OCR GATEWAY GCSE BIOLOGY B1

B1

Name Eukaryotic cells

Plant, animal

Name Prokaryotic cells?

Bacteria

\\\\e.g E.Coli

State the main differences in the structures found in eukaryotic and prokaryotic cells

EUKARYOTIC: nucleus, cytoplasm, cell membrane, mitochrondria

PROKARYOTIC:cell wall, genetic material, cell membrane, cytoplasm, flagellum, plasmid

Equation that links magnification, image size and real size

image size = magnification x real size

What is resolution?

Resolution is how well you can separately distinguish 2 points close together.

Identify the main components of a light microscope

Steps to observing cells through a microscope

1. Move stage to its lowest position

2. Select objective lens with lowest magnification

3. Place slide on stage

4. Turn coarse focus knob until you see object

5. Turn fine focus knob slowly until object is in focus

6. THEN repeat steps but with higher magnification objective lens

Explain how staining is used to highlight cell features

-particular stains colour specific structures or give colour to colourless cells

-METHYLENE BLUE -nucleus of an animal cell

IODINE - plant cell nuclei

CRYSTAL VIOLET - stains bacterial cell walls

What is a electron microscope?

-high energy electrons as the light source

-greater resolution

-allowed scientists to see detail within subcellular structures like chloroplasts

State differences between light and electrons

PriceSizeResState(PSRS)

LIGHT - cheap, small/portable, simple to prepare sample, specimens can be living or dead, resolution up to 0.2μm, shows images in natural colour

ELECTRON - expensice, large/difficult to move, sample prepartion is complex, shows image in b&w, specimens need to be dead, resolution up to 0.1μm

TAKE A BREAK: its DNA next ew

State the role of DNA in the body

-chemical instructions to individual characteristics

Describe the structure of DNA

-two strands joined by bases (A+T, G+C)

-made of nucleotides(slice of pizza) joined all together

-each nucleotide(slice) is made of a sugar, phosphate group and base

Differences between mRNA and DNA

-DNA itself is too big to leave nucleus

-copy of the DNA is made called mRNA-

-mRNA is like a single strand of DNA

What is transcription?

Transcription is process where mRNA is produced

Describe process of transcription

1. DNA around a gene unzips so both strands are separated

2. One of DNA strands acts a template

3. Complementary bases attach to the strand being copied

4. This forms a strand of complimentary mRNA

What is translation?

Translation is the process where proteins are made. The mRNA attaches to a ribosome.

Describe process of translation?

1. Ribosome 'reads' the nucleotides on the mRNA in groups of three called codons. Each triplet codes for a specific amino acid

2. Ribosome keeps reading and adds more amino acids

3. Amino acids join in a chain forming a protein

Describe the function of an enzyme using named examples

-build larger molecules from small ones e.g protein synthesis

-break down large molecules into smaller ones e.g digestion

Describe the structure of an enzyme

Describe what happens when an enzyme is denatured

-the substrate no longer binds so rate of reaction decreases

-when all are denatured, reaction stops completely

How does temperature affect enzymes?

-the higher the temp, the faster the reaction

-each enzyme has its optimum pH

-the higher the substrate concentration, the faster the rate of reaction but then becomes constant

What does the graph look like? (temperature)

What does the graph look like? (pH)

What does the graph look like? (substrate)

TAKE A BREAK: photosynthesis and respiration is next its ok

State what is meant by metabolic rate

-the speed at which the chemical reactions in your cells transfer energy from its chemical stores in food

-the higher the metabolic rate, the more food you need to eat

Explain how carbohydrates are synthesised and broken down

-synthesised from glucose monomers

-starch is a carbohydrate

- starch is broken down with enzyme amylase

Explain how proteins are synthesised and broken down

-synthesised from amino acids

-broken down by protease enzymes

Explain how lipids(fats) are synthesised and broken down

-synthesised from 3 fatty acids and glycerol molecule

-broken down by lipase in small intestine

- contain bile to increase SA

What is equation of aerobic respiration?

glucose + oxygen = carbon dioxide + water

What is equation of anaerobic respiration?

in animals = glucose => lactic acid (cramp)

FERMENTATION

in plants = glucose=> ethanol (C2H5OH) + carbon dioxide

Main differences between aerobic and anaerobic respiration

-anaerobic = 2 atp

- aerobic = 38 atp

TAKE A BREAK: next up photosynthesis!!

What is equation of photosynthesis?

carbon dioxide + water=> glucose+ oxygen

What are the 2 main stages of photosynthesis?

STAGE 1- light dependent

energy transferred from light splits water molecules into O2 and H+ ions

STAGE 2- light independent

CO2 combines w the H+ions to make glucose. The glucose produced is immediately used in respiration

How to test for starch

1. take leaf and place in boiling water to kill it

2. place leaf into boiling tube of boiling ethanol to remove all chlorophyll to stop the plant from photosynthesising

3. wash leaf with water to remove the ethanol and soften the lead and spread it out on a white tile

4. add drops of iodine solution if starch is present iodine will turn from yellow-brown to blue-black.

How to make the test for starch more accurate

test that the plant has photosynthesised by destarching the plant. meaning making sure that no starch is present in the leaves. to do this, keep the plant in dark for min 24 hrs.

How to prove that light is needed for photosynthesis

take a destarched plant and cover part of 1 of its leaves with black card or tin foil. light cannot reach the covered area of the leaf. place plant in sunlight for several hours and remove the card from leaf. finally test leaf for presence of starch

How to prove that CO2 is needed for photosynthesis

take a destarched plant and place insdie a polythene bad before sealing the bag add a pot of soda lime that will absorb CO2 and water vapour.

leave plant in sunlight. then test for starch

How to prove that O2 is given off during photosynthesis

place upturned test tube above an aquatic plant eg cabomba.

put apparatus in light for max photosynthesis.

once you have a full tube of gas, place glowing splint inside tube. it should relight if oxygen is actually present

What factors affect photosynthesis

light intensity, CO2, temperature

How does light affect photosynthesis

when testing this couting bubbles w ur eyes is bad bc u could miss one n bubbles could be different sizes

How does CO2 affect photosynthesis

How does temperature affect photosynthesis

Calculate relative light intensity using the inverse square law

RLI= 1/distance from light source "2

Explain how factors interact to limit the rate of photosynthesis

at some point increasing the factor no longer make sa difference to rate bc one of the other factors is short supplied