What does a nucleus do in a cell?
It controls the cell's activities and contains the genetic material for cellular reproduction.
What is the function of cytoplasm?
It's where most of the chemical reactions take place in a cell
What does the cell membrane do?
It controls what comes in and goes out of a cell.
What do mitochondria do?
Sub-cellular structures where aerobic respiration takes place
What do ribosomes do?
Ribosomes synthesise proteins
What is a cell wall made of?
Cell walls are plants' cells - they are made of cellulose to strengthen the cell.
What is the function of chloroplasts?
Chloroplasts - found in plant cells - make glucose (food) for the plant through photosynthesis.
Name the two main kinds of cell
Prokaryotic cells (bacterial) Eukaryotic cells (plant, animal, fungal)
What are some of the main differences between prokaryotic and eukaryotic cells?
Prokaryotic cells are: Smaller Genetic material is not in a nucleus Genetic material is in a single DNA loop and there may be one or more small rings of DNA called PLASMIDS They do not contain mitochondria or chloroplasts
What kind of shapes can bacteria have?
Spherical Spiral Rod Curved rod
What are flagella?
Tails on cells to move them around (e.g. sperm cells or bacteria)
Explain the nature of plasmids
They are loops of DNA found in bacteria. They can be transferred from one cell to another, allowing bacteria to pass genes around. They are also useful for scientists to insert genes into different bacteria.
Define 'resolution' in the context of microscopes
The ability to discern more than one object - e.g., cells can't be seen with the naked eye, but under a microscope, they begin to be 'resolved'.
What do electron microscopes do?
They pass electrons through a specimen being 'viewed' giving a much clearer image.
What is the formula for calculating magnification?
Magnification = size of image/size of real object
What sub cellular structure controls activities in the cell?
Where are proteins made in a cell?
On the ribosomes
Note three structures found in plant cells that are not found in animal cells
Cell wall Chloroplasts Permanent vacuole
What is the function of cell sap?
To support the cell
Where is DNA found in bacteria?
Arrange in order of size (largest to smallest) bacterium, liver cell, nucleus, ribosome
Liver cell Nucleus Bacterium Ribosome
What is a micrometre?
What is an ecosystem
All the organisms living in a habitat and all the non-living parts of that habitat
So - snails and rocks!
polar bears and ice!
Define biological competition
Living species trying to get enough resources to survive
What is interdependence?
Different species relying on each other for food, shelter, pollnation, seed dispersal...
If one species is removed, it can affect the whole community.
"a"- as a prefix means "without" in Greek
bios in Greek means life.
Define four abiotic factors that affect living communities
soil pH and mineral content
wind intensity and direction
C02 levels for plants
O2 levels for animals
Define three biotic factors that can affect a habitat
Changes in food availability
Change in number of predators
Introduction of pathogens/diseases
One species outcompeting another
How does a biologist define a population
A group of organisms of one species living in a habitat
What are "adaptations"?
Features that organism have that enable them to survive in their normal conditions
What are extremophiles?
Organisms that live in extreme conditions
- salt concentrations
Eg. bacteria living on glaciers or near deep sea vents
What is a transect line used for?
A line placed across a field on which a quadrat is placed to count species etc
What is a stable community to a biologist?
All species and environment factors are in balance so relevant population numbers are stable
Describe a chromosome
The nucleus of a cell contains chromosomes made of DNA
Each chromosome carries hundreds of genes.
In body cells, chromosomes are found in pairs with one chromosome coming from each parent.
Humans have 23 pairs,
Dogs have 30 pairs.
Genes contain the code to make different proteins and so control the development of different characteristics.
Describe the cell cycle
DNA is copied and new chromosomes are made
Cell undergoes mitosis
Each cell grows and makes new sub-cellular structures
DNA is copied...
A cell grows and increases the number of sub-cellular structures (ribosomes, mitochondria)
The DNA replicates to form two copies of each chromosome
one set of chromosomes is pulled to each end of the cell
the nucleus divides
the cytoplasm and cell memberanes split to form identical cells
Why is mitosis important?
It makes new cells for the organism
- asexual reproduction
What are stem cells?
- they have not yet become 'specialised'
They are found in embryos, umbilical cords (embryonic stem cells),
and some organs and tissues (adult stem cells)
What are stem cells used for?
- treating conditions where cells are damaged (paralysis, diabetes)
-replace damaged cells
What is therapeutic cloning?
Use of patient's own stem cells for replacing damaged cells/tissues
- no risk of rejection
What are meristems and why may they be useful?
