Unit 3/6 Flashcards Preview

A Level Biology > Unit 3/6 > Flashcards

Flashcards in Unit 3/6 Deck (11):
1

describe how the effect on the heart in daphnia can be investigated practically, and discuss whether there are ethical issues n the use of invertebrates

- caffeine is a stimulant (alcohol is a depressant and will do the opposite)
- cardiac muscle has intrinsic rhythmicity
- this cardiac rhythm is maintained by a wave of excitation which travels across the heart muscle which is generated in the heart muscle
- SAN sets up wave of excitation that travels across the atria which depolarizes the cells and causes the atria to start contacting
- wave of excitation reaches the AVN
- AVN slightly delays the wave
- AVN slightly delays the wave of depolarization
- Electrical impulse travels down the purkyne fibers in the bundle of His
- penetrates through the septum and around ventricles
- depolarization starts at the bottom so the muscles contract at the bottom first to squeeze the blood out
- stimulation of the SAN causes more waves of depolarization and shorter delay at the AVN. this causes a increase in heart rate

2

describe how to investigate the vitamin C content of food and drink

DCPIP is blue, but when the vitamin C (absorbic acid) is added it reduced the DCPIP to a colorless solution

3

describe how membrane structure can be investigated practically, e.g. by the effect of alcohol concentration or temperature on membrane permeability

- red pigment in beetroot is found in the cell vacuole surrounding the tonoplast
- pigment cannot through the membrane but can pass through cell wall if membrane is disrupted
- increased temperatures causes and increase in the kinetic energy of phospholipids in the cell membrane, thus causes gaps. the proteins also denature at high temperature, causing gaps in the membrane
- increased alcohol concentration will dissolve the dissolve the phospholipids as it is soluble in organic solvents, thus causing large holes in the membrane

4

describe how enzyme concentration can affect the rates of reaction and how this can be investigated practically by measuring the initial rate of reaction

- enzymes are globular proteins made of a sequence of amino acids
- they are biological catalyst which speed up reactions without being used up themselves
- their structure is important as they are folded into a unique 3D way so that they have a specific active site
- substrate will bind to active site to form enzyme-substrate complexes
- the more enzymes present, the more active sites available, this the rate of reaction increases
- substrate will become limiting factor

5

describe the stages of mitosis and how to prepare and stain a root tip squash in order to observe them practically

PROHAPSE
- chromosomes coil and condense
- 2 daughter chromatids attached by centromere
- nucleolus breaks down and disappears centrioles move to opposite poles, separate and form spindles
METAPHASE
- nuclear membrane breaks down
- spindle fibers attach to centromeres
- chromatids are moved along the equator on the metaphase plate
ANAPHASE
- spindle fibers contract and shorten pulling apart the chromatids towards the opposite poles of the cell, the centromeres split to form the V shape
- this process needs energy in the form of ATP from respiration
TELOPHASE
- nucleoli, centrioles and nuclear envelope form
- chromosomes unravel and become less dense
- spindle fiber breaks down
CYTOKINESIS
- division of cytoplasm occurs
- in plants the membrane will separate to create two genetically identical daughter cells, in plants a cellulose wall builds up to create two separate cells

6

describe how totipotency can be demonstrated practically using pant tissue culture techniques

- stem cells - undifferentiated cells that have the potential to develop into many different types of specialized cells as their genome contains all/most genes
- totipotent - an undifferentiated cell which can differentiate into any specialized cell
- pluripotent - an undifferentiated cell which can differentiate into any specialized cell apart from embryonic cells
- multipotent - undifferentiated cell which can differentiate into several related cells

7

describe how to determine the tensile strength of plant fibers practically

CELL WALL:
- this gives the cell it's regular shape and gives it strength and support so it will not burst in solution with high water potential
- made from insoluble cellulose, microfibrils and hemicellulose
- if strengthened with Suberin or lignin, the cell wall permeability increases so water can no longer pass through
MIDDLE LAMELLA:
- first layer to form when plant cell divides
- made of pectin and polysaccharides which act like glue to hold the neighboring cells together
- pectin forms with calcium ions to make calcium pectate
CELLULOSE:
- made of long chains of beta glucose joined together by 1,-4 glycosidic bonds (polysaccharide)
- each alternate group is inverted as this allows hydrogen bonds
- the chains are straight and unbranched so are able to be cross linked
- group of cellulose molecules bound together with hydrogen bonds form microfibrils
MICROFIBRIL:
- group of cellulose molecules bound together through hydrogen bonds
- form helical arrangements and bind with other polysaccharides to form hemicellulose

8

describe how to investigate plant mineral deficiencies practically

NITRATES:
- nitrate ions are used to make amino acids, these are subsequently used to make proteins
- proteins are used for structures in plant to build biomass and allow growth to occur
- enzymes are proteins, thus nitrates are needed for enzymes, without enzymes the metabolic reactions of the cell would stop
DEFICIENCY:
- older leaves turn yellow and die, growth is stunted
CALCIUM:
- calcium ions are used in middle lamella of plant cells which combines with the pectate to form the calcium pectate which holds the cells together
- these play a role on the permeability of the cell membrane
DEFICIENCY:
- growing points die back and young leaves turn wrinkled and yellow
MAGNESIUM:
- these are needed to produce the green pigment chlorophyll, thus are needed to photosynthesis to occur
DEFICIENCY:
- yellow areas develop in older leaves and growth slow
PHOSPHATE:
- phosphate ions are needed for the phosphate groups in ATP and ADP, these are needed to store and transfer energy in the cell
- needed to synthesis nucleic acids
DEFICIENCY:
- green leaves with dark purple veins observed

9

describe how DNA can be amplified using the polymerase chain reaction (PCR)

- heat stable DNA polymerase must be used
- optimum temperature of 72 degrees
- needs to bind to primer to begin synthesis

10

describe how to investigate the effect of different antibiotics on bacteria

there are two different types of antibiotic
- bacteriostatic - completely inhibits growth of the microorganism
- bacteriocidal - kills bacteria by inhibiting enzymes which produce the cell wall and breaking the cell wall down

characteristics of bacterial cells:
- prokaryotic
- cell wall - peptidoglycan
- no mitochondria - respiration occurs in mesosome
- slime capsule
- genetic material is a nucleotide, with plasmids present too

11

describe how to investigate the effects of exercise on tidal volume and breathing rate using data from the spirometer traces

- the ventilation center is located inn the medulla oblongata and involves the negative feedback system during breathing
- impulses from the ventilation center which travels along