Edexcel IGCSE Biology Paper 1

What are the characteristics of living things?

Move, respire, sensitivity, grow, respire, excrete, nutrition, control

Describe eukaryotic cells

Example

Complex large cell

Contain Nucleus

Any mammal/insect cell

Describe prokaryotic cells

Example

Small simple cell

No nucleus

Floating DNA

Amoeba/Chlorella

Animal cell:

Structure

Carbohydrate store

Example

Multicellular

Contain: No cell wall

Store carbs as Glycogen

Any mammal/insect

Plant cell:

Structure

Carbohydrate store

Example

Cell wall, vacuole, chloroplasts

Store carbs as starch or sucrose

Beans/maize

Fungi:

Structure

Feeding method

Store carbohydrates

Example

Body called mycelium made up of hyphae (thread like structures)

Cell walls made of chitin

Saprotrophic nutrition - release enzymes into surroundings to dissolve food

Store carbs as glycogen

Yeast

Describe the levels of organization

Organelle, cell, tissue, organ, organ system

What is the function of the mitochondria?

cellular respiration for energy

function of ribosomes

protein synthesis

function of chloroplast

Contains chlorophyll which absorbs light energy for photosynthesis

function of vacuole

Stores water, salts, proteins and carbs and provides structure

Define pathogen

disease causing organism

Describe viruses

Example

small cells, can only reproduce in living cells, no cellular structure, protein coat and contain DNA or RNA

HIV

Describe bacteria

single celled, no nucleus, contain circular chromosomes of DNA, contain plasmids (extra bits of DNA)

Lactobacillus

Define cell differentiation

the process by which cells become specialized in structure and function

Structure and elements in carbohydrates

Carbon, Hydrogen, Oxygen

Starch/Glycogen

Structure and elements in lipids

Carbon, Hydrogen, Oxygen

fatty acids and glycerol

Structure and elements in proteins

Carbon, Hydrogen, Oxygen, Nitrogen

Amino acids

How to test for starch

addition of Iodine (orange) reacts with starch to produce brown/blue color

How to test for lipids

Add drops of Sudan III

Shake

Red lipids settle on top

How to test for proteins

Biuret test

Add biuret solution and shake

blue -> pink if present

How to make a food sample

Break food in pestle and mortar

stir with distilled water

filter solution to remove solids

How to test for glucose

Benedict Solution in a hot water bath - blue -> turns green-yellow-brick red

Describe the process of photosynthesis

light energy is absorbed by chlorophyll in chloroplasts

used to convert carbon dioxide and water into

sugar (glucose) (oxygen is released)

word and chemical equation for photosynthesis

Carbon dioxide + water > glucose + oxygen

6CO2 + 6H2O = C6H12O6 + 6O2

Adaptations of a leaf

Large surface area

Upper epidermis transparent allows light in

most chloroplasts found in palisade cells near top

waxy cuticle prevents water loss

What do plants need mineral ions for

Growth

What is a plants use for nitrates

Deficiency symptoms

Used for supply of nitrogen to make amino-acids and protein which is used for growth

