BIOLOGY Exam 2023

Nucleus

Contains genetic material (DNA) which controls the activities of the cell

Has the information needed to produce new cells

\
Found in plant and animal cells

Cytoplasm

Where most chemical reactions take place

\
Found in plant, animal and bacteria cells

Mitochondria

Respiration(energy is produced) takes place here

The mitochondria provide energy for the cell

\
Found in plant and animal cells

**Cell membrane**

Creates a barrier between the cell and the outside world 

Controls what can flow in and out of the cell

\
Found in plant, animal and bacteria cells

Ribosomes

Found in the cytoplasm are the site of protein synthesis

They read dna from the nucleus and build protein using these instructions

\
Found in plant and animal cells

Chloroplasts

Absorb light and energy for photosynthesis

Contains the pigment chlorophyll

Only found in some parts of the plant (green parts)

\
Found in plant cells

Vacuole

Filled with cell sap

Keeps the cell turgid

A permanent element of plant cells

\
Found in plant cells

**Cell wall**

Provides extra support to the plant

Helps the cell maintain its square/ rectangular shape

\
Found in plant and bacteria cells

**Genetic material**

Free to move around the cell, not contained by the nucleus 

Loop of dna

\
Found in bacteria cells

Plasmid

Small loop of dna

It often codes for traits to do with  protection

E.g. resisting against drugs

\
Found in bacteria cells

**Slime capsule**

Provides protection

Sits outside of the cell wall

\
Found in bacteria cells

Flagella

Provides movement to get food and move away from danger

\
Found in bacteria cells

Prokaryotes

They have no nucleus and mitochondria

\
Bacteria cells

Eukaryotes

Any cell with a clearly defined nucleus

\
Animal and plant cells

Procaryote or Eukaryote

open picture to see

specialised cells

open picture to see

Respiration

\
Oxygen + Glucose = Carbon Dioxide + Water + Energy

\
\* muscle cells need energy to contract, have lots of mitochondria

Oxygen for respiration

1. Breathe O2 in air
2. O2 fills lungs, alveoli
3. Diffusion across alveoli to blood (down conc gradient)
4. O2 travels in red blood cells to respiring cells

Glucose for respiration

1. Get from food
2. Goes to small intestine
3. Diffuses from villi
4. Transported to respiring cells

CO2 for respiration

1. Released from respiration
2. Travels in blood to lungs
3. Diffuses from blood to lungs
4. Breathe it out

Diffusion

the net movement of particles from an area of high concentration to an area of low concentration down a concentration gradient

**Factors affecting diffusion**

1. Concentration gradient 

steeper = faster

\

2. Temperature

An increase in temperature means the particles in a gas or a solution have more kinetic energy so move around faster and speeds up diffusion

**Surface area**

Large active organisms cannot reply upon their body surface

Surface area relative to volume is insufficient for exchange - the distances are too great

Large organisms have special surfaces to allow exchange of substances

**SA:V ratio**

As the organism size increases, the SA:V ratio decreases

\
**Surface area**

Length x width x number of sides

= 4πr2 

\
**Volume**

Length x width x height

= 3/4πr3 

\
The bigger the sa:v ratio, the faster the diffusion

\
Folded membrane = larger SA

**Exchanging materials**

Cells need O2 + glucose for respiration

Cells don't need CO2

These substances diffuse across the cell membrane

**Exchange surfaces**

* Large SA allows more gas exchange
* Thin (1 cell thick) walls give a short diffusion pathway
* Rich blood supply maintains a steep conc gradient
* Ventilation maintains a steep conc gradient

**Alveoli - lungs**

* Enormous surface area
* One cell thick flattened surface
* Rich blood supply
* Maintains steep concentration gradient

CO2 and O2 is exchanged

CO2 out, O2 into bloodstream

**Small intestine - digestive system**

* Has villi with large surface area (small hairs)
* Microvilli (also increase surface area)
* Rich blood supply

Glucose is diffused for respiration

Glucose goes from villi to blood supply

**Root hair cell - roots of plant**

* Large surface area (root hair)
* Steep concentration gradient 

Water, mineral ions, oxygen are taken in so that the plant can respire

\

1. Minerals dissolve on the plant water
2. The water takes the minerals up to the leaves

**Osmosis**

The movement of water molecules across a partially permeable membrane, from an area of high water concentration (dilute solution) to an area of low water concentration (concentrated solution)

other things about osmosis

Partially permeable membranes only let certain substances through

Substances dissolved in water are called solutes

Cytoplasm has a high concentration of solutes and a low concentration of water. This means water tends to move into the cell by osmosis. If too much water moves into the cell, it might burst

Plant cells have a cell wall which prevents it from bursting. Instead, we say that the cell is turgid

If too much water leaves the cell, it may become dehydrated, which we call flaccid

( water = high → low concentration)

( solutes = low → high concentration)

