GCSE Biology

What are the differences between plant and animal cells?

Plant

> has a cell wall

> only one vacuole

> chloroplasts

Animal

> no cell wall

> multiple vacuoles

> no chloroplasts

List all of the organelles which define an animal cell.

> nucleus

> cell membrane

> cytoplasm

> vacuoles

> mitochondria

What is the function of the nucleus?

contains genetic information contained in chromosomes which are assembled into DNA

Which cell organelle is responsible for protein synthesis?

ribosomes

Which cell organelle contains chlorophyll and is the site of photosynthesis?

chloroplast

Where is the site of aerobic respiration in a cell?

mitochondria

What is the function of vacuoles?

storage > contain a solution

What is a cell wall made of?

cellulose

Describe the function of the cytoplasm.

clear jelly which contains dissolved substances > site of many metabolic reactions

How many nanometres are in a metre?

1 billion or 1x10^9

What are the differences between a light and electron microscope?

> electron microscopes have a higher magnification and resolution

> in light microscopes, the source of the image is light waves whereas in electron microscopes the source of the image is electron beams

> electron microscopes are more expensive

> the specimen has to be dead to view it under an electron microscope but a light microscope can view either live or dead specimens

> in a light microscope the image is moving and in colour but in an electron microscope the image is still and in black and white

> light microscope preparation is chemicals but electron microscope preparation is more complex and the specimen has to be coated in materials and dehydrated

What are the differences between the scanning (SEM) and transmission electron microscopes (TEM)?

> SEM is used to scan external features

> TEM is used to view internal features

What is the difference between magnification and resolution?

magnification tells us how much bigger the image will appear, resolution is how clear the image is

What are the 7 characteristics of life?

MRSGREN

Movement

Respiration

Sensitivity

Growth

Reproduction

Excretion

Nutrition

What is the equation for magnification?

magnification = image size / actual size

What features of a sperm cell make them suitable for sexual reproduction?

> flagellum which helps them move towards the egg

> haploids (one set of chromosomes)

> mitochondria to give them energy from respiration to move

What are the differences between prokaryotic and eukaryotic cells?

prokaryotic cells do not have DNA contained inside a nucleus or organelles

Why are viruses not considered living?

they cannot reproduce by themselves > which is one of the MRSGREN requirements

How do bacteria divide?

binary fission

What are the 3 phases of the cell cycle?

1. Interphase

2. Mitosis

3. Cytokinesis

What are the 3 stages of interphase?

1. G1 > the cell carries out normal activities e.g respiration

2. S > DNA replicates to form two copies of each chromosome

3. G2 > further growth occurs; organelles such as mitochondria replicate and the DNA is checked for errors and any repairs are made

What happens during mitosis and cytokinesis?

Mitosis > the stage where the chromosomes separate and the nucleus divides into 2 within the cell

Cytokinesis > the stage where cells physically divide into 2

What are stem cells?

undifferentiated cells with the potential to divide and produce new specialised cells such as nerve cells or muscle cells

Where do stem cells come from in humans?

embryos, blood in the umbilical cord, bone marrow

Why are stem cell transplants required?

> for spinal injuries

> for loss of eyesight

> degenerate diseases such as Alzheimer's or Dementia

> treatments such as chemotherapy

> damaged cornea treatment

> skin grafts

How are stem cells used to treat a damaged cornea?

> stem cells removed from patient's good eye and placed on a sheet of amniotic membrane

> cells are immersed in a solution of patient's blood, insulin and hydrocortisone

> cells grow on filling surface of membrane

What are the potential future uses of stem cells?

> therapeutic cloning

> replacing tissues

> other research

Explain why a bone marrow transplant is needed for Leukaemia.

> bone marrow is where blood cells are produced

> chemotherapy destroys these cells because they caused Leukaemia which is when too many white blood cells are made

> this bone marrow is replaced by a matching donor

What are the advantages of a stem cell transplant?

> can cure conditions that were previously untreatable such as paralysis

> long term treatment of conditions

> make other treatments such as chemotherapy successful

What are the disadvantages of stem cell transplants?

