IB Bio SL - Cells & Cell Transport

Outline the cell theory

cells are the unit of structure & function in living things
- living organisms are composed of cells
- cells are the smallest unit of life
- cells come from preexisting cells

Define unicellular

organisms made up of one cell but still carry out all the functions of life (metabolism, homeostasis, growth, reproduction, etc)

Define multicellular

organisms made up of many cells, where individual cells are specialized for one particular function

stem cell

cells that retain their ability to divide & differentiate into carious cell types

surface area to volume ratio

limits cell size to ensure there is enough surface area for gas exchange, supply of nutrients, and removal of waste between cells

cell wall

tough and slightly elastic; made of cellulose and present only in plant cells

Pili

structure on cells that enables attachment to surfaces and other bacteria

Nucleoid

a singular, circular chromosome of DNA in the cytoplasm, attached to the plasma membrane

hydrophilic

water-loving

osmosis

diffusion of water molecules across a partially permeable membrane from a region of high water concentration to a region of lower water concentration

active transport

uptake of substances against a concentration gradient from an area of low concentration to high concentration. requires ATP energy input and is also called a "pump

protein pump

used for active transport across membrane with the use of ATP

mitochondria

organelle in eukaryotic cells where ATP is made through cellular respiration

rough endoplasmic reticulum

site in eukaryotic cells where protein synthesis of proteins that will be exported from cells occurs

Prokaryote

cells smaller than eukaryotes. lack membrane bound nucleus & organelles. single circular chromosome of DNA known as naked DNA. contain ribosomes and divide by binary fission.

plasma membrane

made of a phospholipid bilayer with proteins floating within the phospholipids. purpose is to isolate the cell's contents from the external environment, regulate exchange of essential substances between cell & environment, and communicate with other cells

Flagella

used for movement in prokaryotic cells

fluid mosaic model

illustrates the cell (plasma) membrane.

Phospholipids

make up double layer of plasma membrane & responsible for isolating functions of the membranes with its hydrophilic head & hydrophobic tail

facilitated diffusion

movement across the membrane down the concentration gradient with the help of a channel or carrier protein

Exocytosis

transport of large materials through the membrane and out of the cell

Nucleus

control center of eukaryotic cells, contains DNA & is surrounded by the nuclear envelope

Golgi apparatus

stacks of flattened membranous sacs that function in sorting, classifying, and modifying proteins

smooth endoplasmic reticulum

produces phospholipids, steroids, fatty acids, & detoxifying chemicals in eukaryotes

Eukaryotic

cell found in animals. has a nucleus & organelles such as ribosomes, smooth er and rough er, golgi apparatus, lysosomes, centrioles, etc.

Cytoplasm

site of chemical reactions of life in cells

Ribosomes

site of protein synthesis - manufacture proteins

Hydrophobic

water hating

Diffusion

net movement of molecules down a concentration gradient from regions of high concentration to low

Endocytosis

intake of large materials across plasma membrane & breaks off material into a large sac called a vesicle

Vesicle

membranous sac formed by phospholipids during endocytosis

Nucleolus

inside nucleus, where rRNA is made and where ribosomes are put together

Lysosome

small sacs of digestive enzymes that break down complex molecules

Chloroplast

found only in plant cells, filled with chlorophyll & is the site of photosynthesis

Discuss evidence for the cell theory

Some evidence that supports the cell theory is that unicellular organisms are made of one cell but still carry out all the functions of life. Also, no spontaneous generation of cells forms from nonliving matter.

Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles, and cells using the appropriate SI units

Molecules are 1 nm. Thickness of cell membrane is 10 nm. Viruses are 100 nm. Bacteria are 1 um. Organelles are up to 10 um. Most cells measure up to 100 um.

Explain the significance of the surface area to volume ratio as a factor limiting cell size

the surface area to volume ratio should stay relatively low in order to keep a lower surface area for gas exchange, supplying of nutrients, and removal of waste from the cell.

What is meant by stating that multicellular organisms show emergent properties?

Stating that multicellular organisms have emergent properties means that it has properties that in total are greater than the sum of all its individual parts - the system is greater than all its components.

What are stem cells? Why are they useful for therapeutic treatments of different disorders?

1. Stem cells are cells that retain their ability to differentiate & divide into various cell types. They are useful for treatments of disorders because they are flexible and can grow into any type of mature cell, even cells that can replace damaged cells

Outline one therapeutic use for stem cells.

one use of stem cells is for treatment of patients with Alzheimer's or Parkinson's diseases. Stem cells are used to replace damaged cells within the body

Compare & contrast prokaryotic and eukaryotic cells

Prokaryotic cells lack a nucleus and membrane-bound organelles

Compare & contrast plant & animal cells

1. Animal cells do not have chloroplasts or a cell wall. Also, in plant cells there is usually one large, central vacuole, while in animals there are many smaller ones.

Outline two roles of the extracellular matrix

The extracellular matrix is home to glycolproteins, formed by animal cells for support, adhesion, and movement and also to the cell wall, made of cellulose & helps maintain shape in plants

Explain how the hydrophobic and hydrophilic properties of phospholipids help to maintain the structure of cell membranes

Cell membrane structure is maintained because the hydrophobic tails always want to be away from water and the hydrophilic heads want to be around water. As a result, the phospholipids arrange themselves into a bilayer with the tails on the inside and the

Describe how the fluidity of the membrane allows it to change shape, break, and re-form during exocytosis & endocytosis

Due to the structure of the membrane, it is flexible enough to change shape, break vesicles, and reform vesicles during exocytosis and endocytosis. To do this, vesicles fuse with the membrane & in endocytosis, materials are absorbed and encased in a vesic