Download Cells, Genetics and Human Body Systems Unit Notes

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Biology Review
Unit Notes
 Cells
ANIMAL CELL
Animal Cell Structures (called organelles) and Functions
Nucleus: directs all cell activities, contains the cell’s genetic/hereditary material (DNA in chromosomes)
Nuclear envelope/membrane: determines what goes in and out of nucleus
Cytoplasm: gel-like substance that holds organelles
Cell membrane: determines what goes into and out of cell, provides shape and support
Endoplasmic reticulum: passageways that transport materials (mostly proteins) throughout cell
Ribosomes: make proteins
Mitochondria: “power-house of the cell” where respiration occurs to give the cell energy
Golgi Bodies/Complex: packages and transports materials for the cell
Vacuoles: store food, water, and waste for the cell
Lysosomes: break down dead cell parts
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PLANT CELL
Additional structures found in plant cells and their functions:
Cell wall: nonliving material (made of cellulose) that supports and protects the cell
Chloroplasts: contain the green pigment chlorophyll, where photosynthesis takes place
(Plant cells also tend to have one large vacuole for storing water, instead the many smaller vacuoles that
an animal cell has.)
 Cell Processes
Reproduction
Body cells reproduce by the process of cell division. If a cell were to just divide, however, each new
“daughter” cell would have only half the number of chromosomes, therefore only half the directions for
survival and wouldn’t live. So before cell division, the cell must undergo mitosis, which is the duplication
of the chromosomes. Because only one parent is involved (no sperm or egg), this is a type of asexual
reproduction.
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Sex cells (eggs and sperm) reproduce slightly differently. If they just did mitosis and cell division, then
every sperm and egg would have the full count of chromosomes (in humans, that’s 23 pairs or a total of
46). Then, if a sperm and egg meet, the resulting fertilized egg would have double the number of
necessary chromosomes (92) with too many directions for survival and would die. Therefore, sperm and
egg cells, unlike every other type of cell in the body, should only have half the number of chromosomes
(23). The process where sex cells duplicate their chromosomes, then split in half, then split in half again,
is called meiosis. The result is four “daughter” cells. [Organisms that reproduce using sperm and eggs
perform sexual reproduction.]
Transport
Most materials move into and out of the cell through the cell membrane simply because of a difference in
concentration of substances. For instance, if there is more oxygen (O2) outside of the cell in the
bloodstream than there is inside the cell, those O2 molecules will try to balance themselves out by moving
into the cell. If there is more carbon dioxide (CO2) inside the cell, those CO2 molecules will try to balance
themselves out and leave the cell to go into the blood. This simple movement of molecules from an area of
high concentration to an area of low concentration is called diffusion. If the substance moving across a
cell membrane is water (H20), it’s a special kind of diffusion called osmosis.
Energy
Cells get energy to live through the process of cellular respiration. Although the chemical formula for
this process can seem scary at first, it really makes a lot of sense if you think about it. You eat food so
you’ll have energy. You already know that you breathe in oxygen and breathe out carbon dioxide, and you
already know that you sweat and urinate water out of your body. The chemical formula for this process
just looks at this in a little more detail. For instance, most of the food you eat gets broken down by your
digestive system into a simple sugar called glucose (C 6H12O6). The glucose goes into all of your body cells,
along with oxygen, and then into the mitochondria where they are broken down into individual carbon,
hydrogen, and oxygen atoms. Then, these atoms rearrange themselves into new substances (water and
carbon dioxide), giving off a whole bunch of energy in the process which the cell uses to live. The water
and carbon dioxide leave the cells, go through the body, and are excreted by you.
Chemical reaction for respiration:
C6H12O6
+
glucose
O2
H2O
oxygen
water
+
CO2
+
energy
carbon dioxide
Respiration is done by all plant and animal cells to get energy to survive. Since plants don’t ingest food,
they need to make their own in a process called photosynthesis., which is essentially the opposite of
respiration. Think about it: you know plants take in water and breathe in your carbon dioxide, and you
know they give off our oxygen and they make their own food (glucose)vwith sunlight (energy).
Chemical reaction for photosynthesis:
H 2O
water
+
CO2
carbon dioxide
(sunlight)
C6H12O6
glucose
+
O2
oxygen
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 Genetics
A chromosome is a long piece of DNA. Each chromosome is divided up into smaller segments that each
control a specific characteristic or trait about you. These segments are called genes (so genes control
traits). Recall that each sperm has one set of chromosomes (23) and each egg has one set of
chromosomes (23), all with genes that control the same traits. When the sperm and egg meet, the
resulting fertilized egg contains two sets of directions for each trait. These “directions” are in the form
of alleles. Some traits are controlled by only set of genes, others are controlled by several. In addition
to genes, environmental factors play a part in your traits. [For example, you may have the genes for being
tall, but if you don’t eat right or get a disease, you may end up not being tall.]
For some traits, there can be different forms of alleles which may recessive or dominant. The dominant
allele covers or masks the recessive one if both are present, so the dominant one shows up only. For
example, in pea plants: the trait of seed color can have a green allele or yellow allele. Green is dominant.
Since every organism has two alleles for each trait, a pea plant can have two green alleles for seed color,
two yellow alleles, or one of each. If it has both green, the seeds will be green. If both are yellow, the
seeds will be yellow. If there is one of each, the seeds will be green only, because we said green is
dominant and that means the yellow allele (recessive) gets hidden.
When writing alleles, capital letters are used to represent the dominant traits; lower case letters are
used to represent recessive traits. The first letter of the word that is dominant is usually the letter
chosen, but not always. For example, the allele for green seed color would be “G”; the allele for yellow
seed color would be “g”. A pea plant can be GG, Gg, or gg for seed color. If both alleles are identical (GG
or gg) the organism is said to be purebred for that trait. If both are different (Gg) the organism is
hybrid for that trait.
Genotype refers to the actual genes an organism has.
Phenotype refers to the traits the organism shows or exhibits.
EX/ The genotype of a purebred dominant pea plant for see color is GG, the phenotype is green.
A Punnett square is used to predict the probability of certain traits showing up when parents are
“crossed.” Generally, the alleles the father has for the trait go on the top of the square; the mother’s go
on the side.
Example: Freckles are dominant in people. What is the probability that a man who is purebred dominant
for freckles with have a child without freckles if he marries a woman with no freckles?
The man’s genotype is FF. Since his wife has no freckles her genotype must be ff (because if she had the
dominant gene she would show freckles).
F
f
f
Ff
Ff
F
Ff
Ff
It is impossible for these parents to have a child
without freckles because the father can only
give the dominant gene to his children.
Outcome: 100% hybrid offspring
100% freckles
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 Human Body Systems
Levels of organization in the body:
cells

