Biology Paper 1 : ALL TOPICS 1 - 4 (Cell bio,organ.,infec. dis.,bioene.)

Describe eukaryotic cells (plant and animal cells)

Cells that contain a nucleus that encloses DNA(genetic information) and other organelles

What are eukaryotes?

Organisms that are made up of eukaryotic cells e.g. plants or animals.

What is a prokaryote?

A single-celled organism that dosnf’t have a nucleus e.g. bacteria + Significantly smaller than a eukaryotic cell

What do Prokaryotic cells contain?

Single Loop of DNA

Plasmids=Small rings of DNA

Cytoplasm

What is a Bacterial Cell(prokaryotic)?

-A type of prokaryotic cell

-Don’t have a nucleus & their genetic material is a single Loop of DNA in the cytoplasm

MAY ALSO HAVE:

Small rings of DNA = Plasmids

EG of bacteria = bacterium

Size of Cells

Centimetres (cm):

1/100 of 1 Metre (m)/100cm = 1 cm

Millimetres (mm):

1 cm / 10mm = 1mm

Micrometers (μm):

1 M /1,000,000 = 1 μm

Commonly used to measure: size of cells & their components

Nanometers (nm):

1 M / 1,000,000,000 = 1 nm

Used to measure : size of smaller cellular components (e.g protein)

What’s the order of magnitude?

A way of comparing the sizes of objects by how many powers of 10 they are bigger / smaller by A

EG: if something is 10 times bigger = 1 order of magnitude larger

1 order of magnitude = 10*

2 orders of magnitude = 100*

3 orders of magnitude’s = 1000*

How to carry out the order of magnitude

Order of magnitude = largest size divided by smaller size → count the powers of 10

What does an animal cell consist of?

• Nucleus

• Mitochondria

• Cell membrane

• Cytoplasm

• Ribosomes

What does a plant cell consist of?

• Nucleus

• Mitochondria

• Cell membrane

• Cytoplasm

• Ribosomes

• Rigid cell wall

• Chloroplasts

• Permanent vacuole

What does a bacterial cell consist of?

• cell membrane

• cell wall

• cytoplasm

• Loop / circular strand of DNA

• plasmids

• Ribosomes

• (Flagella-help swim )only in some

Function of nucleus

Contains genetic material & controls the activities of the cell

Function of mitochondria

-site of aerobic respiration

-releases energy for the cells.

Function of cytoplasm

Gel-like substance where most of the chemical reaction happen.

It contains enzymes that control these chemical reactions.

Function of cell membrane

Holds the cell together and controls what enters and leaves the cells

Function of ribosomes

Site of protein synthesis

- These are where proteins are made in cells

Describe the cell wall in plants and it’s function

• Made of cellulose

• Gives the plant cell it’s shape and strengthens it.

Describe the permanent vacuole and it’s function

• Contains cell sap ( a weak solution of sugars and salts) which helps keep cell turgid

Describe the chloroplasts and their function

• Contain chlorophyll which is the site of photosynthesis

• Also contains enzymes needed for photosynthesis

• Also provides colour green

Animal cell specialisation

• Most animals cells are specialised.

• This means that they have adaptations which help them to carry out their particular function.

• When cells become specialised, scientists call that differentiation.

How are sperm cells specialised to carry out their function?

Function: To join with an ovum (egg cell) in a process called fertilisation. During fertilisation the genetic information of the ovum and the sperm cell combine.

Adaptations:

1. Contain only half the genetic information of a normal adult cell.

2. Sperm cells have a long tail = allows them to swim to the ovum.

3. Streamlined head = swim to the ovum.

4. Sperm cells are packed full of mitochondria = transfer the energy needed for the tail to move

5. The outer layer of the sperm head (acrosome) stores digestive enzymes= can break down the outer layer of the ovum.

How are nerve cells specialised to carry out their function?

Function: To send electrical impulses around the body.

Adaptations:

1. Long axon= carries electrical impulses from one part of the body to another, to cover more distance

2. Axon is covered in myelin=insulates the axon and speeds up the transmission of nerve impulses.

3. Synapses=(The end of the axon)= junctions which allow the impulse to pass from one nerve cell to another.

4. Dendrites=increase the surface area so that other nerve cells can connect more easily.

How are muscle cells specialised to carry out their function?