> stem cells are difficult to locate

> stem cells can be rejected, so must be a close tissue match

> procedures can be risky and few are successful yet

> stem cells could give rise to cancer as they are very similar

> stem cells can be infected with viruses

Evaluate the use of embryonic stem cells. (4)

For

> saves a life

> can also cure/prevent illness in the future

Against

> some people believe that life begins at conception which means the embryo is alive so their use is 'killing' an embryo

> could also transfer viruses

What is diffusion?

the movement of molecules from a region of higher concentration to a region of lower concentration

Fill the gap > Molecules can be described as moving _______ the concentration gradient.

down

Why does diffusion not occur in solids?

particles in solids cannot move freely they only vibrate

Why do gases diffuse faster than liquids?

gas particles have more kinetic energy and can move more freely

What factors affect rate of diffusion?

> temperature

> surface area

> concentration gradient

> distance the particles have to diffuse across

Why does temperature affect rate of diffusion?

the more heat energy the particles are given the greater the kinetic energy

Why does concentration gradient affect the rate of diffusion?

molecules will appear to move in a direction where they are less concentrated; the bigger the difference the greater the effect

Why does surface area affect the rate of diffusion?

more places for the molecule to pass through so more surface area = faster rate of diffusion

Why does the distance the molecule has to diffuse across affect diffusion?

molecules move quite slowly due to their kinetic energy so the further they have to go the slower the process will be

What is the surface area to volume ratio of a cube with sides 3cm?

surface area = 3^2 x 6= 54

volume = 3 x 3 x 3 = 27

surface area = 57cm^2

volume = 27cm^3

SA:V ratio = 2:1

True or false: a higher surface area to volume ratio increases rate of diffusion

True

Name 3 natural examples of diffusion.

> villus in the small intestine

> alveoli in lungs

> placenta

> leaves

> fish gills

What is osmosis?

the movement of water molecules from an area of high concentration to an area of low concentration across a partially permeable membrane

How do plants absorb water?

through the root hair cells

What is turgor pressure?

the pressure of water pushing the cell surface membrane against the inelastic cell wall

Describe what happens within a cell as water moves into plant cells.

> as water moves into plant cells the cytoplasm and vacuole swell

> the cytoplasm presses out against the cell wall but the cell wall resists and presses back (the cell is turgid)

> the cell wall stops the plant cell from bursting

What do plants without wood rely on to support their leaves and stems?

the turgidity of their cells

What happens when you put a plant cell in a high solute concentration?

> plasmolysis (where a cell loses water)

> cytoplasm of the plant cell shrinks

> cell membrane pulls away from the cell wall

Why does plasmolysis normally kill the plant cell?

the cell membrane becomes damaged as it is torn away from the cell wall

What does flaccid mean in plant cells?

where the cell loses water and becomes floppy > when this happens the plant wilts

What would happen if you put an animal cell in pure water?

> water would move into the cell until the cell membrane could not stretch any more

> the cell would burst (because there is no cell wall to stop the cell bursting)

What would happen if you put an animal cell in a more concentrated solution than its cytoplasm?

cell would lose water and shrivel up (erenation)

What is active transport?

the movement of molecules or ions from a region of low concentration to a region of high concentration

Which of the following 3 processes require energy?

active transport, osmosis, diffusion

active transport

How do cells get the energy for active transport?

respiration

What is the function of the villi in the small intestine and how are they adapted to it?

> to allow essential nutrients to absorb into the blood stream

> large surface area and rich blood supply

Explain 3 adaptations of alveoli in the lungs which allow for efficient gaseous exchange.

> large surface area which increases the rate of diffusion

> cell wall is one cell thick which decreases the distance of diffusion therefore increasing the rate

> lined with capillaries which makes a rich blood supply and therefore more oxygen

Describe why diffusion is important to animals and plants.

Animals

> villi in the small intestine help get essential nutrients into our blood stream

> alveoli in the lungs allow for gaseous exchange which we need to breathe

> in the placenta diffusion is used to allow essential nutrients for growth to the embryo

> fish gills help the fish to breathe underwater and survive

Plants

> osmosis in the root hair cells helps the plant absorb water

> active transport through the roots help the plant to absorb vital nutrients

What is the formula of glucose?