Hypertonic

If a solution will make the cell lose water, because the solution has a higher concentration of solute and a lower concentration of water

High solute, loses water

R for raisin, shrivelled

\
\* hypertonic - plant cell becomes PLASMOLYSED \*

Hypotonic

If a solution will make a cell take on water (because it has a lower concentration of solute)

Low solute, takes on water

\
O for balloon blown up, full of water

Isotonic

Solution will not make the cell gain or lose any water because the solution has the same concentration of solute as the cell

\
Neutral

microscopy

labelled diagram

Magnification

How much bigger the image you see is that the actual specimen

Resolution

The smallest distance you can see between two separate points

\
(how clear the image is)

**Light microscopes**

* Small, cheap
* Used in schools
* Magnification of up to x2000

**Electron microscopes**

Large, expensive

Kept in special rooms to control temperature, pressure and humidity

Uses a beam of electrons to form an image

Magnification of up to x2000000

**Onion microscope experiment**

1. Peel a thin layer of onion off the cut onion
2. Place the layer of onion carefully on the glass slide, and cover with a cover slip
3. Stain the layer of onion with Iodine
4. View your onion cells.

**Onion microscope experiment - How do you avoid air bubbles?**

Place the coverslip onto the onion from the corner and gently lower it down

**Onion microscope experiment - What do you do if you put too much Iodine on your onion?**

Dab the excess off with a tissue

**Onion microscope experiment - Why do you start at the lowest magnification?**

To locate the cells on the slide, then magnify further

**Active transport**

The movement of molecules across a cell membrane, from a region of low concentration to a region of high concentration, requiring energy from respiration

**Osmosis potato experiment**

1. Cut potato pieces to similar size, weight
2. Fill beakers with solutions, ranging from 0 to 0.8 grams of sugar dissolved in
3. Leave the potato in the beakers
4. Measure the masses again

\
Lots of salt solution take water from potato through osmosis, decreasing the mass

\
No salt solution gives water to potato through osmosis, increasing the mass

Organelles

A subcellular structure that has a specific job to perform in the cell

\
* Nucleus
* Mitochondria
* Ribosomes
* Cell membrane
* Cytoplasm 

Cells

The fundamental unit that makes up living things

\
* Red blood cells
* White blood cells
* Nerve cells
* Epithelial cells
* Muscle cells
* Glandular cells

Tissues

A group of similar cells that work together to perform a particular function

\
* Epithelial tissue
* Muscle tissue
* Glandular tissue
* Nerve tissue

Organs

A group of different tissues that work together to perform a particular function

\
* Heart
* Lungs
* Stomach
* Pancreas
* Liver
* Skin
* Testes/ ovaries

**Organ system**

A group of organs that work together to perform a particular function

\
* Digestive system
* Cardiovascular system
* Reproductive system
* Circulatory system

Organisms

Multiple organ systems working together to form the organisms

\
* Human

**Circulatory system**

* Heart
* Blood vessels
* Blood

**Blood vessels**

* Veins 
* Arteries
* Capillaries

Blood

* White blood cells
* Red blood cells


* Plasmid
* Platelets

Plasma

Plasma is the liquid that all the other things are suspended in

Most substances are carried in the plasma

When plasma leaves your capillaries it becomes tissue fluid

It carries many things such as:

\
* Carbon dioxide back to the lungs
* Waste products to your kidneys
* Hormones
* Dissolved food (glucose)

**Red blood cells**

There are more red blood cells than any other type of cell in your body

They pick up oxygen from the air in your lungs and carry it to where it is needed

They are adapted to this because:

* They are biconcave discs (increased surface area to volume ratio for diffusion)
* Packed with red pigment protein haemoglobin that binds to oxygen
* No nucleus for more space for haemoglobin

When haemoglobin is full of oxygen, it is called oxyhaemoglobin and is bright red

When it doesn't have much oxygen in it is a darker purple colour (why the blood in our veins is purple and arteries red)

**White blood cells**

They destroy pathogens

Under a microscope, they are purple with darker purple blobs inside (the nucleus)

Bigger than red blood cells and there are fewer of them

They do have a nucleus and form part of the body’s defence system against harmful microorganisms

Lymphocytes form antibodies against harmful microorganisms

Phagocytes engulf (surround) and digest invading bacteria and viruses

The rest form antitoxins against poisons made by microorganisms

Platelets

Small fragments of cells

No nucleus

Important in helping the blood clot at the site of a wound

**Blood clotting**

A series of enzyme controlled reactions that result in converting fibrinogen into fibrin

This produces a network of protein fibres that capture lots of red blood cells and more platelets to form a jelly 

This stops you bleeding to death

This protects new skin as it grows and stops bad bacteria entering through the wound

**Respiration equation**

Glucose + Oxygen = Carbon Dioxide + Water (+ energy)