Special areas in plants that house their stem cells
- easy for cloning the plant
- help clone nearly extinct species
GM crops bred to resist disease
Define (cellular) diffusion
Why does it happen?
The net movement of particules across cell membranes from an area of high concentration to an area of low concentration
Because particles move randomly an spread out
E.g., O2 and CO2
Urea from cells into blood
DIgested food molecules into blood
What factors affect (cellular) diffusion?
(think particle theory - more energy, more movement)
Surface area of the membrane
*Unicellular organisms have large surface area to volume ratio allowing molecules to easily diffuse
*Multicellular organisms have low surface area to volume ratio, so they have developed specialised cells to help with diffusion: e.g, small intestines, lungs - large surface area, moist.
What maintains the concentration gradient in animals?
Rich blood supply
What speeds up gaseous exchange in plants
(i.e., keeps the concentration gradient diffusion working?)
The diffusion of water from a dilute solutoin to a concentrated solution through a semipermeable membrane
Explain (cellular) active transportation
When substances are moved against a concentration gradient
- this requires energy
E.g., mineral ions brought in from the soil into root hair cells
and sugar molecules from the lower concentration in the gut into the blood stream
**active transport stops in the absence of oxygen or in the presence of metabolic poisons such as cynanide, arsenic, belladonna, and strychnine
What happens when cells differentiate?
- may change shape
- have different sub-cellular structures to assist in its specific functions
Name some specialist cells
Red blood cells
Root hair cells
Draw and name the main parts of a motor neuron
Draw an name the main parts of a sperm cell
Draw and label the main parts of a muscle cell
Describe xylem cells
Arranged end to end, end walls break down to form hollow tubes
Cell walls are strengthened by lignin
Describe phloem cells
End walls allow sugars through but support the tubes
Arranged end to end into tubes
Compare xylem and phloem cells graphically
Draw and label a root hair cell
What are enzymes?
Biological catalysts that speed up reactions in living organisms.
They are large proteins and have an active site inside a space
Enzymes do specific reactions
And work best at optimum temperatures and pH levels
What is tissue?
Group of cells with a similar structure and function
What is an organ?
Group of diiferent tissues working together to perform a specific job
E.g. stomach contains muscle tissue, glandular tissues (secrete juices), and epithelial (covering) tissue
What is an organ system?
Several organs working together to perform a broader function
E.g., Digestive system contains - mouth, oesophagus, stomach, smaller intestine, larger intestine, rectum and anus - and accessories, liver, gall bladder and pancreas.
Define an organism
A collection of organ systems that make up an living entity
What is denaturing?
When high temperatures or extreme acidic/alkline levels disrupt enzymes such that they denature (fall apart)
What is the "lock and key" theory of enzymes?
A model that explains how enzymes seem to work
- the chemical that reacts is the substrate (the key)
- it fits into the enzymes active site (the lock)
Emil Fischer (1894!!)
Name four digestive enzymes and their functions
Protease - breaks down proteins/amino acide: produced in stomach, pancreas and small intestine
Lipase - breaks down fats/oils into fatty acids and glcyerol: produced in pancreas and small intestine
Carbohydrase - breaks down carbohydrates
Amylase - breaks down starches into sugar (maltose): produced in salivary glands and pancrease
What is bile and where is it made?
Bile is an alkaline liquid to neutralise stomach acids,
Bile also emulsifies fats to increase their surface area
Both of which enables enzymes to work quicker on them
It is made in the liver and stored in the gall bladder
What is the function of the epidermis on a leaf?
Epidermis - 'top layer of skin' - covers the outer surfaces of the plant for protection
What happens in the pallisade mesophyll in a leaf?
It's the main site for photosynthesis
What is the function of spongy mesophyll in a leaf?
It has air spaces to all gases to diffuse through the leaf
What do xylem vessels do in a leaf?
They transport minerals and water from the roots and also help support the plant.
"Reach for the xy..."
xy rhymes with sky
What do phloem vessels do in a plant?
They transport dissolved sugars through the plant (from leaves downward)
This is called translocation
phloe = flow down
What is meristem tissue in a plant?
Meristem tissue is found at the tips of the roots and shoots where new cells are produced for root growth
Is a leaf a plant organ?
What process describes how water enters plant root cells?
Through which cells does water evaporate and diffuse out of a plant
Stomata (small pores)
What term is used to describe the loss of water from leaves?
What factors affect transpiration?