C6H12O6

What is the formula for aerobic respiration?

glucose + oxygen > carbon dioxide + water

C6H12O6 + 6O2 > 6CO2 + 6H2O

Which of the following carbohydrates are soluble in water? > glucose, maltose, starch, glycogen, cellulose

glucose, maltose

What is a monosaccharide?

simple sugar

What is a disaccharide?

two monosaccharides (simple sugars) joined together

What is a polysaccharide?

a complex carbohydrates that is made up of more than two monosaccharides

How do plants store carbohydrates?

as starch or sucrose

How do animals store glucose?

as glycogen

What type of carbohydrate is cellulose?

polysaccharide

What type of carbohydrate is glycogen?

polysaccharide

What are carbohydrates made up of?

carbon, hydrogen, oxygen

What are lipids made up of?

carbon, hydrogen, oxygen

What 4 smaller molecules are fat molecules made of?

3 fatty acids and glycerol joined together

What are the 3 functions of fats?

energy storage, insulation, protection of vital organs

True or false - a gram of carbohydrate releases twice as much energy as a gram of fat

False - a gram of fat gives twice as much as a gram of carbohydrate

What do cells use first when they need energy - carbohydrates or fats?

carbohydrates - most cells only use fats when all the available carbohydrates have been used

What makes fats useful for storing energy?

they contain extra energy

Why do many plants store oils in their seeds?

they provide a good source of energy for germination

What is the adipose tissue?

the cells underneath the skin which become filled with large droplets or fat or oil to store until energy is needed

Why do some animals have thick layers of adipose tissue 'blubber'?

their environment may be very cold and fat is effective at keeping an animal warm

What are proteins made up of?

carbon, hydrogen, oxygen, nitrogen and sometimes sulfuric

Which long chain of molecules join together to form a protein?

amino acids

How many different kinds of amino acids are there?

20

Describe 3 functions of proteins.

1. Making new cells

many proteins in food are used to make new cells which are needed for growth and repairing damaged parts of the body; cell membranes and cytoplasm in particular contain a lot of protein

2. Making antibodies

proteins are also needed for making antibodies which help destroy bacteria and viruses in the body

3. Making enzymes

proteins make up enzymes which catalyse reactions

Name a protein which is soluble in water, and a protein which is insoluble in water.

soluble in water - haemoglobin

insoluble in water - keratin

What does metabolism mean?

sum of all reactions that take place in a cell or the body

Describe two differences between anabolic and catabolic reactions.

Anabolic reactions

> build molecules up

> require energy

Catabolic reactions

> break molecules down

> release energy

Where does the energy for anabolic reactions come from?

respiration

What are the two types of metabolic reactions?

anabolic and catabolic

True or false - metabolic reactions often take place on their own. Give a reason for your answer.

False - they are controlled by enzymes

Fill the gaps -

_________ is the sum of all the reactions that happen in a living organism. These reactions include ___________ of food, aerobic and anaerobic _____________ and _________ synthesis. Most of these reactions are controlled by _________.

Metabolism, digestion, respiration, protein, enzymes

What is required by the body to provide energy?

glucose

Why can starch not be absorbed into the blood stream?

because the molecules are too big

What enzyme breaks starch down into maltose?

amylase

Explain why the small intestine has to produce maltase for effective digestion.

maltose molecules are too big to be effectively absorbed into the blood stream - maltase breaks down maltose into glucose which can be easily absorbed into the blood stream to provide energy

Rank the following in increasing size:

Tissue, Organ, Cell, Organ system, Organism, Muscle

cell, tissue, muscle, organ, organ system, organism

Which digestive organ produces bile?

the liver

Where is bile stored?

gallbladder

What is the function of the small intestine in digestion?

breaks down food and then absorbs it into the blood stream

How does the stomach aid digestion?

> breaks down food using acids and enzymes until it is a smooth paste

Where is amylase produced?

salivary glands, pancreas, small intestine