Biology Unit 2 AQA Revision notes

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Bio B2 revision notes
Cells
What is the function of a cell's nucleus? What is the function of the ribosomes?
To control the activities of the cell To act as the site for protein synthesis
Which of these is a part found in plant cells but not in animal cells?
Cell wall
Which part is missing from human red blood cells?
Nucleus
What is diffusion?
The movement of particles( net movement) from high concentration to low concentration
What would not speed up diffusion in what substance moves out of respiring cells?
an animal cell? Carbon dioxide
Make the cell rounder
How are bacterial cells different from animal cells?
They have a cell wall and no nucleus
How are yeast cells different from bacterial cells?
They have a nucleus
Animal cells and plant cells both contain:
cell membrane, cytoplasm, nucleus, ribosomes, mitochondria
Plant cells also contain these parts, not found in animal cells:

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Definitions:
Nucleus- controls all activities of the cell. It contains the genes on the chromosomes
Cytoplasm- A liquid gel in which most of the chemical reactions needed for life take place.
Cell membrane- Controls the passage of substances into and out of the cell
Mitochondria- structures in the cytoplasm where oxygen is used and most of the energy is released
during respiration
Ribosomes- Where protein synthesis takes place.
Plants cells
Plant and algal cells are similar.…read more

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Tissues and organs:
Tissue- group of cells with similar structure+ function working together.
Glandular tissue- contain secretory cells that produce substances such as enzymes and hormones.
Epithelial tissue- covers the outside of your body as well as your internal organs.
In PLANTS: -epidermal tissue: cover the plant.
-mesophyll tissue: contain lots of chloroplasts, carry out photosynthesis.
- xylem + phloem: transport tissues in plants, carry water e.g.
Organs: made up of tissues.
The pancreas makes hormones to control our blood sugar.…read more

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We can manipulate the levels of light, temperature and co2 artificially to increase rate of
photosynthesis.
How plants use glucose:
During photosynthesis, plant and algal cells use insoluble glucose for:
-respiration
-to convert into insoluble starch for storage
-to make fats or oils for storage
-to make fats, proteins or cellulose for use in the cells + cell walls.
Making the most of photosynthesis:
Factors like light levels, low temperature and co2 levels affect photosynthesis.…read more

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Transect: Line transect is common. They are NOT random. Stretch tape between two points. Sample
organisms along line at regular intervals . You can measure factors like light, soil that affect growth
along the line.
Proteins, catalysts and enzymes:
Protein molecules are made up of long chains of amino acids
Proteins act as structural components of tissues, as hormones, as catalysts and antibodies.
Enzymes are proteins. Amino acid chains are folded to form the active site.…read more

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The acidic liquid coming from your stomach needs to become an alkaline mix, so
Your liver makes a greenish yellow alkaline mix (bile). It is stored in your gall bladder.
As food comes into the small intestine from the stomach, bile is squirted on it.
Bile neutralises acid. Makes alkaline.
Bile also emulsifies fats in your food. Breaks up large drops of fats into smaller droplets.…read more

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Most of the reactions in aerobic respiration take place inside the mitochondria.
The energy released during respiration is used to build large molecules from smaller ones and
allow muscles to contract. In mammals and birds it allows them to maintain and steady body
temperature.
The effect of exercise on the body:
The energy released during respiration is used to allow muscles to contract.
When you use your muscles you need more glucose and oxygen + produce more co2.…read more

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Aerobic respiration releases more than lactic acid to be:
anaerobic respiration. Broken down to form carbon dioxide and water.
Cell division and growth:
Different forms of the same gene- alleles.
Chromosomes found in nucleus of cell chromosomes contain genes genes are made of DNA
Mitosis:
Body cells divide by mitosis to make more identical cells for growth, repair and replacement
-No variation. Produces two identical cells (same genetic information).
-Before a cell divides it makes new copies of the chromosomes in the nucleus.…read more

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Embryonic stem cells (from human embryos) and adult stem cells (from adult bone marrow) can be
made to differentiate into many different types of cells.
Stem cells have the potential to treat previously incurable conditions. We may be able to grow nerve
cells or whole new organs for people who need them.
Problems with stem cells:
-Many embryonic stem cells come from aborted embryos or spare embryos in fertility treatment.
Ethical issues.
-Some people feel that embryos cannot give permission. Violation of its human rights.…read more

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They can be produced from very tiny samples of DNA from body fluids such as blood, saliva and
semen.
Each individual has their own pattern, which can be used to identify you.
Inheritance in action:
Humans have 23 pairs of chromosomes. In 22 cases, each chromosome in the pair is a similar shape.
One pair of chromosomes is different (sex chromosomes) XX- female XY-male.
Punnet square can be used to predict outcome of different genetic crosses.…read more

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