Function: To contract (get shorter) quickly

Adaptations:

1. Contain protein fibres which can change their length

2. When muscle cell contract these protein fibres SHORTEN=decreasing the length of the cell

3. Have lots of mitochondria = transfer energy needed for contraction.

4. Work together to form =muscle tissue

5. They can store glycogen( a chemical that can be broken down into glucose and used in cellular respiration).

Plant cell specialisation

• Most plant cells are specialised.

• They have special adaptations which help them to carry out their particular function.

• When cells become specialised =that process is called differentiation.

Specialised root hair cell + Function:

Function: Absorbing water and minerals

Adaptations:

1. Have root hairs = increase surface area available so it can absorb water +dissolved minerals

2. Don’t contain chloroplast as underground

3. Have= large permanent vacuole that speeds up the movement of water by osmosis.

4. Have many mitochondria that transfer the energy needed for the active transport.

Xylem Cells Specilaised+ function:

Found in: Pants stem

Form:Long tubes

Function: To carry water and dissolved minerals ions from the roots to the leaves.

Adaptations:

1. The end walls in xylem cells are broken down forming a long tube so water and dissolved minerals can easily flow through.

2. Xylem cells have no nucleus ,cytoplasm or vacuole, no organelles ALLOWs=water & dissolved minerals to flow through more easily.

3. Thick walls which Contains lignin: makes xylem cells very strong & help support plant (but as cell walls are covered in lignin) =causes xylem cells to die

Xylem Specialisation + its function

Functions: To carry dissolved sugars up+down plant & from the leaves to other parts of the plant (consist of 2 diff types of cells)

Adaptations:

1. (Cell 1)Phloem vessel cells =very few sub cellular structures to help the flow of substances.

2. Phloem vessel cells have NO nucleus +only limited cytoplasm

3. (Cell 2)Sieve plates = (broken cell walls=sieve plates)=Allows dissolved sugars to move through cell interior

4. Phloem vessel cell has a companion cell connected by pores=provide energy to transport substances in the phloem.(mitochondria in comp. Cel provides energy to phloem vessel cell)

How to use a Optical Microscope to view a prepared slide

PREPARE THE SLIDE:

1)Place slide onto stage , use the clips to hold the slide in place Using forceps peel of the epidermal layer of an onion

2)Add a drop of water onto a slide using a pipette and place the tissue onto the slide ensuring it lays flat

3)Add 2 drops of iodine solution to stain the cells

4)Gently place the coverslip on top ensuring there’s no air bubbles

USING THE MICROSCOPE:

5)Place the slide onto the stage of the microscope

6) Using the ‘coarse focussing dial’ slowly turn to position objective lens almost touching the microscope slide

7)Look through the eyepiece and slowly turn the ‘coarse focussing dial’ to raise the ‘stage’ until it comes into view and focuses

8)Use ‘fine focusing dial’ to bring cells into a clear focus

9)Switch to a ‘higher magnification’ for more detail

10) work out total magnification =‘Eye piece lens’ * ’objective lens’

11)Adjust ‘fine focussing dial’ to bring cells back to focus

OBSERVING & DRAWING:

12)Use a pencil to make a clear, labelled drawing of some of the cells & include magnification scale

13)Mag. Scale = place a clear ruler over the stage =measure the diameter it in ‘millimetres’ and include the magnification

OPTICAL MICROSCOPE CAN ONLY SHOW LIMITED DETAIL :no ribosomes etc

Calculate the Total Magnification

Total Magnification = Eyepiece Lens Magnification × Objective Lens Magnification

E.G: ‘Eye piece lens’ magnification= 10x

‘Low-power objective lens’ magnification=4x. 10×4 = total mag.=40x

Actual Size of Cell = Image Size ÷ Magnification (use a ruler to measure the image size in mm, convert to micrometers if needed)

Disadvantages of light microscopes

• They have limited magnification

• Limited resolution (image is blurred)

Resolution

• The shortest distance between two points on an object, that can still be distinguished as two separate entities.

• A measure of how detailed the image is.