tissues

organs

organ systems

organism
 Important tissues and their functions:
Blood: transports materials throughout the body
Bone: supports and protects body and organs
Muscle: helps the body to move; aids in circulation, digestion, and respiration
Nerve: carries messages throughout the body
Skin: covers and protects the body; excretes wastes
 Important organs and their functions:
Heart: pumps blood
Kidneys: remove wastes from the blood
Lungs: exchange gases with the environment
Stomach: breaks down food by physical and chemical means
Brain: controls thinking and voluntary actions
 Human body systems and their functions:
Skeletal: supports body, protects internal organs
Muscular: moves organs and body parts
Nervous: controls body activities; carries and interprets messages
Endocrine: regulates body activities with hormones
Digestive: breaks down food into a usable form
Circulatory: transports needed materials to cells and carries away wastes
Respiratory: exchanges gases with the environment
Excretory: removes wastes from the body
Reproductive: produces offspring
Examples of organs
or parts
skull, ribs
arm/leg muscles
brain, spinal cord
adrenal glands
stomach, intestines
heart, arteries, veins
lungs, bronchi
kidneys, lung, skin
ovaries, testes
* The most important thing for you to understand about the human body systems is that they work
together. For example, the digestive system breaks down food, but those nutrients rely on the
circulatory system to get them to all the cells and the wastes from the use of that food is removed from
the body by the excretory system. All of these systems are regulated by the endocrine system.