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Flashcards in T1 - Key Concepts in Biology Deck (78):
1

Definition of cell

The building blocks of every organism in the planet

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2 types of cells

Eukaryotic and prokaryotic

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Eukaryotic cell

Complex cells (including plant and animal cells)

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Prokaryotic cells

Smaller and simpler cells (including bacteria)

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Eukaryotes

Organisms that are made up of eukaryotic cells

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Prokaryote

Prokaryotic (single cell organisms)

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Subcellular structure of an animal cell

Nucleus
Cytoplasm
Cell membrane
Mitochondria
Ribosome

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Nucleus

Contains genetic material that controls the activities in the cell. Genetic material is arranged into chromosomes

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Cytoplasm

Gel like substance where most of the chemical reactions happen. It contains enzymes that control these chemical reactions

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Cell membrane

Holds the cell together and controls what goes in and out

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Mitochondria

These are where most of the reactions for respiration takes place. Respiration transfers energy that the cell needs to work

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Ribosomes

These are involved in the translation of genetic material in the synthesis of proteins

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What are the extra things that plant cells have and animal cells don’t?

Cell wall
Large vacuole
Chloroplasts

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Cell wall

Made of cellulose, it supports the cell and strengthens it

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Large vacuole

Contains cell sap, a weak solution of sugar and salts. It maintains the internal pressure to support the cell

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Chloroplasts

These are where photosynthesis occurs which makes food for the plant. They contain a green substance called chlorophyll

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Subcellular structure of a bacterial cell

Pilli
Chromosomal DNA
Ribosomes
Cell membrane
Plasmid DNA
Flagellum

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Pilli

Hollow hair like structures made of protein allow bacteria to attach to other cells to transfer genetic information

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Chromosomal DNA

One long circular chromosome which controls the cells’ activities and replication. It floats free in the cytoplasm

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Plasmid DNA

Small loops of extra DNA that aren’t part of the chromosome. Plasmids contain genes for things like drug resistance and can be passed between bacteria

21

Flagellum (pl flagella)

A long hair like structure that rotates to make the bacterium move. It can be used to move the bacteria away from harmful substances like toxins and towards good things like nutrients or oxygen

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Multicellular organism

Contain lots of different types of cells (ie cells with different structures)

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Specialised cells

Cells that have a structure which makes them adapted to their function

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Examples of specialised cells

Egg
Sperm
Ciliated epithelial

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Haploid cell (in sperm and egg cell)

Both the nucleus of an egg and sperm cell only contain half the number of chromosomes that’s in a normal body cell

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Main functions of an egg cell

Carry the female DNA
Nourish the developing embryo in the early stages

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How is the egg cell adapted to its function?

It contains nutrients in the cytoplasm to feed the embryo
It has a haploid nucleus
Straight after fertilisation, it’s membrane changes structure to stop any sperm getting in (so the offspring will have the right amount of DNA)

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What is the function of a sperm cell?

To transport the make DNA to the female’s egg

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How is the sperm cell adapted to its function?

Long tail to swim to egg
Lots of mitochondria in the middle section to provide energy needed to swim
Has an acrosome at the front where it stores enzymes needed to digest its way through the membrane of the egg
Haploid nucleus

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Function of an epithelial cell

Line the surface of organs

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Function of ciliated epithelial cells

Move substances

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How is the ciliated epithelial cells adapted to its function?

It has cilia (hair like structures) which beat to move substances in one direction along the surface of the tissue

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Example of ciliated epithelial cells?

The lining of the airways where they help to move mucus up to throat so it can be swallowed and doesn’t reach the lungs

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Microscope

Use lenses to magnify things such as cells and increase the resolution of an image

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Resolution

How well a microscope distinguishes between two points that are close together (higher resolution means that an image can be seen more clearly and in more detail)

36

Light microscopes

Invented in the 1590s
They work by passing light through a specimen
They let us see things like nuclei and chloroplasts and we can also use them to study living cells

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Electron microscopes

Invented in the 1930s
They use electrons rather than light
Have a higher magnification and resolution

38

What is the equation for magnification?

