they are small compared to other plant cells, they have very thin walls, small vacuoles and no chloroplasts
what are some advantages of using embryonic stem cells?
- could help to save existing lives (can be used to treat a range of illnesses)
- not physically painful to the donor
what are some disadvantages of using embryonic stem cells?
- it prevents new lives from forming (religious groups etc are against it)
- it’s easier to use those that are grown in a body because it’s more predictable
- not very many willing donors
what are alveoli?
small air sacs in the lungs that serve as the gaseous exchange surface, they provide a large surface area for efficient exchange
what is the aorta?
the main artery that takes oxygenated blood away from the heart to the body
what is an atrium?
the upper chamber of the heart that receives the blood from the veins
what does biconcave mean?
describes the shape of red blood cells which increases the surface area for gaseous exchange
what is blood?
a tissue that contains red blood cells, white blood cells, plasma and platelets
what is a double circulatory system?
a circulatory system found in mammals in which the blood passes through the heart twice in a full body circuit
what is the heart?
the organ that pumps blood around the body
what is plasma?
a pale yellow liquid found in the blood that carries water, enzymes, salts, nutrients, proteins, urea and hormones
what is the pulmonary artery?
the main artery that carries deoxygenated blood away from the heart to the lungs
what is the pulmonary vein?
the main vein that carries oxygenated blood back to the heart from the lungs
what are red blood cells?
cells in the blood that carry oxygen and remove carbon dioxide
what is a single circulatory system?
a circulatory system in which the blood passes through the heart only once in a full body circuit
what are valves?
structures found at each end of both ventricles that prevent back flow of blood (ensuring blood flows in one direction), valves can also be found in veins
what is the vena cava?
the main vein that carries deoxygenated blood back to the heart from the body
what are ventricles?
the lower chambers of the heart that receive blood from the atria and pump it to the arteries, the human heart has two ventricles
what are villi?
small projections from the small intestine that increase the surface area for food absorption
what is the relationship between size and SA:V?
as an organism gets bigger, it’s SA:V gets smaller
how are amoeba adapted for substance exchange?
amoebas are single celled organisms and so have a very high SA:V, substances can diffuse directly in and out of the cell
how are alveoli adapted for substance exchange?
air is moved into and out of your lungs when you breathe, ventilating the millions of tiny air sacs called alveoli; the alveoli have an enormous SA and a very rich blood supply, both of which make your lungs very effective for gas exchange
how are villi adapted for substance exchange?
they increase the SA of the gut for absorption of food molecules
how are flatworms adapted for substance exchange?
a worm’s respiratory surface is it’s skin, a flatworm will have a higher SA:V than a regular worm
how are root hairs adapted for substance exchange?
plant roots have a very large SA, which is increased more by the root hair cells to make the uptake of water and mineral ions more efficient; water is constantly moved away from the roots in the transpiration stream, maintaining a steep concentration gradient into the cells
how are leaves adapted for substance exchange?
plant leaves are modified to make gas and solute exchange as effective as possible; flat, thin leaves, the presence of air spaces in the leaf tissues and the stomata all help to provide a big SA, this maintains a steep concentration gradient for the diffusion of substances such as water, mineral ions and carbon dioxide
how are fish gills adapted for substance exchange?
gills are made up of gill filaments; these are stacked up in a pile, at right angles to the filaments are gill lamellae (which increase the SA of the gills)
what muscle tissue makes up most of the heart?
cardiac muscle
explain why the muscular wall of the left ventricle is thicker than the right ventricle
the muscle in the left ventricle has to be very thick, to pump at a high pressure (through the aorta), this makes the blood travel all the way around your body
what is the role of an artery?
blood is carried away from the heart under high pressure by the arteries, the blood is at high pressure due to the strong contractions of the heart
how are arteries adapted?
to withstand the high pressure, the artery walls are thick and very muscular; the arterial wall will expand due to the force of a contraction then recoil to push the blood forward
what is the role of a vein?
the veins return blood to the heart and have valves to prevent blood flowing backwards
how are veins adapted?
blood pressure in the veins is very low, the veins have a large diameter which offers the least resistance to blood flow
what is the role of a capillary?
capillaries link the arteries and veins ins tissues and organs; the network of capillaries means that every cell is close to a capillary for exchange of substances
how are capillaries adapted?
the walls of the capillary are semipermeable and one cell thick to allow this
what are the four components of blood?