Advantages of electron microscope

• Greater magnification (than light microscopes)

• Greater resolution (than light microscopes)

Equation for magnification

magnification= size of image/ size of real object

What are chromosomes made out of?

The molecule DNA?

How many of each chromosome do body cells contain?

Two-they’re paired

• except gametes

How many pairs of chromosomes do human body cells contain?

23

Which certain cell has chromosomes which are not paired?

Gametes- They have 23 single chromosomes

What do chromosomes carry?

Genes- which determine many of our features

Cell division by mitosis

1. The DNA replicates to form two copies of each chromosome. The cell also grows and copies it’s internal structure, such as mitochondria and ribosomes.

2. Then (mitosis takes place.) One set of chromosomes is pulled to each end of the cell. The nucleus also divides.

3. The cytoplasm and cell membrane divide to form two identical daughter cells.

What is the cell cycle?

When a cell divides in a series of stages.

Functions of mitosis

• Mitosis is essential for growth and development of multicellular organisms (e.g. plant and animals).

• Mitosis takes place when an organism repairs itself (e.g. when a broken bone heals).

• Mitosis happens during asexual reproduction.

What is a stem cell?

A undifferentiated cell of an organism which has the potential to develop+differentiate to form certain other types of cells.

What is cell differentiation?

The process by where a cell becomes specialised to perform a specific cell

(Undergoes changes in structures/function/gene expression allowing it to develop into a specific type)

What are embryonic stem cells?

Stem cells in early human embryos.

1)Humans start when a sperm cell joins with an ovum in other words an egg cell = fertilisation

2)The fertilised ovum now undergoes mitosis and it forms a ball of cells called an embryo

3)over time these cells continue to undergo mitosis they also change & begin to form specialised cells (e.g nerve/muscle cells) = go through differentiation

4)Overtime these cells form the adult organism They’re capable of turning into any type of body cell.

5) Go back to our early stage embryo can see that these cells have not differentiated any one of these cells is capable of differentiating into any type of body cell scientists call =embryonic stem cells

Where can adult stem cells be found?

Bone marrow

Why is bone marrow different to embryonic stem cells?

Adult stem cells cannot differentiate into any type of cell- the stem cells in the bone marrow: such as cells found in blood: red blood cells, white blood cells and platelets.(to form cells found in out blood )

What is leukaemia?

A cancer of the bone marrow.

How does medicine use bone marrow? (Transplants)

Stem cells transferred from the bone marrow of a healthy person can replace faulty blood cells in the patient who receives them.

1) patients existing bone marrow is destroyed using :RADIATION

2)Patient receives a transplant of bone marrow from donor

3)Stem cels in bone marrow DIVIDE & FORM NEW bone marrow —also DIFFERENTIATE & form BLOOD cells

Problems with bone marrow transplant

• Donor must be compatible with the patient — otherwise white blood cells produced by the donated bone marrow could attack the patient’s body.

• Viruses can be passed from the donor to patient.

• Procedure can be painful

Two ways stem cells can be used in medicine

• Bone marrow transplant

• Therapeutic cloning (embryo )

What is produced in therapeutic cloning?

An embryo with the same genes as the patient.

What’s Therapeutic cloning and the it’s process ?

1)A process where scientists create embryonic stem cells to match a patients own cell

2) An embryo is produced with the same genes as the patient.

3)Stem cells from the embryo can be transplanted into patient without being rejected by the patient’s immune system.

4)Once inside the patient, the stem cells can then differentiate to replace cells which have stopped working correctly.

What can therapeutic cloning be used for?

A whole range of medical conditions such as diabetes or paralysis

• diabetes- check key cards

Disadvantages of therapeutic cloning

Some people have ethical objections to this procedure as embryos are destroyed in process and people view embryos as potential life.

PLANT STEM CELLS - What can meristem tissue in plants do?

Differentiate into any type of plant tissue, at any point in the life of the plant.

(Roots & buds contain meristem tissue)

What can meristem tissue be used for?

Stem cells from meristems in plants can be used to produce clones of plants quickly and economically.

• Rare species can be cloned to protect them from extinction.