Arteries

* oxyenated


* Carry blood away from heart
* Carries blood at high pressure
* Carries oxygen - rich blood from the heart to the body’s cells
* Has thick elastic and muscular wall

**Capillaries**

* Carries blood TO AND FROM the body’s cells
* Connects an artery to a vein
* Has a very thin wall made up of a single layer of cells
* Has a thin wall  so that substances can be exchanged between the blood and body cells

Veins

* Carry blood back to heart
* Carries blood at low pressure
* Carries oxygen - poor blood from the body’s cells to the heart
* Has a thin wall and contains valves

lumen

hole that blood flows through - like the cardboard of a toilet - roll

how to remember which way arteries and veins go

__A__rteries go __away__ from the heart and so start with __A__ 

Veins move blood into the heart and have an in

**What is a double circulatory system?**

* Two separate pumps


* Left pump = deals with oxygenated blood from the lungs to the body
* Right pump = deals with deoxygenated blood from the body, taking it back to the heart

Pulmonary artery

carries blood to lungs

vena cava

blood into heart from body

right atrium

has thin walls

low pressure

tricuspid valve

stops backflow to atrium

right ventricle

thick wall

pumps blood to lungs

high pressure

aorta

carries blood around the whole body

pulmonary vein

carries blood into heart from veins

left atrium

has thin walls

low pressure

bicuspid valve

stops backflow to atrium

left ventricle

VERY thick walls

pumps blood to the body except lungs

high pressure

ventilation

ventilation moves air in and out of the lungs and maintains a steep concentration gradient

the passage of air in and out of the lungs

1. nose
2. trachea
3. bronchi
4. bronchioles
5. alveoli
6. bronchioles
7. bronchi
8. trachea
9. nose

inhilation

1. intercostal muscles contract
2. ribs move upwards and outwards
3. diaphragm flattens
4. volume of chest increase
5. pressure inside the chest decreases
6. air is drawn into the lungs

exhilation

1. intercostal muscles relax
2. ribs move downwards and in
3. diaphragm becomes a more curved shape
4. volume of chest decreases
5. pressure inside the chest increases
6. air is forced out of the lungs

cardiovascular disease

a general term which refers to conditions affecting the heart and/or blood vessels

risk factors for CVD

* unhealthy diet
* no physical activity
* smoking
* harmful use of alcohol
* obesity
* second hand exposure to smoking
* high blood pressure
* high cholesterol
* gender (men have more bad cholesterol than women)

coronary heart disease

a condition where the blood vessels supplying the heart (coronary artery) are narrowed or blocked

stents

a mesh that opens up the artery back to the right shape. it is inserted in the leg and is inflated when in the correct position

stents - benefits

surgery is quick

lasts a long time

stents risks

surgery so has the risk of infection

could get blood clots near the stent

abiotic factor

non-living elements of an ecosystem

EG =

* climate
* temperature
* water
* soil type

biotic factor

living elements of an ecosystem

EG =

* plants
* animals

abiotic factors and how they are measured

light intensity - light meter

temperature - thermometer

moisture levels - probe

soil Ph - probe

wind and speed direction - anemometer

CO2 levels for plants - probe

O2 levels for aquatic animals - probe

examples of biotic factors

plants, animals, fungi or protists

availability of food

new predators arriving

new pathogens

one species outcompeting another so the numbers are no longer sufficient to breed

random sampling

1. draw a grid in your area and use a random number generator to select th coordinates
2. use quadrats to do your experiment

stomata

The stomata allow carbon dioxide into the air spaces in the leaf and allow water and oxygen to leave.

\

1. Sensitive to light

* Close at night. No photosynthesis. No need for CO2
* Open during the day. Photosynthesis takes place. Need O2

\

2. Conserve water vapour

* Leaf has lots of water Guard cells are turgid. Stomata open
* Can afford to lose water
* Leaf has little water. Guard cells are flaccid. Stomata closed
* Can’t afford to lose water

waxy cuticle

Waterproof layer to prevent water loss

Transparent to let light in

Protect the leaf without blocking the sunlight

palisade cells

Lots of chloroplasts for photosynthesis

Ordered, tightly packed to maximise this

air spaces

Allow the movement of gases (CO2 + O2)

Increase surface area

cells not tightly packed

Have a large surface area available for gas exchange

guard cells

Open and close the stomata depending on the water content of the leaf (control water loss)

transpiration

Plants continually lose water to the air

more about transpiration

* Transpiration happens more quickly in hot, dry and windy conditions


* Most plants have a waxy layer called the waxy cuticle on their leaves which prevent water loss


* Water lost through transpiration is normally lost through the stomata


* The guard cells control the size of the stomata, so can regulate the amount of water lost by transpiration


* If plants are losing water faster than they are gaining it, the stomata close


* If this didn’t happen, the plants would wilt and die

upper epidermis

Thin and transparent

Allows more light to reach the palisade cells