Magnification = image size / real size
(The sizes have to be in the same units !!!!!)

39

Catalysts

Substance which increases the speed of a reaction, without being changed or used up in the reaction

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Why do chemical reactions need to be carefully controlled?

To get the right amounts of substances

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How can you make a reaction happen more quickly?

Raising temperatures

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Substrate

Molecule changed in the reaction

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Active sight

The part where it joins on to its substrate to catalyse the reaction

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How many substrates do enzymes usually work with?

1 - said to have high specificity for their substrate

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‘Lock and key’ mechanism

For the enzyme to work, the substrate has to fit into the active site. If the substrate’s shale doesn’t match, the reaction won’t be catalysed

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What are the 3 things that affect the rate of a reaction?

Temperature
pH
Substrate concentration

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What happens if the reaction gets too hot?

Some bonds holding the enzyme together will break. This changes the shape of the enzyme’s active site so the substrate won’t fit any more (denatured enzyme)

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Optimum temperature

The temperature that enzymes work best at

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What happens if the pH is too high or too low?

The pH interferes with the bonds holding the enzymes together, this changes the shape of the active site and denatures the enzyme

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Optimum pH

The pH that enzymes work best at. It’s often neutral (pH7) but not always eg pepsin (enzyme that breaks down proteins in the stomach) works best at pH2 so it’s well suited to acidic conditions

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How does increasing the substrate concentration increase the speed of reaction?

Because it’s more likely the enzyme will meet up and react with a substrate molecule. But, when all the active sites are full, adding more will make no difference

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Rate of reaction

How fast / how much something changes over time

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Equation for rate of reaction

Rate = amount it has changed by / time taken

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Name 3 big molecules

Proteins, lipids, carbohydrates

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Why do organisms need to break big molecules down into smaller components?

Easier to digest
Growth
Respiration in plants

56

What is the name of the enzyme that breaks carbohydrates into simple sugars?

Carbohydrases

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What is the name of the enzyme that breaks down starch?

Amylase

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What is the name of the enzymes that convert proteins into amino acids?

Protease

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What’s the name of the enzyme that converts lipids into glycerol and fatty acids?

Lipase

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What happens to the pH when lipids are broken down?

The fatty acids will lower the pH of the solution they’re in

61

How can organisms synthesise carbohydrates and proteins?

Carbohydrates - joining simple sugars
Proteins - joining amino acids

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What solution is used to test for sugars?

Benedict’s reagent

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What solution is used to test for starch?

Iodine

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What test is used to test for lipids?

Emulsion test

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What test is used to test for proteins?

Biuret test

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If starch is present, what will the colour will be?

Blue-black

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If starch is not present, what will the colour be?

Browny-orange

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If there are lipids present, what colour will the solution be?

Milky colour, more lipid = more milky colour

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If there’s no protein present, what will the colour of the solution be?

Blue

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If there is protein present, what colour will the solution be?

Purple

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Calorimetry

An experiment where food is burnt to see how much energy it contains

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Equation for how many joules of energy the food contains

Energy in food (J) = mass of water (g) x temp. change in water (degreesC) x 4.2

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Equation for the energy per gram of food

Energy in food (J) / mass of food (g)

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Diffusion

Gradual movement of particles from places where there are MORE to LESS

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What states does diffusion occur in?

Liquid and gas

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Osmosis

Movement of water molecules across a partially permeable membrane from a region of HIGH WATER CONCENTRATION to a region of LOW WATER CONCENTRATION

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Partially permeable membrane

Membrane with very small holes in so only small molecules such as water can pass

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Active transport

Movement of particles across a membrane from a region of LOWER concentration to a region of HIGHER concentration (against a concentration gradient)