• Stem cells can also be used to grow crops of identical plants that have desired features for farmers, e.g. disease resistance

What is diffusion?

Diffusion is the spreading out of particles resulting in a net movement from an area of high concentration to an area of low concentration.

Diffusion of O2 and CO2

Cells need oxygen for respiration, which is carried out by the mitochondria.

Cells are surrounded by a high concentration of oxygen as oxygen is transported into the bloodstream from the lungs.

The oxygen molecules move into the cell by diffusion from an area of high concentration to an area of low concentration.

The oxygen is used to generate energy in respiration and this produces the waste gas carbon dioxide.

That means there’s a higher concentration of carbon dioxide inside the cell than outside so the carbon dioxide moves out of the cell by diffusion.

What is urea?

A waste products produced inside cells.

Diffusion of urea

It diffuses out of the liver cells (high concentration) into the blood plasma (low concentration) and is excreted by the kidneys.

Factors that affect the rate of diffusion and how?

1)CONCENTRATION GRADIENT =The greater then concentration gradient, the higher the rate of diffusion.

2)TEMPERATURE = The higher the temperature, the greater the rate of diffusion, as the particles have more kinetic energy and are moving faster.

3)SURFACE AREA = The larger the surface area (of the cell membrane), the greater the rate of diffusion.

Surface area to volume ratio of amoeba

Amoeba are single-celled organisms. A single-celled organism has a relatively large surface area to volume ratio.

This allows sufficient transport of molecules into and out of the cell to meet the needs of the organism can rely on diffusion

Definition of Surface Area to Volume Ratio (SA:V)

The relationship between the amount of surface a cell has (its membrane) and the amount of space inside the cell (its volume)

The ratio of the total surface area of a cell / object to its volume = measures how much area is available for the exchange of materials (nutrients & waste) relative to the cells size

• If cell gets larger , its volume increases faster than its surface area =means if cell becomes too big there won’t be enough surface area to allow efficient exchange of materials with the environment

Steps to calculate Surface Area to Volume Ratio (SA:V)

Steps to Calculate Surface Area to Volume Ratio (SA:V)

1. Find the Surface Area (SA)

For a cube, use the formula:

Surface Area = 6 × (side length) 2

Each cube has 6 faces, and the area of one face is side x side.

2. Find the Volume (V)

For a cube, use the formula:

Volume = (side length)3

Multiply the length, width, and height (since a cube has equal sides).

3. Calculate the Surface Area to Volume Ratio (SA:V)

SA: V= Surface Area / Volume

EXAMPLE:Let's say we have a cube with a side length of 2 cm:

1. Surface Area:

6x (2x2) =6 x 4 = 24 cm?

2. Volume:

2x2 x 2 = 8 cm'

3. SA:V Ratio:

24 / 8 =3 : 1

This means for every 1 unit of volume, the cube has 3 units of surface area.

As organisms get larger, what happens to the SA:V ratio

It decreases (this is a problem for multi-cellular organisms)

Problem of having a low SA:V ratio on multicellular organisms.

• Their surface area is not large enough for their volume.

• Cells on the surface can get enough oxygen simply by diffusion however, not enough oxygen can diffuse into the centre of the organisms as they’re too far away from the surface.

• Due to this, multicellular organisms have exchange surfaces and a transport system to solve this problem.

How have animals solved the issue of their surface area not being large enough and far ways from the surface ?

1)Animals have special structures for gas exchange with a very high surface area EG: lungs & mammals

2)Animals have a transport system to carry gases around the body

Describe how the gills in fish are adapted for exchanging materials.

Gills are covered in a very large number of fine filaments- where gases pass in and out of the blood. (Deoxygenated blood passes into the filament.Then oxygen from the water diffuses into the blood. Oxygenated blood is then returned to the body).

• Adaptations of filaments for efficient diffusion:

  • Give the gills a massive surface area

  • Thin membrane to provide a short diffusion pathway.

  • The filaments have an efficient blood supply to take the oxygenated blood away. This ensures that the concentration gradient is always high.

What is osmosis?

Osmosis is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.

What’s a partially permeable membrane?

A membrane than only allows some molecules to pass through.

