topic 1 - key concepts

Question 1

explain how animal cells are adapted to their functions

Answer 1

nucleus - contains genetic material arranged in chromosomes
cell membrane - holds the he cell together and controls what goes in and out
Mitochondria - where most of the reactions for respiration take place
ribosomes - translation of genetic material and the synthesis of proteins
cytoplasm - gel like substance for chemical reactions to take place, contains enzymes that control chemical reactions

Question 2

explain how plant cells are adapted to their functions

Answer 2

cell wall - made of cellulose to support and strength cell
chloroplasts - photosynthesis occurs which makes food for plant. contain chlorophyll
vacuole - contains cell sap, supports cell by maintaining internal pressure

Question 3

explain how bacteria cells are adapted to their function

Answer 3

chromosomal DNA - floats in cytoplasm and controls cells activities and replication
plasmid DNA - extra DNA not part of chromosome which contains genes for things like drug resistance, can be passed between bacteria
flagella - used to move away from harmful toxins and towards nutrients or oxygen,

Question 4

describe how sperm cells are specialised to adapt to their function

Answer 4

acrosome -

Question 5

describe how egg cells are specialised to adapt to their function

Answer 5

nutrients in cytoplasm - to feed embryo
haploid nucleus - half number of chromosomes for normal body cell
changes in cell membrane after fertilisation - changes structure to stop sperm

Question 6

describe how ciliated epithelial cells are specialised to adapt to their function

Answer 6

cilia - move substances in one direction along the surface of the tissue

Question 7

Explain how changes in microscope technology, including
electron microscopy, have enabled us to see cell structures and
organelles with more clarity and detail than in the past and
increased our understanding of the role of sub-cellular
structures

Answer 7

electron microscopes - use electrons not light - giving a higher magnification and resolution - to see smaller things with more detail - like internal structures - giving a greater understanding of how cell and sub cellular structures work - that light couldnt do

Question 8

Demonstrate an understanding of number, size and scale,
including the use of estimations and explain when they should be used

Answer 8

estimating can help you check that your answer is correct,

Question 9

Demonstrate an understanding of the relationship between
quantitative units in relation to cells

Answer 9

milli - mm - 10 to the power of negative 3 in sf
micro - um - 10 to the negative 6 in sf
nanometre - nm - 10 to the negative 9 in sf
picometre - pm - 10 to the negative 12 in sf

Question 10

Core Practical: Investigate biological specimens using
microscopes
including magnification calculations and labelled
scientific drawings from observations

Answer 10

1. thin slice to allow light
2. take a clean slide use pipette to put drop of water on, use tweezers to place specimen on slide
3. add stain to specimen if it is transparent or colourless to make it easier to see
4. place cover slip and use mounted needle to lower it on slide, pressing down gently to avoid air bubbles, clip onto stage
5. lowest powered objective lens
6. use coarse adjustment knob to move stage u, look down eyepiece move stage down until specimen is in focus
7. fine adjustment knob until you get clear image, clear ruler on stage to measure diameter of field of view
   8.if need greater magnification use a higher powered objective lens and repeat steps

Question 11

Explain the mechanism of enzyme action including the active
site and enzyme specificity

Answer 11

for enzyme to work it has to fit into active site if it doesn’t fit the reaction wont be catalysed - this means that enzymes have a high specificity for their substrate

Question 12

Explain how enzymes can be denatured due to changes in the
shape of the active site

Answer 12

enzymes can be denatured if the active sights shape changes this means the substrate wont fit into the enzymes - this could happen if the temperature is to hot or if the pH is to high / low

Question 13

explain the effects of temperature on enzyme activity

Answer 13

temperature changes rate of an enzyme catalysed reaction, high temp increases rate of reaction - too hot bonds that hold enzyme together will break - active sight wont fit so the enzyme denatures

Question 14

explain the effect of substrate concentration on enzyme activity

Answer 14

higher substrate concentration faster reaction - because enzyme will meet and react with substrate molecule - however once all active sites are full having more substrates wont make difference to reaction

Question 15

explain the effects of pH on enzyme activity

Answer 15

if pH is too high or too low the pH interferes with bonds holding the enzyme - denatures enzyme - optimum pH is often 7 and this makes enzyme work better

Question 16

core practical: investigate the effect of pH on enzyme activity

Answer 16

how pH effects amylase activity.
enzyme amylase catalyses the break down of starch to maltose. easy to detect starch using iodine solution - if starch is present iodine solution will change from browny-orange to blue-black

1. put drop of iodine into every well of spotting tile
   2.set up Bunsen burner and heat proof mat with tripod and gauze, putting a beaker of water over Bunsen and heating until 35 degrees, keep temp constant throughout experiment
2. syringe 3 cm cubed of amylase solution and 1 cm cubed of a buffer solution with pH 5 to a boiling tube. put tube into beaker of water and wait for 5 mins
   4.using different syringe add 3 cm cubed starch solution to boiling tube
   5.mix and stop clock
3. use continuous sampling to record how long it takes for amylase to break down the starch, do this by taking a fresh sample with a pipette form the boiling tube every 10 seconds and putting it in the well
   7.when iodine solution remains browny orange the starch isn’t present
   8.control variables to get a fair test

Question 17

demonstrate an understanding of rate calculations for enzyme activity (+formula)

Answer 17

formula - rate = 1000 / time

ex - at pH 6 time taken for amylase to break down all of the starch in a solution was 50 seconds. so rate pf reaction = 1000 / 50 = 20s-1 ( units in s-1 since rate is given per unit of time)

Question 18

Explain the importance of enzymes as biological catalysts in the
synthesis of
carbohydrates, proteins and lipids and their
breakdown into sugars, amino acids and fatty acids and glycerol

Answer 18

catalyst is something that increases rate of a reaction without being used up or changed in reaction.

enzymes are used to synthesise carbohydrates, proteins and lipids from their smaller components - carbohydrates can be synthesises by joining together simple sugars

proteins are made by joining amino acids together

enzymes synthesise lipids from fatty acids and glycerol

and enzymes catalyse the reaction needed to do this

Question 19

explain how substances are transported into and out of cells by diffusion

Answer 19

diffusion is the net (overall) movement of particles from an area of higher concentration to an area of lower concentration. -
this transports small molecules through the cell membrane like glucose and amino acids, water and oxygen.

Question 20

explain how substances are transported into and out of cells using osmosis

Answer 20

osmosis is the net movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration. -

Question 21

explain how substances are transported into and out of cells by active transport

Answer 21

active transport is the movement of particles across a membrane against a concentration gradient using energy transferred during respiration -

Question 22

core practical: investigate osmosis in potatoes
(doing the experiment first)

Answer 22

1. prepare sucrose solutions of different concentrations ranging from pure water to very concentrated sucrose solution
2. cut potato into same size pieces about 1 cm in diameter
3. divide cylinders into groups of 3 and use mass balance to measure mass of each group
4. place one group in each solution
5. leave for at least 40 mins
6. remove an pat dry to remove excess water to ensure accurate measurements of their final masses
7. weigh each group again and record results
8. only thing being changed in experiment is sucrose solution concentration.

Question 23

Calculate percentage gain and loss of mass in osmosis

Answer 23

calculate the percentage change in mass for each group of cylinder before and after time in sucrose

percentage change = final - initial mass / initial mass . times by 100

ex start was 13.2g end was 15.1g, calculate percentage change in mass
15.1 - 13.2 /13.2 times 100 = 14.4 %

positive result = gained mass
negative result = lost mass