Stunted growth

Leaves go yellow

What is a plants use for Phosphates

Deficiency symptoms

Used for making DNA and cell membranes as well as for respiration and growth

Poor root growth

Leaves turn purple

What is a plants use for Potassium

Deficiency symptoms

Help enzymes for photosynthesis and respiration

Poor flower/fruit growth

discoloured leaves

What is a plants use for magnesium

Deficiency symptoms

Used for making chlorophyll

Yellow leaves

Bodies use for Carbohydrates

Found in

Energy

Pasta, rice, sugar

Bodies use for Lipids

Found in

Energy, energy storage, insulation

Fish, butter

Bodies use for Protein

Found in

Growth and tissue repair

Meat, fish

Bodies use for Vitamin A

Found in

Improve vision - hair and skin

Liver

Bodies use for Vitamin C

Found in

Prevent scurvy

Citrus fruits - lemons, orange

Bodies use for Vitamin D

Found in

Increases calcium absorption

Eggs

Bodies use for Calcium

Found in

Strong bones and teeth

Dairy products

Bodies use for Iron

Found in

Make haemoglobin for blood

Red meat

Process of food digestion

Mouth

Oesophagus

Stomach

Duodenum

Ileum

Colon

Rectum

Anus

Digestion - what happens in the mouth

Mastication - more surface area for enzymes

Amylase in saliva breaks starch into maltose

Digestion - what happens in the oesophagus

Peristalsis - circular muscle contraction moves boluses of food down

Digestion - what happens in the Stomach

Mechanical digestion - churning food

Hydrochloric acid kills bacteria

Pepsin breaks protein down into amino-acids

Digestion - what happens in the Duodenum

Pancreatic juice added - protease/trypsin - protein

- amylase - starch

- lipase - lipids

Bile added - neutralises acid

- emulsifies lipids

Digestion - what happens in the Ileum

Food absorption

Villi (covered in microvilli) Very high surface area

Adaptations of Villi and the Ileum

Ileum is very long so time to absorb all nutrients

Villi and micro-villi create high surface area

Villi have a one layer thick surface - short diffusion pathway - increased rate

Lots of capillaries assists good absorption

Digestion - what happens in the Colon

Water absorbed

Digestion - what happens in the Rectum and Anus

Rectum - Faeces stored

Anus - Egestion - Faeces removed

Digestion - what happens in the Liver

Bile produced

Stored in Gall bladder

Digestion - what happens in the Pancreas

Protease, amylase and lipase produced

Released into Duodenum

Describe aerobic respiration

Word and chemical equation

Lots of oxygen available

Lots of ATP produced

Describe anaerobic respiration

Word equation

Insufficient oxygen available

Produces much less ATP

Lactic acid produced in Humans

Ethanol and C02 produced in plants

Gas Exchange:

Describe the Thorax

Trachea (surrounded by cartilage prevents collapse)

Bronchi

Bronchioles

Alveoli

Surrounded by ribs with intercostal muscles

Diaphragm at bottom

Thoracic cavity surrounded by airtight pleural membranes

Describe breathing in

Intercostal muscles and diaphragm contract

Thorax volume increases

Decrease in pressure drawing air in

Describe breathing out

Intercostal muscles and diaphragm relax

Thorax volume decreases

Pressure increase forcing air out

What are the adaptations of alveoli for gas exchange?

Huge number in lungs

Very small means increased surface area

One cell thick walls - short diffusion pathway

many capillaries to maintain a high concentration gradient

Effects of smoking on the lungs

List 5 in detail

Damages the alveoli reducing their surface area

leading to diseases like emphysema

Tar in cigarettes damages the cilia in the trachea and lungs

These stop dust and bacteria entering the lungs

Increases risk of chest infections

Tar irritates bronchi and bronchioles causing excess mucus production - smokers cough

Carbon monoxide in the smoke reduces the oxygen in blood

The body counters by increasing heart rate and blood pressure, which damages artery walls.

Increases chance of blood clots

Increases risk of coronary heart disease

Smoke contains carcinogens that cause cancer

(Nicotine also increases heart rate)

Why can unicellular organisms rely on diffusion for movement of substances

They are very small so have a large SA:Volume ratio

Why do multicellular organisms need a circulatory system for movement of substances

They are large so have a low SA:Volume ratio meaning substances cannot diffuse through them and so they need a system

Name the main components of blood

Red blood cells

White blood cells

platelets

plasma

Blood:

What is plasma?

Pale yellow liquid that carries everything in blood

including:

Digested food products

CO2

Urea

Hormones

List 3 adaptations of red blood cells

Biconcave shape - high surface area for absorbing oxygen

Contains haemoglobin which contains Iron

allows blood to carry oxygen

No nucleus creates space for more haemoglobin

Describe how the immune system works including descriptions of the two types of white blood cell.

Phagocytes - detect foreign things

Digest the object using enzymes

Non-specific - destroy everything foreign

Lymphocytes - Find foreign antigens (attached to pathogens)

Produce antibodies that are specific to the antigen

antibodies attach to the pathogen and mark them to be destroyed

Memory cells remember a specific antigen and can produce antibodies very quickly if the pathogen enters the body ever again.

