Science 2.1-2.3

Chapter #1 test

What is cell division?

What is cell division?

The process of a parent cell divides into two or more daughter cells.

Three functions of cell division

growth, repair, and reproduction

Why do cells not increase in size to grow?

There are limits to sizes of a cell. Once a cell grows beyond a certain size, it cannot function efficiently.

Why are cells replaced, and where do the new cells come from?

Cells are replaced when they are old or die. Cells come from pre-existing cells.

Asexual reproduction

unicellular organisms use cell division to form two identical bacteria.

Why do cells reproduce at different rates and different times?

Certain cells, such as hair or skin cells, reproduce quickly as they are needed very often.

What does the animal cell have that the plant cell does not?

The centriole.

What does the plant cell have that the animal cell does not have?

the vacuole and chloroplasts

the nucleus

the control centre of the cell. it directs all cell activities, including cell division. it is surrounded by the nuclear membrane that allows material in and out of the nucleus.

chromosomes

the material that directs all the activities of the cell, which is contained in the nucleus. of DNA (also known as deoxyribonucleic acid) and protein. Generally, all human cells have 23 pairs of these, or 46 total, half coming from your mom and the second half from your dad.

DNA

a very long molecule that looks like a twisted ladder. Each chromosome is made of one extremely long strand of this. it directs all cell structures and activities, including repairing worn and damaged cells and replacing dead cells.

eukaryotic cells

has a nucleus surrounded by a membrane. plants, animals, fungi, and protists have these.

prokaryotic cells

have no nucleus. bacteria have these.

nucleolus

A structure found in the nucleus of the cell. The site for the production and assembly of the ribosomes. Once assembled, the ribosomes move into the cytoplasm.

ribosomes

tiny organelles in the cytoplasm. they make the proteins that the cell need in order to function properly. either free in the cytoplasm or attached to endoplasmic reticulum.

endoplasmic reticulum

transport materials throughout the cell. has ribosomes attached is called rough insert answer that transports proteins throughout the cell. has no ribosomes attached is called smooth insert answer. Smooth insert answer manufactures and transports fats in the cell.

Cytoplasm

contains all the organelles in the cells, and most of the cell’s activities occur there, and nutrients are absorbed, transported, and processed here. Inside the insert answer, there are tiny tubes called microtubules. Microtubule allow the movement of organelles within the cell and provide support for the cell. is contained inside the cell membrane.

Centrioles

organelles made of special microtubules. They are found in almost all animal cells, and are active during cell division.

DNA molecule

made of two strands of smaller molecules, called nucleotides that are composed of a sugar molecule, a phosphate molecule, and a nitrogenous base molecule. the sides of the ladder are made of the sugar and phosphate molecules joined together. the rungs of the ladder are made of pairs of nitrogenous bases. each molecule splits in many places between the base pairs like a broken zipper.

nitrogenous base

adenine, thymine, cytosine, and guanine. these pairs always form each rung of the DNA ladder, adenine with thymine and cytosine with guanine. a rung is always made of cytosine and guanine (c-g) or adenine and thymine (a-t)

genetic code

bases in a DNA molecule are like the characters in the code. DNA has a four-character code, the DNA’s nitrogenous bases. these bases combine to form three-letter words that are three bases long like GGC or TAC. each three-letter word codes for the production of one of 20 different amino acids.

amino acids

small molecules which make protein

gene

the DNA molecule in a chromosome is organized into answer. a short section of DNA containing instructions to make a specific protein, determined by the order of the bases.

genome

all of an organism’ genes is called the genome. the human genome is contained in the 23 pairs of chromosomes in the nucleus of almost every cell in the body.

making a protein

also known as protein synthesis. firstly, the DNA segment that makes up a gene is used to make another molecule, RNA (ribonucleic acid. then, a gene segment of DNA separates and an RNA molecule is constructed from a half of the DNA, and then carries the code from the gene to the nucleus to a ribosome in the cytoplasm.

RNA

only has one strand

DNA

two strands and have base pairs

enzymes

special proteins that control specific chemical reactions.

common proteins

hemoglobin, insulin, keratin, collagen, enzymes, antibodies, fibrinogen, lactase, growth hormone, prolactin, and follicle stimulating hormone.

gene

Slightly different variations or traits are produced as there are different versions of the same answer. For sexual reproduction, there is an unique combination of genes.