GCSE OCR GATEWAY BIOLOGY PAPER 1

what are the types of cell

Prokaryotic and Eukaryotic

what types of cells are eukaryotic

Plant, animal and fungal cells

what type of cells are prokaryotic

bacterial

Animal cells contain

Nucleus, cytoplasm, cell membrane, mitochondria, ribosomes

Plant cells contain

Nucleus, cytoplasm, cell membrane, mitochondria, ribosomes, cellulose cell wall, chloroplasts, vacuole

nucleus

contains DNA in the form of chromosomes that control cell's activities

cytoplasm

A jellylike fluid inside the cell in which the organelles are suspended, and most chemical reactions happen

mitochondria

the site of cellular respiration , and contain the enzymes needed for reactions involved

ribosome

site of protein synthesis

cell membrane

holds cell together, selectively permeable , so controls what goes in/out. contain receptor molecules that are used for cell communication

vacuole

Cell organelle that stores materials such as water, salts, proteins, and carbohydrates

Cellulose cell wall

Gives structure and strength

chloroplasts

Site of photosynthesis; contains chlorophyll

bacteria cells contain

plasmids, chromosomal DNA , cell membrane, cytoplasm

plasmids

small loops of extra DNA that aren't part of a chromosome . contain genes for things like drug resistance, and can be passed btn bacteria

What do microscopes do

Magnify images and increase resolution

chromosomal DNA

Controls the cells activities and replication, one long circular chromosome

name three kinds of microscope

TEM, SEM, Light Microscope

Resolution

how close together 2 objects can be, and still be seen as separate objects

When were light microscopes invented?

1590s

when were electron microscopes invented?

1930s

TEM

Transmission Electron Microscope; used to study parts inside of a cell, only dead cells can be observed 3D images

not portable, expensive.

SEM

Scanning Electron Microscope; Scans a beam of electrons across the surface of the specimen.

light microscope

eyepiece lens, objective lens, stage, clip, handle, lamp, focusing knobs

eyepiece lens

looked through to see the image and also magnifies the image

objective lens

magnifies the image - usually 3 different objective lenses

4

10, 40

stage

supports the slide

clip

holds slide in place

handle

To carry the microscope with

lamp

illuminates the specimen, so it can be seen more easily

focusing knobs

move the stage up and down to bring the image into focus

how to prepare a specimen

take a thin slice on a slide , add stain if needed so that it is easier to see. place coverslip onto the slide - gently lowering with a needle so there are no air bubbles.

How to view a specimen using a light microscope

-lowest powered lens

- coarse adjustment knob till specimen just in focus

- fine adjustment knob until clear image

-if need greater mag, swap objective lenses

magnification =

image size

------------

actual size

DNA

deoxyribonucleic acid

DNA structure

double helix

polymer

T and A, G and C

base forms cross inks to base on other strand

complimentary base pairing

hydrogen bonding between particular bases; in DNA, thymine (T) pairs with adenine (A), and guanine (G) pairs with cytosine (C); in RNA, uracil (U) pairs with A, and G pairs with C

dna monomer

nucleotide

what does a nucleotide contain

phosphate, sugar, base.

DNA is made of

nucleotides

it is a polymer

enzymes

biological Catalysts for chemical reactions in living things

proteins

lock and key theory

a substrate fits into its enzyme just like a key fits a lock

enzymes are

specific

enzyme's active sit fits onto the substrate perfectly

substrate

reactant of an enzyme-catalyzed reaction

enzyme's peak function

optimum

what happens if enzyme gets too hot

some of the bonds holding the enzyme together break, the active site changes shape, so it is no longer complementary to the substrate - denatures

is denaturing reversible?

No, it is irreversible

what effects enzyme rate of reaction

temp

pH

enzyme conc

substrate conc

enzyme conc on rate of reaction

The more enzyme molecules there are in a solution, the more likely a substrate molecule will meet up with one and join with it. So increasing the concentration of the enzyme increases the rate of reaction.

But, if the amount of substrate is limited, there comes a point when there are more than enough enzyme molecules to deal with all the available substrate, so adding more enzyme has no further effect.

substrate conc on rate of reaction

The higher the substrate concentration, the faster the reaction - it's more likely the enzyme will meet up and react with a substrate molecule.