- plasma
- red blood cells
- white blood cells
- platelets
what is the function of plasma?
- transports digested food, urea, hormones etc
what is the function of red blood cells?
- biconcave shape
- no nucleus
- transports oxygen
what is the function of white blood cells?
- part of immune response
- ingesting pathogens
- producing antibodies
what is the function of platelets?
- involved in blood clotting
what is the reversible reaction for the transport of oxygen?
oxygen + haemoglobin <=> oxyhaemoglobin
what are companion cells?
the active cells of the phloem, they provide energy for the phloem to transport substances
what are guard cells?
cells that control the opening and closing of the stomata
what is lignin?
a material that lines the xylem vessels and provides strength and support
what are phloem?
a plant tissue that transports sugars from the source to the sink
what is a potometer?
a piece of capillary tube that is used to investigate the rate of transpiration; water loss from the surface of the lead is measured by the distance that the air bubble travels over a certain period of time
what are sieve tubes?
plant cells that have no nuclei and are connected via the cytoplasm
what is transpiration?
the loss of water from the surface of the leaves by evaporation from the open stomata
what is translocation?
the process of transporting sucrose around the plant
what is water potential?
measure for the tendency of water to move from one area to another area
what is water needed for in a plant?
- photosynthesis
- to support the cells (turgor pressure)
what are xylem?
a specialised plant tissue that transports water and dissolved minerals from the roots to the leaves of the plant
what are dissolved minerals needed for in a plant?
to make proteins and other molecules in leaf cells in order to grow e.g. nitrates from the soil
what is sugar needed for in a plant?
- respiration
- to make other molecules i.e. cellulose
- to store in roots
how do root hair cells set up a water potential gradient to get water into the root by osmosis?
- water enters the root hair cell by osmosis
- the root hair cell contains dissolved nutrients and minerals, giving it a low water potential
- these minerals have been pumped into the cells by active transport
- soil water has higher water potential
- water enters the cell by osmosis from a high water potential to a low water potential
how are minerals taken up by the plant?
when the concentration of minerals in soil is lower than inside the plant, active transport is used to absorb the minerals against the concentration gradient
what would happen if the plant relied on diffusion to absorb minerals?
the cells would become drained of minerals because they would travel down the concentration gradient (minerals e.g. nutrients and phosphates)
what is the structure of xylem?
- thick, cellulose wall, strengthened by lignin
- inside of cell is hollow (xylem vessels are dead cells)
what is the structure of phloem?
- made of living cells
- they have plasmodesmata (holes in the cell walls)
what is the function of xylem?
- transports water and minerals up the stem from the roots to the shoots and leaves
- this transport occurs in one direction (up) only
what is the function of phloem?
- transports sugars produced in the leaves up and down the stem to growing and storage tissues, this is called translocation
where do xylem tissues transport from/to?
from the roots to the shoots and leaves
where do phloem tissues transport from/to?
from the leaves or storage tissue e.g. a potato to wherever respiration is taking place or to the storage organs
what factors affect the rate of transpiration?
- temperature
- humidity
- light intensity
- air movement
why does an increase in air movement increase transpiration rate?
because water vapour is quickly removed after diffusing out of the stomata creating a greater diffusion gradient
why does an increase in temperature increase transpiration rate?
because water evaporates more quickly from leaf cells and diffuses faster
why does an decrease in humidity increase transpiration rate?
because the concentration of water vapour in the air outside he leaf is low so evaporation of water and diffusion of water is fast
why does an increase in light intensity increase transpiration rate?
because the rate of photosynthesis is high, needing more carbon dioxide
how is the rate of transpiration measured?
using a potometer
what is each stoma surrounded by?
two guard cells
what happens to the guard cells when light intensity is high?
when light intensity is high, the guard cells gain water and become turgid; they curve out, opening the stomata and allowing CO2 in and oxygen and water out
what happens to the guard cells under low light intensity or lack of water?
low light intensity or lack of water causes the guard cells to lose water closing the stomata
what is the link between guard cell photosynthetic rate and transpiration?
- as guard cells photosynthesise they make oxygen and glucose
- an increase in the concentration of this in the cell causes water to move in by osmosis
- this makes the guard cell more turgid
- this causes the stoma to open, allowing more gas exchange
