Investigating Cells

Basic revision for Investigating Cells topic, made using a revision booklet. As much detail as required.

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What 6 features does a PLANT CELL have?

1. Cell wall - gives plant cell rigid shape

2. Chloroplasts - contain a chemical called chlorophyll to carry out photosynthesis

3. Vacuole - space used to store useful substances

4. Cell Membrane - controls substances entering and exiting the cell

5. Cytoplasm - site of chemical reactions

6. Nucleus - controls cell activities

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What 3 features does an ANIMAL CELL have?

1. Cell Membrane - controls substances entering and leaving the cell

2. Cytoplasm - site of chemical reactions

3. Nucleus - controls all cell activities

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DIFFUSION

Diffusion is the movement of a substance from an area of high concentration to area of low concentration until evenly spread. This is the process by which substances like oxygen, water, urea and carbon dioxide enter and leave cells.

Importance to a cell:

Entering a cell - oxygen, water, glucose, amino acids.

Exiting a cell - water, urea, carbon dioxide.

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OSMOSIS

Osmosis is the technical term for the diffusion of water through a selectively-permeable membrane

Effects of osmosis on cells:

Blood Cells

  • water in>water out - Bursts
  • water in=water out - no change
  • water in

Plant Cells

  • water in>water out - turgid (swollen, but not burst)
  • water in=water out - no change
  • water in<water out - plasmolysed (shrunk but cell wall rigid).
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CELL DIVISION (MITOSIS)

Mitosis:

  • The division of a cell into two daughter cells.
  • The two daughter cells are genetically identical.
  • Genetically identical cells are calles clones.

Chromosomes and genes:

  • Chromosomes are long thread-like structures in the nucleus
  • There are 46 chromosomes in a human nucleus

Stages of mitosis:

  • Chromosomes double
  • Chromosomes shorten and thicken - 2 chromatids, attatched by a centromere
  • Chromosomes line up at the equator - cetromeres attatch to spindle fibres
  • Chromatids (1/2 a chromosome) move to opposite poles - spindle fibres pull chromosomes apart
  • Nuclei reform and cytoplasm divides - 2 indentical daughter cells are created.
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ENZYMES

Enzymes are biological catalysts -

  • Catalysts speed up the rate of a reaction, but are unchanged themselves.
  • Enzymes are proteins found in living cells.

How enzymes work:

  • All enzymes work on only one substance - this substance is the enzyme's substrate. 
  • Enzyme and substrate join
  • Shapes of enzyme and substrate fit closely together
  • A change occurs in the substrate and the product is released

The enzymes are specific to that substrate.

Optimum Rates

The optimum rate of an enzyme is the rate at which it works best. This can be affected my PH, temperature etc.

Above about 50 degrees, enzymes are denatured.

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BASIC ENZYMES

BREAKDOWN

    Substrate                          Enzyme                     Product

  • hydrogen peroxide           catalase                      oxygen + water
  • starch                               amylase                      maltose
  • fats                                   lipase                          fatty acids + glycerol
  • protein                              pepsin                         polypeptides

SYNTHESIS

  • glucose-1-phosphate      phosphorlyase             starch
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AEROBIC RESPIRATION

The formula for aerobic respiration is:

glucose + oxygen ------> energy + water + carbon dioxide

Food contains the chemical energy we need to fuel out bodies. Fats contain twice as much energy as carbohydrates or proteins.

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KEY WORDS

DENATURED - when an enzyme is destroyed, perhaps because it gets too hot, it is denatured.

OPTIMUM - this is the peak activity rate of an enzyme.

SUBSTRATE - this is the substance upon which an enzyme works.

SPECIFIC - when talking about enzymes and their substrates, enzymes only work on ONE subtance (substrate). The enzyme is SPECIFIC to that substrate.

SYNTHESIS - this is the word used to describe the buildup of a substance from smaller molecules to larger molecules. For example: the enzyme phosphorylase builds up G-1-P and changes it into starch.

DEGRADATION - this is another word for breakdown. It is used when talking about enzymes that DEGRADE their substrate and release their product.

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STAINS & INDICATORS

IODINE                                                 stains               PLANT CELLS (yellow)

METHYLENE BLUE                            stains               ANIMAL CELLS(blue)

BICARBONATE INDICATOR              turns                RED ---> YELLOW (in presence of carbon dioxide)

BENEDICT'S SOLUTION                    turns               BLUE---> RED (in presence of glucose)

IODINE                                                turns                BROWN ---> BLACK (in presence of starch)

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