Topic 1 Flashcards by Tristan Krawczyk-Lee

Tests for reducing sugars using Benedict’s reagent

Add Benedict’s reagent to a sample and let it in water bath to 75°C
No reducing sugars —-> higher concentration
Blue (none) > Green > Yellow > Orange > Brick red

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Biuret test for proteins

Add drops of potassium hydroxide solution to make solution alkaline
Add copper (II) sulfate solution
No protein = solution remains blue
Protein = solution turns purple

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Emulsion test for lipids

Shake sample with ethanol until it dissolves and pour solution into water
If lipids, they will precipitate out of solution as a milky emulsion
More lipids = more noticeable milky colour

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Iodine taste for starch

Add iodine solution to test sample
If starch, solution changes from brown to black
No starch = remains brown

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Energy in food formula (calorimetry)

Mass of water (g) * temp change in water (°C) * 4.2

Energy per gram = energy in food (J) / mass of food (g)

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Potato cylinder in 0% sucrose solution

OSMOSIS
Water concentration is higher in solution
Water molecules move from solution into potato cylinder, from area of high concentration into low concentration of water
Mass of cylinder increases and cells become turgid

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Potato cylinder in 80% sucrose concentration

OSMOSIS
Water concentration higher in potato cylinder
Water molecules move from potato cylinder into solution, from a high concentration of water to low concentration of water
Mass of cylinder decreases and cells become less turgid/shrink.

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Active transport

Movement of particles from an area of low concentration to high concentration, up the concentration gradient, using energy transferred in respiration

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Diffusion

Movement of particles from an area of high concentration to low concentration, down the concentration gradient
A passive process

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Nucleus

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

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Mitochondria

Where most of the reactions for aerobic respiration take place.

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Cytoplasm

Gel-like substance where most chemical reactions happen. Contains enzymes that control the chemical reactions.

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Cell membrane

Holds cell together and controls what does in and out.

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Ribosomes

Involved in translation of genetic material and synthesis of proteins.

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Cell wall

Made of cellulose, supports and strengthens cell.

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Large vacuole

Contains cell sap and maintains internal pressure to support cell.

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Chloroplasts

Where photosynthesis occurs to make food. Contains chlorophyll.

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Chromosomal DNA

Controls cell’s activities and replication and floats free in the cytoplasm.

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Flagellum

Long hair-like structure that rotates to make the bacterium move. Used to move away from harmful substances such as toxins and towards beneficial things such as oxygen and nutirents.

Plasmid DNA

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

Specialised cell

Cells that have structures that make them adapted to their function.

How are egg cells adapted to their function

Contains nutrients in the cytoplasm to feed embryo.
Haploid nucleus to fuse with other haploid nucleus to make a diploid zygote.
Membrane changes structure after fertilisation to stop any more sperm getting in so offspring have the right amount of DNA.

How are sperm cells adapted to their function

Long tail so can swim to egg.
Lots of mitochondria in middle section to provide energy to swim.
Acrosome at front of head where enzymes stored to digest through membrane of egg cell.
Contains nutrients in the cytoplasm to feed embryo.
Haploid nucleus to fuse with other haploid nucleus to make a diploid zygote.

How are ciliated epithelial cells adapted to their function

Line surface of organs and have cilia on their top surface.

Cilia beat to move substances in one direction along surface of tissue.

Example where ciliated epithelial cells are

Lining of airways have these to move mucus to the throat to be swallowed.

Resolution definition

How well a microscope distinguishes between two points that are close.

Light microscopes

Use light to view living cells and can be used to view nuclei and choloroplasts.

Electron microscopes

Use electrons rather than light and have higher magnification and resolution so things so smaller things such as inside of mitochondria can be viewed. Can't be used to view living cells.

How to view specimen with light microscope

Thin slice of specimen. Use drop of water to keep specimen in place on slide. Add stain such as iodine. Place cover slip and press down so no air bubbles and clip it to stage. Use coarse adjustment knob to move stage up to lens and looking down eye piece, move stage down until its in focus then adjust with fine adjustment knob until clear. Use clear ruler to find FOV by measuring diameter visible and switch to high magnification lens if necessary.

Total magnification formula

Total magnification = eyepiece lens magnification * objective lens magnification

Magnification formula

Magnification = Image size / Real size

Enzyme

A biological catalyst that increases the speed of a reaction without being changed or used up.

Lock and key mechanism

Enzymes only work with one substrate. | For enzyme to work, the substrate has to fit into the active site.

Effect of temperature on rate of enzyme-controlled reaction

Higher temp increases rate at first. Optimum point is where enzyme is most active. If too hot, bonds holding enzyme together break and active site changes shape so substrate won't fit anymore. Enzyme is denatured.

Effect of pH on rate of enzyme-controlled reaction

If pH is too high or too low, the pH interferes with bonds holding enzyme together so the shape of active site changes and enzyme is denatured. Most enzymes have optimum pH of 7 but some that work in the stomach works best at pH 2.

Effect of substrate concentration on rate of enzyme-controlled reaction

Higher substrate concentration increases rate of reaction as it is more likely that the enzyme will meet up and react with a substrate molecule. Only true up to a point because all the active sites can become full and adding makes no difference.

Investigating effect of pH on enzyme activity

Spotting tile with iodine drop in each. Keep water at 35C and put test tube with 3cm3 of amylase solution and 1cm3 of buffer solution pH 5. Add starch at sample the amylase every 10 secs using the iodine. Brown means no starch. Repeat with different pHs and compare how pH affects time taken for all starch to be broken down.

Control variables in investigating effect of pH on enzyme activity

Concentration and volume of amylase solution. | Temp of water

Why does the body have enzymes?

The molecules in food are too big to pass through the walls of the digestive system so enzymes break them down into smaller molecules so they pass through the walls of the digestive system easily to enter the blood stream.

Why do plants have enzymes?

Energy is stored as starch and when the plant needs energy, enzymes break down the starch into sugars that can be respired to release energy.

What does carbohyrase break down

Carbohydrates into simple sugars

What does protease break down

Proteins into amino acids

What does lipase break down

Lipids into glycerol and fatty acids

What else can enzymes do?

Catalyse reactions that synthesise smaller molecules.

How to do calorimetry?

``` Weigh mass of food and skewer it. Put set volume of warer in tube. Measure temp of water and set fire to food and hold food underneath tube. Relight if necessary. Measure temp of water Use formula. ```