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Unit 3 G7: Cells
Transcript of Unit 3 G7: Cells
Unit 3: For the Love of Cells
Let's take a closer look into the cell
Phospholipids line up so hydrophilic (water-loving) heads point outwards and hydrophobic (water-fearing) tails point inwards.
The bilayer makes the cell membrane selectively permeable.
Videos to help you understand
Animal & Plant Cells
What do you already know about cells?
Wood Stem Cell
Cell: smallest unit that can carry on all the processes of life.
Cork oak tree
Hooke described a "great many
boxes," similar to cells where monks live.
Drawing by Hooke
Anton van Leeuwenhoek
In the 19th century 3 German scientists
- Matthias Schleiden: plants composed of cells.
- Theodor Schwanns: animals composed of cells.
- Rudolf Virchow: cells come from other cells.
Ideas led to the Cell Theory...
Cell Theory: 3 Parts
1. All living organisms made of one or more cells.
2. Cells are the basic units of structure and function in organisms.
3. Cells only come from the reproduction of other cells.
Common Biology Theme: Form follows function.
A cell's function influences its physical features.
Cell's shape is simple or complex, depending on its function. Cell's evolve to perform specific function.
Ex. 1: Nerve Cell: long extensions that reach out in various directions allow the cell to send and receive nerve impulses.
Ex. 2: Skin Cell: flat plate-like shape of skin cells allows function of covering and protecting surface of the body.
Ex. 3: White blood cells: can change shape; leave blood, enter areas surrounding blood vessels so they can attack bacteria.
Question: Why does the egg cell take on the shape it has?
Similarities of all cells:
1. All have outer boundary. The PLASMA MEMBRANE acts as a barrier between inside and outside; all materials enter or exit through it.
2. They have an inner fluid called CYTOPLASM containing the cytoskeleton and all of the organelles except the nucleus.
3. They carry DNA for carrying out their functions and reproducing. DNA floats freely in some cells, in others it is held in the nucleus.
Your body contains at least 200 different cells.
A few cells can be seen without a microscope: egg cell and giraffe nerve cell (2m long!).
Prokaryotes: do not have a membrane-bound nucleus or membrane-bound organelles.
Eukaryotes: have a membrane-bound nucleus and membrane-bound organelles.
A bit more detailed...
Animal cells contain lipids called sterols.
Major sterol in animal cells is cholesterol; makes cell firmer and prevents from freezing at low temps.
Integral proteins transport molecules into the cell. Some act as sites where chemical messengers such as hormones bind.
Animal v/s Plant Cell: 3 Main differences
1.) Plant cells have cell wall: rigid, outside p.m.
2.) Plant cells contain central vacuole: reservoir, stores water, enzymes, up to 90% of cell
3.) Plant cells contain plastids (chloroplasts, leucoplasts, and chromoplasts)
Site of photosynthesis (how plants make food)
Contains chloroplasts; green pigment that absorbs energy from sunlight for use in photosynthesis.
Organelles that store starch, oil, and protein.
Common in storage roots (potatoes and carrots.
Two main types:
1.) cartenoids (store yellow and orange pigment
2.) chlorophyll (store green pigment).
What do you think this is from?
Passive Transport: when substances move across the cell membrane without any energy added.
Diffusion: simplest type of P.T. - movement of molecules from higher to lower concentrations; driven by molecules' kinetic energy; leads to equilibrium.
Equilibrium: the concentration of molecules are the same throughout a space
Osmosis: process of water molecules to diffuse across
a cell membrane from an area of higher concentration to an area of lower concentration;
passive transport of water.
Direction of Osmosis
Diffusion Across a Selectively
Permeable Membrane Lab
Active Transport: When cells move materials from an area of lower concentration to higher concentrations; requires energy from the cell.
1. Endocytosis: the cell ingests external fluid, large particles, and other cells; forms a vesicle.
Exocytosis: substance is released from the cell through a vesicle that transports the substance to the cell surface and then fuses with the membrane to let it out. Cells use exo. to release proteins, waste products and toxins that could harm cell
ATP: Adenodine Triphosphate
Energy in ATP is used in cells to do work.
What do you notice about this equation?
Respiration takes place day and night in all cells.
Energy produced by glucose in respiration is needed
for all living things.
Respiration takes place in the mitochondria.
Photosynthesis: happens in chloroplast.
Respiration: happens in the mitochondria.
You will now design a lab to test respiration!
Two types: Mitosis and Meiosis.
The purpose of MITOSIS is to create new cells for growth, development and repair.
The purpose of MEIOSIS is to produce haploid eggs and sperm (23 chromosomes in humans) so fertilization can produce a diploid zygote (fertilized egg with 46 chromosomes in humans).
Chromosome: inside a nucleus, contains DNA.
Chromatid: each half of DNA.
Centromere: chromatids attach here.
Each human cell has 46
chromosomes or 23 pairs of
Chromosome #'s of various species
carrot - 18
chimpanzee - 48
dog - 78
horse - 64
sand dollar - 52
Haploid v/s Diploid
Cells with 2 sets of chromosomes are DIPLOID.
All human cells except reproductive cells (egg/sperm) are normally DIPLOID.
Cells with half the number of cells that are present in diploid cells are HAPLOID.
Egg and sperm cells are HAPLOID.
If reproductive cells were diploid the new cell would have too many chromosomes and be unfunctional.
Mitosis: Results in new cells with identical genetic material to the original cell.
Multiple stages to the split. Let's fill out a Mitosis Worksheet together to understand the different phases.
Meiosis: In animals results it produces gametes (sperm and egg cells) with 23 chromosomes each.
What are the forms and functions of various types of cells?
How might the use of stem cells change the evolution of humans?
Should we control who