Topic 1 - Key Concepts In Biology

nucleus, cell membrane, mitochondria and ribosomes

nucleus, cell membrane, cell wall, chloroplasts, mitochondria, vacuole and ribosome

chromosomal DNA, plasmid DNA, cell membrane, ribosomes and flagella, slime coat

Controls the cells activities and contains the DNA.

to control what enters and leaves the cell and helps separate one cell from another

A watery jelly where the activities of the cell take place

Contains chlorophyll which absorbs light energy from sunlight for photosynthesis

Stores cell sap, helps keep the cell firm and rigid

Makes new proteins for the cell

Where aerobic respiration takes place

Made of cellulose and supports and protects the cell

To protect the bacteria- not all bacteria have this

To help bacteria move (Not all bacteria have this)

Bacteria do not have a nucleus but have a large loop (chromosomal DNA) of DNA and a small loop (plasmids) of DNA

1) The tip of the head contains a small vacuole called the Acrosome which contains enzymes to digest the egg's jelly coat and burrow inside

2) The tail (flagella) swings side to side, allowing the sperm to swim

3) A large amount of mitochondria are arranged in a spiral around the top of the tail, to release a lot of energy to move to the egg

4) Haploid nucleus

1) The cell membrane fuses with the sperm cell membrane. After fertilisation, the cell membrane becomes hard to stop other sperm from entering

2)The jelly coat protects the egg and hardens after fertilisation to ensure only 1 sperm enters the egg cell

3) The cytoplasm is packed with nutrients to supply the fertilised egg cell with energy and raw materials for the growth of the embryo

4) Haploid nucleus

membrane bound organelles

When the egg cell is fertilised the two haploid nucleus, (with only one set of chromosomes each )fuse to form a diploid nucleus with two sets of chromosomes each

The ciliated cells Have membranes with many tiny folds called microvilli. These adaptations increase the surface area of the cell. The more area for molecules to be absorbed, the faster absorption happens.

The cilia epithelial cells have hair like cilia which move side to side to sweep substances ( the egg cell) along.

Total magnification = eyepiece lens magnification x objective lens magnification

size of image / size of specimen

Passes a beam of light through a specimen which travels through the eyepiece lens, allowing the specimen to be observed.

The eyepiece lens has a magnification of 10 x. You then turn the objective lens to the appropriate lens with the set magnification. Multiply both values together. Use the focus knob to focus on the specimen then fine focus knob to further get a clearer image

1) We can observe living organisms and movement
2) Colour Images
3) Easily prepared samples
4) Relatively large field of view
5) Inexpensive
6) Portable
7) Easy to use

Cannot view tiny cell parts, molecules
Smaller magnification
Limited resolution

It uses a beam of electrons which are focused using magnets. The electrons hit a fluorescent screen which emits visible light, producing an image.

transmission electron microscope (TEM) and scanning electron microscope (SEM)

Greater magnification and resolution than light microscopes since beams of electrons have a smaller wavelength than photons of light

● Expensive
● Large so less portable
● Require training to use
● Only dead specimens can be observed

Allow small sub cellular structures to be absorbed in more detail

Enable scientists to develop more accurate explanations to how sub cellular structures work

m ( x 10 ^-3)

µ ( x 10 ^ - 6)

n ( x 10 ^ -9)

p (x 10 ^-12)

animal and plant cells

bacteria cells

The circle of light you see when looking down a microscope

The dials/wheels in a microscope which move the stage to find the image and bring it into view

lens closest to the specimen

This is the lens closest to your eye. It normally has a 10 x magnification

To colour the cell and to help see the organelles

To protect the ocular lens from damage

To hold the specimen in place

To swab places to get cells

As a lock-and-key model. The enzyme is the right size and shape for the reactant(s) it is catalysing, so they fit in the active site and the reaction takes place, before the products are released. The reaction can continue to happen in it, until the enzyme becomes denatured- it changes shape.

It helps speed up cell reactions without being changed themselves and can be used again.

