OCR Biology: Module 2

2.1.1 CELL STRUCTURE

2.1.1 CELL STRUCTURE

How many lenses does a light microscope have?

2

objective lens & eye piece lens

In a scientific drawing, name four rules that apply to label lines.

No arrow heads, drawn with a ruler, can't cross, parallel to top of page

What is the equation for magnification?

Magnification = (size of image)/(size of object)

What is resolution?

The ability to see separate objects as separate entities

micrometer : nanometer

1 μm : 1000 nm

millimetre : nanometre

1 mm : 1,000,000 nm

millimetre : micrometers

1 mm : 1000 μm

What are the two types of electron microscope?

TEM and SEM

Which microscope (out of light, TEM and SEM) has the best resolution?

TEM

Which microscope (out of light, TEM and SEM) gives 3D images?

SEM

differences between light and electron microscope

difference between prokaryotic cells and eukaryotic cells

- DNA

- Ribosomes

- Cell wall

- Organelles

- prokaryotes can have circular DNA but no nucleus

- eukaryotic = 80s, prokaryotic = 70s

- prokaryotes have cell wall made of peptidoglycan, in eurkaryotic cells chitin is used for fungi and cellulose for plants

- eurkaryotic cells have membrane-bound organelles

animal cell diagram

What is the function of a nucleus?

contains DNA and controls cell activity

What is the function of a nucleolus?

Producing ribosomes

What is the function of mitochondria?

Sites of cellular respiration

What is the function of a vesicle?

To store and transport molecules

What is the function of a lysosome?

contain enzymes to break down waste material e.g pathogens

What are the three components of a cell's cytoskeleton?

Microfilaments, microtubules and centrioles

What is the function of the cytoskeleton?

Give the cell its shape and stability

What is the function of microfilaments?

Cell movement and cell contraction

What is the function of microtubules?

Movement of organelles and cell shape

(spindle fibres made of microtubules)

what are centrioles made of?

microtubules

What is the function of centrioles?

Assembly and organisation of spindle fibres

What is the function of cilia?

Causes objects adjacent to the cell to move

e.g move mucus away from lungs

What is the function of flagella?

Motility

What is the function of the smooth endoplasmic reticulum?

Lipid and carbohydrate synthesis and storage

What is the function of the rough endoplasmic reticulum?

synthesis and transport of proteins

function of golgi apparatus

Modifies and processes proteins and then packages them into vesicles

Where can ribosomes be found?

Cytoplasm and rough ER

What is the function of ribosomes?

Protein synthesis

Name the three places the proteins go after being synthesised in the ribosome.

Transport vesicle, Golgi apparatus, secretory vesicle

What are plant cell walls made of?

Cellulose

not selectively permeable

What is the function of a vacuole?

Maintain turgor

What is the membrane of a vacuole called?

Tonoplast

What is the function of chloroplasts?

Photosynthesis

Name two organelles found only in a plant.

large permanent vacuole and chloroplast

How is DNA presented in prokaryotic cells?

Circular

2.1.1 CELL STRUCTURE

2.1.1 CELL STRUCTURE

2.1.2 BIOLOGICAL MOLECULES

2.1.2 BIOLOGICAL MOLECULES

Which ions are necessary for nerve impulse transmission?

Calcium, sodium, potassium

What are calcium ions necessary for?

Nerve impulse transmission and muscle contraction

What are sodium ions necessary for?

Nerve impulse transmission and kidney function

What are potassium ions necessary for?

Nerve impulse transmission and stomatal opening

What are hydrogen ions necessary for?

Catalysis of reactions and pH

What are nitrate ions necessary for?

Formation of amino acids and proteins in plants

What are hydrogen carbonate ions necessary for?

Blood pH maintenance

What are chloride ions necessary for?

Balance charges in cells

What are phosphate ions necessary for?

Formation of cell membrane, ATP and bones

What are hydroxide ions necessary for?

Catalysis of reactions and pH

Which elements are carbohydrates made from?

Carbon, hydrogen and oxygen

Which elements are lipids made from?

Carbon, hydrogen and oxygen

Which elements are proteins made from?

Carbon, hydrogen, oxygen, nitrogen and sulfur

Which elements are nucleic acids made from?

Carbon, hydrogen, oxygen, nitrogen and phosphorus

Which property of water allows it to form hydrogen bonds?

Polarity

O is 𝛿 ⁻, H is 𝛿⁺

Why is water liquid at room temperature?

Hydrogen bonds

high specific heat capcity

Which properties of water make it a good transport medium?

Adhesion, cohesion and polarity

Which properties allow water to support life?