Osmosis of animal cells

• The cytoplasm is a relatively concentrated solution so if an animals cell is placed into water, then osmosis will take place.

• In hypotonic conditions Water will move by osmosis from outside the cell to inside the cell.

• This causes the cell to expand or possibly burst.

• In hypertonic conditions If an animal cell is placed into a very concentrated solution, then water will move out of the cell by osmosis and the cell will shrink.

• In isotonic conditions there is no change

Osmosis of plant cell

• The cytoplasm is a relatively concentrated solution so if an plant cell is placed into water, then osmosis will take place.

• Water will move into the cell by osmosis and the cell will expand.

• Unlike an animal cell, plant cells have a cell wall which prevents the cell from bursting so the cell becomes turgid after water moves into it by osmosis.

• If a plant cell is placed into a concentrated solution, then water moves out of the plant cell by osmosis, causing the cell to shrink/become flaccid.

Effect of osmosis on plant tissue (REQUIRED PRACTICAL)

1. Peel the potato, because the potato skin can affect osmosis.(acts as a semi-permeable barrier)

2. Use a cork borer to produce three cylinders of potato. Using a cork borer makes all of the cylinders the same diameter.

3. Use a scalpel to trim the cylinders to the same length (around 3cm).

4. Measure the length and the initial mass of each cylinder (using a ruler and balance)

5. Now add each cylinder into a test tube. Add 10cm³ of 0.5 molar sugar solution into the first test tube.

6. Add 10cm³ of 0.25 molar sugar solution in the second test tube.

7. Add distilled water into the third test tube. (distilled water contains no dissolved substances which could affect the rate of osmosis)

8. Leave the potatoes overnight and allow osmosis to take place.

9. Next remove the potato cylinders and gently blot dry with paper towel to remove any excess solution (which could affect mass. Also don’t press too hard so that you don’t force water out of cells).

10. Measure the lengths and the mass of the cylinders again and calculate the % change using the formula. And record measurements in table

11. Plot a graph of change in mass (in g) against concentration of sugar solution

12. Plot a graph of change in length (in mm) against concentration of sugar solution

percentage change formula

FINAL MASS - INITIAL MASS / INITIAL MASS X 100

What does it mean when potato has no change in mass

Concentration of water inside and outside the cell was the same so no overall osmosis took place.

Safety precautions taken during osmosis practical:

1)Handle the scalpel/knife carefully when cutting potatoe cylsinders

2)clean up any spills Immediately

3)ensure all equipment is used appropriately to prevent accidents

What is active transport?

Moves a substance from a more dilute solution to a more concentrated solution (against the concentration gradient), using energy from respiration.

Difference between diffusion and active transport

DIFFUSION :

• Particles move down the concentration gradient

• Doesn’t require energy from respiration

  ACTIVE TRANSPORT:

• Particles are moved against the concentration gradient

• Does require energy from respiration

What are 2 Example of active transport?

1) In plant cells - Root Hair cell

2)In animal cells - Lumen(inner-space of a tube-like structure,where digested food passes through) (cavity(hollow space) in the small intestine)

Active transport in the Lumen

Lumen - the cavity of the small intestine where food is digested

-you can find molecules produced when foods digested EG: sugars such as glucose —>in the example : the concentration of sugars in the lumen is lower than the concentration of sugars inside the cell so these sugars cannot diffuse into the cell instead the sugars are carried by active transport as needs energy (has more mitochondria for respiration)to move from low to high —>once inside this cell the sugars can be transported into the blood and carried around the body —>the glucose is moved against the concentration gradient from the lumen into the cell

Active transport in Root Hair Cell

-Root hair surface are found on the surface of plant roots absorb mineral ions by active transport

Why it’s needed:

-the concentration of mineral ions (e.g nitrates/magnesium ) in the soil is often lower than the inside root hair cells

-so mineral ions must be moved against the concentration gradient , from low (soil) to high (inside the root)

-requires energy - diffusion wouldn’t work

TOPIC 2 : ORGANISATION

What is a Tissue?

A tissue is a group of cells with a similar structure and function.

What is an Organ?

An organ is a group of tissues working together for a specific function e.g. the stomach. The stomach contains muscle tissue and glandular tissue (which releases enzymes).