This is only true up to a point though. After that, there are so many substrate molecules that the enzymes have about as much as they can cope with (all the active sites are full, and adding more makes no difference.)

respiration

Respiration is the process of transferring energy from the breakdown of glucose (a sugar).It goes on in every cell in all living organisms, all the time — it's a universal chemical process.

what does aerobic respiration make

large quantities of ATP

equation for cellular respiration

C6H12O6 + 6O2 --> 6CO2 + 6H2O + energy

what kind of reaction is respiration

exothermic

anaerobic respiration

Respiration that does not require oxygen

anaerobic respiration in animals

glucose --> lactic acid + energy

what is lactic acid

C3H6O3 and it causes your muscles to burn during hard exercise

allows for muscles to be used when respiring anaerobially

oxygen debt

the amount of oxygen required after physical exercise to convert accumulated lactic acid to glucose

anaerobic respiration in plants

glucose --> ethanol + carbon dioxide + energy

fermenatation

anaerobic respiration in yeast

when might anaerobic respiration in plants happen

waterlogged soil, where there is little oxygen

Compare anaerobic and aerobic respiration

-Aerobic respiration is with oxygen, anaerobic is not

-Aerobic transfers more energy than anaerobic

-Aerobic produces carbon dioxide and water, anaerobic only produced lactic acid/ethanol + carbon dioxide

-They are both exothermic reactions

-They both use glucose

biological molecules

carbohydrates, proteins and lipids can be broken down so that energy can be transferred to ATP through respiration the energy stored in ATP is then available for the cell to use.

Carbohydrates are made of

carbon, hydrogen, oxygen

Carbohydrate monomer

glucose and fructose

carbohydrate polymer

starch, cellulose, glycogen

How are carbohydrates digested

salivary amylase (mouth)

pancreatic amylase

sucrase/maltase/lactase (intestinal)

this breaks them back down into sugars

proteins (polymer) made of

amino acids (monomer)

amino acids

a simple organic compound containing both a carboxyl (—COOH) and an amino (—NH2) group.

How are proteins digested

pepsin in the stomach and small intestine

protease

Lipids are made of

fatty acids and glycerol

Lipids are not polymers because

The molecules do not repeat in a chain

How are lipids digested?

pancreatic lipase and intestinal lipase

Tests for biological molecules

starch - iodene - browny orange to blue-black

lipids - ethanol - milky emulsion

proteins - biuret - blue-purple

reducing sugars - benedict's - blue-green-yellow-red

non reducing sugars - HCl - coloured precipitate

Test for protein

add sodium hydroxide solution to make the solution alkaline

add copper (II) sulfate

if protein will go purple

if no protein blue

Non-reducing sugar test

Using a new sample of the test solution, add dilute hydrochloric acid and heat in a water bath that's been that's been set at 75 °C. Add sodium hydrogen-carbonate (to neutralize it) then carry out the Benedict's test as above. A coloured precipitate means there are non-reducing sugars present .If the solution stays blue, the test solution didn't contain any sugar at all.

Photosynthesis

Conversion of light energy from the sun into chemical energy.

What are the two stages of photosynthesis?

light dependent and light independent

light dependent stage

the first stage of photosynthesis; it requires light energy that is absorbed by chlorophyll; water molecules split to produce oxygen gas and hydrogen ions

light independent stage

carbon dioxide gas and H+ ions combine to make glucose

Photosynthesis equation

6CO2 + 6H2O --> light --> C6H12O6 + 6O2

What is the site of photosynthesis?

Chloroplast

what is glucose from photosynthesis used for

respiration, stored as starch, stored as sucrose, cellulose cell wall, combines with mineral to make lipids and amino acids, oils for storage in seeds

What type of reaction is photosynthesis?

endothermic

factors affecting rate of photosynthesis

light intensity, carbon dioxide concentration and temperature

photosynthesis and light

Light transfers the energy needed for photosynthesis .As the light level is raised, the rate of photosynthesis increases steadily - but only up to a certain point .Beyond that, it won't make any difference — it'll be either the temperature or the CO, level which is the limiting factor.

distance from light and light intensity

inversely proportional

light intensity equation

1/distance^2

carbon dioxide and photosynthesis

As the CO2 level is raised, the rate of photosynthesis increases steadily - but only up to a certain point .Beyond that, it won't make any difference — it'll be either the temperature or the light intensity, level which is the limiting factor.

how to control CO2 conc in photosynethsis

dissolve different amounts of sodium hydrogen-carbonate in water

Temperature and photosynthesis

Usually, if the temperature is the limiting factor it's becauset's too low — the enzymes needed for photosynthesis workslowly at low temperatures

But if the plant gets too hot, the enzymes it needs for photosynthesis and its other reactions will be denatured— the rate of reaction decreases

This can start to happen at about 45 °C (pretty hot for outdoors, but greenhouses can get that hot if you're not careful).

Experimentally, the best way to control the temperature of a boiling tube is to put it in a water bath.

what are the stages of the cell cycle

G1, S, G2, M

what happens in gap phase 1

Cell grows and new organelles and proteins are made

what happens in the synthesis phase

DNA replication

what happens in gap phase 2

Cell keeps growing and proteins needed for cell division are made

What happens in mitosis?

cell division

what are the stages of mitosis

interphase, prophase, metaphase, anaphase, telophase, cytokinesis

interphase

period of the cell cycle between cell divisions

prophase

chromosomes supercoil and supercondense , and centrioles form at the poles

nucleus dissolves

organelles replicate

metaphase

chromosomes line up at the equator and spindle fibres attach at the centromere