- Temperature (higher = more transpiration)
- Wind (faster air flow = higher rate of evaporation)
- Light (more light, stomata open more)
- Humidity (increase = less transpiration as concentration gradient for diffusion of water into the air is lower)
What is the function of guard cells in a plant?
They open and close stomata
why are stomata closed at night?
They close because carbon dioxide is not needed for photosynthesis, so closing the stigmata reduces water loss.
Explain how guard cells work
- When water is plentiful the guard cells take up water and become turgid (swollen).
- This causes the stigmata to open.
- So gases for photosynthesis are free to move in and out of the stigmata along with water from transpiration.
- BUT when water is scarce losing water makes this tomato change shape and close.
- This stops the plants from losing water through transpiration.
What is translocation?
The movement of food (dissolved sugars) through the phloem tissue in a plant.
What is a pathogen?
Microorganisms that cause infectious (communicable) diseases
How are pathogens spread?
Vectors (other organisms that carry the pathogen which don't get the disease themselves)
How can the spread of infectious diseases be hindered?
- Increasing immunity through diet/gut flora (post GCSE answer!)
- Destroying vectors
- Isolating infected persons
- Vaccines (potentially - side effects/increased viral resistance)
Name some viral diseases
Human immunodeficiency HIV -> can cause AIDS
Human papilloma virus HPV
Tobacco mosaic virus (TMV)
How do bacterial pathogens affect healthy cells?
They can damage cells directly
or they produce toxins that damage tissues
Explain how salmonella is introduced and affects the body
1) It is a bacterial infection
2) It is ingested from food (chickens, eggs) that is not cooked properly or prepared unhygienically
3) The bacteria secrete toxins that can cause fever, diarrhoea
* potential defence: vaccinating chickens.
How is gonorrhea spread and what are its symptoms?
Bacteria transmitted sexually
Thick yellow/green discharge from the vaine/penis with pain urinating
Treated with penicillin but evidence of resistance
What are protists?
What widespread disease (which calls more people than any other on the planet) is due to protists?
Single celled eukaryotic organisms
The protist uses a specific mosquito which passes it into human blood upon sucking blood.
Malaria causes fever and can be fatal.
Prevention is with nets around the bed, although it seems that people of African genes have a greater immunity than Europeans say.
What kind of disease is Rose Black Spot?
Fungal spores are carried on the wind to affect plants.
The infected leaves develop black spots, turn yellow and drop off early.
A decrease in foliage causes the plant to not grow as fast as photosythesis is reduced.
Treated with fungicides and burning affected material.
What are pathogens?
Microorganisms that enter the body and cause disease
What are communicable diseases?
Diseases that can easily spread
What are bacteria?
Very small cells- reproduce rapidly
Are viruses cells?
No- they’re 1/100th the size of a bacterium
What do viruses do?
Live inside cells, use cells machinery to replicate then burst releasing virus
What do viruses do to make you feel ill?
What are Protists?
Single celled eukaryotes
What are parasites transferred by?
What is hyphae?
A thread like structure of fungi
What do hyphae do?
Grow and penetrate human skin and the surface of plants causing disease
What are the three ways pathogens can be spread?
Water, Air and Direct Contact
Name 3 viral diseases
Measles, HIV and tobacco mosaic virus
What are the symptoms of measles?
Red skin rash and signs of a fever
How is measles spread?
Droplets- sneezes or cough
How is HIV spread?
Sexual contact or bodily fluids (blood)
What are the symptoms of HIV?
Flu like symptoms
What time of cells does HIV attack?
What does TMV affect?
TMV symptoms on a plant?
Mosaic pattern of leaves and discoloured
Why can’t TMV infected plant carry out photosynthesis?
Because of the discolouration
Name a fungal disease?
Rose black spot
What does rose black spot do to plants?
Cause black spots on rose plants and leaves drop off
How does rose black spot spread?
Through water or wind
Name a diseased cause by a protist?
What vector carries malaria?
How can people be protected from malaria?
Insecticides and mosquito nets
Name 2 bacterial diseases
Salmonella and Gonorrhea
What is salmonella?
Type of bacteria that causes food poisoning
What are the symptoms of salmonella?
Fever ,stomach cramps, vomiting and diarrhoea
How can you get salmonella?
Eating food that has been contaminated with salmonella bacteria
How is salmonella prevented?
Poultry are given vaccinations against salmonella
What is Gonorrhoea?
Sexually transmitted disease
Symptoms of Gonorrhoea?
Pain when urinating, thick yellow discharge
How is Gonorrhoea prevented?