⚬ high specific heat capacity allows stable temp. for enzyme function

⚬ ice = lower density so floats which insulates

⚬ surface tension so habitat for invertebrates

⚬ high latent heat of evaporation means sweat cools you down

⚬ effective solvent for metabolism

examples of each:

1) monosaccharide

2) disaccharide

3) polysaccharide

1) glucose, fructose, ribose

2) lactose, sucrose

3) glycogen, celluose, starch

What is the chemical formula of glucose?

C₆H₁₂O₆

Describe the structure of alpha-glucose?

the difference between beta, remember ABBA

Describe the structure of beta-glucose?

Which bond is formed between glucose molecules?

draw it

1,4-glycosidic bond

formed in a condensation reaction

What are the two polysaccharides known as starch?

Amylose and amylopectin

(made up of alpha glucose)

difference between amylose and amylopectin (structure)

amylose only has 1,4 glycosidic bonds (linear)

amylopectin has 1,4 and 1,6 glycosidic bonds (branched)

In what form is alpha glucose stored in animals?

Glycogen

similar to amylopectin as has 1,4 and 1,6 also but more branched

what are the key properties of amylopectin and glycogen which make them good for storage

insoluble, branched, compact

What is cellulose formed from?

Beta glucose

how do beta glucose's react together to form cellulose

alternate beta glucose molecules are turned upside down

forms a straight chain, unbranched

What is the Benedict's test for?

Reducing sugars (can donate electrons)

How to carry out a Benedict's test

1) heat sample and Benedict's reagent to 80 degrees celsius

2) observe colour change

3) if reducing sugar present, a brick red precipitate will form

colour change (green → yellow → orange → red) indicate conc. of reducing sugar

How to carry out a Benedict's test for non-reducing sugars

1) add HCl and heat to 80 degrees with Benedict's reagent

2) then neutralise with alkali as Benedict's doesn't work in acid

How can a colorimeter be used to measure the conc. of a reducing sugar

1) calibrate colorimeter using distilled water

2) Do Benedict's on range of known concentrations of glucose

3) filter the solutions to remove precipitate

4) measure % transmission of each of the solutions using colorimeter

5) plot a calibration curve with known concentrations

6) repeat with unknown concs. of glucose and use calibration curve to find the conc.

What does iodine test for?

What is a positive result?

Starch

if starch present the solution changes from brown to blue-black

how to test for lipids

1) add sample to ethanol and shake

2) empty the liquid into distilled water

3) A milky-white emulsion is a positive test result: lipid is present

What does Biruet's test for?

How to carry it out?

proteins

1) crush sample in water

2) add Biruet to liquid food sample and shake

3) if protein present, will observe colour change from blue to violet purple

define:

- metabolism

- catabolic reactions

- anabolic reactions

- sum of total of all the chemical reactions that take place in an organism

- breaking larger molecules into smaller ones

- building smaller molecules into larger ones

What is the structure of a triglyceride?

One glycerol and three fatty acids

What are the bonds formed between glycerol and a fatty acid?

Ester bonds in a condensation reaction

What is the term for a fatty acid chain with double bonds present?

unsaturated

What is the term for a fatty acid chain with no double bonds present?

Saturated

What is the term for a fatty acid chain with one double bond?

Monounsaturated

What is the term for a fatty acid chain with more than one double bond?

Polyunsaturated

What is the structure of a phospholipid?

Glycerol, two fatty acids and a phosphate group

roles of lipids

- membrane formation

- hormones

- electrical insulation

- waterproofing

- thermal insulation

- energy store

What are the monomers of polypeptides?

draw the structure

Amino acids

how do amino acids link?

peptide bonds in a condensation reaction

what enzymes break down proteins

proteases

What is the primary structure of proteins?

The sequence of amino acids

What is the secondary structure of proteins?

hydrogen bonds form alpha helix's or beta pleated sheet's

What is the tertiary structure of proteins?

further folding of secondary structure

- hydrophobic and hydrophillic interactions between polar and non-polar R-groups

- hydrogen bonds

- ionic bonds between oppositely charged R-groups

- disulfide bonds between sulfur atoms in R-group

What is the quaternary structure of proteins?

Interactions between subunits (2 or more polypeptides)

what is the structure of haemoglobin?

4 subunits (polypeptides) which consist of 2 alpha chains and 2 beta chains

each subunit wraps around a haem group (a prosthetic group) which contains Fe²⁺

Name a globular protein.

Insulin / enzymes

What is a conjugated protein

a protein with a prosthetic group

Name a conjugated protein.

Haemoglobin

Name three fibrous proteins.

Keratin, elastin and collagen

why is keratin strong

- many disulfide bonds as has lots of cysteine

structure of collagen

properties of collagen

- 3 polypeptides twisted like a rope

- lots of H bonds

- flexible

- strong