They enable reactions to take place at lower temperatures.

the place on the enzyme where the substrate binds

This is because the active site has a complementary shape for its substrate

reactants in an enzyme-catalysed reaction

They help break down large, insoluble food molecules into small soluble ones that can be absorbed into the bloodstream by the small intestine and be delivered to cells in the body.

The active site changes shape and can no longer bind to the substrate to form an enzyme/substrate complex.

The molecules do not have as much kinetic energy so move less, thus the probability of collisions occurring decreases so there are fewer collisions between the enzyme and substrate, less enzyme substrate complexes form, thus a lower rate of reaction

The molecules have a lot kinetic energy so move more, thus the probability of collisions occurring increases so there are more collisions between the enzyme and substrate, more enzyme substrate complexes form, thus a higher rate of reaction

The enzyme's active site has become denatured so no longer binds to the substrate to form enzyme substrate complexes, thus the rate of reaction decreases

The enzyme has become denatured so no longer binds to the substrate to form enzyme substrate complexes, thus the rate of reaction decreases

There are more substrate- thus more substrate concentrated in a certain volume. The probability of collisions occurring increases so there are more collisions between the enzyme and substrate, more enzyme substrate complexes form, thus a higher rate of reaction

All of the active sites are occupied, so no more substrates can bind and the reaction is as fast as possible.

starch is broken down to simple sugars by amylase

Broken down to amino acids by protease

Broken down to fatty acids and glycerol by lipase

Test for proteins, positive=violet, negative=light blue

Tests for starch, positive = Blue/Black Negative = Yellow/orange

Tests for lipids, Positive= turns cloudy (white emulsion) Negative = stays clear

Tests for reducing and non reducing sugars, Blue = No reducing sugar, Green = very little reducing sugar, Orange= more reducing sugar, Red = Lots of reducing sugar

measures the change in energy by using temperature

A piece of food is burned and the released energy is used to heat a known quantity of water. The temperature change of the water is then used to determine the amount of energy in the food and how may calories per gram.

Energy released per gram of food (J)= (Mass of water (g) X 4.2 X temperature rise (°C) ) / mass of food (g)

Taking longer than usual to place the food under the test tube: Some energy being transferred to the surroundings and not the water

Having less water in the test tube: it is easier to hat up and increase the temperature.

the flame going out before all of the food is burnt: All the energy in the food will not be transferred into heating the water.

The net movement of particles from an area of high concentration to an area of low concentration.

difference in the concentration of a substance from one location to another

diffusion of water molecules across a partially permeable membrane. So a solvent flows from a dilute solution to a more concentrated one

It traps large soluble molecules inside and outside the cell and allows smaller soluble molecules into the cell

The water will move into the cells of the potato, across the partially permeable membrane, from a dilute solution (the water) to a concentrated solution (the cytoplasm of the potato cells).

The water will move into the red blood cell, across the partially permeable membrane, from a dilute solution (the water) to a concentrated solution (the cytoplasm of the red blood cell). The red blood cell has no cell wall, so it will burst.

Movement of molecules against the concentration gradient (from a low to a high concentration of the molecule). This process requires energy.

protein carry things past the hydrophobic region of the cell membrane via protein channels in the cell membrane

Diffusion and osmosis

They would have many mitochondria to release energy for transport through aerobic respiration.

Place the potato pieces in different concetrations of a solution (such a sugar or salt solution. Find the start and end mass for each potato piece and calculate the percentage change in mass. Draw a graph of the results and find the point where the line crosses the x-axis. This concentration of solute would result in no net movement of water in or out of the cell, and is the concentration of solute in the cell.

Percentage change allows you to compare different potato pieces with different starting masses.

Surface area of the potato - large SA = faster rate of osmosis. Time to leave the potato slice in each solution. Drying the potato before measuring the mass to make sure no liquid is on the outside of the potato. Make sure the potato is completely covered with the solution.

smaller molecules i.e water, oxygen, glucose, amino acids

Temperature, surface area, difference in concentration

The flat platform where the slide is placed

The part of a microscope that is rotated to change the magnification lens in use

The upper part of the microscope that can be moved up or down to focus on the image