What are Organ Systems?

Organs grouped together Organ systems which work together to form organisms.

Why are food molecules digested?

Food contains three main nutrients: carbohydrates (eg starch) , protein and lipids (fats)Because they are too large to be absorbed into the bloodstream.

What happens during digestion.

Large food molecules are broken down into small molecules by enzymes. These small molecules can then be absorbed into the bloodstream.

Now the products of digestion are then used by the body to build new carbohydrates lipids and proteins.

Some of the glucose produced is used in respiration.

The Digestive system

1. Food is chewed in the mouth. Enzymes in the saliva begin to digest the starch into smaller sugar molecules.

2. The food then passes down the oesophagus into the stomach. In the stomach, enzymes begin the digestion of proteins. The stomach also contains hydrochloric acid which helps the enzymes to digest proteins.

3. The food spends several hours in the stomach, The churning action of the stomach muscles turns the food into a fluid increasing surface area for enzymes to digest.

4. The fluid now passes into the small intestine and at this point chemicals are released into the small intestine from the liver and the pancreas. The pancreas releases enzymes which continue the digestion of starch and protein and they begin the digestion of lipids. The liver releases bile which helps to speed up the digestion of lipids as it emulsifies fats. Bile also neutralises the acid released from the stomach.

5. The fluid makes its way down the rest of the small intestine. The walls of the small intestine release enzymes to continue the digestion of proteins and lipids. In the small intestine, the small food molecules produced by digestion are absorbed into the bloodstream either by diffusion or active transport.

6. Now the fluid makes it’s way through the large intestine where water is absorbed into the bloodstream.

7. Finally the faeces is released from the body.

definition of enzymes

• Biological catalysts that speed up chemical reactions in living organisms without being used up..

What is the structure & function of enzymes

• Large protein molecules.

• They have a groove on their surface called the active site.(specific)

• The active site is where the only one substrate attaches to.

• The substrate is the molecule that the enzyme breaks down

• They work best at optimum temperature and pH -extreme conditions can cause denaturation

The lock and key theory

• If the active site and substrate are complementary then the enzyme breaks down the substrate into the products.

• Enzymes are specific- the substrate must fit perfectly into the active site.

• Enzymes are not used up.

• The enzyme is the lock and the substrate is the key

• Each enzyme has a specific active site that only fits one substrate

• When the substrate binds an enzyme-substrate complex forms

• The reaction takes places , the products are released and the enzyme can be reused

• If temperature gets too high or pH levels are extreme then the active site denatures which changes shape

What do digestive enzymes do?

Digestive enzymes convert large food molecules into small soluble molecules that can be absorbed into the bloodstream.

What are proteins broken down by?

• Enzyme called proteases

• This is found in the: stomach, pancreatic fluid and small intestine.

What are proteins?

• Long chains of chemicals called amino acids.

• When we digest protein, the protease enzyme converts the proteins back to the individual amino acids, and they are then absorbed into the bloodstream.

• When the amino acids are absorbed by the body cells, they are joined together in a different order to make human proteins.

What are Carbohydrates ?

Large molecules made from sugars

What are carbohydrates broken down by?

Enzymes called carbohydrase- an example of this is amylase which breaks down starch.

Amylase is found in the saliva and pancreatic fluid and small intestine.

What is starch?

• A chain of glucose molecules.

• When carbohydrates like starch are digested, we produce simple sugars

What is a lipid molecule?

• A molecule of glycerol attached to three molecules of fatty acids.

• When lipids are digested, we produce glycerol and fatty acids.

What are lipids broken down by?

Enzyme called lipase

Lipase is found in the pancreatic fluid and the small intestine.

What’s bile Bile and what it does

• Made in the liver but stored in the gallbladder.

• Help to speed up digestion of lipids, but it’s not an enzyme.

• Bile emulsifies lipids- it converts large lipid droplets into smaller droplets. This massively increases the surface area of the lipid droplets which increases the rate of lipid breakdown by lipase.

• Bile is alkaline which allows it to neutralise stomach acid, creating alkaline conditions in the small intestine. This increases the rate of lipid digestion by lipase as the lipase work best in these conditions.