B1 Key Concepts

animal cells

nucleas

contains genetic material

cytoplasm

jelly like material, contains organelles, where chemical reactions happen

cell membrane

controls what substances go in and out of the cell

mitochondria

contains enzymes for respiration

ribosomes

where protein synthesis takes place

plant cells

chloroplast

organelle that contains the green pigment chlorophyll, which absorbs light energy for photosynthesis

cell wall

structure and protection for the plant, made from cellulose

permanent vacuole

filled with cell sap to help keep the cell swollen

Bacteria cell

Chromosomal DNA

the DNA of bacterial cells is found loose in the cytoplasm

Plasmid DNA

bacterial also have small, closed - circles of DNA called plasmids present in the cytoplasm

Flagella

Bacteria can have one or more flagella, used for movement

Cell Wall

same as plant cells but not made from cellulose

why is a sperm cell adapted to its function

acrosome - contains enzymes so the sperm can penetrate the egg

haploid nucleas - contains the genetic material for fertilisation

mitochondria - to release energy needed to swim and fertilise an egg

tail - enables the sperm to swim

why is an egg cell adapted to its function

cytoplasm - contains nutrients for the growth of the early embryo

haploid nucleus - contains genetic material for fertilisation

The cell membrane changes after fertilisation by a single sperm so that no more sperm can enter

why is a ciliated epithelial cells adapted to its function

cilla on the surface beat to move fluids and particles up the trachea

microscopes

• light microscopes

• electron microscopes - uses beams of electron instead of light, this allows for much higher magnification and resolution than light microscopes.

Explain the mechanisms of enzymes action

The enzyme is lock the substate is the key. Just as a specific key fits into a specific lock, each enzyme is shaped to fit a specific substrate molecule.

When does an enzyme denature

• extremes of Ph

• high temperature

Core practical: Investigate the effect of Ph on enzyme activity

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rate calculation for enzyme activity

Why are enzymes important in the synthesis and breakdown of biological molecules?

• Enzymes are biological catalysts that speed up reactions in the body

• They help build carbohydrates, proteins and lipid

• They also help break down these molecules into smaller units

  • Carbohydrates into sugars

  • Proteins into amino acids

  • Lipids into fatty acids and glycerol

Test for starch

• reagent = iodine solution

• positive result = turns blue - black if starch is present

Test for reducing sugars

• reagent = Benedict solution

• method = heat the sample with Benedict solution

• positive results - blue to brick red if reducing sugars are present

test for proteins

• reagent = biuret solution

• positive results = turns purple if proteins are present

test for fats (lipids)

• reagent = ethanol and water

• method = mix the sample with ethanol then add water

• positive result = cloudy white emulsion forms if fats are present

diffusion

movement of particles from high concentration to low concentration

osmosis

high concentration to low concentration but through water

active transport

low concentration to high concentration which requires energy

Describe the method for the osmosis experiment using potato cylinders.

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What is the aim of the experiment investigating osmosis in potato cylinders?

• To investigate the effect of sucrose solutions on the mass of potato cylinders.

• To determine the concentration of the cell sap in potato cells.

Variables in the osmosis experiment with potatoes?

• Independent Variable: The concentration of sucrose solutions (0%, 20%, 30%, 40%, 60%, 80%, and 100%).

• Dependent Variable: The change in mass of the potato cylinders.

• Control Variable: each cylinder is left in the sucrose solution.

Calculate percentage gain and loss of mass in osmosis

Calorimetry

Used to measure the energy content of food

• small samples of material are placed in the machine which burns them the energy given off when the material burns is measured