Antibiotics and barrier methods when having sex (comdoms)
4 ways spread of disease can be reduced
Being hygienic, destroying vectors, isolating infected individuals , vaccination
The largest organ that helps acts as a barrier is?
What in your nose trap particles that could contain pathogens?
Hair and mucus
What does the stomach produce to kill pathogens?
What kicks in if pathogens make it into your body?
What is the most important part of your immune system?
White blood cells
Name 3 ways white blood cells attack invading microbes?
Consuming them(phagocytosis), Producing antibodies, producing antitoxins
What are in vaccinations?
Small amounts of dead or inactive pathogens
What does the MMR vaccine contain?
Measles, mumps and rubella
Pros of a vaccine
Control lots of diseases that were common, prevents epidemics
Cons of a vaccine
Don’t always work, can have a bad reaction
What drug relieves pain?
Pain killers (aspirin, paracetamol)
What kills bacteria?
2 ways bacteria could be resistant to antibiotics
Bacteria mutate or if you have an infection
What are the resistant bacteria called?
What can the resistant strain do to the body?
Cause a serious infection that can’t be treated by antibiotics
How can doctors slow down the rate of resistant strains?
Not to over prescribe antibiotics
Name the drug that comes from willow
Name the drug that comes from foxgloves
Who discovered penicillin
Three stages of drug testing
Human cells and tissues, 2 live animals, human volunteers in a clinical trial
What produces antibodies?
What are monoclonal antibodies produced from?
Lots of clones of white blood cells
What do tumor cells do?
Divide lots so they can be grown easily
B-lymphocytes and tumor cells bind to make what?
What do hybridoma produce?
What are monoclonal antibodies useful?
They target a specific cell
Name something monoclonal antibodies are used in?
Pregnancy tests , treat diseases (cancer), research (measure hormone levels)
Side effects of monoclonal antibodies?
Fever, vomiting and low blood pressure
3 diseases plants get?
Bacterial, viral and fungal
Signs a plant has a disease
Stunted growth, spots on leaves, patches of decay, abnormal growth, malformed stems, discolouration
How can you identify a plants disease?
Gardening manual or internet, taking to a laboratory, testing kits
What are plants physical defences
Waxy Cuticle, cell walls (contain cellulose), dead cells around stems
What are plants chemical defences?
Antibacterial chemicals (mint plant and witch hazel), produce poisons (deadly nightshade and foxglove)
What are plants mechanical defences?
Thorns and hairs, leaves that droop or curl, plants mimic other organisms (ice plant family- look like stones)
which side of the heart does de-oxygenated blood enter?
the right side
what if the heart mainly made of?
how does the heart keep the blood flowing in the right direction?
valves to stop back flow
through which artery does oxygenated blood leave?
how do muscles in the heart keep your resting heart rate controlled?
producing electrical impulses which spread through the heart causing them to contract
what are two features of an artery?
1. walls are strong and elastic so it can cope with high pressure 2. thick walls compared to the lumen
what are two features of a capillary?
1.permiable walls so substances can diffuse in and out 2. supply cells with food and oxygen and take away waste like CO2
what are three features of a vein?
1. thin walls because blood at lower pressure 2. large lumento help blood flow 3. valves to keep blood flowing in right direction
what is the main function of red blood cells?
to carry oxygen around the body
what is the main function of white blood cells?
to defend against infection
what is the main funtion of platelets?
to help blood clot
what is conorary heart disease?
the conorary arterie gets blocked by layers of fatty material building up so less oxygen is supplied to the heart
what are stents used for?
tubes inserted inside arteries to keep them open and allow blood to flow
what are statins used for?
drugs that reduce amount of 'bad' cholesterol in your bloodstream
what procedures can be done if there is a heart faliure?
transplants of the whole heart or valves
what can be used when a lot of blood is lost?
artificial blood like a salt solution or a blood transfusion
what are non communicable diseases?
diseases that cannot spread between people or animals and people
Name three types of non comunicable diseases?
asthma, cancer and coronary heart disease
what are 3 factors that can effect your health?
diet, stress and life style choices (including alcohol, drugs, promiscous sex, poverty)
what are 4 risk factors that directly cause a disease?
1. smoking 2.obesity 3.alcohol 4.exposure to certain radiation
what causes cancer?
uncontrolled cell growth and division which forms a tumour
what are two types of cancer?
1.benign- stays in one place and isnt cancerous 2. malignant-tumour grows and spreads to neighbouring tissues, cancerous