How does exercise affect heart rate?

During exercise muscles contract more

So need more energy

So the body respires more

More CO2 produced

Receptors in aorta detect increased CO2 - signal brain

so heart pumps faster to increase blood flow to remove it

How does adrenaline affect heart rate?

Adrenaline binds to heart receptors

Heart pumps faster and harder

more oxygen gets to muscles

ready to escape/for action

List 3 factors that can lead to coronary heart disease

High saturated fat in diet

Causes fatty deposits in arteries.

Smoking causes arterial damage

Fatty deposits more likely to form.

Low exercise leads to high blood pressure which damages the arteries.

Fatty deposits more likely to form.

What causes a heart attack? (Coronary heart disease)

Coronary arteries to the heart get blocked by fatty material.

Blood flow is restricted causing lack of oxygen to the heart.

Can cause a heart attack.

Describe an artery

Carry blood away from the heart

High pressure

Strong elastic sides

Thick layer of muscle

Medium Lumen

Describe a capillary

Very tiny

Permeable walls

One cell thick walls - increase rate of diffusion

Very small lumen

Describe a vein

Culmination of capillaries

carry blood to the heart

Low pressure - valves prevent blood changing direction

Large lumen

What does Pulmonary mean?

To do with the lungs

What does Hepatic mean?

To do with the liver

What does Renal mean?

To do with the kidneys

How does the body respond to the environment?

Receptors in sense organs (eyes, ears etc) detect stimuli

Effectors (muscle, glands etc) communicate with the receptors by the nervous system or hormonal system

Define homeostasis

Maintaining a stable internal environment (including water content and body temperature)

What is geotropism?

a plant's response to gravity

What is phototropism?

A plant's response to light

When a shoot is exposed to light, where does the auxin go?

To the shade which increases growth on that side bending the shoot towards the light.

How does the sensory nervous system work?

Consists of brain and spinal cord only

•Receptors detect stimuli

•Send electrical impulses along sensory neurones to the CNS

•CNS sends impulses to an effector using motor neurones

•Effector responds

How are neurones connected?

•Synapses are connections between two neurones

•Signal is transferred by chemicals called neurotransmitters which cross the gap

•causing a new signal on the other side

Describe the reflex arc

stimulus → receptor → sensory neurone → central nervous system → motor neurone → effector → response

Label the structure of an eye

Eye: What does the conjunctiva do?

Lubricates and protects the eye surface

Eye: What does the Sclera do?

tough outer layer - protects the eye

Eye: What does the cornea do?

Refracts light into the eye

Eye: What does the iris do?

it contracts and expands to let enough light into the eye so it can focus on the retina

Eye: What does the optic nerve do?

Carries impulses from the eye to the brain

How does the eye respond to dim light?

Radial muscles contract making the pupil larger

Circular muscles relax

How does the eye respond to bright light?

Circular muscles contract making pupil smaller

Radial muscles relax

What is the optimum temperature for the body?

37 degrees celsius

How does skin react when you are too hot?

Lots of sweat produced - evaporates taking heat away

Blood vessels near skin widen - vasodilation - more blood near skin so more heat lost

Hair lies flat

How does skin react when you are too cold?

Blood vessels near surface constrict - less blood to lose energy - vasoconstriction

Shivering increases respiration so more heat created

Hairs stand up to insulate the body with air

Adrenaline source/role/effect

Adrenal Gland/Fight or flight/Increases heart rate, blood flow to muscles and blood sugar levels

Insulin source/role/effect

Pancreas/Control blood sugar level/stimulates the liver to convert glucose into glycogen

Testosterone source/role/effect

Testes/male sex hormone/(see puberty)

Progesterone source/role/effect

Ovaries/Supports pregnancy/Maintains the lining of the uterus

Oestrogen source/role/effect

Ovaries/female sex hormone/controls menstrual cycle and (see puberty)

What is asexual reproduction?

The production of genetically identical offspring from a single parent

What is sexual reproduction?

Reproduction involving fusion of a male and a female gamete to create diverse offspring.

Define mitosis

cell splits to form two cells with identical sets of chromosomes