important 2.0

What happens in G1 phase

Organelles are duplicated

• mitochondria + chloroplasts -self replicate through binary fission

• to allow each daughter cell to have the same number of organelle

DNA - uncondenses - so RNA polymerase can access genes

Cell grows - gains more cytoplasm

New proteins are made

Many active processes are taking place = requiring high rate of respiration

What happens in the S phase

DNA REPLICATION

as cannot start mitosis safely without replication

What happens in G2 phase

• Cell further grows

• further photosynthesis and respiration needed for energy

What are the three checkpoints in the cell cycle

• G1/S checkpoint

• G2 checkpoint

• metaphase checkpoint

What happens in the G1 checkpoint

• restriction point

• cells can only pass if they have grown large enough

• if organelles have been duplicated successfully

• has chemicals needed for replication

• no DNA damage

• no large scale chromosomal mutations (chromosomes split in half/damaged by UV radiation)

What happens in G2 checkpoint

• checks that DNA has been fully replicated without any errors

• makes sure that any DNA damage has been repaired

• checks if cell is large enough + has enough energy supply for mitosis

What happens if it does not pass any checkpoint

• self destruct (apoptosis) = prevents potential cancerous cells from dividing

• cells also attempt to repair damage

• IF CANNOT then = enter G0 phase

What is G0 phase

• phase that allows a cell to exit cell cycle

• some in G0 due to damage or due to cell type

• (neurons/rbc) - enter forever

Name the three parts of the cytoskeleton

• microfilaments

• intermediate filaments

• microtubules

Structure of microfilaments

• Not hollow

• smallest

• actin (polymer of protein)

Function of microfilaments

• helps to hold the cell shape

• helps cell to move and change shape

structure of intermediate filaments

• medium size

• polymer of mix of proteins

Function of intermediate filaments

• holds nucleus and other organelles in place

• Involved in cell communication

Structure of microtubules

• hollow

• largest

• polymer of protein = tubulin

• motor proteins use ATP to move cargo on this

Function of microtubule

• provides pathways for vesicle transport

• moves undulipodia and cilia

• forms mitotic/meiotic spindle

Define active transport

The net movement of substances

• against their concentration gradient

• using ATP

• and carrier proteins

Explain how cell surface membranes contribute to process of cell signalling

• there is a release of a signal molecule via exocytosis

• glycoproteins/glycolipids have receptors for these molecules

• the receptors are specific - and so the shape of receptors and molecule are complementary

• this attachment causes change on the cell surface membrane

• this change now allows the entry of some signal molecules through the membrane

Define cell signalling

• communication between cells

Why is it essential for genetic material to replicate before cell division?

• cells need to be genetically identical - and you are producing 2 daughter cells

• and for both daughter cells to receive full count of chromosomes

function of squamous epithelial tissue

• acts as a surface for a short diffusion pathway

Suggest two ways that cell division in plants differ from in animals

• nuclear envelope does not reform in most plant cells in telophase 1 in meiosis

• cell plate forms

• cytokinesis starts from the middle of cell

What is precision and ways to improve it

• do not vary from mean

• lower precision = higher standard deviation

• repeating trials - allows data to cluster around the mean

• higher increments in equipment

What is accuracy and ways to improve it

• really close to actual answer

• identifying anomalies

• accuracy improves when your instruments or tools are calibrated properly

Adaptations of xylem and its use

• hollow for continuous water transport

• walls strengthened with lignin - prevent collapse

• narrow vessels - increase capillary action

• lignin - allows adhesion of water molecules to walls

• has bordered pits

If cell has more chromosomes then necessary after completing the cell cycle, which checkpoint failed and why?

• M checkpoint (metaphase)

• because chromosomes have not been aligned correctly at the spindle - causing chromatids to be pulled apart incorrectly

Method to successfully extract DNA - and reason for steps

• Pestle and mortar/Blend

  • Breaks down cells walls of onion cells

• Add salt to mixture

  • breaks the H bonds between DNA and water molecules

• Add onion pieces with detergent and in hot water bath

  • Both disrupt the phospholipid bilayer - releasing DNA

• Cool mixture in ice bath

  • prevents DNA itself from breaking down

• Filter mixture

• Add ice cold ethanol to test tube

  • Nucleic acids are insoluble in this - DNA forms a white precipitate

How smoking causes smokers cough

• forms tar

• smoke destroys cilia

• smoke stimulates goblet cells to release more mucus

• so the mucus builds up and is not removed

• causing pathogens to build up

• the cough is an attempt to increase the airflow

How smokers cough can lead to further problems in lungs in the future

• the frequent coughing can damage airways such as trachea and alveoli

• the damage to alveoli causes a reduced SA for gas exchange

• the airways walls (smooth muscle) thicken due to increase in inflammation

• and so the lumen of airways narrow

• causing airflow to restrict

• increase in pathogens - likely to catch diseases

How refreshing air in alveoli helps to maintain a steep diffusion gradient

• increases the pO2 in alveoli

• this means the conc. of O2 in alveoli > in blood

• this also decreases the pCO2 in alveoli

• means the conc of CO2 in alveol < blood

• causing a steep diffusion gradient

Function of golgi

• production of vesicles

• modification of proteins

Describe how to use a spirometer to measure rate of O2 uptake

Draw line along the peaks in the trace and calculate the gradient of the line

How does the increased permeability of capillary walls effect surrounding tissues?

