Biology OCR A level paper 1

Magnification of light microscope

X1500

Resolution of light microscope

0.2micrometers

Magnification of a scanning electron microscope

X500000

Resolution of scanning electron microscope

0.002 micrometers

Magnification of a transmission electron microscope

X1,000,000

Resolution of a transmission electron microscope

0.0002 micrometers

What can be used as a counterstain

safranin dye

Magnification

How many times larger the image is than the actual size of the object being viewed

Resolution

How detailed the image is. How well the microscope distinguishes between 2 points that are close together.

Nucleolus

Produces ribosomes. Made of protein and RNA, which is used to make rRNA, which combines with protein to form ribosome.

What's the plasma membrane made off

Many lipids and proteins

Centrioles

Small, hollow cylinders made of microtubules

Microfilaments

Contractile fibres formed from actin, responsible or cell movement and contraction during cytokinesis

Microtubules

Determine shape of cell and act as tracks for the movement of organelles

Intermediate fibres

Give cell mechanical strength and help maintain their integrity

Vacuoles

Membrane lined sacs containing cell sap. Important in maintenance of turgor.

Tonoplast

Membrane of vacuole and is selectively permeable

DNA in prokaryotic cells

Circular, proteins fold and condense DNA, one molecule, chromosome

DNA in eukaryotic cells

Linear, associated with proteins called histones forming chromatin, multiple chromosomes

Cell wall in prokaryotic cells made from

Peptidoglycan/murein

Call wall in fungi made from

Chitin

Flagella in prokaryotic cells

Made of flagellin, arranged in a helix

Flagella in eukaryotic cells

Made of microtubules, arranged 9+2 formation

Importance of cytoskeleton

Provide mechanical strength, aiding transport within cells, enabling movement

High latent heat of evaporation

Lot of energy used up when water evaporates - coolant

Biuret test tests for?

Proteins

Biuret test method

1. Add few drops of NaOH

2. Add copper sulfate solution

Positive result for biuret test

blue to purple

What does Benedict's test for

reducing sugars (all monosaccharides, glucose, & some disaccharides, maltose & lactose)

Method for benedicts test

Add benedicts reagent and heat in water bath

Positive result for benedicts test

blue --> coloured ppt (brick red)

Benedicts test for non-reducing sugars method

break down into monosaccharide by adding dilute HCl & heating in water bath.

Neutralise with sodiumhydrogencarbonate

Carry out benedicts

Non reducing sugar example

sucrose

Iodine test tests for?

Starch

Iodine test method

Add iodine dissolved in KI solution

Positive result for iodine test

browny orange to dark blue-black

Emulsion test tests for?

Lipids

Emulsion test method

Shake test substance with ethanol for about a minute

Poor solution into walk

Positive result for emulsion test

Solution turns milky

Biosensors

A device that used a biological molecule to select a chemical

Stationary phase example in chromatography

Silica gel

Purines

Adenine and Guanine (double ring)

Pyrimidines

Cytosine and Thymine and Uracil (single ring)

How to biosensors work

Biological molecule produces a signal, chemical, which is converted to an electrical signal by a transducer and processed

Semi conservative

Both the copies retain one of the original strands from the parent DNA and one new strand

degenerative

More possible combinations of triplets than there are amino acids

How many amino acids are there

20

How many triplets are there

64

tRNA

Carries amino acids to the ribosome during translation. In cytoplasm. Has an amino acid binding site and an anticodon

rRNA

Moves along mRNA strand and helps catalyse formation of peptide bonds between amino acids. Forms the 2 subunits of ribosome along with protein.

mRNA

Made in the nucleus. 3 adjacent bases, codon. Carries genetic code from nucleus (DNA) to cytoplasm.

Template strand is also knowns as the

antisense strand

Haemoglobin structure

conjugated, globular protein, with prosthetic R group Fe2+, 4 polypeptide chains

Insulin structure

2 polypeptide chains held by disulphide bonds

Amylase

enzyme that catalyses break down of starch in digestive system, secondary structure alpha helix & beta sheets

Globular proteins

Round, compact, soluble

Collagen

connective tissue (skin, bones)

Keratin

Flexible or hard/tough - skin, hair, nails, external

Elastin

Elastic connective tissue, allows tissues to return to original shape once stretched

Fibrous proteins

Insoluble, strong, tough, rope-shaped

alpha glucose + fructose -->

sucrose

beta glucose + galactose -->

Lactose

2 alpha glucose -->

Maltose

What's starch made from

amylose and amylopectin

amylose estruture

alpha helix 1,4 compact good for storage

amylopectin structure

alpha helix 1,4 and 1,6 (slightly branched) - glucose can be released quickly

Glycogen structure

alpha glucose, branched

Structure of cholesterol

hydrocarbon ring structure with OH group attached to hydrocarbon tail

Conjugated protein

Protein with a non-protein group attached

How do enzymes work

Lower the activation energy by creating a transition state between the enzyme and the substrate that is more stable than the uncatalysed reaction

Example of an intracellular enzyme

Catalase - H2O2 --> H2 +O2

Example of an extracellular enzyme

Amylase, in saliva, hydrolysis of starch --> maltose

Trypsin

Trypsin

produced by cells in the pancreas & secreted into small intestine & catalyses the hydrolysis of peptide bonds, big polypeptides into smaller ones

Vmax

The maximum rate at which an enzyme can catalyse a reaction or the maximum initial velocity the reaction can only be increased up to a certain point.

Temp coefficient, Q10

Measure of how much the rate of reaction increases with a 10.C rise in temp

Cofactor

A non protein substance bound to enzymes so they work

cofactor for amylase

Cl-

Coenzymes

Cofactors that are organic molecules (C bases), participate in reaction & changed b it

Prosthetic group for carbonic anhydrase

Zn 2+

Irreversible inhibitor of cytochrome c oxidase

cyanide

Intrinsic proteins

Trans membrane proteins that are embedded through both layers of a membrane

Glycoproteins

Attached carbohydrate chain, role in cell adhesion and as receptors for chemical signals (bigger than glycoplipid on diagram)

Glycolipids

attached carbohydrate chain, cell markers or antigens

Function of glycolipids and glycoproteins

Stabilise membrane by forming H bond with surrounding water molecules, act as receptor for cell signalling, antigens involved in the immune response

Simple diffusion

Diffusion in the absence of a barrier or membrane

Facilitated diffusion

Diffusion across a plasma membrane through protein channels and carrier proteins

Antihistamines

block histamine receptors preventing histamines binding, preventing inflammation

Bulk transport

How large molecules move into and out of cell (endocytosis and exocytosis)

Phagocytosis what substance

solids

Pinocytosis what substance

liquids

Hypotonic solution

solution with higher water potential than cell so water moves into cell

Isotonic solution

Solution with same water potential as cell

Hypertonic solution

Solution with lower water potential than cell, water moves out

Why does a cell enter G0

differentiation-specialised cell no longer able to divide, damaged DNA

S1

DNA replication

G1 check point checks for

SNGD

size, nutrients, growth factors, DNA damage

G2 check point checks for

SRD

size, DNA replication, DNA damage

Mitosis for?

Growth, tissue repair, asexual reproduction in plants, animals and fungi.

Cytokinesis, animal cells

Cleavage furrow forms

Cytokinesis plant cells

Vesicles from golgi body assemble in same place as metaphase plate, Vesicles fuse with each other and cell surface membrane, then divides.new sections of cell wall then form