• more tissue fluid is formed as more blood plasma leaves the capillaries

• increases pressure in tissue as volume increases

• swelling/oedema can occur

What causes fluctuation as the blood flows along the aorta

• the systole pressure increases

• diastole pressure decreases

Suggest advantages of keeping blood inside vessels

• higher blood pressure

• increase rate of flow

• flow can be diverted

How is a wall of artery adapted to withstand pressure NOT maintain

• wall is thick - as it has a thick layer of collagen

• which provides strength

Explain why the wall of left ventricle is thick

• more muscle for more force

• creates a higher pressure to push blood against greater resistance

• to pump blood further

How pressure changes in the heart bring about the closure of the AV valve

• ventricular systole occurs

• the contraction raises ventricular pressure

• which is higher than atrial pressure

• the pressure pushes valve shut

Adaptations of sieve tubes for mass flow

• elongated elements

• sieve plates

• little cytoplasm

• elements are joined end to end to form column

Describe and explain how transpiration contributes to the mechanism of water transport up the stem

In leaf:

• water loss is replaced

• via apoplast/symplast/vacuolar pathway

• down the water potential gradient

• lost water is replaced by water from xylem

Stem/xylem

• this creates a low hydrostatic pressure at top of leaf

• water moves down the pressure gradient - towards the leaf

• under tension by mass flow

• due to cohesion, a chain of water molecules form = transpiration stream

Describe how the RER and the Golgi apparatus are involved in the production of a secretory vesicle that contains protein

1. proteins are synthesised at ribosomes in RER

2. then they are passed into the cisternae of RER

3. then can be folded to have carbohydrates added

4. then packaged into transport vesicles

5. these move to Golgi via microtubules

6. they fuse with the Golgi - the proteins are then modified in Golgi and packaged into secretory vesicle

How to prepare a microscope slide

• (pond water - use a pipette to place a drop onto slide) - prepare sample

• place coverslip over sample

• ensuring no air bubble

Outline the method that students would use to carry out an investigation into the effect of temperature on the diffusion rate in their model cells?

1. Add glucose to dialysis tubing

2. secure dialysis tubing before addition of glucose

3. place tubing in a water bath and remove sample at set time intervals

4. add benedicts solution to sample

5. use calorimeter to obtain absorption values

6. repeat at different temp

How does the induced fit hypothesis for enzymes work?

• substrate binds to active site of enzyme

• temporary bonds are formed between the R groups of the substrate and the active site

• causes shape of active site to change

• this puts strain on the substrate bonds

• and so lowers the activation energy

describe the role of mitosis in fragmentation (asexual reproduction)

• produces many cells for growth

• which are genetically identical to mother

Properties and function of collagen

• fibrous protein

• structural component in skin, tendons, bones, teeth etc

• 3 polypeptide chains

• wound around each other - rope like structure

• provides strength + flexibility

Describe how to use colorimeter

• calibrate calorimeter with distilled water

• then place samples in a cuvettes

• use a range of known concentrations first

• then measure these values of absorption

• then measure the value of absorption of the sample

Function - How are sieve tube elements used in phloem

• translocation

• transport of, assimilates/ (organic) solutes/sucrose/amino acids.

• tissue made up of sieve tube elements and companion cells.

• allows mass flow / transport down a pressure gradient

• up and down plant / From source to sink/ bidirectional.

• allows movement with less resistance.

• (assimilates/AW used in) respiration / synthesis of (named) molecule

Structure - sieve tube elements in phloem

• living cells

• long / hollow/ continuous, tubes

• stacked end to end, to allow mass flow/ for less resistance/ to connect source to sink

• no nucleus/little cytoplasm/few organelles

• end walls are sieve plates

• walls are, thin

• (walls are) not lignified

• sieve, plates /pores, to allow (named) solutes through/ limit size passing through

• sieve pores linking cytoplasm of adjacent cells

• sieve, pores/plates to reduce (rate of) flo

Function - How are companion cells used in phloem

• ‘life (non-structural) support’ to sieve tube elements

• gains sucrose from, mesophyll cell/source

• (gains sucrose using) protons/ H+ /energy/ active transport/active loading

• allow / load, sucrose/ (organic) solutes (into sieve tube element)

Structure - how are companion cells used in phloem

• (dense) cytoplasm / (lots of) mitochondria

• (large) nucleus.

• plasmodesmata, (connecting to sieve tube elements).

What is chi squared test used for

• used on data that has been observed

• when we know what the expected values are

• compares observed with expected

What is degrees of freedom - how to find out

• used for chi test

• helps decide if data is significant or not

• df = (number of rows - 1) x (number of columns -1)

  • in table

What is spearmans rank correlation coefficient

• used to see if 2 different variables are correlated in a linear pattern

• using a scatter graph

how to find d (difference in spearmans test)

• order the two sets of variables in size order and rank them

• then match the rankings together

• and find the difference between the rankings

What is unpaired t test used for

• comparing the means of two groups of different individuals

• independent

• two different categorical groups

What is paired t test for

• comparing two sets of data that came from the SAME individual

cell cycle